Roman Croitor
email: romancroitor@europe.com

Systematical position and paleoecology of the endemic deer Megaceroides algericus Lydekker, 1890 (Cervidae, Mammalia) from Late Pleistocene -Early Holocene of North Africa

Keywords: Cranial morphology, Pachyostosis, Evolution, Ecomorphology, Taxonomy, Paleobiogeography

    Systematical position and paleoecology of the endemic deer Megaceroides algericus Lydekker, 1890 (Cervidae, Mammalia) from the late Pleistocene-early Holocene of North Africa

Introduction

Cervidae represents a successful family of ruminants that arose in the mid-Tertiary period in Eurasian tropics, however, because of its specific evolutionary and ecological strategy, this rich in species and ecological forms family, apart from a few exceptions, failed to colonize the African continent. According to [START_REF] Geist | Deer of the World: Their Evolution[END_REF], cervids with their low forage habit specialization are poor food competitors with other groups of herbivores, like bovids and equids, in old species-rich ecosystems among coevolved ecological specialists. Ecologically opportunistic cervids are most successful in young ecosystems with large amplitude of environmental fluctuations [START_REF] Geist | Deer of the World: Their Evolution[END_REF]. The paleontological record and modern fauna give only two examples of successful evolutionary survival of cervids on the African continent: Megaceroides algericus (Lydekker, 1890) and Cervus elaphus barbarus Bennet, 1833 [START_REF] Gentry | Cervidae[END_REF].

The origin and systematical position of the mysterious North African fossil deer Megaceroides algericus is a subject to debates and contradictions in the scientific literature for more than a century. The extinct species M. algericus represents the exceptional zoogeographic instance of an endemic extremely specialized form of deer that evolved on the African continent. The second African cervid, Cervus elaphus barbarus, is a primitive small-sized subspecies of red deer, which survived until the present days and does not show unusual or particular evolutionary specializations, possibly with exception of some traits of paedomorphosis [START_REF] Geist | Deer of the World: Their Evolution[END_REF]. The isolated and very restricted North African distribution of M. algericus represents a very interesting, but still poorly understood evolutionary and paleozoogeographic case. The present article propose a taxonomic, morphological, morpho-functional, paleobiological, and phylogenetic study of the "thick-jawed deer" M. algericus that aims to contribute to the better understanding of this rare zoogeographic instance of endemic North African cervid.

Historical background

The first description of the species belongs to Lydekker (1890). He described a maxilla with an upper tooth series comprising P 4 -M 3 of a medium-sized deer from Hammam Mescoutine (Algeria) as Cervus algericus, noting a strongly developed cingulum, and assumed a possible phylogenetic relationship of the new species with the giant deer Megaloceros giganteus. Some-what later, Pomel (1892) created another species Cervus pachygenys, which was based on a very pachyostotic and quite bizzare ("pathological", according to [START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] lower mandibles from Neolithic of Algeria. The sample described by [START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] also included an isolated upper molar without lingual cingulum. [START_REF] Joleaud | Sur le Cervus (Megaceroides) algericus Lydekker, 1890[END_REF][START_REF] Joleaud | Cervus (Megaceroides) algericus Leydekker, 1890[END_REF] brought together in synonymy Lydekker's and Pomel's species and stressed the affinity between the African deer and the European giant deer, assuming for the African form an intermediate position between Megaloceros and Dama. [START_REF] Joleaud | Sur le Cervus (Megaceroides) algericus Lydekker, 1890[END_REF][START_REF] Joleaud | Cervus (Megaceroides) algericus Leydekker, 1890[END_REF] placed the North African deer in his new subgenus Megaceroides within the genus Cervus in order to underline its assumed archaic character and transitional systematic position. [START_REF] Arambourg | Note préliminaire sur un nouvelle grotte à ossements des environs d'Alger[END_REF][START_REF] Arambourg | Mammifères fossiles du Maroc[END_REF] elevated Megaceroides to the genus level and reported on some new important findings of cranial remains of Megaceroides algericus from Algeria (Guyotville) and Morocco (Ain Tit Mellil). [START_REF] Arambourg | Mammifères fossiles du Maroc[END_REF] provided figures of those findings, but did not describe them in details.

The studies of Italian researchers published in the second half of the XX-th century gave a new impetus to the debates on taxonomy and systematical position of the endemic African cervid. [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF] proposed a new evolutionary and systematic model of the genus Megaloceros, which included all giant and some smaller plesiometacarpal Old World cervids, including presumed descended Late Pleistocene dwarfed forms from Mediterranean islands and Megaceroides algericus. [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF] divided the genus Megaloceros Brookes, 1828 (the genus name Megaceros Owen, 1843 was applied in the cited work) into two informal evolutionary branches called the "giganteus group" and the "verticornis group" after the best known species representing each stock. Megaceroides algericus, according to [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF], is a terminal form of the "verticornis group" with signs of evolutionary "degeneration", such as a small body size, the extreme degree of hyperostosis, and a very marked shortening of the muzzle. Azzaroli (1953: page 48) recognized that the relationship of M. algericus with European forms is not clear, therefore he avoided using the name Megaceroides in his evolutionary model of giant deer. Nonetheless, [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF] indicated some morphological characters of Megaceroides algericus, such as the flattened shape of the frontlet and traits of "stunting" in the antler morphology and overall size, which permitted to Azzaroli to include the North African cervid in his "verticornis group". [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF] noticed that M. algericus coincides in some features with Sinomegaceros pachyosteus (placed by [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF] in the "giganteus group") in its smaller body size, the extreme degree of hyperostosis, and the shortening of the muzzle. Ambrossetti (1967) accepted Azzaroli's opinion and placed all "verticornis-like" deer from Europe together with Algerian endemic deer in the subgenus Megaceros (Megaceroides). Later, [START_REF] Azzaroli | Large early Pleistocene deer from Pietrafitta lignite mine, Central Italy[END_REF] elevated Megaceroides to the generic rank. [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF] suggestion on the morphological affinity between Megaloceros algericus and Sinomegaceros pachyosteus was supported later by [START_REF] Thomas | La faune quaternaire d'Algerie[END_REF] and Hadjouis (1990).

Finally, [START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF][START_REF] Azzaroli | Forest Bed elks and giant deer revisited[END_REF] assumed that Megaceroides algericus and Praemegaceros dawkinsi (=Megaceroides dawkinsi according to [START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF] resulted from a similar evolutionary processes of dwarfing caused by geographical isolation in unfavorable conditions. The flat shape of the frontal bones, the similarly diminished body size, and the disproportionately thin antler beams with respect to relatively large antler burrs and robust pedicles are regarded as stunting traits shared by M. algericus and P. dawkinsi [START_REF] Azzaroli | Large early Pleistocene deer from Pietrafitta lignite mine, Central Italy[END_REF]. [START_REF] Kahlke | Die Cerviden-Reste aus dem Tonen von Voigtstedt in Thüringen[END_REF] proposed the old genus name Praemegaceros [START_REF] Portis | Elenco delle specie di Cervicorni fossili in Roma e attorno a Roma[END_REF] (substituting the genus name Orthogonoceros Kahlke, 1956 with type species Cervus verticornis Dawkins, 1872) for European deer of the "verticornis group", thus disregarding [START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF] suggestion of a close phylogenetic relationship between Megaceroides algericus and the "verticornis group". Somewhat later, [START_REF] Radulesco | Sur un nouveau cerf megacerin du pleistocene moyen de la depression de Brasov (Roumanie)[END_REF] published a detailed taxonomical study of Pleistocene large-sized deer and confirmed the validity of the genus name Praemegaceros for the "verticornis group", acting as first revisers. The endemic British deer Cervus dawkinsi Newton, 1882 was designated as a type species of the genus Praemegaceros [START_REF] Radulesco | Sur un nouveau cerf megacerin du pleistocene moyen de la depression de Brasov (Roumanie)[END_REF]. From that point, debates on the taxonomy of large-sized deer from Pleistocene of Western Palearctic became very confusing, since the disputed genera Praemegaceros and Megaceroides were typified by poorly known endemic and morphologically odd species Praemegaceros dawkinsi and Megaceroides algericus. Vislobokova (2012aVislobokova ( : page 687, 2012b: page 58;: page 58;2013: page 911) regards Cervus verticornis Dawkins, 1872 as the type species of Praemegaceros and granted to [START_REF] Kahlke | Die Cerviden-Reste aus dem Tonen von Voigtstedt in Thüringen[END_REF] the title of first reviewer of the genus. Nonetheless, Vislobokova (2012b: page 61;2013: page 913) in also proposes Cervus dawkinsi as a type species of the nominotypical subgenus Praemegaceros (Praemegaceros). It is necessary to keep in mind that Praemegaceros [START_REF] Portis | Elenco delle specie di Cervicorni fossili in Roma e attorno a Roma[END_REF] was originally based on Cervus dawkinsi, while Cervus verticornis together with Cervus savini Dawkins, 1887 and Cervus falconeri Dawkins, 1868 were included in Praedama [START_REF] Portis | Elenco delle specie di Cervicorni fossili in Roma e attorno a Roma[END_REF][START_REF] Portis | Elenco delle specie di Cervicorni fossili in Roma e attorno a Roma[END_REF][START_REF] Radulesco | Sur un nouveau cerf megacerin du pleistocene moyen de la depression de Brasov (Roumanie)[END_REF][START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF] and, therefore, can not be used as type species for Praemegaceros. According to the Article 44 of ICZN, a genus and its nominotypical subgenus are denoted by the same type species. Hadjouis (1990) regarded Megaceroides as a subgenus of Megaceros Owen and proposed an improved neodiagnosis for Megaceroides and a synonymy list of M. algericus. In opinion of Hadjouis (1990), the morphology of the dentition (first of all, the strongly developed cingulum on upper molars) and the extremely strong mandibular pachyostosis approach M. algericus to the Asian large-sized deer Sinomegaceros pachyosteus, thus one more time supporting the [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF] previous observation. The missing posterior tine in antlers of M. algericus was regarded by Hadjouis as one of the most important characters distinguishing the African endemic deer from European giant deer. Nonetheless, the viewpoint of Hadjouis has been contested by [START_REF] Azzaroli | Large early Pleistocene deer from Pietrafitta lignite mine, Central Italy[END_REF] and [START_REF] Azzaroli | Forest Bed elks and giant deer revisited[END_REF], who put in question the taxonomical value of the cingulum in upper molars and the mandibular pachyostosis, which, according to the Italian authors, are quite variable in large-sized deer. [START_REF] Abbazzi | Remarks on validity of the generic name Praemegaceros Portis 1920, and an overview on Praemegaceros species in Italy[END_REF] pointed out the resemblance of neurocranium shape of Megaceroides algericus with Praemegaceros solilhacus (Robert, 1829) and P. dawkinsi, however, she did not discuss the phylogenetic position of M. algericus and, following the opinion of Hadjouis (1990), restricted Megaceroides to the type species. [START_REF] Gentry | Cervidae[END_REF] included Megaceroides in the synonymy of Megaloceros. [START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF]Vislobokova ( , 2012aVislobokova ( , 2012b[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF] included Megaceroides in the tribe Megacerini Viret, 1961 that contains a large number of continental and insular Late Miocene -Pleistocene cervids presumably closely related to the genera Megaloceros and Praemegaceros. Vislobokova (2012b[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF] suggests that Megaceroides is a monotypic taxon that includes a single peculiar cervid form closely related to European Praemegaceros and possibly may be included in the latter genus as a subgenus in the case if its belonging to Praemegaceros will be demonstrated. Vislobokova (2012b[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF]) also regards Azzaroli's informal verticornis-group and giganteus-group as subtribes Praemegacerina and Megacerina within the tribe Megacerini. Since the phylogenetic relationships among the so-called "giant deer" (including also some smaller continental forms and insular dwarfs) are not well founded [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF], the new taxonomical units proposed by Vislobokova most probably are polyphyletic.

The taxonomical revision of the genus Praemegaceros and a preliminary account on systematical position, morphology, and paleoecology of Megaceroides algericus were published in our previous reports (Croitor, 4 2004(Croitor, 4 , 2006(Croitor, 4 , 2014;;[START_REF] Croitor | Étude préliminaire des cerfs du gisement Pleistocène inférieur de Ceyssaguet (Haut-Loire)[END_REF][START_REF] Croitor | On the systematic position of the large-sized deer from Apollonia, Early Pleistocene, Greece[END_REF][START_REF] Croitor | Origin and evolution of the late Pleistocene island deer Praemegaceros (Nesoleipoceros) cazioti (Depéret) from Corsica and Sardinia[END_REF]. We pointed out that the morphology of the dentition (the presence of the cingulum in upper molars, the relatively short lower premolar series, and the brachyodonty) approach the Algerian deer to Megaloceros giganteus from moderate latitudes of Central and Western Eurasia [START_REF] Croitor | Étude préliminaire des cerfs du gisement Pleistocène inférieur de Ceyssaguet (Haut-Loire)[END_REF]. Therefore, we adjoined the opinion of [START_REF] Radulesco | Sur un nouveau cerf megacerin du pleistocene moyen de la depression de Brasov (Roumanie)[END_REF] on the validity of the genus name Praemegaceros for the "verticornis group". Later, a direct phyletic relationship between dwarfed Middle Pleistocene Praemegaceros dawkinsi and larger Early Pleistocene Praemegaceros obscurus was suggested [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. This point of view is supported, inter alia, by the presence of vestigial basal antler tines in P. dawkinsi, which are homologous with long and strong basal tines in P. obscurus.

Regarding the size and proportions of the braincase from Ain Tit Mellil discovered by [START_REF] Arambourg | Mammifères fossiles du Maroc[END_REF] and the pachyostotic mandibles from various North African sites, I pointed out the disproportion between the relatively broad and large braincase and the short and weak anterior part of the mandibles, presuming the mixed character of the material ascribed to Megaceroides algericus and, therefore, I proposed to exclude the African material from the taxonomical debates of European large-sized cervid forms [START_REF] Croitor | Late Neogene and Quarternary biodiversity and evolution: Regional developments and interregional correlations[END_REF]. Later, I had the opportunity to study the complete skull of Megaceroides algericus from Guyotville (figured by [START_REF] Arambourg | Note préliminaire sur un nouvelle grotte à ossements des environs d'Alger[END_REF]) that represents a poorly understood and aberrant morphological specialization for Cervidae [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. In my previous publication, only a general description and some measurements of the cranial and mandibular material of M. algericus were published, however, even that brief overview provides arguments against its use as a type species for giant and dwarfed deer arbitrarily placed in the "verticornis group" and now included in the genus Praemegaceros [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF][START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF].

Despite of the available fine cranial and dental material, antlers and postcranial bones of Megaceroides algericus are little known. [START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] described and figured a damaged, but obviously very robust and relatively short cervid radius from Berrouaghia (Algeria) characterized by a comparatively broad bone shaft (the mid-shaft measurement amounts to 40 mm, exceeding the analogous measurements of Megaloceros giganteus) and two fragments of slightly compressed from the sides (latero-medially) antler tines. Hadjouis (1990) described several shed antlers of Megaceroides algericus from Phacocheres (Algeria) with the missing distal part of palmation and the anterior (middle) tine, as well as a fragment of a narrow distal palmation. These specific although very incomplete data on the antler and postcranial morphology of Megaceroides algericus suggest peculiar eco-morphological adaptations, but practically do not contribute to the understanding of paleoecology and evolution of this species.

Nonetheless, despite of long lasting debates on its systematical position and phylogenetic relationships, even the fine available cranial material of Megaceroides algericus is still rather superficially described. In the present paper, a detailed morphological description of the cranial remains and dentition of Megaceroides algericus and a discussion on its paleoecology and phylogenetic relationships are provided.

Material and methods

The described fossil material comes from the old historical collections stored in the National Museum of Natural History in Paris. All fossil remains are yielded by archaeological Paleolithic sites, however, their exact stratigraphic provenance and absolute age remain unclear. Nonetheless, the detailed morphological description of the material included in the study was never published before and represent a significant information gap that impede the advance of our knowledge of taxonomy, systematics and phylogeny of Eurasian large sized and endemic Mediterranean deer. The studied material (Tab. 1) comes from the following sites (Fig. 1 [START_REF] Arambourg | La Grotte de la Carrière Anglade à Guyotville (d'Alger)[END_REF] as a Middle Paleolithic assemblage due to the presence of Rhinoceros mercki and Hippopotamus amphibius. The better preserved antlered skull (distal portions of antlers are not preserved, no collection number) from Guyotville was excavated and briefly described by Arambourg (Arambourg, 1932: fig. 3) and has been mentioned by [START_REF] Azzaroli | Large early Pleistocene deer from Pietrafitta lignite mine, Central Italy[END_REF] with regard to its forehead shape. Hadjouis (1990) quotes briefly some cranial characters based on the specimen from Guyotville and published measurements of its dentition. Only an approximate condylobasal length of this skull could be measured [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF], since its occipital condyles and foramen magnum were destroyed, apparently, by ancient hunters who extracted the brain tissue from the braincase. The sample from Guyotville includes also two hemimandibles (Nr. 336, Nr. 337, "Collection of Arambourg"), which remained unpublished.

Ain Tit Mellil (= Tit Mellil: Vaufrey, 1955), Morocco. The exact stratigraphic origin of the fossil remains is unknown and they age was generally assumed as "the beginning of Würm glaciation" [START_REF] Vaufrey | Prehistoire de l'Afrique[END_REF]. The braincase MOC148 from Ain Tit Mellil (figured in Arambourg, 1938: pl. II, fig. 2) was briefly discussed by Abbazzi (2004: fig. 6) and Vislobokova (2013: fig. 56, a, b).

Grotte de la Madeleine (= Taza 1: Fernandez et al., 2015), Algeria. The Paleolithic site Taza 1 includes three layers dated from >39 000 to 13 800  130 y. BP (uncalibrated: [START_REF] Medig | Les grottes paléolithiques de Taza[END_REF]. Therefore, Late Pleistocene age is assumed for historical collection of fossils yielded by this site [START_REF] Fernandez | The last occurrence of Megaceroides algericus Lydekker, 1890 (Mammalia, Cervidae) during the middle Holocene in the cave of Bizmoune (Morocco, Essaouria region)[END_REF]. The studied material includes two fragmented mandibles: the well preserved right hemimandible figured in [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF] fig. 2 A-B; no collection number) and another specimen with a malformation in the area of processus angularis (no collection number). The museum label provides the following information: "Cervus algericus -figuré: Pl. IV, Fig. 4", however, this label does not contain any bibliographic information. Filfila, Algeria. A Würmian age was assumed for the fauna from Filfila [START_REF] Ginsburg | Une faune würmienne dans un remplissage de fente du massif du Filfila (littoral nordconstantinois, Algérie)[END_REF]. The sample of Megaceroides algericus from Filfila, Algeria [START_REF] Thomas | La faune quaternaire d'Algerie[END_REF] includes a fragment of right upper jaw FIL169 with M 2 and M 3 and three hemimandibles (FIL166, FIL167, and juvenile FIL160). Only the better preserved specimen FIL166 was figured by [START_REF] Thomas | La faune quaternaire d'Algerie[END_REF] and Abbazzi (2004: fig. 7).

The specific character of fossil material (fragmentary skeletal remains, limited number of fossils) restricted the choice of methodological approach. The safest estimation of cranial and dental morphological characters of Megaceroides was possible with involving of few "typical" evolutionary and ecological cervid forms, like Dama dama (apparently, one of the closest to Megaceroides species, which maintains generalized cervid cranial morphology), Megaloceros giganteus (a giant species characterized by pachyostosis as Megaceroides algericus), Muntiacus muntjak (a tropical forest dweller, which possibly maintain the basic for Cervinae cranial morphology and proportions), and Hydropotes inermis (belongs to the subfamily Capreolinae, but represents a rare for cervids example of ecological specialization connected to the periaquatic ecological niche). The comparative craniological material includes a series of skulls and mandibles of the modern fallow deer Dama dama, Muntiacus muntjak, and Hydropotes inermis stored in the osteological collection of the Zoological Museum "La Specola" (ZMS, Florence, Italy) and in the Natural History Museum of London (NHML), red deer Cervus elaphus stored in the zoological collection of the National Museum of Natural History in Paris (NMNH), and Megaloceros giganteus from various Late Pleistocene sites of Ireland (NHML). The main measurements of the comparative material are presented in the tables 2 and 3. The statistical processing of data was not possible because of the restricted number of fossil material, but also because of quality and mixed character of the comparative osteological material, which I had at my disposal: the cranial material of some species (M. muntjak and H. inermis) was not numerous, besides that, many specimens were obtained from parks, zoological gardens, and did not represent natural populations, therefore, the statistical processing of data became senseless. Therefore, a single male skull of each species was selected for the comparative study.

The lengths of dental series are taken at the crown bases or at alveoli. The length of tooth crown is taken as a maximal measurable value. The length of tooth crown in upper cheek teeth is measured at the labial side of grinding surface. The breadth of tooth crown is measured at crown base. The terminology of dental morphology is adapted from Heintz (1971). The applied methodology of cranial measurements is adapted from [START_REF] Vislobokova | The fossil deer of Eurasia[END_REF]. The applied terminology of antler tines follows the homology of tines according to [START_REF] Azzaroli | Large early Pleistocene deer from Pietrafitta lignite mine, Central Italy[END_REF] and [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF].The body mass estimation used here is based on dental variables according to [START_REF] Janis | Correlation of cranial and dental variables with body size in ungulates and macropodoids[END_REF]. Abbreviations used in the text: PP, premolar series; MM, molar series; L, length; H, height; D, width/breadth. Holotype: the left maxilla with P 3 -M 3 (Lydekker, 1890; figured on page 602), P 2 is completely destroyed, while M 2 and M 3 are damaged; the cast is stored at the Natural History Museum of London (Lydekker, 1890: p. 604), collection number M10647 [START_REF] Gentry | Cervidae[END_REF]. The length of upper molar series M 1 -M 3 amounts to 58.5 mm (measured from the figure). The location of the original fossil specimen is unknown. The holotype is characterized by the strong development of a basal enamel cingulum in the upper molars.

Type locality and horizon: Late Pleistocene from Hammam Meskoutin, Guelma (Algeria).

Occurrence: Late Pleistocene -Holocene (ca. 24,000 to 6641-6009 yr. BP; [START_REF] Fernandez | The last occurrence of Megaceroides algericus Lydekker, 1890 (Mammalia, Cervidae) during the middle Holocene in the cave of Bizmoune (Morocco, Essaouria region)[END_REF]. (Lydekker, 1890: page 603): Somewhat smaller than Cervus cashmirianus, with brachyodont molars, having a very large inner cingulum, and the external surface complicated by the excessive development and reflection of the lateral ridges of the outer crescents so as to form distinct pockets on this surface at the base of the ridges in question.

Original diagnosis

Emended diagnosis (this work):

A cervid species of medium size, slightly larger than modern fallow deer and smaller than red deer. The skull is very broad: the skull breadth attains more than 60% of the condylobasal length. Splanchnocranium is relatively short: the length measured from the anterior edge of the orbits to the prosthion makes is shorter than 1/2 of the condylobasal length. Skull bones with exception of zygomatic arches are very thick. Braincase is moderately flexed: the angle between parietal bones and face profile amounts to ca. 135°; parietal bones are flat. Pedicles are moderately long (their length approximately equals to their transversal diameter), deflected sideward and some-what backward. Frontal bones are flat and very broad. Orbits are comparatively large; their anterior edges lay at the level between M 2 and M 1 . Ethmoidal vacuities are completely closed. Preorbital fossae are not developed. Basioccipitale is broad and bell-shaped. Upper canines are missing. The cingulum in upper molars is variable: it may be well-developed, or almost completely missing. Lower fourth premolar (P4) is molarized: its metaconid is fused with paraconid. Mandible is very pachyostosic, with low anterior part. The transversal section of the anterior portion of the hemimandible is circular. Antlers terminate with a palmation. The proximal part of antler beam has a circular transversal section and lacks basal tines. The tine inserted on the anterior side of the beam (homologous with the middle tine in Megaloceros giganteus) is situated from the burr at a distance ca. two times exceeding the diameter of antler base.

Description:

SKULL: The cranium from Guyotville belongs to a rather aged individual with completely obliterated sutures and deeply worn upper dentition (Figs. 2,3). The area of left eye socket is damaged. The basioccipital part and anterior part of premaxillary bones are destroyed, so the condylobasal length and some other measurements of the skull are given with approximation (Tab. 4). The overall shape of cranium is atypical. The relatively short and very broad skull of Megaceroides algericus is unique among fossil and living cervids (Fig. 2). Interestingly enough, the length proportions of the cranium are modified insignificantly: the eye sockets are in normal position for a deer of such a size, the relative length of facial part before eye sockets is the shortest among deer involved in comparison (even some-what shorter than in the insular dwarf Praemegaceros cazioti), however, the difference is not significant (Fig. 4) and the length proportions may be regarded as normal for a deer of this size of subfamily Cervinae. The position of bregma between the posterior edges of pedicles and the position of nasion slightly caudally with respect to anterior edges of eye sockets are similar to the morphological condition found in Megaloceros giganteus. The orbito-frontal portion of the cranium is rather short, as in Dama and Megaloceros: the anterior edge of orbit is situated above the M 2 -M 3 border. The eye sockets are relatively large, as in Dama.

The relative length of the upper tooth row with respect to basal length of skull amounts to 29.5%, being fairly close to the ratio found in Megaloceros, Axis and Dama. Nonetheless, the position of upper cheek tooth row shifted toward the anterior represents a specific character of M. algericus (Fig. 5). The anterior displacement of the upper tooth row in Megaceroides algericus, apparently, resulted from the strong reduction of the predental length of the skull (distance between P 2 and prosthion). The parietal bones are flat. The face profile is straight. The braincase of Megaceroides algericus may be considered as rather flexed: the angle between parietal plane and the facial profile amounts to 135° and shows an intermediate condition between Dama and Megaloceros (Fig. 6).

The cranial bones are very thick, reminding the cranial hyperostosis described in Megaloceros.

However, unlike in Megaloceros, the vomer apparently is not affected by hyperossification (Fig. 3). The zygomatic arches are markedly thin and feeble, contrasting with overall robustness of the skull.

The pedicles are rather long, set obliquely on the skull and some-what deflected toward the rear and the sides. The pedicles are slightly compressed in the antero-posterior direction, however this compression is not as strong as in advanced species of Praemegaceros (P. verticornis, P. dawkinsi, and P. solilhacus). The frontal bones are very broad (corresponding The area for the musculus masseter attachment on the upper maxilla is situated above the anterior edge of M 1 and posterior edge of P 4 . The predental portion of the skull (anterior parts of maxillae and praemaxillary bones) is very broad and relatively short.

The braincase MOC148 from Ain Tit Mellil is similar in morphology and proportions to the previous specimen, but is characterized by slightly smaller size and by a more convex profile of the forehead (Figs. 7A,8). The basioccipital bone in MOC148 is broad and bell-shaped (Fig. 7B), with a transversal extension in the area of the pharyngial tubercles (the tubercles for the attachment of the Musculus rectus capitus ventralis major). The breadth of basioccipitale at tubercles amounts to 52.1 mm. The preserved left bulla tympani is rather large, rounded, projecting outside (as in Dama), compressed in the medio-lateral direction, with the following dimensions: 35.0 × 20.1 mm. The anterior bony thorn of bulla tympani is not present in Megaceroides, unlike some Cervinae (Cervus, Rucervus). The foramina ovale are comparatively small, with irregular shape approaching to a triangular outline. The dimensions of foramina ovale are the following: 6.6 × 6.0 mm (sin); 7.0 × 5.4 mm (dx). The nasal bones are extended behind the line connecting the anterior edges of orbits (Fig. 9). I did not have an opportunity to make a direct comparison of crania of Megaceroides algericus and Sinomegaceros pachyosteus from China, nonetheless, it is useful to compare at least the general shape of Megaceroides algericus with skull of Sinomegaceros from Choukoutien figured by [START_REF] Young | On the Artiodactyla from the Sinantropus site at Choukoutien[END_REF]. It seems that the skull of Sinomegaceros pachyosteus is broadest at the level of orbits reminding Megaceroides algericus, thou its broadening is not so extreme as we can see in the African deer. One can notice that the skull is broadest in Sinomegaceros pachyosteus at the posterior edge of the orbits, while the skull of Megaceroides algericus is broader at the anterior edge of the orbits. This difference is conditioned, apparently, by the orientation of orbits, which are more forward oriented in Sinomegaceros pachyosteus. One can assume that the noticed difference of orbit orientation represents an adaptation to forested environment in Sinomegaceros pachyosteus. Therefore, the side orientation of orbits in Megaceroides algericus should be regarded as a specific adaptation for open landscape in hoofed mammals allowing a widest possible field of view in order to escape approaching predators. M. algericus is characterized by some-what more flexed braincase than S. pachyosteus (the angle between parietal plane and face profile line measured from the specimen figured by [START_REF] Young | On the Artiodactyla from the Sinantropus site at Choukoutien[END_REF] amounts to ca. 145°), and both cervids are more advanced in this case than M. giganteus characterized by a weak flexion of braincase (see [START_REF] Vislobokova | The fossil deer of Eurasia[END_REF] for progressive change of this character in Cervidae). S. pachyosteus shows a different position of its orbit with respect of upper tooth row: according to the figure of [START_REF] Young | On the Artiodactyla from the Sinantropus site at Choukoutien[END_REF], the anterior edge of orbit is situated above the anterior part of M 2 (not above M 2 -M 3 border as in Megaceroides algericus). Possibly, this difference is caused by relatively diminished size of teeth in M. algericus and their oral "migration". UPPER TEETH: The anterior part of the maxillas is preserved and show that there were no canines (their alveoli are not present) in the specimen from Guyotville. Cheek teeth are relatively small (Tab. 5). The relative size of upper third molar is visibly reduced; therefore M 2 is noticeably larger than M 3 . Only a moderately developed entostyle is present on the lingual side of the upper molars. The entostyle of the upper molars is flattened and well-expressed in the studied additional material. It may extend and partially edge with lingual base of tooth crown; however a continuous (antero-linguo-posterior) large cingulum is not developed. There are no hypoconal spur and other enamel folds on upper molars. The lingual side of the P 4 is not split into protocone and hypocone, not even grooved. The lingual side of P 4 is bordered with a weak cingulum-like enamel fold.

The fragment of a maxilla with M 2 -M 3 FIL-169 belongs to an older individual as indicated by the advanced stage of tooth crown wear (Fig. 10). The angle between labial and lingual walls of upper molars (Fig. 10) amounts to 37º, as in Dama dama. The hypoconal fold is present only in M 3 . Two small enamel folds are found on the external side of anterior hypoconal wing in M 2 .

It is necessary to indicate that the additional material on upper dentition described in the present paper does not fully correspond to the morphology and measurements of the holotype of Megaceroides algericus. Unlike the holotype from Hammam Meskoutin, the additional material of M. algericus represents a deer form with some-what smaller upper cheek teeth (length of M 1 -M 3 tooth series amounts to 54.1 mm in the specimen from Guyotville against 58.5 mm in the holotype of M. algericus), the cingulum in upper molars of the additional material is not developed, while M 3 is significantly reduced in size (this specific size reduction in the specimen from Hammam Meskoutin is not observable). It is not clear yet, if we observe a broad individual variation in dental morphology, or a true evolutionary process (see discussion).

LOWER MANDIBLE: The body of the lower mandible is very low and thick (Fig. 11). The symphysal portion of the mandible is high (Fig. 12, Tab. 6). The diastemal part of the mandible is relatively very short. The anterior portion of the mandible from M1 to the symphysis has a cylindrical shape. Behind the M 1 , the mandible becomes higher and more robust. The maximal thickness of mandible is behind M 3 , in the area of musculus masseter insertion. The available fossil material does not display clear sexual dimorphism of mandibular pachyostosis observed in M. giganteus. The juvenile mandible FIL 160 is already pachyostotic, although it is less thick than the mature specimens. The lower side of horizontal part of mandible is convex. The processus angularis is moderately expressed. The ascending part of mandible is sloped backward and forms with the horizontal body of mandible an angle amounting to 60º. The posterior side of the ascending ramus is concave. The coronoid processus is short and cone-shaped. The shape of articulation condyle is cylinder-like. The distance between the cranio-mandibular articulation condyle and the M 3 is relatively large if compared to the majority of deer involved in the comparative study. This morphological trait is in accordance with the forward displacement of the upper tooth rows. The lower tooth row is displaced orally due to the very short diastema and obliquely set ascending portion of mandible (Fig. 13).

LOWER TEETH: The crowns of lower cheek teeth are relatively small and rather short and broad (Tab. 7). At the initial stage of wear, protoconid and hypoconid of P 4 may not be completely fused (Fig. 11B); however, the fourth premolar usually shows a complete molarization with complete conjunction of protoconid and hypoconid at a more advanced stage of wear. The size of the crown of P 2 is much reduced, so it remains untouched even in a deeply worn dentition, as may be seen in the specimen FIL166 (Fig. 12).

The specific proportions of lower tooth row are characterized by relatively reduced size of M 3 , if compared to the larger and broader M2 and M1. The premolar series is comparatively short, however, a broad variation is observed here. The premolar/molar length ratio amounts to 60.5% in the mandible FIL166, while the same tooth series ratio in the two specimens from Phacocheres amounts to 45.0% and 52.9% (Hadjouis, 1990).

DENTAL WEAR: The dental wear in Megaceroides algericus brings interesting details that reveal some earlier overlooked anatomical and paleoecological peculiarities of this species. The entire lower tooth row is worn evenly (with exception of P 2 , which is not worn) in all studied specimens of M. algericus, unlike in the majority of deer, which normally show a more advanced wear of M 1 . The statistical processing of mesowear traits is not possible because of the poorly preserved dental material, however, some of observations are interesting and worth mentioning. The character of the tooth row wear varies suggesting a rather broad range of food habits in Megaceroides algericus. Generally, the dental cusps are very low and rounded; nonetheless, the wear surface of the enamel in the majority of specimens available for observation is finely polished, suggesting the predominated dental attrition. However, the grinding surface of the mandible FIL166 is striated by transverse traces of wear caused by a coarse forage material. The direction of wear traces forms an angle of 60º with the tooth row axis. This observation suggests a comparatively wide angle formed by hemimandibles, which apparently attained 60º (Fig. 14). Such a broad angle between hemimandibles is in accordance with the particularly broad skull. ANTLERS: The complete antlers of Megaceroides algericus are unknown. The cranium from Guyotville preserved only the proximal parts of the antlers. The left antler is broken just at few centimeters above the burr, while the right antler is broken at 20 cm above the burr. The antlers are normally developed (the beam diameter is not disproportionally thin with respect to the burr size and the diameter of pedicle) and do not show any sign of "degeneration" reported by [START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF]. The proximal portion of the right antler beam is straight and directed sideward, backward and slightly upward. The antler beam is cylinder-shaped and some-what more robust than the supporting pedicle. The antero-posterior diameter of the right antler beam above the burr amounts to 53.0 mm; the latero-medial diameter amounts to 56.0 mm. The same measurements of the left antler amount to 53.3 mm and 55.5 mm respectively. The basal tine is not present in Megaceroides algericus. The next middle (or anterior) tine is inserted on the anterior side of the beam. The cross-section of the basal part of the middle tine is ellipse-shaped (its maximal diameter amounts to 40.6 mm, minimal diameter amounts to 22.0 mm). The distance between antler burr and the base of the middle tine amounts to 96 mm. The antero-posterior diameter of the antler beam between the burr and the middle tine amounts to 42.4 mm. The height of the middle tine ramification is 140 mm. The antler becomes flattened in the area of the middle tine insertion and the above situated distal portion of antler extends into a palmation: the maximal diameter of antler above the middle tine (where the antler is broken) amounts to 59.3 mm; the minimal diameter at the same level is 41.3 mm.

Discussion

Evolutionary significance of pachyostosis

The extreme cranial pachyostosis of Megaceroides algericus requires a special discussion here. There are few examples of pachyostosis among mammals. Most of the cases are known in ruminants, and cranial and mandibular pachyostosis in cervids is one of them [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF]. The pachyostosis of limb bones recorded in the Lower Miocene giraffoid Lorancameryx pachyostoticus from Spain represents another phenomenon of bone thickening recorded in ruminants [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF]. Although the character of pachyostosis in Lorancameryx differs histologically and physiologically from the cranial bone thickening in cervids, [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF] regard both cases as different manifestations of the similar physiological and evolutionary process. [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF] noticed that the limb bone pachyostosis in Lorancameryx occurred in the same geological epoch when several groups of ruminants evolved horns and horn-like cranial appendages. Therefore, according to [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF], the pachyostosis and the bony cranial appendages represented a similar physiological response to certain environmental changes and acted as "bone sinks" where excess tissue was stored during the rich in nutrition vegetation growth seasons. According to [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF], the pachyostosis of cervids also could represent a similar secondary metabolic response to exogenic factors, primarily marked seasonality.

The inert bone tissue was deposited in Lorancameryx on the limb bone diaphysis (especially on radius and ulna) every year starting from the subadult age [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF], while in Megaloceros giganteus the mandibular pachyostosis developed through depositing of additional lamellar bone tissue during the early adult age and no visible changes in the state of pachyostosis were recorded during the subsequent adult life [START_REF] Lister | The evolution of the giant deer, Megaloceros giganteus (Blumenbach)[END_REF]. According to [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF], the tissue of pachyostotic bone in Megaceroides algericus and Sinomegaceros pachyosteus shows the annual cyclic rhythm as in the case of Lorancameryx.

Therefore, it seems that the pachyostosis of Megaceroides algericus has a different physiological and ontogenetic background than the pachyostosis of Megaloceros giganteus.

Several authors repeatedly reported the development of mandibular pachyostosis in

Praemegaceros and some other large-sized cervid forms [START_REF] Kahlke | On the evolution of pachyostosis in jaw-bones of Choukoutien giant-deer Megaceros pachyosteus (Young)[END_REF][START_REF] Kahlke | Die Cerviden-Reste aus dem Tonen von Voigtstedt in Thüringen[END_REF][START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF][START_REF] Azzaroli | Forest Bed elks and giant deer revisited[END_REF][START_REF] Vislobokova | The fossil deer of Eurasia[END_REF][START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF]Vislobokova, , 2012aVislobokova, , 2012b[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF], which, according to the mentioned authors, represent a specific side effect of gigantism in cervids and is regarded as an important taxonomical character distinguishing the phylogenetic branch of giant deer from other phylogenetic branches within the subfamily Cervinae. However, a simple scattered diagram of mandible proportions shows that the mandible shape in large-sized Praemegaceros is very similar to the morphological condition found in Eucladoceros and Dama [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. Van der [START_REF] Made | Phylogeny of the giant deer with palmate brow tines Megaloceros from west and Sinomegaceros from east Eurasia[END_REF] found signs of mandibular pachyostosis in a wide variety of cervids and assumed that this specific character evolved among cervids several times in parallel and denied its plesiomorphic significance for the phylogenetic group of giant deer. Therefore, the sporadic occurrence of mandibular pachyostosis in various cervid lineages can not be used as a meaningful taxonomic character at the tribe level. The wellexpressed cranial and mandibular pachyostosis is recorded only in very few cervid genera, such as Sinomegaceros from Eastern Asia, Megaloceros from Central and Western Eurasia, and Megaceroides from North Africa. [START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF] reports also the mandibular thickening in Late Miocene mediumsized forms of the genus Praesinomegaceros from South Siberia. [START_REF] Kahlke | On the evolution of pachyostosis in jaw-bones of Choukoutien giant-deer Megaceros pachyosteus (Young)[END_REF] studied the variation of the cross-sections of mandibles in Sinomegaceros pachyosteus from Choukoutien and suggested that the mandible thickening in this deer is a dimorphic character. [START_REF] Kahlke | On the evolution of pachyostosis in jaw-bones of Choukoutien giant-deer Megaceros pachyosteus (Young)[END_REF] also assumed that the increased mandible thickening in S. pachyosteus was a gradual evolutionary process. Nonetheless, the mandibular pachyostosis in Sinomegaceros evolved much earlier in another much smaller form with small antlers. [START_REF] Tleuberdina | Late Neogene fauna of South-East of Kazakhstan[END_REF] reported a rather small-sized Late Neogene species (the estimated body mass based on dental measurements did not exceed 50 kg) Sinomegaceros robustus from South-East of Kazakhstan. The roe-deer sized S. robustus is characterized by primitive unmolarized P 4 , small antlers with distal palmations (burr diameters amount to 18.0 and 16.2 mm), and pachyostotic lower mandible with almost circular cross-section [START_REF] Tleuberdina | Late Neogene fauna of South-East of Kazakhstan[END_REF]. According to [START_REF] Shikama | Megacerid remains from Gunma Prefecture, Japan[END_REF], a certain degree of pachyostosis is recorded also in Sinomegaceros yabei. Three mandible specimens of S. yabei, two of which certainly belong to a male, are characterized by a rather moderate degree of pachyostosis similar to the specimens of M. giganteus tentatively ascribed to females by [START_REF] Lister | The evolution of the giant deer, Megaloceros giganteus (Blumenbach)[END_REF] and [START_REF] Croitor | Giant deer Megaloceros giganteus Blumenbach, 1799 (Cervidae, Mammalia) from Palaeolithic of Eastern Europe[END_REF]. [START_REF] Lister | The evolution of the giant deer, Megaloceros giganteus (Blumenbach)[END_REF] supposed that pachyostosis represents an adaptation that enhanced the skeletal calcium store, related to the large size of antlers. [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF] supported this point of view, noticing that the enhanced mineral storage in head skeleton is an important physiological adaptation permitting the fast growing of large antlers during the relatively short vegetation season. Perhaps, the pachyostosis in Megaloceros giganteus was physiologically connected with such specific for giant deer morphological characters, as an ossified vomer, complete and early obliteration of cranial sutures, diminished size of foramen ovale, and the development of additional enamel folders (cingulum) at the base of molars in some evolutionary most advanced populations of giant deer [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. Sanchez-Villagra (2010) reported an exceptionally high for Cervidae number of cranial suture fusion in Megaloceros giganteus (20 cranial sutures in giant deer against 10 in modern elk Alces alces), nonetheless, he excluded the simple mechanical adaptation of the advanced bone suture fusion to large and heavy antlers. The high number of suture fusion in giant deer contrasts with the general trend of ruminants toward the diminished number of fused cranial sutures, which is not correlated with body size and apparently represent a specific bio-mechanic adaptation to rumination [START_REF] Bärmann | A Phylogenetic Study of Late Growth Events in a Mammalian Evolutionary Radiation -The Cranial Sutures of Terrestrial Artiodactyl Mammals[END_REF]. Therefore, one can assume that the high number of cranial suture fusion in Megaloceros giganteus represents another specific consequence of pachyostosis. However, Bärmann and Sanchez-Villagra (2011) report the high number of cranial suture fusion also for some other ruminant genera (Ocapia, Tragelaphus, Kobus, and Antilocapra), seeking the explanation in biomechanical factors. Van der [START_REF] Made | Phylogeny of the giant deer with palmate brow tines Megaloceros from west and Sinomegaceros from east Eurasia[END_REF] remarked that the function of temporary storage of minerals should be followed by signs of resorption in pachyostotic mandibles. Actually, even non-pachyostotic bones represent a dynamic system constantly undergoing resorption and deposition of minerals and no particular "scars" of resorption on bone tissue could be seen, taking apart the cases of pathology [START_REF] Alberts | The molecular biology of the cell[END_REF]. Vislobokoba (2009, 2012b, 2013) regards the cranial pachyostosis of Megaloceros giganteus as a mechanical adaptation (comparable to cranial pneumatization in Rangifer and Bison) correlated with large and heavy antlers and reports a comparatively weak development of cranial pachyostosis in females of giant deer. This hypothesis is questionable for several reasons. The lower mandible is a pending structure that actually is not exposed to the weight load of antlers and can not have any function of weight support in the skull. It is not clear in this case, which biomechanical advantage could bring a pachyostotic mandible, since the low-crowned and relatively small cheek teeth, the low corpus mandibulae and the relatively small area of insertion of musculus massetter in Megaloceros giganteus and Megaceroides algericus suggest that their thick lower mandibles can not represent any particular mechanical reinforcement advantage [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. Besides that, the pachyostosis is recorded also in the small-sized cervid with tiny antlers Sinomegaceros robustus.

It seems that pachyostosis and accessory cranial bone structures in ruminants (here we can mention horns and horn-like cranial appendages) changed their functional significance during the large-scale evolutionary process [START_REF] Janis | Evolution of horns in ungulates: ecology and palaeoecology[END_REF]. As cervid antlers, pachyostosis originally could serve as "bone sinks" where the excess bone tissue was stored [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF]. It is interesting that all known pachyostotic cervids belong to the subfamily Cervinae and evolved and lived in the most peripheral and extreme parts of the area of distribution of the subfamily: this is the case of the periglacial cursorial open landscape giant Megaloceros giganteus, the forest dwellers of the genus Sinomegaceros that must be susceptible to the repeatedly advancing arid zones of Central Asia, and Megaceroides algericus that evolved in very unusual for cervids environments (will be discussed below), which strongly modified its skeletal morphology. Those species were exposed to the most stressing seasonal environmental conditions among Cervinae, supporting therefore the hypothesis of [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF]. Another argument in the favour of the hypothesis of the similar physiological-evolutionary origin of pachyostosis and antlers in cervids may be sought in the comparison of subfamilies Cervinae and Capreolinae. It seems that the pachyostosis is a peculiar physiological property of the subfamily Cervinae (not tribe Megacerini), which sporadically appears in some specific environmental conditions. Pachyostosis is not known among Capreolinae, however, some members of this subfamily are known to have antlers in females. The best known example is Rangifer tarandus inhabiting the most extreme environmental conditions among Capreolinae, but the occasional presence of small antlers in normally developed females also was reported for Odocoileus and Capreolus [START_REF] Wislocki | Antlers in Female Deer, with a report of Three Cases in Odocoileus[END_REF].

Therefore, the cranial pachyostosis in Megaceroides algericus initially represented a specific physiological mechanism characteristic of some lineages of Cervinae that evolved in extreme seasonal environments. The cervid pachyostosis is not correlated with body mass and size of antlers, since it is recorded in smallsized (Sinomegaceros robustus), medium-sized (Megaceroides algericus), and large-sized (Megaloceros giganteus) cervids. However, all known cases of pachyostosis are combined with palmated antlers (the opposite affirmation is not true: many cervids with palmated antlers have no pachyostosis), suggesting that palmated antlers have not only social evolutionary significance, as it was suggested by [START_REF] Geist | Deer of the World: Their Evolution[END_REF], but also a specific environmental and physiological background.

Paleoecology of Megaceroides algericus

Regarding the pachyostosis of Megaceroides algericus, I would like to point out some of its peculiar traits distinguishing from the pachyostosis in Megaloceros. Not all parts of skull in Megaceroides are equally pachyostotic: zygomatic arches and anterior part of mandible are comparatively weak and not reinforced by pachyostosis. The weak (or better to say, normal) zygomatic arches are needed to ensure the movements of lower jaw and probably that is why they are not affected by distorting pachyostosis. The bony rim of orbits and very broad forehead are particularly pachyostotic and ensure protective shelter for weak zygomatic arches. Other part of the skull (rostrum, braincase) and the posterior part of mandible are also strongly pachyostotic and create a sort of bony helmet. At present, it is difficult to affirm if the cranial pachyostosis in Megaceroides algericus is a matter of sexual dimorphism. The only two known wellpreserved skulls belong to males. The rather small series of available lower mandibles does not show any visible dimorphism. Ontogenetically, the pachyostosis of Megaceroides algericus is also specific. Taking into account the juvenile mandible FIL160 from Filfila and the pachyostotic mandible with deciduous teeth from the grotto of Chenoua (Algeria) figured by [START_REF] Arambourg | Mammifères fossiles du Maroc[END_REF] fig. 8A), the additional bone tissue depositing started in Megaceroides algericus from the early juvenile age, unlike in Megaloceros giganteus. As it already was mentioned above, the tissue of pachyostotic bone in Megaceroides algericus shows an annual cyclic rhythm and therefore increases with age at least during some period of the animal's life [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF].

Whatever was the initial significance of the cranial pachyostosis, it seems that it acquired a new function in Megaceroides algericus. Apparently, the unusual cranial specialization of M. algericus is a result of adaptation to an ecological niche, which was unavailable for ecologically highly competitive (fide Geist, 1998) African bovids. There are no morphological analogies among modern species of deer or other ruminants that could be helpful in the paleoecological interpretations of M. algericus. The anterior part of the mandible, the zygomatic arches and the dentition remain comparatively weak, contrasting with the pachyostotic bones of cranium and the posterior part of the mandible. The processus coronoideus of the lower jaw is short and cone-shaped and the area of insertion of musculus masseter is rather small. Taking in account the studies of cranio-dental adaptations in ruminants [START_REF] Caloi | Functional aspects and ecological implications in Pleistocene endemic cervids of Sardinia, Sicily and Crete[END_REF][START_REF] Janis | Correlations between craniodental morphology and feeding behavior in ungulates: reciprocal illumination between living ans fossil taxa[END_REF][START_REF] Palombo | Food habits of "Praemegaceros" cazioti (Depéret, 1897) from Dragonara Cave (NW Sardinia, Italy) inferred from cranial morphology and dental wear. Proceedings of the International Symposium "Insular Vertebrate Evolution: the Palaeontological Approach[END_REF], the enlisted characters suggest that M. algericus had quite low mastication abilities and was not adapted to process a hard fibrous forage material. The rather weak mastication ability is suggested also by the oral (toward the anterior) shift of cheek tooth row that results a decrease of power moment. The flat and broad skull with broad muzzle of M. algericus vaguely reminiscent of specific cranial shape of such semiaquatic herbivorous mammals as hippopotamuses. The weak mastication abilities and small lowcrowned cheek teeth suggest the semiaquatic or periaquatic habits of M. algericus and specialization to forage on soft water herbage. The reduced preorbital fossae could be another adaptation to a periaquatic habitat, since the peorbital fossae are very small in modern Chinese water deer Hydropotes inermis [START_REF] Flerov | Musk deer and deer. The Fauna of USSR 1(2), Mammals[END_REF]. Another specific morphological character of Megaceroides algericus may be found in the images of this animal from the Paleolithic art. [START_REF] Camps | Le cerf en Afrique du Nord[END_REF] published several Paleolithic images of this deer that show unusual for a cervid very long tail. Among modern cervids of similar body size, the relatively long tail is characteristic of Elaphurus davidianus specialized to humid swamp habitats [START_REF] Flerov | Musk deer and deer. The Fauna of USSR 1(2), Mammals[END_REF].

The assumption of semiaquatic or periaquatic habits of M. algericus is supported by the finely polished by attrition [START_REF] Fortelius | Functional characterization of ungulate molars using abrasion attrition wear gradient[END_REF] grinding surfaces of cheek teeth in the majority of studied specimens. However, the low dental cusps and the grinding surface of lower mandible FIL166 striated by transversal traces of wearing caused by a coarse forage material suggest that the animals were regularly exposed to a stressing shortage of forage, apparently, during the dry seasons, as is was shown, for instance, for modern plains zebra Equus burchelli [START_REF] Kaiser | Tooth wear gradients in zebras as an environmental proxy-a pilot study[END_REF]. The regular exposure to unfavorable seasonal conditions is also supported by the cyclic rhythm of pachyostosis development noticed by [START_REF] Morales | Pachyostosis in a Lower Miocene giraffoid from Spain, Lorancameryx pachyostoticus nov. gen. nov. sp. and its bearing on the evolution of bony appendages in artiodactyls[END_REF].

Cranial helmet-like pachyostosis in M. algericus could have a function of passive defense against such water predators as, for instance, crocodiles, which represent the most frequent danger in African periaquatic biotopes [START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF]. Crocodiles were present in the area of distribution of Megaceroides algericus in the past and survived in the region until the middle of XX century [START_REF] Brito | Crocodiles in the Sahara desert: an update of distribution, habitats and population status for conservation planning in Mauritania[END_REF]. The head of foraging deer is the important part of body most exposed to predator's attacks. The early ontogenetic development of pachyostosis in M. algericus supports this hypothesis, since this character must be vitally important for juveniles too. The thick cranial and mandibular bones must protect animal's head from deep lethal wounding and therefore increase chances of animal to escape from a predator. The cranial pachyostosis inherited from forerunners by Megaceroides should be regarded here as a good example of preadaptation that was maintained by natural selection in new conditions as the adaptation of passive defense. The robust radius and ulna described by [START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] could be a part of such adaptation permitting to the deer to resist the attempts of a crocodile to drag its prey under the water. [START_REF] Abbazzi | Remarks on validity of the generic name Praemegaceros Portis 1920, and an overview on Praemegaceros species in Italy[END_REF], taking into account the brachyodont dentition and shallow mandibular body combined with sideward oriented antlers and large tympanic bullae, arrived to a rather contradictory conclusion that the small-sized M. algericus was an open-landscape browser (see Janis, 1995 and references therein). Although [START_REF] Abbazzi | Remarks on validity of the generic name Praemegaceros Portis 1920, and an overview on Praemegaceros species in Italy[END_REF] reports the large size for upper and lower teeth, this is not the case: the cheek teeth of M. algericus are relatively small, marked by particular size reduction of premolars and third upper and lower molars (M 3 and M 3 ). Nonetheless, the brachyodont first and the second upper and lower molars (M 1 , M 2 , M 1 , and M 2 ) are relatively broad, representing, in my opinion, a sort of grinding millstones for soft water plants.

The composition of faunas associated with M. algericus ecologically is quite heterogenous and may be regarded as a mammal assemblage that inhabited an ecotone near water body. The faunas from Ain Tit Mellil (Morocco) and Filfila (Alger) contain semiaquatic species like Hippopotamus amphibius, forest dwellers like Sus scrofa algeriensis, woodland species like Bos primigenius, Taurotragus, and open landscape species Connochoetes taurinus, Crocuta spelaea, Camelus sp. [START_REF] Arambourg | La Faune Fossile de l'Ain Tit Mellil (Maroc)[END_REF][START_REF] Hadjiouis | Megaceroides algericus (Lydekker, 1890), du gisement des Phacochères (Alger, Algérie). Etude critique de la position systematique de Megaceroides[END_REF].

Systematic position of the genus Megaceroides

The systematical place of such an odd and very specialized species as Megaceroides algericus within Cervinae is not easy task. However, even if the cranial morphology of M. algericus shows some highly specialized traits, the correct assessment of plesiomorphic and apomorphic characteristics allows for revealing the phylogenetic relationships of the North African endemic lineage and its systematical position.

Megaceroides shows the most significant morphological differences from the genus Cervus and allied forms. Unlike deer of the Cervus group (genera Cervus, Hyelaphus, Rusa, and Pannolia), M. algericus is characterized by a broad bell-shaped basioccipitale (as modern Axis, Rucervus, Dama, and the majority of extinct genera of Western Eurasia), relatively large and rounded bulla tympani (as Dama), missing upper canines (as Dama and Megaloceros), and long nasal bones that extend behind the anterior edges of orbits. Excluding pachyostosis as a peculiar specialization, one can notice that Megaceroides possess an advanced cranial morphology if compared to Cervus and allied to Cervus genera of Southern and Eastern Asia. The cranio-dental morphological differences suggest that the lineages of Megaceroides and Cervus diverged as early as Late Miocene.

Obviously, Megaceroides does not belong to the phylogenetic branch of the genus Praemegaceros as it was suggested by [START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF] and [START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF]. Unlike Praemegaceros, Megaceroides is characterized by the relatively longer braincase (a primitive character), the cylinder-shaped pedicles (not compressed antero-posteriorly, or dorso-ventrally, if we take in consideration their strong inclination toward posterior and sidewards on the skull, as in some advanced species of Praemegaceros), the cranial and mandibular pachyostosis, and the long nasal bones [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. The long nasal bones of Megaceroides extended behind the imaginary line connecting anterior edges of orbits represent a good taxonomic character, but are of little interest for the systematical and phylogenetic study, since, probably, they represent here an advanced apomorphic character. However, the relatively long braincase of Megaceroides is an important primitive character that rules out a direct phyletic relationship with geologically older, but more advanced in this case Praemegaceros. The cylindrical shape of pedicles in Megaceroides also suggests that this genus is not related with the advanced Middle Pleistocene species of Praemegaceros (P. verticornis and P. solilhacus), which evolved the bio-mechanically more advantageous dorso-ventrally compressed and latero-medially extended pedicles that acted as a reinforced support with increased area of cross-section for large and heavy antlers [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. The peculiar dorso-ventrally compressed shape of pedicles is maintained even in the secondary dwarfed P. dawkinsi with diminished antlers.

The cranial and dental morphology of Megaceroides and Dama shows some more resemblances (Tab. 8). Megaceroides shares with Dama the broad bell-shaped basioccipitale, the large orbits, the large rounded bulla tympani, the flexed braincase, the long nasal bones (however, this character is also apomorphic in Dama: [START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF], the missing upper canines, and the similar proportions of lower tooth row: PP/MM in Megaceroides varies between 45.0% and 60.5%, while in modern Dama dama varies between 46.0% and 61.6% [START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF]. Unlike Dama, the braincase of Megaceroides is some-what less flexed; the parietal and frontal bones are flat; the pachyostosis is strongly pronounced (it is completely absent in Dama); the rather long pedicles are set obliquely on the skull (not short and vertically oriented as in Dama); the ethmoidal vacuities are completely closed; and upper molars are supplemented with a variable lingual cingulum. Such cranial characters as the less flexed braincase and obliquely set frontal pedicles define M. algericus as a more primitive cervid form than fallow deer. The closed ethmoidal vacuities in M. algericus, apparently, resulted from the pachyostosis of face bones.

Megaceroides and Megaloceros share the developed cranial pachyostosis, the bell-shaped basioccipitale, the missing upper canines, the presence of a variable cingulum in upper molars, and long nasal bones extended behind the imaginary line connecting the anterior edges of orbits (Tab. 8). The shape and relative length of the braincase, the position of the antler pedicles, developed cingula in upper molars, and the cranial hyperostosis of Megaceroides algericus suggest its greater affinity with Megaloceros giganteus. Unlike Megaloceros, Megaceroides is characterized by enlarged rounded bulla tympani, a flexed braincase, a lacking basal tine, and relatively larger orbits with respect to the condylo-basal length. However, the relatively large orbits may be a secondary effect caused by the shortened splanchnocranium. It seems that proportions of the lower tooth series in Megaceroides (PP/MM -45.0%, 52.9%, 60.5%: Croitor, 2014) tend to be more advanced than in Megaloceros giganteus from Ireland (PP/MM -53.6-61.1%, based on the sample stored in NHML), and significantly more advanced (according to evolutionary trends in Cervidae described by [START_REF] Vislobokova | The fossil deer of Eurasia[END_REF] than in the primitive form of Megaloceros giganteus from Bisnik, Poland (PP/MM -61.9-65.6%: [START_REF] Croitor | Giant deer Megaloceros giganteus Blumenbach, 1799 (Cervidae, Mammalia) from Palaeolithic of Eastern Europe[END_REF]. The presented here analysis of cranial characters of various Eurasian cervids confirms the old assumption of [START_REF] Joleaud | Sur le Cervus (Megaceroides) algericus Lydekker, 1890[END_REF] on intermediary morphological and systematic position of Megaceroides between Megaloceros and Dama. The peculiar combination of cranial and dental characteristics of the African deer confirms the reasonability of the elevation of Megaceroides at the generic level proposed by [START_REF] Arambourg | Note préliminaire sur un nouvelle grotte à ossements des environs d'Alger[END_REF][START_REF] Arambourg | Mammifères fossiles du Maroc[END_REF].

Molecular phylogenetic study has revealed that the fallow deer is the closest to Megaloceros giganteus modern cervid, although the evolutionary divergence between Megaloceros and Dama has occurred very early, 4-5 Myr [START_REF] Lister | The phylogenetic position of the 'giant deer' Megaloceros giganteus[END_REF] or even 10.7 Myr ago [START_REF] Hughes | Molecular phylogeny of the extinct giant deer, Megaloceros giganteus[END_REF]. The close phylogenetical relationship between M. giganteus and D. dama is also supported by some shared characteristics of the cranial morphology: both species share a relatively long braincase, long nasal bones (synapomorphy), a relatively short orbito-frontal portion of skull (the anterior edge of the orbit is situated above M 2 ), missing upper canines, and a similar shape of the broadened basioccipitale at the level of the pharyngial tuberosities. [START_REF] Pfeiffer | Die Stellung von Dama (Cervidae, Mammalia) im System plesiometacarpaler Hirsche des Pleistozäns -Phylogenetische Rekonstruktion -Metrische Analyse[END_REF] suggestion on close relationship between the giant deer and the red deer based on the postcranial morphology analysis is disputable. The use of postcranial morphology in phylogenetic reconstructions is unsafe since limb bones are greatly influenced by various environmental and biomechanical factors like landscape character, ground surface character, type of locomotion, body mass, social behavior, etc. [START_REF] Köhler | Skeleton and Habitat of recent and fossil Ruminants[END_REF]. The missing studies analyzing plesiomorphic and apomorphic characters of postcraial skeleton represent the main methodological problem in this case. Therefore, a cluster analysis of postcranial morphology rather reveals ecological and biomechanical similarity than a genuine phylogenetic relationship. The molecular phylogeny research carried out by [START_REF] Kuehn | Molecular phylogeny of Megaloceros giganteus -the Giant Deer or just a Giant Red Deer?[END_REF] suggests a close relationship between giant deer and red deer, but, according to [START_REF] Hughes | Molecular phylogeny of the extinct giant deer, Megaloceros giganteus[END_REF], these results come from a wrong determination of fossil specimens or from contamination during the DNA amplification process. The obtained by [START_REF] Kuehn | Molecular phylogeny of Megaloceros giganteus -the Giant Deer or just a Giant Red Deer?[END_REF] genetic evidence on close relationship between giant deer and red deer is "almost certainly the result of contamination" (A. Lister, pers. comm.).

The palmed antlers of Megaceroides algericus with the lacking basal tine (Fig. 15) are of minor significance for the present study, since the palmations may have evolved independently in each phyletic lineage, while the basal tines have tend to reduce in cervid forms with secondary reduced body size, as for instance in Praemegaceros dawkinsi and numerous dwarfed insular species [START_REF] Azzaroli | Il nanismo nei cervi insulari[END_REF][START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF][START_REF] Caloi | Il Cervo Pleistocenico di Sardegna[END_REF][START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF][START_REF] Croitor | Origin and evolution of the late Pleistocene island deer Praemegaceros (Nesoleipoceros) cazioti (Depéret) from Corsica and Sardinia[END_REF]. [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF], [START_REF] Thomas | La faune quaternaire d'Algerie[END_REF] and [START_REF] Hadjiouis | Megaceroides algericus (Lydekker, 1890), du gisement des Phacochères (Alger, Algérie). Etude critique de la position systematique de Megaceroides[END_REF] noticed that the shape of the lower mandible and skull of Megaceroides algericus is similar to the mandibles of Simomegaceros pachyosteus from Choukoutien (China). At least superficially, the skull shape of Sinomegaceros pachyosteus with its little flexed braincase, broad orbito-frontal part, and short splanchnocranium seems to be a less accentuated version of Megaceroides algericus. Megaceroides is characterized by the presence of a well-developed middle tine, which normally is lacking in Sinomegaceros [START_REF] Shikama | Quaternary cave and fissure deposits and their fossils in Akiyosi District[END_REF][START_REF] Shikama | Megacerid remains from Gunma Prefecture, Japan[END_REF][START_REF] Made | Phylogeny of the giant deer with palmate brow tines Megaloceros from west and Sinomegaceros from east Eurasia[END_REF]. Van der [START_REF] Made | Phylogeny of the giant deer with palmate brow tines Megaloceros from west and Sinomegaceros from east Eurasia[END_REF] regard the absence of the middle tine as an essential diagnostic character of Sinomegaceros that is shared with Arvernoceros. However, a small knob-like vestige of the middle tine is present in some specimens of S. pachyosteus [START_REF] Kahlke | On the evolution of pachyostosis in jaw-bones of Choukoutien giant-deer Megaceros pachyosteus (Young)[END_REF], therefore, caution is needed. The area of distribution of the genus Sinomegaceros in Eastern Asia was latitudinally limited to between 50° and 25°. According to Vislobokova (2012aVislobokova ( , 2012b[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF] Sinomegaceros was a southern ecological counterpart of Alces and, therefore, could not disperse to North and West because of the ecological competition with Alces. Van der [START_REF] Made | Phylogeny of the giant deer with palmate brow tines Megaloceros from west and Sinomegaceros from east Eurasia[END_REF], taking in account the combination of dental, antler, cranial, and postcranial characters in large-sized deer from West and East of Eurasia, exclude the possibility of migrations of large-sized deer from the eastern part of Asia to the West. Considering this, the cranial shape affinity between Sinomegaceros and Megaceroides could be a curious example of convergence. Ultimately, only an extensive morpho-functional study of the cranial and whole skeletal morphology of Sinomegaceros may clarify the nature of this convergence.

Taxonomical context of Megaceroides algericus

The taxonomical significance of rather variable dental morphology of Megaceroides algericus, such as the varying cingulum in upper molars and the broad variation of tooth row proportions, is still unclear. Possibly, we are dealing in this case with chronological forms of the endemic North African deer: an older larger form from Hammam Meskoutin with strong cingulum and normally developed M 3 , and a more specialized descent form with smaller dentition, reduced cingulum and marked reduction of M 3 and M 3 . One can assume that the thick-jawed deer described by [START_REF] Pomel | Sur deux Ruminants de l'époque néolithique en Algérie : Cervus pachygenys et Antilope maupasi[END_REF] and figured in the later publication [START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] represents a late form distinguished by relatively smaller M3 (Tab. 7). If this is true, [START_REF] Pomel | Sur deux Ruminants de l'époque néolithique en Algérie : Cervus pachygenys et Antilope maupasi[END_REF][START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] name Cervus pachygenys proposed for the African Neolithic cervid form with pachyostotic mandibles and upper molars without cingulum could be used at list as a subspecies Megaceroides algericus pachygenys [START_REF] Pomel | Sur deux Ruminants de l'époque néolithique en Algérie : Cervus pachygenys et Antilope maupasi[END_REF]. In this case, the lower mandible from Berrouaghia (Algeria) described and figured by [START_REF] Pomel | Sur deux Ruminants de l'époque néolithique en Algérie : Cervus pachygenys et Antilope maupasi[END_REF][START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] pl. VII-VIII) should be regarded as the holotype of M. algericus pachygenys.

The taxonomical position of the genus Megaceroides needs to be clarified too. [START_REF] Viret | Artiodactyla. Traite de Paleontologie[END_REF] proposed to place the giant deer in a separate tribe Megacerini based on the genus Megaceros Owen, 1844. This point of view is accepted and defended by [START_REF] Vislobokova | The fossil deer of Eurasia[END_REF][START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF]Vislobokova ( , 2012aVislobokova ( , 2012b[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF] and di [START_REF] Di Stefano | The mesopotamian fallow deer (Dama, Artiodactyla) in the Middle East Pleistocene[END_REF]Petronio (2000-2002). According to [START_REF] Lister | Case 2606: Megaloceros Brookes, 1828 (Mammalia, Artiodactyla): proposed emendation of the original spelling[END_REF], the genus name Megaloceros Brookes, 1828 has priority over Megaceros Owen, 1844 and this viewpoint was accepted uncritically. Somewhat later, [START_REF] Lister | The evolution of the giant deer, Megaloceros giganteus (Blumenbach)[END_REF] substituted Megacerini Viret with Megalocerini and supposed that Dama could be the only survived genus of this tribe. [START_REF] Abbazzi | Megaceroides solilhacus and other deer from the middle Pleistocene site of Isernia La pineta (Molise, Italy)[END_REF] quoted Lister's tribe name as Megalocerini [START_REF] Viret | Artiodactyla. Traite de Paleontologie[END_REF][START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF] accepts the genus name Megaloceros, however she continues to use the tribe name Megacerini based on Megaceros. [START_REF] Grubb | Valid and invalid nomenclature of living and fossil deer[END_REF] pointed out that Megacerini Viret, 1961 is a junior synonym of Megalocerotinae Brookes, 1828. Therefore, the correct name of the tribe should be Megalocerotini Brookes, 1828. According to [START_REF] Grubb | Valid and invalid nomenclature of living and fossil deer[END_REF], the genera Praemegaceros, Megaceroides, Megaloceros, and Sinomegaceros belong to the tribe Cervini Goldfuss, 1820, therefore Megalocerotini Brookes, 1828 is a synonym of Cervini Goldfuss, 1820. [START_REF] Vislobokova | The fossil deer of Eurasia[END_REF][START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF]Vislobokova ( , 2012aVislobokova ( , 2012b;;[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF] considers that the tribe of giant deer includes eight genera: Megaloceros, Praemegaceros, Sinomegaceros, Praesinomegaceros, Praedama, Orchonoceros, Arvernoceros, Neomegaloceros. In my opinion [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF], the quoted list of genera represents a rather eclectic group including forms that belong to several different phylogenetical stocks, as well as poorly known cervid forms, such as Neomegaloceros gracilis and Praedama savini (see the discussion below). [START_REF] Radulesco | Sur un nouveau cerf megacerin du pleistocene moyen de la depression de Brasov (Roumanie)[END_REF] and Azzaroli andMazza, (1992, 1993) regard Eucladoceros as a primitive forerunner of Praemegaceros, seeking support for this hypothesis in the homologous general construction of antlers. Moreover, Praemegaceros shares essential cranial characteristics and antler morphology with Eucladoceros and the direct phylogenetical relationship between those two genera is accepted by many authors [START_REF] Radulesco | Sur un nouveau cerf megacerin du pleistocene moyen de la depression de Brasov (Roumanie)[END_REF][START_REF] Azzaroli | Critical Remarks on some Giant Deer (genus Megaceros Owen) from the Pleistocene of Europe[END_REF][START_REF] Azzaroli | Large early Pleistocene deer from Pietrafitta lignite mine, Central Italy[END_REF][START_REF] Abbazzi | Remarks on validity of the generic name Praemegaceros Portis 1920, and an overview on Praemegaceros species in Italy[END_REF][START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF][START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF]. Earlier, I proposed to include Praemegaceros and Eucladoceros together with Orchonoceros in the tribe Eucladocerini [START_REF] Croitor | The Plio-Pleistocene deer of the Republic of Moldova. Their biostratigraphic and paleogeographic significance[END_REF], but, according to the current state of knowledge, this taxon also falls under synonymy of Cervini Goldfuss, 1820.

The assumed direct phylogenetical relationship between Megaloceros and Praedama is based on a single character, the flattened basal tine [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF][START_REF] Vislobokova | The fossil deer of Eurasia[END_REF][START_REF] Made | Phylogeny of the giant deer with palmate brow tines Megaloceros from west and Sinomegaceros from east Eurasia[END_REF], which could be just an apomorphic character. The fine series of antler material from Forest Bed (stored in NHML) and the complete antler from Suessenborn, Germany (Kahlke, 1969: tab. XXXIV) show a series of characters that suggests a significant morphological distance between Praedama savini and Megaloceros giganteus: unlike giant deer, the antler base in Praedama savini is characterized by a specific quadrangular cross-section, while the compressed from the sides whole antler and the dichotomous pattern of bifurcation of crown tines rather reminds Eucladoceros [START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF]. The flattened proximal part of basal tine of Praedama savini (the complete basal tines are unknown) that is regarded as a good argument for close relationship between Megaloceros and Praedama, is characteristic of Eucladoceros dicranios too. The dental and mandibular remains of Praedama from Cueva Victoria do not show any trace of cingulum in upper molars and have no clearly expressed mandibular pachyostosis (van der [START_REF] Made | The latest Early Pleistocene giant deer Megaloceros novocarthaginiensis n. sp. and the fallow deer Dama cf. vallonnetensis from Cueva Victoria (Murcia, Spain). In: Geología y Paleontología de Cueva Victoria[END_REF]. The skull morphology of Praedama is unknown; therefore, well-founded arguments on phylogenetic relationships of this endemic European genus for the present moment are missing. We need more fossils and better arguments that will help to reveal the systematic position and phylogenetic relationships of Praedama.

Arvernoceros ardei is another species, which was regarded as a forerunner of M. giganteus because of its palmated basal tine and associated with its antlers isolated upper molars with cingulum [START_REF] Heintz | Les Cervidés Villafranchiens de Franse et d'Espagne[END_REF]. The very large-sized deer Arvernoceros verestchagini from the Early Pleistocene of Eastern Europe and Greece maintained a rather simple antler construction, a simple unmolarized lower fourth premolar, and lacks a cingulum, hyperostosis, and other characters that undoubtedly could indicate a relationship with Megaloceros [START_REF] Croitor | On the systematic position of the large-sized deer from Apollonia, Early Pleistocene, Greece[END_REF]. The general pattern of antler construction of Arvernoceros recalls that of Sinomegaceros (van der [START_REF] Made | Phylogeny of the giant deer with palmate brow tines Megaloceros from west and Sinomegaceros from east Eurasia[END_REF] and modern Rucervus [START_REF] Croitor | Systematical position and evolution of the genus Arvernoceros (Cervidae, Mammalia) from Plio-Pleistocene of Eurasia. Oltenia[END_REF]. According to genetic data, Rucervus duvaucelii has a detached position among modern Cervinae, having diverged very early (Late Miocene) from the main group of Old World deer together with Axis axis [START_REF] Pitra | Evolution and phylogeny of old world deer[END_REF].

The last problematic deer, Neomegaloceros gracilis from the Late Miocene of Ukraine was proposed by [START_REF] Korotkevich | A new deer form from Neogene deposits of Southern Ukraine[END_REF] as a forerunner of Praemegaceros verticornis since its antler is characterized by a distal palmation and an additional tine, which was interpreted as homology to the posterior tine in Praemegaceros. The first tine of Neomegaloceros is situated very high on the anterior side of the beam. The antler beam in Neomegaloceros is not curved in the areas of first and posterior tines as in Praemegaceros. The general antler shape of Neomegaloceros does not show any similarity with antlers of Praemegaceros. The distal palmation of the antler is regarded by [START_REF] Korotkevich | A new deer form from Neogene deposits of Southern Ukraine[END_REF] as an important character proving the direct phyletic relationship between Neomegaloceros and Praemegaceros. However, the palmed antlers appear only in the most advanced forms of Praemegaceros, while earlier forms Praemegaceros obscurus, P. pliotarandoides, and P. verticornis dendroceros bear antlers without palmations (Azzaroli andMazza, 1992, 1993;[START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF]. The so-called "posterior tine" appears in the several cervid lineages, represented by such genera as Rangifer, Megaloceros, Praedama, and some Sinomegaceros. It seems that the "posterior tine" developed several times independently in cervid forms adapted to open environments and, possibly, had a function of removing the flying parasites from the back in the rutting males, thus increasing their combat capacities. Neomegaloceros rather is a junior synonym of Cervavitus and belongs to the subfamily Capreolinae Brookes, 1828 [START_REF] Croitor | Late Neogene and Quaternary biodiversity and evolution: Regional developments and international correlations. Volume I[END_REF][START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF]. Therefore, the tribe of so-called giant deer sensu lato proposed by [START_REF] Vislobokova | The fossil deer of Eurasia[END_REF][START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF][START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF]) is a polyphyletic group that includes various lineages not only from the subfamily Cervini, but also from the subfamily Capreolini. Most of the cervids included by [START_REF] Vislobokova | The fossil deer of Eurasia[END_REF][START_REF] Vislobokova | A new species of Megacerini (Cervidae, Artiodactyla) from the late miocene Taralyk-Cher, Tuva (Russia), and remarks on the relationships of the group[END_REF]Vislobokova ( , 2012aVislobokova ( , 2012b;;[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF] in the tribe of giant deer represent the peculiar eco-evolutionary type or "constellation" (if we apply the term used by [START_REF] Geist | Deer of the World: Their Evolution[END_REF] of open landscape giants with very large antlers (Megaloceros, Praemegaceros) and forest/woodland giants with smaller antlers (Arvernoceros, Sinomegaceros) approaching to the ecoevolutionary type of modern Alces alces.

The tribe Megalocerotini Brookes, 1828 sensu stricto should be restricted only to the genera Megaloceros, Megaceroides, and Dama, however, it is difficult in this case to propose a reliable differential diagnosis of the tribe. [START_REF] Grubb | Valid and invalid nomenclature of living and fossil deer[END_REF] grouped all Old World deer with small or missing upper canines and large complicated antlers into the single tribe Cervini Goldfuss, 1820. Possibly, the tribe Cervini Goldfuss, 1820 could be restricted to the phylogenetic branch of Cervus and related genera (or subgenera) Hyelaphus, Rusa, Panolia, and Przewalskium, since this cervid group shares similar cranial and dental characteristics (the presence of small upper canines, the narrow triangular basioccipitale) and genetical analysis revealed their monophyly [START_REF] Pitra | Evolution and phylogeny of old world deer[END_REF]. However, the craniodental morphology of Plio-Pleistocene Eurasian Cervinae is still imperfectly studied and data for the classification of the subfamily Cervinae at the tribal level are insufficient.

Zoogeographic context and origin

The area of distribution of Megaceroides algericus limited by Atlas Mountains from the South has a refugial character, as it was reported for many other African species of Mediterranean affinity [START_REF] Brito | Crocodiles in the Sahara desert: an update of distribution, habitats and population status for conservation planning in Mauritania[END_REF]. [START_REF] Joleaud | Cervus (Megaceroides) algericus Leydekker, 1890[END_REF] assumed that Megaceroides algericus dispersed into Northern Africa through the Strait of Gibraltar. According to [START_REF] Thomas | La faune quaternaire d'Algerie[END_REF], the most plausible migration path for African deer is the "Libyan-Egyptian" way, i. e. via the south and south-east coast of Mediterranean sea. [START_REF] Fernandez | The last occurrence of Megaceroides algericus Lydekker, 1890 (Mammalia, Cervidae) during the middle Holocene in the cave of Bizmoune (Morocco, Essaouria region)[END_REF] consider that the way of dispersal across the Strait of Gibraltar seems to be more probable than the hypothetical arrival from the Libyan-Egyptian or Sicilian-Tunisian routes, which requires more evidences. The remains of Megaloceros, the most probable forerunner of Megaceroides algericus, are not known southern Italy [START_REF] Lister | The evolution of the giant deer, Megaloceros giganteus (Blumenbach)[END_REF]. The undeniable remains of Megaloceros giganteus are reported only from northern part of Iberian Peninsula [START_REF] Lister | The evolution of the giant deer, Megaloceros giganteus (Blumenbach)[END_REF]. The presence of giant deer in the area of Madrid (Sesé andSoto, 2000, 2002: page 332, fig. 16) and in the fauna of Bolomor Cave near Valencia (Peris et al., 1997: page 26) based on poorly diagnostic material that needs a confirmation. Van der Made (2014) described a new species Megaloceros novocarthaginiesis from the end of Early Pleistocene of Cueva Victoria, Spain. The new species is very close to Praedama savini (Dawkins, 1887) and differs from the latter only by somewhat larger size and higher position of the basal tine, therefore I prefer to include this species, if its taxonomic status will be confirmed, in the genus Praedama. Among noteworthy characters, the absence of any trace of cingulum in upper molars should be mentioned (van der [START_REF] Made | The latest Early Pleistocene giant deer Megaloceros novocarthaginiensis n. sp. and the fallow deer Dama cf. vallonnetensis from Cueva Victoria (Murcia, Spain). In: Geología y Paleontología de Cueva Victoria[END_REF].

The closer phylogenetic relationships between Megaloceros, Megaceroides, and Dama are supported also by paleobiogeographic data. The Mediterranean basin is the area of evolutionary radiation of the genus Dama (up to 7 fossil and modern species, including present day Dama dama from Anatolia and Dama mesopotamica from Near East), which is known only from Western Eurasia [START_REF] Croitor | Deer from Late Miocene to Pleistocene of Western Palearctic: matching fossil record and molecular phylogeny data[END_REF]. Until now, the highest taxonomical diversity of the genus Megaloceros is described from Western Europe [START_REF] Azzaroli | The Deer of the Weybourn Crag and Forest Bed of Norfolk[END_REF]Vislobokova, 2012aVislobokova, , 2012b[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF]. Therefore, Megaceroides algericus from the zoogeographic point of view is a part of evolutionary radiation of the Megaloceros-Dama lineage that took place in Western Eurasia and Mediterranean area. The medium-sized cervid from the Middle Pleistocene of Near East described by di [START_REF] Di Stefano | The mesopotamian fallow deer (Dama, Artiodactyla) in the Middle East Pleistocene[END_REF] as Dama clactoniana mugarensis is of special interest for the present discussion. This cervid form is characterized by a flattened antler beam, a flattened basal tine terminated by a bifurcation and a well-developed cingulum in upper molars [START_REF] Di Stefano | The mesopotamian fallow deer (Dama, Artiodactyla) in the Middle East Pleistocene[END_REF]. The lower premolar series seems to be relatively long (66%, measured from the photo in di Stefano, 1996) and represents a primitive condition similar to Megaloceros giganteus from Bisnik (Poland). The relatively robust radius of di Stefano's deer (radius length is ca. 215-220 mm, mid-shaft breadth is ca. 29 mm: di Stefano, 1996: fig. 8) is another character that distinguishes this cervid from the equal-sized representatives of the genus Dama and reminds the morphological condition described by [START_REF] Pomel | Caméliens et Cervidés. Carte géologique de l'Algerie[END_REF] in Megaceroides. Taking in account such specific characters, as cingulum in upper molars, low positioned flattened and bifurcated first antler tine, and flattened antler beam, one can assume that the medium-sized cervid from the Near East is a primitive or dwarfed form of giant deer Megaloceros mugarensis [START_REF] Di Stefano | The mesopotamian fallow deer (Dama, Artiodactyla) in the Middle East Pleistocene[END_REF] and may represent a transitional form between Megaloceros and Megaceroides.

The medium-sized Megaloceros mugarensis [START_REF] Di Stefano | The mesopotamian fallow deer (Dama, Artiodactyla) in the Middle East Pleistocene[END_REF] from the Middle Pleistocene of Near East is the most probable forerunner of Megaceroides algericus. The indirect support for this assumption is provided by [START_REF] Thomas | La faune quaternaire d'Algerie[END_REF], who reports the earliest scanty and poorly preserved fossil cervid remains from the Middle Pleistocene of North Africa.

Conclusions

Megaceroides algericus from the Late Pleistocene -Early Holocene of Northern Africa is a highly specialized cervid that evolved in the most extreme for the family Cervidae geographical area and environmental conditions. The genus Megaloceros from the Middle -Late Pleistocene of the boreal latitudes of Eurasia is phylogenetically nearest to Megaceroides. The medium-sized Megaloceros mugarensis [START_REF] Di Stefano | The mesopotamian fallow deer (Dama, Artiodactyla) in the Middle East Pleistocene[END_REF] from the Middle Pleistocene of the Near East is the most probable forerunner of Megaceroides algericus and the linking form between Megaloceros giganteus and Megaceroides algericus. The most probable way of dispersal of Megaceroides algericus to Africa is the south-east coast of Mediterranean sea, the so-called "Libyan-Egyptian" way.

The unusual cranial morphology of Megaceroides algericus is regarded here as a combination of specific ancestral morphological and physiological characteristics (first of all, cranial pachyostosis) and new apomorphic characters (relatively diminished dentition with reduced size of P 2 , P 2 , M 3 , and M 3 , weak zygomatic arches and anterior part of mandible, short and broad splanchnocranium with shifted orally cheek tooth rows) that represent an adaptation to the new ecological niche, which permitted to avoid a direct competition with ecologically highly competitive bovids: this is a niche of a periaquatic or semiaqualic herbivore that feed on soft water plants. This explains the generally weak dentition and other cranial structures that are involved in the forage processing. The unusually thick helmet-like cranial bones acquired the new function of passive defense against the predators that usually wait for their prey at watering place. Unlike Megaloceros, the pachyostosis in Megaceroides ontogenetically evolved earlier in juvenile individuals with deciduous cheek teeth and had several cycles of seasonal growth. Phylogenetically, Megaceroides belongs to the Megaloceros-Dama branch and stands more close to Megaloceros.

The taxonomy of the subfamily Cervinae is poorly developed at the tribal level. The tribe Megalocerotini Brookes, 1828 sensu lato (= Megacerini [START_REF] Viret | Artiodactyla. Traite de Paleontologie[END_REF]fide Vislobokova, 1990, 2009, 2012a, b;[START_REF] Vislobokova | Morphology, Taxonomy, and Phylogeny of Megacerines (Megacerini, Cervidae, Artiodactyla)[END_REF] is a polyphyletic group that includes specific large-sized eco-evolutionary type of cervids, which evolved independently in several lineages, and some poorly known forms that have similar apomorphic antler characters. The tribe Megalocerotini Brookes, 1828 sensu stricto with only genera Megaloceros, Megaceroides, and Dama represent a real phylogenetic branch, however, it is difficult to give an adequate taxonomical definition for this restricted group containing extremely specialized forms representing various eco-evolutionary types, first of all because the similar cervid eco-evolutionary types can be found in other phylogenetic branches of the subfamily Cervinae Goldfuss, 1820 [START_REF] Geist | Deer of the World: Their Evolution[END_REF].

  The associated with Mousterian industry local fauna from Guyotville was characterized by

Figure 1 .

 1 Figure 1. Fossiliferous sites considered in the present study: 1, Ain Tit Mellil (Morocco); 2, Berrouaghia (Algeria), the type locality of Cervus pachygenys Pomel, 1892; 3, Guyotville (Algeria); 4, Phacocheres (Algeria); 5, Grotte de la Madeleine (Algeria); 6, Filfila (Algeria); 7, Hammam Meskoutin (Algeria), the type locality of Cervus algericus Lydekker, 1890.

Figure 2 .

 2 Figure 2. Megaceroides algericus (Lydekker, 1890): the male skull from Guyotville (now Ain-Benian, Algeria) stored in Paris (NMNH, "Collection of Arambourg", no number): A, side view; B, frontal view; C, palatal view. Scale bars: 5 cm.

Figure 3 .

 3 Figure 3. Megaceroides algericus (Lydekker, 1890): the semischematic drawing of the palatal view of the male skull from Guyotville showing the damaged parts (shaded). Scale bar: 5 cm.

Figure 4 .

 4 Figure 4. The ratio between the length of face (measured from the anterior edge of orbit to prosthion) to the condylo-basal length of the skull of Megaceroides algericus from Guyotville compared to Dama dama (47.1.1.4, NHML), Praemegaceros obscurus (IGF4024, adapted from Croitor, 2014), Praemegaceros cazioti (adapted from Caloi and Malatesta, 1974), Megaloceros giganteus (M28968, NHML), and Cervus elaphus (Nr. 1927-58, NMNH).

Figure 5 .

 5 Figure 5. The position of the upper tooth row in Megaceroides algericus from Guyotville compared to large-sized deer (Megaloceros giganteus and Praemegaceros obscurus), an insular dwarfed deer (Praemegaceros cazioti), and medium-sized continental deer (Dama dama and Cervus elaphus). The provenance of specimens involved in the comparison is indicated in the Figure 4.

Figure 6 .

 6 Figure 6. The angle between facial and neural parts of skull in Megaceroides algericus from Guyotville (A) compared to Megaloceros giganteus ruffi from Bruhl, Germany (Stuttgart Museum, adapted from Vislobokova, 2012b) and Dama dama (ZMS, coll. 451, c.12058). Scale bars: 5 cm.

Figure 7 .

 7 Figure 7. Megaceroides algericus (Lydekker, 1890): the braincase MOC148 (NMNH) from Ain Tit Mellil (Morocco); A, side view; B, basal view. Scale bar: 5 cm.

Figure 8 .

 8 Figure 8. Megaceroides algericus (Lydekker, 1890): the semi-schematic drawing of the specimen MOC148 (NMNH) from Ain Tit Mellil (Morocco) showing damaged (shaded) and missing (dashed line) parts from the side view. Scale bar: 5 cm.

Figure 9 .

 9 Figure 9. Megaceroides algericus (Lydekker, 1890): the frontal view of the skull fragment MOC148 (NMNH) from Ain Tit Mellil (Morocco); nas., posterior parts of nasal bones. Scale bar: 5 cm.

Figure 10 .

 10 Figure 10. Megaceroides algericus (Lydekker, 1890): fragment of right upper jaw FIL169 (NMNH) with M 2 and M 3 from Filfila (Algeria). Scale bar: 3 cm.

Figure 11 .

 11 Figure 11. Megaceroides algericus (Lydekker, 1890): the lower mandible (dx, no number, NMNH) from Grotte de la Madeleine (Algeria); A, lateral view of mandible with transversal crosssections taken in front of P 4 and behind of M 3 ; B, occlusion view of P4. Scale bar: 5 cm.

Figure 12 .

 12 Figure 12. Megaceroides algericus (Lydekker, 1890): the lower mandible (sin, FIL166, NMNH) from Filfila (Algeria), lateral view and dental grinding surface. Scale bar: 5 cm.

Figure 13 .

 13 Figure 13. Proportions of lower mandible (FIL166, MNMH) of Megaceroides algericus compared to Muntiacus muntjak (ZMS, c.780), Hydropotes inermis (ZMS, c.1441), Dama dama (ZMS, c.12061), and Praemegaceros cazioti (COS19040, adapted from Croitor et al., 2006); M3-art., the distance between M3 and the mandibular articulation; M1M3, the length of lower molar series; P2P4, the length of lower premolar series; C-P2, the length of diastema (distance measured between lower canine and P2).

Figure 14 .

 14 Figure 14. The reconstruction of angle between hemimandibles of Megaceroides algericus (Lydekker, 1890) based on the specimen FIL166 (MNMH). The arrows indicate the direction of the wearing traces caused by coarse forage.

Figure 15 .

 15 Figure 15. Comparison of antler morphology of giant cervids and their endemic small-sized relatives: A, Megaceroides algericus (Allo. 61.12) from Late Pleistocene of Phacochères (Algeria; reversed image adapted from Hadjiouis, 1990;); B, Megaloceros giganteus from Lough Gur, Limerick (Ireland; adapted from Reynolds, 1929); C, Praemegaceros dawkinsi from Middle Pleistocene of Mundesley, Norfolk (Great Britain; M18706, NHML, reversed); D, Praemegaceros obscurus from Early Pleistocene of Salcia (Moldova, Institute of Zoology of the Academy of Sciences of Moldova, no number); b., basal tine; sb., sub-basal tine; ds., dorsal tine; m., middle tine; p., posterior tine; cr., crown tine; pl., palmation. Scale bars: 10 cm.

Table 1 .

 1 Fossil material of Megaceroides algericus(Lydekker, 1890) from National Museum of Natural History in Paris studied in the present work.No number; here is indicated as Fil/nn. The fragment of mandible with P 4 Filfila unpublished

	Collection number and additional	Specimen			Site	Original citation
	information
	No number; labeled as "Cervus	The right hemimandible with P 4 -	Grotte de la	Described in Croitor (2006: Fig.
	algericus, figuré: Pl. IV, Fig. 4", no	M3			Madeleine	2 A-B, p. 94) as Megaceroides
	bibliographic reference. Here is					algericus (Lydekker)
	indicated as GM/1.
	No number; here is indicated as GM/2. The hemimandible with M2-M3,	Grotte de la	unpublished
					showing	a	pathologic	Madeleine
					malformation on processus
					angularis
	No	number,	"Collection	of	The almost complete skull with	Guyotville	Cervus	(Megaceroides)
	Arambourg". Here is indicated as the	proximal parts of antlers		algericus Lydekker (Arambourg,
	"skull from Guyotville".						1932: Fig. 3, p. 137)
	Nr. 336, "Collection of Arambourg"		The left hemimendible with M2	Guyotville	unpublished
					and M 3
	Nr. 337, "Collection of Arambourg"		The left hemimandible with P4-	Guyotville	unpublished
					M3
	MOC148, "Mission Arambourg"		The damaged neurocranium with	Ain Tit Mellil	Cervus	(Megaceroides)
					frontal bones and a right basal		algericus Lydekker (Arambourg,
					part of antler				1938: Pl. II, Figs. 2, 2a)
	Fil-160				The juvenile hemimandible	Filfila	unpublished
	Fil-166				The left complete hemimandible	Filfila	Megaceroides	algericus
					with P 2 -M 3				(Lydekker) (Thomas, 1979;
									figured)
	Fil-167				The fragment of hemimandible	Filfila	unpublished
					with M 2 and M 3
	Fil-169				The right maxilla with M 2 and M 3 Filfila	unpublished

Table 2 .

 2 Cranial measurements of the modern and fossil deer involved in the present comparative study. CBL, condylo-basal length; P 2 -M 3 , length of upper cheek tooth row; M 3 -oc., distance between M 3 and posterior edge of occipital condyle; M 1 -M 3 , length of upper molar series; P2-P4, length of upper premolar series; P 2 -pr., distance between P 2 and prosthion; or-pr., distance between orbit and prosthion; Dor., horizontal diameter of orbit; or-oc., distance between orbit and posterior edge of occipital condyle.

	species	source/collection	CBL	P 2 M 3	M 3 oc	M 1 M 3	P 2 P 4	P 2 pr.	or-pr.	Dor.	or-oc.
	Praemegaceros	Caloi	and	300.0	101.0	132.7	62.0	45.0	73.5	149.0	44.0
	cazioti	Malatesta (1974)
	Praemegaceros	IGF4024, Croitor	470.0	141.8	200.0	84.0	61.3	143.0	270.0		140.0
	obscurus	(2014)
	Dama dama	47.1.1.4 (NHML)	270.0	77.0	116.8	47.8	31.0	77.0	144.0	52.8	93.0
	Dama dama	c.12058 (ZMS)		270.0	81.7	112.8	49.8	34.2	76.0	145.7	42.8	84.7
	Megaloceros	M28968 (NHML)	505.0	150.0	223.0	90.0	60.0	137.4	290.0	56.1	185.2
	giganteus
	Cervus elaphus	1927-58 (MNHN)	353.0	109.8	131.4	68.7	45.2	111.8	207.0

Table 3 .

 3 Mandibular measurements of the modern and fossil deer involved in the present comparative study. C-P2, length of diastema (distance between C and P 2 ); P 2 -P 4 , length of lower premolar series; M 1 -M 3 , length of lower molar series; M 3 -art., distance between M3 and mandibular articulation; gn.-M1, distance between gnation and M1; M1-art., distance between M1 and mandibular articulation; art.-gn., distance between mandibular articulation and gnation. -art. gn.-M 1 M 1 -art. art.-gn.

	species M 3 Muntiacus muntjak source/collection C-P 2 P 2 P 4 M 1 M 3 c.780 (ZMS) 40.0 24.5 38.0 34.4	67.3	64.3	135.6
	Hydropotes inermis	c.1441 (ZMS)	42.0	20.2	32.3	32.8	70.3	57.1	126.4
	Dama dama	c.12061 (ZMS)	56.5	34.3	56.0	73.7	105.0	120.0	222.0
	Praemegaceros cazioti COS19040, Croitor et al. (2006) 50.4	37.6	62.0	80.0	115.0	126.2	235.0

Table 6 .

 6 Megaceroides algericus(Lydekker, 1890): measurements of lower mandibles; GM/1, unnumbered specimen from Grotte de la Madeleine with P 4 -M 3 ; GM/2, unnumbered specimen from Grotte de la Madeleine with malformation.

		FIL166	GM/1	GM/2	GTV337	GTV336	FIL167	FIL160
	Measurements
		sin	dx	dx	sin	sin
	L P 2 -M 3	95.2
	L P2-P4	35.0
	L M1-M3	57.5	65.8		61.6
	L M 2 -M 3	42.1	45.2	41.0	42.8	46.0	43.7
	L horizontal ramus	215.+
	L diastema	45.+
	L P 2 -for. mentale	20.3
	H at ½ diastema	20.0
	H under P2	18.7
	D under P 2	15.4
	H under M1	21.5	19.0	20.3	19.8
	D under M1	21.8	22.8		20.4		21.2	19.0
	H under M 2 /M 3	30.8	34.6	33.4		35.0	34.3	32.5
	D under M2/M3	27.6	31.1	33.8	29.3	32.1	29.2	23.0
	D maximal	37.2	34.3	35.5	36.3	39.0	36.2
	H ascending ramus	100.6		96.0	108.4	109.2
	L articulation -gnation	230.0
	L articulation -M3	88.3	75.2			92.7	84.5

Table 7 .

 7 Megaceroides algericus(Lydekker, 1890): measurements of lower cheek teeth.

	Tooth		Fil-166	Fil-167	Fil/nn	GM/1	GM/2	Nr.336	Nr.337	Pomel
	measurements								(1892)
	P3	L	13.8
		D	9.3
	P4	L	13.1		13.6	15.5			13.7
		D	11.4		10.2	11.7			10.4
	M 1	L	18.2			17.2			19.2
		D	14.3			13.9			14.0
	M2	L	18.4	19.2		19.8	18.0	20.2	19.0	20.0
		D	13.8	14.0		15.0	14.1	14.0	12.9	15.0
	M3	L	23.9	24.1		23.0	23.0	25.8	23.0	22.0
		D	11.7	11.7		13.2	12.1	14.0	12.4	10.0

Table 8 .

 8 The comparative account of cranial characters and proportions (with respect to condylo-basal length, CBL) of Megaceroides algericus, Megaloceros giganteus and Dama dama.

	Characters		Megaceroides algericus	Megaloceros giganteus	Dama dama
	1. Length of face before	quite short (48.4 % of CBL)	relatively long (57.4 % of CBL)	moderately short (53.3 % of
	orbits						CBL)
	2. Relative breadth of	62.4% of CBL	39.6-43.1% of CBL	35.7-41.9 % of CBL
	skull
	3. Angle between axes	135º ( moderately flexed	155º	(little	flexed	120º (flexed neurocranium)
	of face and braincase		neurocranium)	neurocranium)
	4. Relative size of orbits relatively large (18.6 % of CBL)	relatively small (11.1 % of CBL) relatively large (19.6 % of CBL)
	5. Development of	Pachyostosis of cranial bones	Pachyostosis of cranial bones	No pachyostosis
	pachyostosis		and lower mandible strongly	and lower mandible strongly
				developed	developed
	6. Shape of parietal	Flattened parietal bones	Flattened parietal bones	Convex parietal bones
	bones
	7. Shape of frontal	Flattened frontal bones	Concave frontal bones	Convex frontal bones
	bones
	8.	orientation	of	Pedicles deflected caudally and	Pedicles deflected caudally and	Vertically oriented pedicles
	pedicles		sideward	sideward
	9. Position of nasal	Posterior edge of nasal bones	Posterior edge of nasal bones	Posterior edge of nasal bones
	bones		extends behind the anterior	extends behind the anterior	extends behind the anterior
				line of orbits	line of orbits	line of orbits
	10. Position of orbits.	Anterior edge of orbit situated	Anterior edge of orbit situated	Anterior edge of orbit situated
				above M 2	above M 3		above M 2
	11. Length of naso-	Naso-premaxillary suture is	Naso-premaxillary suture is	Naso-premaxillary suture is
	premaxillary suture		long	long		short
	12. Development of	reduced	reduced or well-developed	well-developed
	preorbital fossae
	13. Development of	closed	reduced or completely closed	very large
	ethmoidal orifice
	14. Size and shape of	rather large and rounded	intermediate size	very large and rounded
	bulla tympani
	15. Shape of mandible	Ascending part of mandible is	Ascending part of mandible is	Ascending part of mandible is
				sloped backward	set vertically	set vertically
	16. Development of	A variing cingulum is present	A variing cingulum is present	No cingulum
	cingulum
	17. Angle between	37º	45º		37º
	lingual and labial sides
	of M 2

Méditerranéenne des Sciences de l'Homme, Aix-en-Provence) for the provided missing references and suggestions on age of the fossiliferous sites considered in the paper.

Acknowledgements:

This research was supported by CNRS (2003) and Aix-Marseille University (2006). I thank Dr. Jean-Philippe Brugal (Maison Méditerranéenne des Sciences de l'Homme, Aix-en-Provence) for the provided possibility to carry out this study. Many thanks to Prof. Pascal Tassy (National Museum of Natural History in Paris) for the provided access to the fossil material, Dr. Paola Jenkins (Natural History Museum of London) and Dr. Paolo Agnelli (Zoological Museum "La Specola", University of Florence) for access to the osteological material stored in the collections under their care. I also thank Dr. Gertrud Rößner and Dr. Jan van der Made for their valuable comments and criticism that helped to improve the article. I am grateful to Dr. Philippe Fernandez (Maison