Raúl O Gómez

Tomás Ventura

Guillermo F Turazzini

Laurent Marivaux

Rubén Andrade Flores

Alberto Boscaini

Marcos Fernández-Monescillo

Bernardino Mamani Quispe

Mercedes B Prámparo

Séverine Fauquette

Céline Martin

Philippe Münch

François Pujos

Pierre-Olivier Antoine
email: pierre-olivier.antoine@umontpellier.fr

Marcos Fernández

Ruiz Leal

A new early water frog (Telmatobius) from the Miocene of the Bolivian Altiplano

Keywords: Achiri, Altiplano, calibration point, frog, Miocene, Telmatobius

We describe the new frog Telmatobius achachila sp. nov. from the late Middleearliest Late Miocene of Achiri, based on a partial skeleton found at 3960 m above sea level in the Bolivian Altiplano. This skeleton, attributed to an adult male, constitutes the first documented fossil record of the speciose living genus Telmatobius, endemic to the Andean Cordillera and the Altiplano. Phylogenetic analyses confirm the new species as being part of the crown group, and diverging both later than the T. verrucosus group and earlier than the T. bolivianus, T. marmoratus, and T. macrostomus groups. Coupled with its accurate stratigraphic provenance and age, such phylogenetic position provides a relevant calibration point for timing the evolutionary history of these highland, mostly aquatic frogs. The skeleton of T. achachila indicates that several of the osteological peculiarities of extant Telmatobius were already acquired c. 12 Ma ago, including some that might be linked to their aquatic lifestyle. Together with mixed montane-rainforest pollen vegetation uncovered in the same level, this fossil specimen further provides key data allowing for a more accurate reconstruction of ancestral habitats and elevation ranges of Telmatobius, agreeing with the previously-postulated conditions in which these Water frogs might have first evolved.

Ultimately, this discovery adds to the scarce evidence of a humid tropical Bolivian Altiplano just prior to i) the Late Miocene uplift pulse of the Central Altiplano and ii) the drastic climate deterioration that occurred in Late Miocene times onward, leading to the harsh highlandsteppe environments reigning there today.

INTRODUCTION

FROGS of the genus Telmatobius Wiegmann, 1834 constitute the most diverse group of anurans in the Andean highlands, with 61 extant species in the genus [START_REF] Frost | Amphibian Species of the World: an Online Reference[END_REF] ranging from roughly the equator in the north to nearly 30°S in Argentina [START_REF] Cei | Speciation and adaptative radiation in Andean Telmatobius frogs[END_REF][START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]Barrionuevo 2017). Most species inhabit high altitudes in the Andes, surpassing 3000 m above sea level (ASL) and up to 5244 m [START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF][START_REF] Lavilla | El género Telmatobius en la República Argentina: una síntesis[END_REF][START_REF] Seimon | Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciation[END_REF], whereas only a dozen of species can be found today at average elevations between 1500 and 2500 m ASL (Wiens 1993;De la Riva & Harvey 2003;De la Riva et al. 2012). The genus name Telmatobius, as their common name (Water frogs), alludes to their mostly aquatic habits in a variety of environments, including mountain streams of temperate humid realms such as cloud forests, as well as streams, ponds, peat bogs, thermal springs, and lakes of the colder and drier highlands of the Altiplano and Puna [START_REF] Vellard | Estudios sobre batracios andinos. I. El grupo Telmatobius y formas afines[END_REF][START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF]Barrionuevo 2017). The aquatic highland species adapted to the harsh conditions of highland environments [START_REF] Vellard | Estudios sobre batracios andinos. I. El grupo Telmatobius y formas afines[END_REF][START_REF] Sáez | Phylogeny of Telmatobius marmoratus complex (Anura, Telmatobiidae) reveals high cryptic diversity in the Andean Altiplano[END_REF], such as the endangered Titicaca Water Frog (Telmatobius culeus; IUCN SSC Amphibian Specialist Group 2020), show morphological, physiological, and ecological peculiarities related to feeding and communicating underwater (Barrionuevo 2016;[START_REF] Brunetti | Silent sounds in the Andes: Underwater vocalizations of three frog species with reduced tympanic middle ears (Anura: Telmatobiidae: Telmatobius)[END_REF][START_REF] Muñoz-Saravia | Foraging strategies and ecology of Titicaca water frog (Telmatobius culeus)[END_REF], as well as to enduring low oxygen levels and pronounced temperature fluctuations [START_REF] Hutchison | Aquatic life at high altitude: respiratory adaptations in the Lake Titicaca frog, Telmatobius culeus[END_REF][START_REF] Weber | Enthalpic consequences of reduced chloride binding in Andean frog (Telmatobius peruvianus) hemoglobin[END_REF][START_REF] Muñoz-Saravia | Temperature exposure and possible thermoregulation strategies in the Titicaca water frog Telmatobius culeus, a fully aquatic frog of the High Andes[END_REF].

The mode of life of these frogs under extreme environmental conditions would have shaped their relatively conserved external phenotype [START_REF] Vellard | Estudios sobre batracios andinos. I. El grupo Telmatobius y formas afines[END_REF][START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF][START_REF] Sáez | Phylogeny of Telmatobius marmoratus complex (Anura, Telmatobiidae) reveals high cryptic diversity in the Andean Altiplano[END_REF], which, coupled with the low genetic divergence shown by some highland clades [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF][START_REF] Sáez | A new endemic lineage of the Andean frog genus Telmatobius (Anura, Telmatobiidae) from the western slopes of the central Andes[END_REF][START_REF] Sáez | Phylogeny of Telmatobius marmoratus complex (Anura, Telmatobiidae) reveals high cryptic diversity in the Andean Altiplano[END_REF], suggest that most lineages within Telmatobius diversified quite recently, during Pliocene times (i.e. less than 5 million years ago; [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]. This has made it difficult to resolve their evolutionary relationships based on external morphology or molecular data alone (De la Riva et al. 2012;Barrionuevo 2017), yet the monophyly of Telmatobius is currently considered well supported [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF][START_REF] Sáez | A new endemic lineage of the Andean frog genus Telmatobius (Anura, Telmatobiidae) from the western slopes of the central Andes[END_REF][START_REF] Sáez | Phylogeny of Telmatobius marmoratus complex (Anura, Telmatobiidae) reveals high cryptic diversity in the Andean Altiplano[END_REF]Barrionuevo 2017), and includes species formerly assigned to Batrachophrynus (Aguilar & Valencia 2009;[START_REF] Frost | Amphibian Species of the World: an Online Reference[END_REF]. In contrast to the pattern shown by soft anatomy and gene data, skeletal morphology in Telmatobius shows substantial interspecific variation (Trueb 1979;Wiens 1993;De la Riva et al. 2012;Barrionuevo 2018), although intraspecific variation in some osteological features has also been described (e.g. [START_REF] Sinsch | Reassessment of central Peruvian Telmatobiidae (genera Batrachophrynus and Telmatobius): osteology, palmar morphology and skin histology[END_REF]Barrionuevo 2013). This substantial interspecific variation has led to reporting species' osteology (De la Riva et al. 2012) and to infer their phylogenetic relationships based on osteology (Barrionuevo 2017). Molecular [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF][START_REF] Sáez | A new endemic lineage of the Andean frog genus Telmatobius (Anura, Telmatobiidae) from the western slopes of the central Andes[END_REF]) and morphological (Aguilar & Valencia 2009;Barrionuevo 2017) phylogenetic cladistic analyses recovered four major clades within the genus: i) the T. verrucosus group, including mostly semiaquatic species from the cloud forests and adjacent humid paramos in Bolivia and Peru [START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF][START_REF] Aguilar | Morphological variation of Telmatobius atahualpai (Anura: Telmatobiidae) with comments on its phylogenetic relationships and synapomorphies for the genus[END_REF]; ii) the T. bolivianus group, with primarily aquatic forms inhabiting streams in mountain forests and other habitats at intermediate elevations in Bolivia and Argentina [START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF][START_REF] Lavilla | El género Telmatobius en la República Argentina: una síntesis[END_REF]; iii) the T. macrostomus group, mostly aquatic species from the Andean highlands in Peru (Aguilar & Valencia 2009;Barrionuevo 2017); and iv) the T. marmoratus group, including the T. hintoni and T. zapahuirensis groups of [START_REF] Sáez | A new endemic lineage of the Andean frog genus Telmatobius (Anura, Telmatobiidae) from the western slopes of the central Andes[END_REF], mainly consisting of aquatic species from the dry Altiplano-Puna highlands in Peru, Bolivia, Chile, and Argentina [START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF][START_REF] Lavilla | El género Telmatobius en la República Argentina: una síntesis[END_REF]Formas et al. 2006;Aguilar & Valencia 2009;Barrionuevo 2017).

Telmatobius has been hypothesised to have a forest origin in the Andean region, likely during the Miocene, with highland species in drier habitats having evolved more recently when the Andean uplift promoted isolation of different populations [START_REF] Duellman | The herpetofauna of the Andes: patterns of distribution, origin, differentiation, and present communities[END_REF][START_REF] Cei | Speciation and adaptative radiation in Andean Telmatobius frogs[END_REF][START_REF] Lynch | Origins of the high Andean herpetological fauna[END_REF][START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]). However, this hypothesis and the chronology and geography of the early diversification of Telmatobius remain highly speculative [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]. This is due in part to the uncertain timing of the diversification of Telmatobius [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF][START_REF] Sáez | A new endemic lineage of the Andean frog genus Telmatobius (Anura, Telmatobiidae) from the western slopes of the central Andes[END_REF], which, in turn, relates to the lack of reliable fossil calibration points [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]. The fossil record of Telmatobius is almost null, as unfortunately observed for most anuran genera from the Neotropics [START_REF] Gómez | Oldest record of Leptodactylus Fitzinger, 1826 (Anura, Leptodactylidae), from the early Pliocene of the South American Pampas[END_REF][START_REF] Turazzini | El inusual hallazgo de una asociación diversa de anuros en Yacimiento Constitución (Pleistoceno Tardío, Mar del Plata) con el primer registro fósil de Pseudis Wagler (Hylidae, Anura)[END_REF][START_REF] Turazzini | First fossil record of the South American frog genus Odontophrynus Reinhardt and Lütken, 1862 (Anura, Neobatrachia)[END_REF][START_REF] Pérez-Ben | A Last Glacial anuran assemblage from the inland Pampas of South America provides insights into climate and environments during Marine Isotope Stage 3[END_REF]Barcelos & dos Santos 2022;Turazzini & Gómez 2023a), and restricted to so far undescribed isolated bones attributed to Telmatobius sp. that have recently been reported from the Pleistocene of Chile (Figueroa-Bravo et al.

2022).

Here we report on an outstanding record from the late Middle-earliest Late Miocene of Achiri, at 3960 m ASL in the Bolivian Altiplano (Fig. 1), which consists of several associated cranial and postcranial bones referable to a single adult male of a new species of Telmatobius. We provide a detailed description of its cranium and postcranium and perform phylogenetic analyses that confirm the new species as part of the crown group Telmatobius.

We also perform stochastic character mapping to reconstruct the ancestral substrate preference, habitat, and elevation range of Telmatobius, highlighting the impact of the new species in inferring the palaeoecology and palaeobiogeography of the group. Finally, we discuss the potential of the new record as a reliable calibration point for timing the evolutionary history of this speciose group of Andean frogs.

GEOLOGICAL SETTING

A few Miocene fossil-bearing loci (levels + localities) have been described near the Achiri village (e.g. [START_REF] Saint-André | Hoffstetterius imperator n. g., n. sp. du Miocène supérieur de l'Altiplano bolivien et le statut des Dinotoxodontinés (Mammalia, Notoungulata)[END_REF][START_REF] Pujos | The Miocene vertebrate faunas of Achiri, Bolivia[END_REF][START_REF] Fernández-Monescillo | Multiple skeletal and dental pathologies in a late Miocene mesotheriid (Mammalia, Notoungulata) from the Altiplano of Bolivia: palaeoecological inferences[END_REF][START_REF] Gaudin | Recognition of a new nothrotheriid genus (Mammalia, Folivora) from the early late Miocene of Achiri (Bolivia) and the taxonomic status of the genus Xyophorus[END_REF][START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF] and references therein; Fig. 1A). All of them were deposited in a vast fluvial and lacustrine plain, and are assigned to the uppermost member (Member 6 or M6) of the volcaniclastic-dominated Mauri Formation [START_REF] Sirvas-Carranza | Consideraciones geológicas de la zona noroeste de la Provincia Pacajes del depto[END_REF][START_REF] Saint-André | Hoffstetterius imperator n. g., n. sp. du Miocène supérieur de l'Altiplano bolivien et le statut des Dinotoxodontinés (Mammalia, Notoungulata)[END_REF]. Classical mammal-yielding levels of the M6, first described half a century ago [START_REF] Hoffstetter | Nouveaux gisements de Mammiferés néogènes dans les couches rouges de l'Altiplano bolivien[END_REF][START_REF] Villarroel | Les mésothérinés (Notoungulata, Mammalia) du Pliocène de Bolivie leurs rapports avec ceux d'Argentine[END_REF], correlate with the mammal-bearing locus (level + site) ACH-27 located c. 80 m above the base of the Cerro Pisakeri (Fig. 1A) and bracketed by volcanic ashes dated by one of us (PM) at 10.42 ± 0.09 Ma and 9.42 ± 0.1 Ma (Late Miocene; [START_REF] Fernández-Monescillo | Multiple skeletal and dental pathologies in a late Miocene mesotheriid (Mammalia, Notoungulata) from the Altiplano of Bolivia: palaeoecological inferences[END_REF][START_REF] Gaudin | Recognition of a new nothrotheriid genus (Mammalia, Folivora) from the early late Miocene of Achiri (Bolivia) and the taxonomic status of the genus Xyophorus[END_REF][START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]Fig. 1B). Over the last decade, our team discovered older fossil-bearing levels within M6 at different sites (loci) at the bottom of the available Cerro Pisakeri stratigraphic section [START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]Fig. 1B). These fine-grained and plant-rich green marls are indicative of lacustrine and low-energy fluvial settings in the area, which is confirmed by the palynological assemblage recovered at the loci ACH-25 and ACH-26 [START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF].

The Telmatobius-yielding locus ACH-14 is a white, tuffaceous, fine-grained laminated siltite of low-energy fluviolacustrine origin, intercalated between green marl-dominated beds that crops out 4 km south of Achiri near the base of Cerro Pisakeri [START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]Fig. 1).

A thorough stratigraphical survey in May 2022 indicated this 50 cm-thick tuffaceous siltite is laterally equivalent to locus ACH-26 in the section (Fig. 1B), instead of being located 3 m above of it as previously illustrated in [START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]. Accordingly, a late Middle to early Late Miocene age can be hypothesised for ACH-14 (see discussion in [START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF].

MATERIAL AND METHOD

The holotype specimen in block MNHN-Bol-V 012795, upon which we erect a new extinct species of Telmatobius, was collected in situ by three of us (POA, BMQ, and RAF) during an expedition in the Bolivian Altiplano at Achiri, in 2011. It is permanently curated in the fossil vertebrate collections of the Museo Nacional de Historia Natural de Bolivia at La Paz (MNHN-Bol-V). Other fossils were collected in the same field campaign, as well as in 2015 and 2022, by members of the same team (POA, RAF, LM, FP, and SF). All fossil specimens (holotype of the new Telmatobius species and other microvertebrate materials) come from the locus ACH-14, from a single lamina of fine-grained tuffaceous siltite of lacustrine origin. The holotype skeleton was collected in the same block with a few remains of a much smaller but putatively-conspecific frog, the remains of which are too fragmentary and do not add meaningful data, and a bird, which will be described elsewhere. Several of these bones have already been mechanically isolated from the matrix, but a few ones belonging to the holotype of the new frog species are still associated in the main block (Figs. 2A,S1). Most of the skeletal elements of the holotype are three-dimensional bones that are preserved as disarticulated but closely associated. Their relative size, number, and morphology strongly indicate that they all belonged to a single adult male frog (Figs. 2B,S1).

For comparisons, we surveyed skeletons of most hyloid families, but also pipids and microhylids, with a focus on Telmatobius and other hyloids currently considered phylogenetically related, primarily relying on direct examination of dry skeletons, clearedand-stained specimens, and three-dimensional (3D) models from CT-data available at MorphoSource (https://www.morphosource.org ), but also on published data (see Appendix S1). The 3D models were generated following the workflow of Buser et al. (2020), using Fiji (ImageJ v.1.53c;[START_REF] Schindelin | Fiji: An open-source platform for biological-image analysis[END_REF]3D Slicer v.4.11.2 (Fedorov et al. 2012;[START_REF] Kikinis | 3D Slicer: a platform for subjectspecific image analysis[END_REF]. Measurements of limb bones were those defined by [START_REF] Lires | Walk before you jump: new insights on frog locomotion from the oldest known salientian[END_REF], but also including the length of metacarpal IV and considering epiphyses. Measurements were taken digitally either on Fiji (from photographs) or 3D Slicer (from 3D models). General anatomical terminology follows [START_REF] Gaupp | Ecker's und Wiedersheim's Anatomie des Frosches[END_REF], [START_REF] Bolkay | Osnove uporedne osteologije anurskih batrahija sa dodatkom o porijeklu Anura i sa slikom narajnova sistema istih[END_REF], [START_REF] Maglia | Skeletal morphology and postmetamorphic ontogeny of Acris crepitans (Anura: Hylidae): a case of miniaturization in frogs[END_REF], and Turazzini & Gómez (2023b), with most Latin terms translated into English. Carpal terminology follows [START_REF] Gaupp | Ecker's und Wiedersheim's Anatomie des Frosches[END_REF], [START_REF] Fabrezi | El carpo de los anuros[END_REF]Fabrezi &[START_REF] Fabrezi | The carpal elements of anuras[END_REF], and pelvic terminology follows Gómez & Turazzini (2016). The orientation of limbs follows [START_REF] Gaupp | Ecker's und Wiedersheim's Anatomie des Frosches[END_REF]. The general taxonomic scheme for anurans follows [START_REF] Frost | Amphibian Species of the World: an Online Reference[END_REF] and the systematic arrangement of Telmatobius follows [START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF] and Barrionuevo (2017).

Phylogenetic analyses

In order to test the evolutionary relationships of the new fossil frog from Achiri, quantitative phylogenetic analyses were performed, incorporating data from MNHN-Bol-V 012795 in the available data matrix of Barrionuevo (2017;hereafter and 256 discrete characters of the adult skeleton, thereby representing a rigorous test of higher level relationships and a potential source of additional apomorphies. We deleted nearly all ceratophryids from this latter dataset, keeping one species of each extant genus, so the final dataset GT21 included a total of 18 non-telmatobiid extant taxa representing eight families, thus providing a broad overlap with the outgroup of dataset B17. The character scoring of the new fossil species is provided in Appendix S2.

Matrices were assembled in MESQUITE v3.6 [START_REF] Maddison | Mesquite: a modular system for evolutionary analysis[END_REF]) and analysed in TNT v1.5 [START_REF] Goloboff | TNT version 1.5, including a full implementation of phylogenetic morphometrics[END_REF]. Parsimony analyses were performed under both equal and implied weights [START_REF] Goloboff | Estimating character weights during tree search[END_REF]) across a range of mild concavity constant values (k = 5-9) and treating multistate characters in dataset B17 as either ordered or unordered, replicating previous settings (Barrionuevo 2017;Gómez & Turazzini 2021a). We performed heuristic searches using 'New Technologies' with sectorial searches, tree fusing, and ratchet, followed by tree bisection-reconnection (TBR) branch swapping to hit independently 10 times the optimal scoring and holding up to 100000 most parsimonious trees (MPTs), plus a final round of TBR. In each case, basic statistics were performed (tree length; Consistency Index [CI]; Retention Index [RI]) and, when appropriate, a strict consensus of the MPTs was calculated to summarise the phylogenetic results. Node support was estimated in TNT v1.5 using the Bremer index (BS) and Jackknifing (JK); the latter was expressed as absolute frequencies calculated with 10000 pseudo-replicates of 10 random sequence additions each followed by TBR swapping, keeping up to 10 trees, with a probability of alteration P = 0.36.

Ancestral reconstructions of substrate preference, habitat, and elevation

We explored the congruence (and potential impact) of palaeoecological, palaeoenvironmental, and palaeoelevation data associated with the new frog from Achiri, as inferred from multiple proxies including stable isotopes, leaf physiognomy, palynology, and skeletal morphology [START_REF] Garzione | Tectonic evolution of the Central Andean plateau and implications for the growth of plateaus[END_REF][START_REF] Martínez | Neogene precipitation, vegetation, and elevation history of the Central Andean Plateau[END_REF][START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF] the level of the antorbital plane (B17, c27: 0 → 1); well ossified crista parotica (GT21, c38: 0 → 1); palatine with slightly expanded medial end (GT21, c183: 0 → 1; indicated by the palatine scar on the sphenethmoid); occipital crest well developed on otic capsule (GT21, c190: 1 → 2); otic capsule with ventrolateral otic ledge completely ossified (GT21, c194: 0 → 1); small coronoid process (B17, c33: 0 → 1; GT21, c60: 1 → 0); partially fused dentary and angulosplenial (B17, c36: 0 → 1; GT21, c219: 0 → 2); hyoid plate with central mineralisation (B17, c37: 0 → 1); sacral oblique crest sharp over diapophyses (GT21, c233: 2 → 3); and scapula with acromial cartilage ossified as an acromial process (GT21, c235: 0 → 1).

Description

The holotype consists of a well-ossified partial skeleton representing a single adult individual of c. 8-9 cm total (snout-urostyle) length (all bones are about the same size of those of Telmatobius species of this length), including most of the skull and the postcranium (Figs. 2, S1). Several osteological features, including the morphology of the hyoid and the humeri, indicate that it was a male (see below).

Cranium. Most of the neurocranium, part of the suspensorium, the right maxilla, and the left premaxilla are preserved. Except for the left premaxilla, all other cranial bones have been mechanically removed from the main block (Figs. 2B,S1). The skull, and particularly the braincase, is well ossified. Dermal bones lack ornamentation. According to the proportions of the preserved bones, the skull would have been wider than long, with large orbits and a preorbital region representing between one-fourth and one-third of the total skull length. The braincase appears to be narrow, and is estimated to be nearly one-fourth of the skull width at the level of plana antorbitale (antorbital planes).

Both otic capsules are preserved; the right one is articulated with the anterior part of the braincase and the left one is isolated but, both otic capsules are broadly invested by the parasphenoid alae ventrally (Fig. 3). Otic capsules are formed by the fusion of paired prootics and exoccipitals into otoccipitals and, when articulated, appear to contact each other along the ventral midline where they form the bony ventral margin of a roughly pentagonal foramen magnum. Whether or not the otoccipitals also contact dorsally is uncertain due to the incompleteness of their dorsomedial margins, but it is clear that the foramen magnum remains moderately separated from the skull table dorsally. Dorsolateral to the foramen magnum and near to it, a well-developed sharp and obliquely oriented occipital crest protrudes from the posterior surface of the otic capsule, almost reaching the top of the otic crest (Fig. 3A).

Parallel and medial to the posteroventral part of the otic crest there is an additional posterior crest (pcr in Fig. 3A). The occipital condyles are located along the ventrolateral margins of the foramen magnum and would be separated from each other by a relatively narrow but distinct intercotylar distance when in articulation. Lateral to each occipital condyle, there is a shallow yet well-delimited condyloid fossa where the jugular foramen (from the brain cavity; et al. 2007) are sharper than the rounded anterior ones. At their intersection, the most medial part of the anterior and posterior eminences is partially invested by the roughly squared posterolateral (paroccipital) process of the frontoparietal, which is preserved on the left otic capsule (Fig. 3C). This process bears a low, sharp ridge extending up to its posterolateral tip, which barely extends above the anteromedial part of the posterior epiotic eminence. Anterior to the contact of this process and the anterior epiotic eminence, the prootic is pierced by a tiny foramen, the identity of which is uncertain. In the anterior view, the anterior wall of the prootic bears a broad, well-delimited pterygoid facet for the medial ramus of the pterygoid (Fig. 3B). Medially to the pterygoid facet, a large prootic (trigeminal) foramen appears to be fully enclosed in prootic ossification, although this condition is uncertain because the anterior margin is broken in the left otic capsule and it is partially obscured by matrix in the right one.

The presence of an operculum and stapes cannot be verified.

The sphenethmoid is also extensively ossified, with its left and right halves fully fused across the midline (Fig. 3C,D). The sphenethmoid ossification extends posteriorly up to the anterior margin of the optic foramen and anteriorly into the posterior part of the septum nasi, also invading the tectum and solum nasi. Anterolaterally, sphenethmoid ossification extends into the most proximal part of the antorbital plane and into the ridge-shaped crista supraorbitalis at the anteromedial corner of the orbit, thereby completely enclosing the orbitonasal foramen. Dorsally, the sphenethmoid is extensive and would have been broadly

exposed between the dermal roofing bones, based on the observation that the nasals (which are not preserved) left no scars on the dorsal surface of the sphenethmoid. Also, the anterior edges of the frontoparietals lie well posterior to the level of the planum antorbitale, only slightly anterior to the anterior margin of the frontoparietal fenestra (Fig. 3C). The frontoparietal fenestra, in turn, would have been only narrowly exposed between the frontoparietals, as indicated by an articulated fragment of the frontoparietal on the right side, which slightly tapers anteriorly into an irregular end. Although the other parts of frontoparietals are poorly preserved, the way in which the braincase is preserved, with right and left otic capsules disarticulated from one another, suggests that the frontoparietals would have remained unfused posteriorly.

Ventrally, the braincase is largely invested by a T-shaped parasphenoid, consisting of an anterior cultriform process and two posterior subotic alae that appear to be fused to the otic capsules (Fig. 3D). Each ala is broad, slightly expanded distally, and slightly curved posterolaterally, and having its ventral surface relatively flat except for a faint curved ridge delimiting a shallow depressed area towards the concave posterior margin. Posteriorly, the parasphenoid ends near the margin of the foramen magnum as a well-developed posteromedial process. The moderately broad, lanceolate cultriform process is relatively long, reaching the level of the plana antorbitale, and its ventral surface lacks any ridges or keels, but has a few short grooves near its anterior end. The latter would have been in tenuous contact with the palatines, as indicated by a palatine scar on the left side of the sphenethmoid ('palf' in Fig. 3D). This scar also shows that palatines were curved and slightly dilated at their medial ends.

The suspensorium is represented by both pterygoids and part of the left squamosal that is attached to a quadrate-quadratojugal complex (Fig. 4A,B). The pterygoids are relatively well preserved, but the medial ramus of the right element and the most anterior point of the anterior ramus of the left one are broken. Each pterygoid is a triradiate bone with a relatively gracile and long anterior ramus that is more than twice as long as either of the other two rami (Fig. 4A). The medial margin of the anterior ramus is evenly concave lengthwise, whereas the lateral margin is almost straight along its anterior half where, in life, it would have paralleled and contacted the maxilla. The anterior ramus has a tapering anterior end that would have reached the antorbital plane in the articulated skull, which is further indicated by the proportions of the braincase and the maxilla (see below). The medial and posterior rami are almost equal in length. The medial ramus is relatively broad with a concave posterior face where the basal process of the cartilaginous palatoquadrate fitted, which in life would have articulated with the otic capsule. The posterior ramus is relatively deep and flat, thereby indicating a broad covering of the palatoquadrate up to the limits of the articular surface with the lower jaw, as also indicated by a broad pterygoid facet on the quadrate-quadratojugal complex (see below).

Only part of the left squamosal ventral ramus is preserved and is firmly attached to the quadrate-quadratojugal complex, investing the posterolateral surface of the latter and limiting the pars articularis dorsally (the part of the quadrate that articulates with the lower jaw; 'q' in Fig. 4B). Although it was found disarticulated from the rest of the skull, it is clear that the squamosal was strongly inclined anterodorsally from this point, as it matches the morphology of other species of Telmatobius. The articulated portion of the ventral ramus of the squamosal is moderately expanded distally and relatively flat in the quadrate region, where its medial margin is distinctly separated from and nearly parallel to the pterygoid posterior ramus, as indicated by the pterygoid facet on the quadrate-quadratojugal complex (Fig. 4B), slightly verging with it anteriorly. The quadrate is heavily ossified and broadly invested posterolaterally and medially by the squamosal and the pterygoid, respectively (Fig. 4B). The relation with the pterygoid is evidenced by a broad square facet on the medial surface of the quadrate up to its articular surface. The latter is saddle-shaped, limited by strong lateral and medial buttresses. Laterally, and fused to the quadrate, there is a small quadratojugal, the maxillary spine of which would not have been articulated extensively with the maxilla.

The right maxilla is preserved almost completely, only lacking most of a relatively delicate jugal process, but some details remain obscured by the matrix or are poorly preserved (Fig. 4C). The maxilla has a nearly straight oral margin and its labial surface is relatively smooth and devoid of ornamentation. The maxilla is dentate and has three distinct parts along most of its length: a pars palatina, directed lingually and bisecting the maxilla into a pars dentalis, extending ventrally, and a pars facialis, extending dorsally. The pars palatina extends from near the anterior tip of the bone up to the anterior end of the subtemporal fossa, indicated by an inconspicuous pterygoid process that marks the posterior-most contact of the maxilla with the palatoquadrate. The pars palatina forms a shelf that is more or less narrow and thin along most of its length, but it is somewhat thicker and blunt around the level of the antorbital plane. The pars dentalis is as long as the pars palatina and only moderately deep, slightly decreasing in depth near its posterior end. It bore teeth all along its length, as indicated by the interdental pillars narrowly separated from one another, but the morphology of individual teeth cannot be determined. The pars facialis is relatively shallow lengthwise, being deepest in the preorbital region, decreasing in depth posteriorly along the orbital region and more abruptly along the jugal process (Fig. 4C). It bears a distinct preorbital process and an inconspicuous postorbital bump that delimits the orbital ventrolateral margin. Anteriorly, the maxilla has a squared anterodorsal margin and a low, round anteroventral process that would have abutted the premaxilla.

The left premaxilla is preserved in the main block with several associated remains on top of the left iliac shaft (see Fig. 2A), exposing its labiodorsal face and, hence, preventing description of its posteroventral surface. The dentate premaxilla is mesiodistally short (Fig. 4D) and has the same three distinct parts of the maxilla. The pars facialis is inconspicuous except for an alary process projecting posterodorsally from the middle of the pars dentalis.

The alary process is relatively short, narrow at its base and slightly dilated distally, being clearly concave posteriorly where it would have lodged the prenasal cartilages. The pars palatina projects posteriorly, particularly posteromedially through a distinct lingual process that appears to have its tip broken (Fig. 4D). The maxillary margin of the premaxilla is relatively straight, supporting the inference of an abutting contact with the maxilla. Two relatively large teeth appear to remain attached to the pars dentalis, but their preservation precludes further detail.

Lower jaw. The lower jaw remains in the main block (Fig. 2A) and preserves an almost complete right dentary (partially concealed by the hyoid) partially fused with part of the angulosplenial, the latter of which lacks the articular region (Fig. 4E). Both bones invest an ossified Meckel's cartilage and remain fused to it, so there is no distinct Meckelian groove in the angulosplenial. The dentary is relatively deep lengthwise relative to most other hyloid anurans, bearing a sharp oral edge towards the symphysis, where it would have fused to the Mentomeckelian bone; however, the latter is concealed by the overlying hyoid labially and matrix lingually. In any case, it appears that the dentary surpasses dorsally the Mentomeckelian bone, forming the oral margin up to or very close to the symphysis.

Posteriorly, due to fusion to the underlying elements, the limits of the dentary are barely distinguishable but for a very shallow and short groove that would indicate a remnant of a Meckelian groove. The angulosplenial preserves leaning out from its dorsal margin, a low but moderately long coronoid process, oriented dorsolingually.

Hyoid. Part of the hyoid plate and the left and right posteromedial processes of the hyoid apparatus are well preserved in the main block (Fig. 2A), with the left process almost intact, whereas the right one, though complete, is fractured in the middle (Fig. 4F). The Pectoral girdle. Most of the pectoral girdle is preserved, including both right and left scapulae and clavicles, the right coracoid, and the left cleithrum. The right half of the pectoral girdle is in the type block (Fig. 2A), whereas the left bones have been removed from the matrix (Fig. S1). The scapula and clavicle are strongly fused to each other, whereas the coracoid seems to have been synostotically connected to both elements (Fig. 6A). The paraglenoid cartilage is completely mineralized forming a very conspicuous paraglenoid ventral protuberance, lateral to the glenoid portion of the clavicle, and a tubercle in the anterior-most portion of the acromial margin. The clavicle is as long as the coracoid and slightly shorter than the scapula, being strongly curved anteriorly. The coracoid is almost symmetrical, with expanded glenoid and sternal portions that are twice as wide as the middle portion of the element. Its anterior margin is concave, whereas the posterior margin is nearly straight. The scapula is a triradiate element of very robust appearance. The pars acromialis is very well developed and fused to the clavicle. The anterior margin bears a conspicuous tubercle/knob (acromial process) next to the one formed by the ossified paraglenoid cartilage, and a well-developed anterior crest with an irregular margin that extends along most of the scapular shaft, resulting in a convex anterior margin of the scapula (Fig. 6A). The scapular shaft is robust. Its lateral margin, which articulates with the suprascapula, is 30% longer than the length of the shaft (as measured between the glenoid and lateral margins). The posterior margin of the shaft is concave, and the shaft itself is markedly arched dorsally. The pars glenoidalis is well developed and bears a conspicuous dorsal longitudinal crest on the internal surface (Fig. S1). The anterior portion of the left cleithrum is preserved (Fig. 6B) and bears a ventral fold that would have folded over the anterior margin of the cartilaginous suprascapula. A spina acromialis sticks out from its anterior margin, the latter of which is roughly 40% longer than the lateral margin of the scapula.

Forelimbs. Both left and right humeri and radio-ulnae are preserved, along with several autopodial elements. The right humerus and radio-ulna are preserved in the main block (Fig. 2A), whereas their left counterparts have been removed from it (Fig. S1). The humerus is robust and well ossified, including the epiphyses (Fig. 6C-E). The humeral diaphysis seems almost straight, but it presents a slight anterior and dorsal bowing that is obscured by the presence of well-developed ventral, medial, and lateral crests (Figs. 2A, 6C-E). The caput humeri (humeral head) is large and slightly compressed lateromedially, bearing two very distinct lateral and medial ventral ridges that delimit a deep longitudinal groove where the paraglenoid ridge of the pectoral girdle fits. On the lateroventral surface of the caput humeri there is a distinct, kidney-shaped glenoid fovea (fovea capitis sensu Gaupp 1896; Fig. 6D), in which the medial scapulo-humeral ligament attaches in extant anurans. The medial ridge of the epiphysis is contiguous with a large ventral (deltoid) crest that projects over the proximal half of the humeral shaft (diaphysis). The margin of this crest is rugose and presents tuberosities on both sides. On its medial surface there is a well-defined medial groove (fossula dividens sensu [START_REF] Bolkay | Osnove uporedne osteologije anurskih batrahija sa dodatkom o porijeklu Anura i sa slikom narajnova sistema istih[END_REF] for the tendon of the coracoradialis muscle, flanked by a low tuberous paraventral crest (parietal crest). The presence of a ligamentous bridge over the medial groove is evidenced by opposing conspicuous bony knobs on ventral (deltoid) and paraventral crests ('lbrb' in Fig. 6C), representing the attachment sites of this ligament. The lateral and medial crests are very well developed, the medial one being much larger and with an irregular margin, and they project dorsally merging at midlength of the diaphysis forming a single dorsal crest that almost reaches the proximal epiphyseal margin (Fig. 6E). The humeral ball is relatively large and well-mineralised, slightly compressed mediolaterally, and flanked by a small lateral epicondyle (ectepicondyle) and a very large medial epicondyle (entepicondyle). The medial epicondyle protrudes distally beyond the distal end of the humeral ball and limits medially with a broad entepicondylar groove. The radio-ulna is about 70% the length of the humerus and its minimum width is 60% of its maximum width (at the distal end) (Fig. 6F). The olecranean process bears a well-developed medial articular facet that fits the entepicondylar groove of the humerus. The distal epiphysis bears a welldeveloped ulnar protuberance that clearly surpasses the polygonal radial portion of the epiphysis and is separated from it by a wide shallow groove.

Both distal carpals 5-4-3 are preserved (Figs. 2B, 6G, H, S1). These relatively large and well-ossified carpals show several anatomical features that, coupled to some metacarpals (see below), allow the reconstruction of most of the manus. In a proximal view (Fig. 6G), a large fossa occupies most of the surface of the bone forming part of the carpal volar fovea (sensu Gaupp 1986). Near its preaxial margin, this fossa is pierced by a large anterior carpal foramen, through which the main terminal branch of the ulnaris nerve passes in anurans. The carpal volar fovea is delimited distally by a faint transverse ridge (carpal transverse crest) that is more protruding towards the preaxial side. The facets for Distal Carpal 2, Element Y, radiale, and ulnare are distinct on the carpal side (i.e. towards the rest of carpals) along a preaxial-postaxial axis (Fig. 6G). The facet for Distal Carpal 2 has a shallowly concave palmar part and a protruding convex dorsal part that would have fitted a concavity on that unpreserved carpal. The facet for Element Y is deeply concave and relatively narrow, facing proximally and somewhat pre-axially, whereas the radial and ulnar facets are comparatively less deep and separated from one another by a groove that formed the distal part of an intercarpal foramen. From the ulnare margin, a small but distinct process ('pem' in Fig. 6G, H) protrudes post-axially and slightly dorsally, where the extensor muscles of the ulna and digit V likely attached [START_REF] Gaupp | Ecker's und Wiedersheim's Anatomie des Frosches[END_REF]. The ulnare facet is well exposed in this proximal view;

it is somewhat triangular and elongate, delimits the carpal volar fovea postaxially, and has its apex towards the palmar side and bordered by a protruding buttress. This configuration, jointly with that of the ulnar portion of the radio-ulna, suggests that the unpreserved ulnare was trapezoidal and deep in the dorso-palmar axis. From the palmar face of Distal Carpal 5-4-3, distal and aligned to the palmar buttress of the ulnare facet there protrudes a round short ridge ('clcr' in Fig. 6G), most likely as a continuation of the longitudinal crest. This ridge, in turn, forms the postaxial margin of the broad saddle-shaped palmar protruding surface of Distal Carpal 5-4-3, where parts of the palmar aponeurosis typically attach [START_REF] Gaupp | Ecker's und Wiedersheim's Anatomie des Frosches[END_REF]. In distal view (Fig. 6H), the process bearing the part of the facet for Distal Carpal 2 distinctly protrudes from the carpal surface. The radiale and ulnare facets are also visible in dorsal view, with the former more exposed than the latter and showing its whole rounded outline. A tiny foramen pierces the concave surface between these facets and the slightly distally protruding articular surfaces for metacarpals IV and V. The latter are mostly visible in distal view (Fig. 6H), showing their bulging, round shapes, which contrast with the more elongate articular surface for metacarpal III that protrudes dorsal to the anterior carpal foramen.

The metacarpals II-V from the right hand, plus a left metacarpal IV and a first phalanx (Figs. 2B, S1) are preserved removed from the block. Metacarpals III-V have a similar minimum width, whereas metacarpal II, although partially preserved, is clearly more robust than the other three. Metacarpal II bears a distinct proximal medial bony excrescence.

Metacarpal IV is longer than III and V, which are nearly equal in length, although the latter is slightly more robust. The phalanx, considering its size and proportion with the metacarpals, seems to be the first phalanx of finger IV.

Pelvic girdle. The pelvic girdle is well preserved in the main block lying on its ventral side and partially overlaid by other bones (Fig. 2A), meaning some of its features are not visible.

The pelvic girdle is completely articulated and lacks distinct sutures between bones, which, taking into account the disarticulated nature of most of the skeleton, clearly indicates that ilia and ischia are entirely fused to each other. It is likely that those bones are also fused to a completely ossified pubis, yet it is obscured by matrix. Both ilia have their shafts fractured, and their anterior ends are broken, but it appears that they slightly curved ventrally and medially, evenly along their length, forming an open V-shaped interiliac profile in dorsal view (Fig. 7A). Iliac shafts are robust, being mediolaterally compressed at their proximal part (towards the ilial body) and slightly dorsoventrally flattened towards their distal ends (towards the ilio-sacral joint). The iliac shaft lacks a distinct dorsal crest, but a blunt and low ridge rises distally, delimiting a shallow but distinct gutter on the medial face of the shaft. The ilium has a well-developed, bell-shaped and nearly symmetrical dorsal prominence, projecting dorsolaterally at the boundary between the iliac shaft and body. On its lateral face, the dorsal prominence bears a distinctly protruding oval dorsal protuberance. Posteromedially, the ilia lack symphyseal tubercles, meaning the interiliac symphysis would have been completely

ligamentous. The fused ischia moderately protrude into a median posterodorsal process capped by an ossified marginal cartilage, and have an almost straight posteroventral margin.

The ischia also protrude laterally, forming well-developed posterior acetabular rims.

Hind limbs. Both femora and the left tibiofibula are preserved, removed from the block (Figs.

2B, S1). Interestingly, the right femur and the tibiofibula present different pathologies; the femur bears an osteomyelitis-like inflammation [START_REF] Rothschild | Herpetological Osteopathology: Annotated Bibliography of Amphibians and Reptiles[END_REF]) of the proximal diaphysis (resulting in a diameter c. 44% larger than its non-pathologic counterpart) (Fig. 7B,C), whereas the tibiofibula has a healed fracture (Fig. 7D). The femur is long and gracile (length roughly 17 times its minimum width), sigmoid, and with a barely noticeable femoral crest. The femoral head is well ossified and bears a conspicuous dorsolateral trochanter (insertion of the external iliac muscle), separated from the rest of the head by a well-defined groove (insertion of the internal obturator muscle) (Fig. 7B). On the medial surface of the femoral head, there is a large groove (fovea capitis sensu Gaupp 1896) for the insertion of the ventral (teres) ligament (Fig. S1). The tibiofibula is slightly longer than the femur (c. 7%), gracile (length roughly 14 times its minimum width), and straight (Fig. 7D). Both epiphyses are well ossified, and the proximal one has a well-defined cnemial crest (sensu Turazzini & Gómez 2023b) that is continuous with an osseous eminentia arquata on the medial margin of the proximal end of the diaphysis.

Remarks

The holotype (MNHN-Bol-V 012795) of Telmatobius achachila closely resembles species of Telmatobius in all aspects of its skeleton, including some features formerly proposed as either typical, diagnostic, or synapomorphic for the genus [START_REF] Lynch | Evolutionary relationships, osteology, and zoogeography of leptodactyloid frogs[END_REF][START_REF] Lynch | A re-assessment of the telmatobiine leptodactylid frogs of Patagonia[END_REF]De la Riva et al. 2012;Barrionuevo 2017): i) frontoparietals do not reaching the antorbital plane; ii) small otic ramus of squamosal not investing crista parotica (inferred in the fossil based on the lack of a squamosal scar on the crista parotica); iii) robust parasphenoid fused to otic capsules; iv) dentate maxilla having a narrow palatal shelf and lacking a distinct pterygoid process; v) pars articularis of the palatoquadrate ossified (quadrate) and fused to quadratojugal; and vi) hyoid plate ossified up to the base of the posterolateral processes. The detailed morphology of some parts of the skeleton of T. achachila that has seldom been described in other anurans, such as the Distal Carpal 5-4-3 or the metacarpal II, also matches that of extant species of Telmatobius examined by us, but contrasts with that of most other anuran groups.

MNHN-Bol-V 012795 shows several features that are uncommon among anurans, but that clearly point to affinities with Telmatobius. Among these, the greatly expanded lateral and medial humeral crests in MNHN-Bol-V 012795 (Figs. 2A, 6C, 8A) can be found in males of only a few neotropical genera: Telmatobius [START_REF] Lynch | Evolutionary relationships, osteology, and zoogeography of leptodactyloid frogs[END_REF][START_REF] Lynch | A re-assessment of the telmatobiine leptodactylid frogs of Patagonia[END_REF]De la Riva et al. 2012; Fig. 8B-D), Alsodes [START_REF] Lynch | Evolutionary relationships, osteology, and zoogeography of leptodactyloid frogs[END_REF][START_REF] Lynch | A re-assessment of the telmatobiine leptodactylid frogs of Patagonia[END_REF]:fig. 9A), Telmatobufo [START_REF] Formas | Osteología, taxonomía y relaciones filogenéticas de las ranas del género Telmatobufo (Leptodactylidae)[END_REF][START_REF] Suazo | In the shadow of dinosaurs: Late Cretaceous frogs are distinct components of a widespread tetrapod assemblage across Argentinean and Chilean Patagonia[END_REF]; Fig. 8E), Leptodactylus (L. pentadactylus and L. latrans species groups; Lynch 1971; Fig. 8F), Rhinella (particularly developed in species of the R. spinulosa species group; Guevara et al. 2022:fig. 3B, D), and a few hylid species in the genera Boana (Duellman et al. 1997;Fig. 8G), Bokermannohyla (Faivovich et al. 2009), Hyloscirtus (Duellman et al. 1997:fig. 4), and Plectrohyla (Duellman & Campbell 1992). However, T. achachila markedly differs in humeral morphology, including that of the lateral and medial crests, from species in all these genera except Telmatobius (Fig. 8). The medial and lateral crests are nearly always enlarged in males of Telmatobius, with only very few exceptions (see scoring of character 52 of Barrionuevo 2017), and merge into a single dorsal crest (Fig. 8A-D). MNHN-Bol-V 012795 shares with other species of Telmatobius the overall proportions of the humerus and its crests, including , a large ventral crest extending over half of the shaft, and in having medial and lateral crests that develop into flanges that gently merge into a single dorsal crest, but also in more detailed features, such as the large and slightly compressed humeral head bearing strong lateral and medial ventral ridges delimiting a deep groove for the paraglenoid ridge, the kidney-shape of the glenoid fovea, and the epicondyle morphology, with a small lateral epicondyle and a very large medial epicondyle that protrudes distally beyond the distal end of the humeral ball. The coalescence of medial and lateral crests into a single dorsal crest does not occur in bufonids, hylids, and most abovementioned anurans (Fig. 8E,G), including

Alsodes [START_REF] Lynch | A re-assessment of the telmatobiine leptodactylid frogs of Patagonia[END_REF]:fig. 9A), and when present it clearly differs in its configuration (Fig. 8F). In addition, T. achachila markedly contrasts from bufonid toads (including Rhinella) in having dentate premaxilla and maxilla, from hylids in its robust pectoral girdle and humerus (e.g. [START_REF] Maglia | Skeletal morphology and postmetamorphic ontogeny of Acris crepitans (Anura: Hylidae): a case of miniaturization in frogs[END_REF]Fig. 8) and B17 and of T. achachila in Appendix S2).

As mentioned above, we interpret that the holotype (MNHN-Bol-V 012795)

represents an adult male, based on enlarged lateral and medial crests of the humerus, which are typical of males of several species of Telmatobius (Lavilla & Ergueta Sandoval 1999;Barrionuevo & Baldo 2009;[START_REF] Aguilar | Morphological variation of Telmatobius atahualpai (Anura: Telmatobiidae) with comments on its phylogenetic relationships and synapomorphies for the genus[END_REF]De la Riva et al. 2012;Barrionuevo 2013; Fig. 8B-D), but also on other features related to extensive ossification and/or hypertrophied structures. Among the latter, a well-ossified pectoral girdle with a large scapular anterior crest, a robust metacarpal II, and a mineralised hyoid plate greatly invaded by posteromedial ossifications, all of which occur in the holotype, have also been regarded as typical of males in some species of Telmatobius (Barrionuevo 2013).

Finally, some osteological features of the holotype might indicate that Telmatobius achachila from Achiri was aquatic, in agreement with the lacustrine setting in which the fossils were found. Noteworthy, the combination of a mineralised hyoid plate with a relatively deep lower jaw decreasing abruptly at the symphysis has been related to inertial suction feeding in a few species of Telmatobius, whereas other congeners lacking these features feed underwater by means of other strategies, including compensatory suction (Barrionuevo 2016).

The morphology of the symphyseal part of the lower jaw of MNHN-Bol-V 012795 cannot be established, but the combination of a relatively deep dentary bearing a sharp oral margin and a at least partially mineralised hyoid plate suggest some suction capabilities for underwater feeding.

PHYLOGENETIC ANALYSES

The parsimony analyses of the datasets GT21 and B17 recovered Telmatobius achachila nested within a well-supported monophyletic Telmatobius under all analytical conditions (Fig. results as those under EW, with T. achachila nested within members of the T. bolivianus group (Fig. S8). A summary of the results using datasets B17 and GT21 is reported over the strict consensus of four MPTs (Fig. 9A) and the single MPT (Fig. 9B), respectively, obtained under implied weighting (with k = 7) and multistate characters unordered.

In all of our analyses monophyly of Telmatobius was supported by ten and four unambiguous osteological synapomorphies using the datasets GT21 and B17, respectively, most of which can be seen in the holotype of T. achachila, as follows: anterior margin of frontoparietals not reaching the level of the antorbital plane (B17, c4: 0 → 1); quadrangular posterolateral process of frontoparietal partially overlapping the epiotic eminence (GT21, c162: 0 → 1); reduced otic ramus of squamosal (GT21, c9: 1 → 0; B17, c31: 1 → 0; inferred from the morphology of the crista parotica); moderately developed pars jugalis of quadratojugal (GT21, c53: 2 → 1); reduced pterygoid process of maxilla (GT21, c213: 1 → 0); well-developed anterior crest on scapula (GT21, c114: 1 → 2); greatly enlarged lateral and medial crests of the humerus (GT21, c242: 0 → 1). In addition, several transformations optimised as autapomorphies of T. achachila (all visible in the holotype) include: slightly expanded medial end of palatine (GT21, c183: 0 → 1; evidenced by the palatine scar on the sphenethmoid); long cultriform process of parasphenoid (B17, c27: 0 → 1); well-developed, sharp occipital crest on exoccipital (GT21, c190: 1 → 2); completely ossified ventrolateral otic ledge (GT21, c194: 0 → 1); dentary sutured (or partially fused) to angulosplenial (GT21, c219: 0 → 2; B17, c36: 0 → 1); small coronoid process (B17, c33: 0 → 1; GT21, c60: 1 → 0); mineralised hyoid plate (B17, c37: 0 → 1); ossified acromial cartilage on scapula (GT21, c235: 0 → 1).

ANCESTRAL SUBSTRATE PREFERENCE, HABITAT, AND ELEVATION

Stochastic character mapping of substrate preference, main habitat, and mean elevation, alternatively excluding or including data from Telmatobius achachila, yielded roughly similar results for most nodes within Telmatobius (Fig. 10A). However, some important differences existed in the reconstructions for the last common ancestor of Telmatobius. When including data from extant taxa only, the last common ancestor of Telmatobius was reconstructed as a semi-aquatic (53.2%) frog that inhabited forests (99.3%) at mid-high elevations of 2500-3500 m (37.1%), although optimisations of substrate preference and elevation range were quite equivocal, since the likelihood of a semi-aquatic habit was only a little higher than an aquatic habit (45.1%) and mid-low and high altitude ranges had only slightly lower likelihoods (36.5% and 36.4%, respectively). When data from T. achachila were considered, a forest habitat was also recovered with a high probability (99.4%) as the ancestral habitat for

Telmatobius, but an aquatic habit (65.9%) and a mid-low altitude range (71.8%) were optimised as largely more probable than their respective alternative states (Fig. 10A). In addition, data from T. achachila also impacted the reconstruction of the elevation range at which the last common ancestor of the T. bolivianus and T. marmoratus species groups might have lived, recovering high-(49.5%) and mid-high (65.2%) altitude ranges as the most probable states excluding or including data of T. achachila, respectively.

DISCUSSION

The genus Telmatobius is speciose and its referred extant species are distributed throughout [START_REF] Lynch | Evolutionary relationships, osteology, and zoogeography of leptodactyloid frogs[END_REF][START_REF] Lynch | A re-assessment of the telmatobiine leptodactylid frogs of Patagonia[END_REF]Trueb 1979;[START_REF] Laurent | Redescripción de Telmatobius hauthali Koslowsky (Anura: Leptodactylidae) y descripción de una nueva especie del mismo género[END_REF][START_REF] Lavilla | Deux nouvelles espèces du genre Telmatobius (Anura : Leptodactylidae) en provenance de El Moreno (Province de Jujuy, Argentine)[END_REF][START_REF] Lobo Gaviola | Osteología Comparada de Tres Especies de Telmatobius (Anura: Leptodactylidae) de la Provincia de Tucumán (Argentina)[END_REF]Wiens 1993;De la Riva 1994;Lavilla & Ergueta Sandoval 1995, 1999;Benavides et al. 2002;Cuevas & Formas 2002;De la Riva & Harvey 2003;Formas et al. 2003Formas et al. , 2006;;[START_REF] Lavilla | El género Telmatobius en la República Argentina: una síntesis[END_REF][START_REF] Sinsch | Reassessment of central Peruvian Telmatobiidae (genera Batrachophrynus and Telmatobius): osteology, palmar morphology and skin histology[END_REF]Barrionuevo & Baldo 2009;[START_REF] Aguilar | Morphological variation of Telmatobius atahualpai (Anura: Telmatobiidae) with comments on its phylogenetic relationships and synapomorphies for the genus[END_REF]De la Riva et al. 2012;Barrionuevo 2013Barrionuevo , 2018;;Báez & Gómez 2018).

Telmatobius achachila has a unique combination of features, including several autapomorphies that set it apart from other species of Telmatobius, and as such justifying the erection of a new species. Some of these diagnostic features appear to be otherwise unique to T. achachila within the genus, or at least among the congeners whose osteology is adequately known, such as the slightly expanded medial ends of palatines (GT21, c183: 0 → 1), the welldeveloped occipital crest on exoccipital (GT21, c190: 1 → 2), the dentary and angulosplenial partially fused (B17, c36: 0 → 1; GT21, c219: 0 → 2), and the scapula with an ossified acromial cartilage (GT21, c235: 0 → 1). These features could be interpreted as the result of hyperossification and/or peramorphic development of the skeleton relative to other species of Telmatobius (Báez & Gómez 2018;Barrionuevo 2018), converging in some aspects with ceratophryids, and more particularly with species of Lepidobatrachus [START_REF] Fabrezi | Morphological evolution in Ceratophryinae (Anura, Neobatrachia)[END_REF]Gómez & Turazzini 2021a;Turazzini & Gómez 2023a). Alternatively, they could have been inherited from a common ancestor, since a sister-group relationship between Telmatobius and Ceratophryidae has previously been proposed by some molecular-based studies (e.g., [START_REF] Grant | Phylogenetic systematics of dart-poison frogs and their relatives (Amphibia: Athesphatanura: Dendrobatidae)[END_REF][START_REF] Fouquet | Unexpected phylogenetic positions of the genera Rupirana and Crossodactylodes reveal insights into the biogeography and reproductive evolution of leptodactylid frogs[END_REF][START_REF] De Sá | Systematics of the neotropical genus Leptodactylus Fitzinger, 1826 (Anura: Leptodactylidae): phylogeny, the relevance of non-molecular evidence, and species accounts[END_REF], although most recent studies have pointed to a more distant relationship between them (e.g., [START_REF] Roelants | Global patterns of diversification in the history of modern amphibians[END_REF][START_REF] Pyron | Biogeographic analysis reveals ancient continental vicariance and recent oceanic dispersal in amphibians[END_REF][START_REF] Feng | Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous-Paleogene boundary[END_REF][START_REF] Hutter | Rapid diversification and time explain amphibian richness at different scales in the Tropical Andes, Earth's most biodiverse hotspot[END_REF][START_REF] Streicher | Evaluating methods for phylogenomic analyses, and a new phylogeny for a major frog clade (Hyloidea) based on 2214 loci[END_REF][START_REF] Hime | Phylogenomics reveals ancient gene tree discordance in the amphibian tree of life[END_REF]. Other features recovered as autapomorphic of T. achachila, although not unique, are shared with very few species within Telmatobius, including a small coronoid process (B17, c33: 0 → 1; GT21, c60: 1 → 0) and a partially mineralised hyoid plate (B17, c37: 0 → 1). Aside from occurring in T. achachila, these features occur jointly only in a few species of the T. marmoratus species group, including T. marmoratus and T. culeus from the Altiplano, which might account for the phylogenetic position recovered with the dataset GT21, yet results with the densely taxonomically sampled dataset B17 show that these similarities are better explained as convergences.

Interestingly, both Telmatobius marmoratus and T. culeus are aquatic inhabitants of Lake Titicaca of the Altiplano of Bolivia and Peru, although the former also thrives in streams, small lakes, and other wetlands across the Altiplano [START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF]. Similarly, T.

achachila appears to be an aquatic frog that lived in a lake at a mid-low elevation (no more than 2000 m ASL) according to geological and palynological data [START_REF] Garzione | Tectonic evolution of the Central Andean plateau and implications for the growth of plateaus[END_REF][START_REF] Boschman | Andean mountain building since the Late Cretaceous: a paleoelevation reconstruction[END_REF][START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]. Curiously, the region of Achiri where the fossils were found is currently both at a similar height (3960 m ASL) and c. 75 km south to the southern shore of the Lake Titicaca (3820 m ASL; Fig. 1), although when T. achachila lived it was located at a much lower elevation than today (c. 1600 m ASL; [START_REF] Mcintosh | Climatic and tectonic implications of the late Miocene Jakokkota flora, Bolivian Altiplano[END_REF][START_REF] Garzione | Tectonic evolution of the Central Andean plateau and implications for the growth of plateaus[END_REF][START_REF] Martínez | Neogene precipitation, vegetation, and elevation history of the Central Andean Plateau[END_REF][START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]). Since T. achachila appears as distantly related to these species, lacking some features recovered as synapomorphic of the T. marmoratus species group (and adjacent nodes) such as the greater anterior extent of frontoparietals (B17, c4: 1 → 0) and otic ramus of squamosal (B17, c31: 0 → 1) (Barrionuevo 2017; this study), it is likely that convergences between them are related to environmental adaptation to an aquatic life. Convergences in aquatic frogs have previously been stressed [START_REF] Emerson | Convergence and morphological constraint in frogs: variation in postcranial morphology[END_REF][START_REF] Moen | Testing convergence versus history: convergence dominates phenotypic evolution for over 150 Million Years in frogs[END_REF][START_REF] Gómez | High ecomorphological diversity among Early Cretaceous frogs from a large subtropical wetland of Iberia[END_REF], including cases between distantly related taxa such as paradoxical frogs and pipids (Turazzini & Gómez 2023b), but also between sister lineages within Pipidae (Gómez & Pérez-Ben 2019) and even between species of Telmatobius (Barrionuevo 2016). Among the latter, a mineralised hyoid plate, coupled with certain features of the lower jaw, has been linked to inertial suction during underwater feeding (Barrionuevo 2016). A mineralised hyoid plate has been reported in several aquatic

Telmatobius (Barrionuevo 2016(Barrionuevo , 2017), including T. macrostomus that also inhabits large lakes, yet in this case it is not coupled with particular lower jaw modifications. In addition, the small coronoid process in T. achachila and the T. marmoratus species group might also be related to a similar development and insertion of adductor mandibulae muscles (= levator mandibulae; Johnston 2011), involved in adducting the lower jaw, but their relation to inertial suction feeding remains unexplored. Interestingly, the only other anurans that have been reported as capable of inertial suction are the hymenochirine pipids [START_REF] Sokol | Feeding in the pipid frog Hymenochirus boettgeri (Tornier)[END_REF][START_REF] Carreno | Aquatic feeding in pipid frogs: the use of suction for prey capture[END_REF], which appear to have a single adductor mandibulae [START_REF] Sokol | Feeding in the pipid frog Hymenochirus boettgeri (Tornier)[END_REF]) and a coronoid process, although not particularly small, distinctly smaller than that of other pipids (Cannatella & Trueb 1988:fig. 5;ROG pers. observ.).

Phylogenetic analyses of dataset B17 under most analytical conditions recovered T.

achachila as an early branch within the Telmatobius tree, crownward to the divergence of the T. verrucosus species group (Fig. 9A), which, taking into account the relatively old age of the fossils, makes T. achachila a key taxon for understanding the early evolution of the group with an important potential impact in the reconstruction of ancestral conditions (Fig. 9B). It should be noted, though, that the inclusion of T. achachila into the data matrices of Barrionuevo (2017) and Gómez and Turazzini (2021a) does not significantly alter the topologies obtained in those studies. However, a few differences exist regarding the dataset B17, since the strict consensus from the analysis under equal weights with multistate characters unordered is much less resolved than the one reported by Barrionuevo (2017:fig. 2), because in our analysis the T. bolivianus species group collapses (Fig. 9A) due to alternative positions of T. achachila (see results). Some other differences with the topology reported by Barrionuevo (2017) A prerequisite for such an enterprise is an adequate timing of the phylogeny of ago, including some that might be linked to their aquatic lifestyle. The finding of T. achachila

in Achiri further provides key data that allowed a more accurate reconstruction of ancestral habitats and elevation ranges of Telmatobius, agreeing with the postulated ancestral conditions in which these frogs might have first evolved [START_REF] Duellman | The herpetofauna of the Andes: patterns of distribution, origin, differentiation, and present communities[END_REF][START_REF] Cei | Speciation and adaptative radiation in Andean Telmatobius frogs[END_REF][START_REF] Lynch | Origins of the high Andean herpetological fauna[END_REF][START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]. This discovery adds to the scarce evidence of a humid tropical Bolivian Altiplano just prior to the critical uplift of the area and the drastic climate deterioration which occurred in Late Miocene times onward, leading to the hostile highlandsteppe environments reigning today.

FIGURE CAPTIONS

  referred as dataset B17) and a taxonomically reduced version of the matrix fromGómez & Turazzini (2021a; hereafter referred to as dataset GT21). The matrix ofBarrionuevo (2017; permalink https://morphobank.org/permalink/?P2723) was initially designed for testing the monophyly of Telmatobius and their internal relationships, including 97 morphological characters (two continuous; 59 of the adult skeleton) scored for 43 species of Telmatobius plus 13 outgroup taxa from five families. This dataset therefore met our purposes of testing the presumed affinities of the new extinct species of Telmatobius, yet the osteological character sampling morphobank.org/permalink/?P4531), originally designed for testing the relationships of extinct and extant Ceratophryidae, included among the outgroup six species of Telmatobius representing several major lineages within the genus plus 15 additional non-ceratophryid taxa

  not visible in the posterior view of the otic capsule because it is concealed by the occipital condyle) and the inferior perilymphatic foramen (from the inner ear space), open extracranially. The superior perilymphatic foramen appears to open intracranially, but lies nearly in the same plane as the posterior one, being visible from a posterior and slightly lateral view. The inner ear space opens laterally through the fenestra ovalis, which is completely bounded in bone and lies relatively deep, being surrounded ventrally by a well-developed ventrolateral otic ledge (sensu Gómez 2016) and anteriorly by the anterior wall of the prootic.The tympanic space is roofed dorsally by a largely-ossified, relatively long and narrow crista parotica, only the distal edge of which would have been delineated in cartilage. There is no evidence of a facet for the otic ramus of the squamosal, suggesting that the latter was inconspicuous and would not have reached the otic capsule. The crista parotica has nearly parallel anterior and posterior margins, being only slightly dilated distally, and would have been directed almost laterally and slightly dorsally in the articulated skull. Dorsally on each otic capsule, the position of the anterior and posterior semicircular canals is clearly marked by well-ossified, distinct epiotic eminences, of which the posterior ones (otic crests sensu Maglia

  posteromedial processes are long and extensively ossified, being distinctly expanded at both of their ends. Their ossification invaded the hyoid plate up to the level of the bases of the posterolateral processes, but would not have progressed into them. The posteromedial processes appear to be only slightly offset from each other relative to their natural position, as the anterior end of the left process barely overlaps the right one, suggesting that a narrow strip of calcified cartilage would have persisted between their anterior ends. In addition, irregular small pieces surrounding the anterior ends of the posteromedial processes presumably correspond to calcified portions of the central region of the otherwise cartilaginous hyoid plate.Vertebral column. Only two partially preserved presacral vertebrae were identified, along with the sacrum and the anterior portion of the urostyle, all prepared out of the main block (Figs.2B, 5, S1). The centrum ofpresacral vertebrae is dorsoventrally compressed, and wider than long in dorsal view. A fairly complete posterior presacral vertebra (Fig.5A, B) shows a compressed centrum with an elliptic cross section. The neural canal is large, much wider and taller than the centrum. The neural arch lamina presents the base of a distinct low and pointed neural spine. The preserved bases of the transverse processes are oriented slightly dorsally.The sacral vertebra (Fig.5C, D) bears a distinct acute neural spine, with oblique crests that continue posterodorsally along the proximal two-thirds of the preserved left diapophysis. The left sacral diapophysis is entirely preserved; it is club-shaped, with its distal end almost twice as wide as its base, and inclined around 15° dorsally and posteriorly. The posterior articulation with the urostyle is bicondylar, with the medially inclined condyles separated by a wide gap. The anterior-most preserved portion of the urostyle (Fig.5E-G) presents a tall neural spine with a broad and flattened anterodorsal process that narrows posteriorly into a tall dorsal crest. A pair of small knobs is present on the neural arch lateral to the spine, and anterior to the small coccygeal foramina.

9 )

 9 , in agreement with the results of our taxonomic comparisons. Analyses under equal(EW) and implied (IW) weights with different values of the concavity constant k yielded very similar results, showing T. achachila nested in all cases within a large clade that is sister to the T. verrucosus group (represented only by T. verrucosus in the dataset GT21). The alsodid genera Eupsophus and Alsodes nearly always emerged as sister groups of Telmatobius using datasets B17 and GT21, respectively. Analysing dataset GT21, the main discrepancy was that T. achachila appeared as sister to T. marmoratus with IW (k = 5-9) in single MPTs (671-681 steps; CI = 0.476-0.483; RI = 0.569-0.581; Fig.S2), whereas it formed part of a polytomy with the latter and species of the T. bolivianus group (i.e. T. hauthali; T. scrocchii) in the strict consensus of six MPTs (671 steps; CI = 0.483; RI = 0.581) from the EW analysis (Fig.S3).Note that theTelmatobius sample in this dataset (seven of 62 species) is too poor to allow a more accurate analysis of relationships within the genus. Analysing dataset B17 under EW with ordered characters yielded 144 MPTs (327.079 steps; CI = 0.363; RI = 0.721), in the strict consensus of which T. achachila emerged in a nested position among members of the T. bolivianus group (Fig. S4). When characters remained unordered this clade collapsed in the strict consensus of 576 MPTs (320.108 steps; CI = 0.371; RI = 0.728), with T. achachila in a broad basal polytomy along some other species crownward to the node Telmatobius (Fig. S5), which was mainly due to T. achachila taking two alternate positions: either within a T. bolivianus group or outside the latter in a more early-branching position. The latter position agreed with the better resolved strict consensus obtained under IW (k = 5-7), with characters either ordered (232 MPTs of 329.332-330.332 steps; Fig. S6) or unordered (four MPTs of 322.430 steps; also with k = 8-9; Figs. S7, S9), in which T. achachila emerged crownward to the T. verrucosus group and to the southern taxa T. ceiorum and T. stephani, in a relatively basal polytomy with a small northern clade (T. truebae + T. niger) and a very large clade including the remaining species of Telmatobius. Analysis of B17 under IW (k = 8-9) with characters ordered (100 MPTs of 328.332 steps; CI = 0.361; RI = 0.720) yielded similar

  are related with different analytical conditions (e.g. treatment of multistate characters), of which the most notable is the relatively basal position of a clade formed by T. ceiorum and T. stephani (Fig.9A), lying well outside the T. bolivianus species group to which they were formerly located(Barrionuevo 2017). It would be worth testing more thoroughly the phylogenetic position of T. ceiorum and T. stephani, but this is beyond the scope of the present work. Interestingly, these two semi-aquatic/aquatic species inhabit montane forests (Yungas) of northwestern Argentina at elevations below 2300 m ASL[START_REF] Lavilla | El género Telmatobius en la República Argentina: una síntesis[END_REF], contrasting with most other members of the T. bolivianus species group that either inhabit highland streams of the Puna/Altiplano or at higher elevations in the montane forests of Bolivia (De la Riva 2005; Lavilla & Barrionuevo 2005; De la Riva et al. 2010). Telmatobius achachila might have also inhabited forests at relatively mid-low elevations (below 2000 m ASL), based on varied sources of geological and palynological data from which it is inferred that forests with conifers (Araucariaceae and Podocarpaceae), legumes, and Polylepis spread in the central Altiplano of Bolivia during Middle-early Late Miocene times (Gregory-Wodzicki 2002; Garzione et al. 2017; Boschman 2021; Prámparo et al. 2022; Fig. 10B). These ancient floras, and others from the Miocene of southern Peru (Martínez et al. 2020), share several components with extant montane forests now restricted along the Andean eastern slopes (Gregory-Wodzicki 2002; Prámparo et al. 2022; Fig. 10B).The phylogenetic reconstructions including data from T. achachila point to ancestral Telmatobius also inhabiting in wetlands surrounded by forests at relatively mid-low elevations (below 2500 m ASL), despite extant species in the early-diverging T. verrucosus species group being found at elevations up to 3500-4000 m ASL(Wiens 1993;[START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF][START_REF] Aguilar | Morphological variation of Telmatobius atahualpai (Anura: Telmatobiidae) with comments on its phylogenetic relationships and synapomorphies for the genus[END_REF]). This agrees with the forest origin proposed for the anuran species of the Andean highlands[START_REF] Duellman | The herpetofauna of the Andes: patterns of distribution, origin, differentiation, and present communities[END_REF][START_REF] Cei | Speciation and adaptative radiation in Andean Telmatobius frogs[END_REF][START_REF] Lynch | Origins of the high Andean herpetological fauna[END_REF][START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]) and the 'Dynamic-Continent Hypothesis' of[START_REF] Lynch | Origins of the high Andean herpetological fauna[END_REF], which predicts that populations began to differentiate as the pre-Andean landscape formed and continued to differentiate as they were further uplifted during Andean rises, and fits well the speciation model proposed for Telmatobius based on molecular data[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF] Fig. 10). It is likely that ancestral Telmatobius began to differentiate in a low-elevated forest habitat in what today is the Central Altiplano during the Early-Middle Miocene, very similar to the inferred palaeoenvironment where T. achachila lived[START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]. At this time, there would have been a forested corridor along the emerging highlands of the Altiplano (Gregory-Wodzicki 2002;[START_REF] Martínez | Neogene precipitation, vegetation, and elevation history of the Central Andean Plateau[END_REF][START_REF] Prámparo | Occurrence of Cyclusphaera scabrata in Achiri (late middle-early late Miocene?, Bolivian Altiplano): paleogeographical implication[END_REF]) that allowed dispersal of early populations northward and southward in similar environments. The marked uplift of the Altiplano and eastern Cordillera during the Late Miocene produced strong climatic and environmental changes in the region[START_REF] Garzione | Tectonic evolution of the Central Andean plateau and implications for the growth of plateaus[END_REF][START_REF] Boschman | Andean mountain building since the Late Cretaceous: a paleoelevation reconstruction[END_REF], which in turn would have caused severe fragmentation of existing frog populations[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]).These early populations either survived in the montane forests in the northern Andes of Peru/Ecuador and along the eastern Cordillera south to the Yungas of Argentina (their descendants would be species of the T. verrucosus and T. bolivianus species groups, plus several early-diverging lineages), or adapted to the new drier highland conditions of the Altiplano/Puna (lineages represented today by species of the T. marmoratus and T. macrostomus species groups). The presence of T. achachila in the late Middle-early Late Miocene of the central Altiplano and the reconstructed ancestral environmental conditions for Telmatobius (Fig.10A) support this biogeographic scenario, although it will remain speculative until more palaeontological data come to light and can be integrated in quantitative biogeographical studies.

FIG. 1 .

 1 FIG. 1. A, location map of Achiri village, Pacajes Province, La Paz Department, Bolivia, marking the type locus ACH-14 (star) and loci ACH-25 and ACH-26 (black dots) in the region of Cerro Pisakeri (Maps data: Google Earth, SIO, NOAA, US Navy, NGA, GEBCO, Image Landsat/Copernicus). B, stratigraphic column of the Member 6 of Mauri Fm. at Cerro Pisakeri (late Middle-early Late Miocene), modified from Prámparo et al. (2022), and location of main fossil-yielding (ACH-XX) loci and volcaniclastic levels (ACH-TUF 1-4). All anuran remains described here originate from ACH-14 locus, laterally equivalent to the pollen-bearing ACH-26 locus. Abbreviations: C, clay; Cg, conglomerate; Si, siltite; Sa, sand.

  , from Leptodactylus in lacking a squamosal-prootic articulation and in having a proportionally longer pterygoid anterior ramus[START_REF] Lynch | Evolutionary relationships, osteology, and zoogeography of leptodactyloid frogs[END_REF][START_REF] Ponssa | Cladistic analysis and osteological descriptions of the frog species in the Leptodactylus fuscus species group (Anura, Leptodactylidae)[END_REF], and from Alsodes and Telmatobufo in having frontoparietals not reaching the antorbital plane, ossification of hyoid posteromedial processes invading the hyoid plate, scapula with an anterior crest and fused to clavicle (variable within Telmatobius), and femoral crest indistinct (see character scorings of species of Telmatobius and Alsodes in datasets GT21

  For these reasons, osteology in general has often been regarded as of limited systematic value for inferring phylogenetic relationships or establishing taxonomic boundaries in the group(Sinch et al. 2005;[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF][START_REF] Sáez | Phylogeny of Telmatobius marmoratus complex (Anura, Telmatobiidae) reveals high cryptic diversity in the Andean Altiplano[END_REF]. However, our findings agree with those ofBarrionuevo (2017) andDe la Riva et al. (2012), demonstrating that osteological characters can be useful in the systematics of Telmatobius. Given that resolving evolutionary relationships of Telmatobius, both among component species and among other hyloid neobatrachians, have proven to be elusive based either on external morphology or on molecular data (e.g.,De la Riva et al. 2012; Barrionuevo 2017;[START_REF] Streicher | Evaluating methods for phylogenomic analyses, and a new phylogeny for a major frog clade (Hyloidea) based on 2214 loci[END_REF][START_REF] Sáez | Phylogeny of Telmatobius marmoratus complex (Anura, Telmatobiidae) reveals high cryptic diversity in the Andean Altiplano[END_REF], osteological data emerges as a particularly informative source of characters for the group(De la Riva et al. 2012; Barrionuevo 2017). However, there is still a paucity of osteological data for several parts of the skeleton and for most species of Telmatobius(De la Riva et al. 2012; Barrionuevo 2017), despite the growing body of osteological descriptions available in the literature

	achachila and extant species of the genus indicate that their overall skeletal anatomy is
	evolutionary conservative, remaining almost unchanged for at least 12 Ma, in agreement with
	previous statements regarding external morphology (Benavides et al. 2002). It is worth noting
	that very few of these osteological features have been considered in most systematic studies
	of Telmatobius (e.g., Lynch 1971; Trueb 1979; Wiens 1993; Lavilla & Barrionuevo 2005;

the Andean and Puna highlands from Ecuador to San Juan Province of Argentina

[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]

), but despite this, its fossil record is almost null. An indeterminate species of Telmatobius has only recently been reported from the Quaternary of the Antofagasta Region of Chile, based on several isolated fossils still undescribed

[START_REF] Figueroa-Bravo | Nuevo yacimiento con vertebrados Pleistocenos del desierto de Atacama. Segundo Congreso Chileno de Paleontología[END_REF]

. The discovery of T. achachila, a new extinct species of Telmatobius from late Middle to early Late Miocene of the Bolivian Altiplano known from cranial and postcranial bones, is a significant and noteworthy achievement that enhances our understanding of the morphology and evolutionary history of this Andean group.

Allocation of Telmatobius achachila to crown-group Telmatobius is grounded on several cranial and postcranial features, including several synapomorphies of the genus recovered as such in the present and former cladistic analyses

(Barrionuevo 2017; Gómez & Turazzini 2021a

; see phylogenetic analyses results). The many features shared by T.

[START_REF] Aguilar | Morphological variation of Telmatobius atahualpai (Anura: Telmatobiidae) with comments on its phylogenetic relationships and synapomorphies for the genus[END_REF] De la Riva et al. 2012; Barrionuevo 2017)

. Additionally, important intraspecific variation has been reported for some skeletal traits

[START_REF] Lobo Gaviola | Osteología Comparada de Tres Especies de Telmatobius (Anura: Leptodactylidae) de la Provincia de Tucumán (Argentina)[END_REF][START_REF] De | Bolivian frogs of the genus Telmatobius: synopsis, taxonomic comments, and description of a new species[END_REF][START_REF] Lavilla | El género Telmatobius en la República Argentina: una síntesis[END_REF][START_REF] Sinsch | Reassessment of central Peruvian Telmatobiidae (genera Batrachophrynus and Telmatobius): osteology, palmar morphology and skin histology[END_REF] Barrionuevo 2013

).

  Telmatobius, but to date only a few studies have tackled this issue[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF][START_REF] Sáez | A new endemic lineage of the Andean frog genus Telmatobius (Anura, Telmatobiidae) from the western slopes of the central Andes[END_REF]. These studies have estimated divergence times for Telmatobius and some of its internal nodes based on Bayesian approaches and a relaxed molecular clock, but since no fossils of Telmatobius were known at that time to be used as calibration points, they relied entirely on constant nucleotide substitution rates of the cytochrome b gene reported in the literature[START_REF] Mueller | Evolutionary rates, divergence dates, and the performance of mitochondrial genes in Bayesian phylogenetic analysis[END_REF], obtaining disparate results under different rates for older nodes[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF]; Fig.10A). The estimated mean divergence time of crown group Telmatobius was as old as 20 Ma (under a slow rate of 1%) to as recent as 10 Ma (under a fast rate of 2%) with large confidence intervals in all cases[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF] Fig. 10A). It is noteworthy that the inclusion of T. achachila in the phylogeny of Telmatobius provides a time-adjusted tree that is highly congruent with the mean estimated divergence times based on Telmatobius achachila sp. nov. from the late Middle-earliest Late Miocene of Achiri, at 3960 m ASL in the Bolivian Altiplano, constitutes the first described fossil of the speciose Andean genus Telmatobius. Phylogenetic analyses confirm the new species as part of the crown group, which, coupled with its accurate stratigraphic provenance and well-delimited (and relatively old) age, make it a reliable and crucial calibration point to timing the evolutionary history of these highland, mostly aquatic frogs. The skeleton of T. achachila indicates that several of the osteological peculiarities of extant Telmatobius already evolved some 12 Ma

a medium-slow nucleotide substitution rate

[START_REF] De La | Systematics of Bolivian frogs of the genus Telmatobius (Anura, Ceratophryidae) based on mtDNA sequences[END_REF] Fig. 10A)

. To be considered as a reliable calibration point, a fossil should have a well-estimated age and its systematic relationships need to be supported on apomorphies

[START_REF] Parham | Best practices for justifying fossil calibrations[END_REF]

, conditions that T. achachila fulfil satisfactorily. Therefore, T. achachila emerges as an excellent calibration point for crown group Telmatobius that helps in timing the evolutionary history of the group.

CONCLUSION

Acknowledgements. We warmly acknowledge Michel Séranne, for participating in the 2022 field campaign at Achiri, Pomata-Ayte, and Choquecota, and sharing his knowledge on

Fauna, Museo Nacional de Historia Natural, Academia Nacional de Ciencias de Bolivia, La Paz, Bolivia; CFA, CEBBAD-Fundación Félix de Azara, Buenos Aires, Argentina; CM, Carnegie Museum of Natural History, Pittsburgh, USA; FCEN, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; FML, Instituto de Herpetología de la Fundación Miguel Lillo, San Miguel de Tucumán, Argentina; IBIGEO, Instituto de Bio y Geociencias del NOA, Salta, Argentina; KU, Biodiversity Institute, University of Kansas, Lawrence, USA; MACN, Museo Argentino de Ciencias Naturales 'Bernardino Rivadavia', Buenos Aires, Argentina; MCZ, Museum of Comparative Zoology, Harvard University, Cambridge, USA; MLP, Museo de La Plata, La Plata, Argentina; MVZ, Museum of Vertebrate Zoology, University of California, Berkeley, USA; UF, University of Florida, Florida Museum of Natural History, Gainesville, USA; USNM, National Museum of Natural History, Washington, USA. Telmatobius. T. atahualpai (LD; Aguilar et al. 2012); T. bolivianus (LD; Lavilla & Ergueta Sandoval 1999); T. brevipes, UF:herp:39760 (CT, ark:/87602/m4/386402) (LD; Wiens 1993); T. carrillae, UF:herp:39717 (CT, ark:/87602/m4/M159469); T. chusmisensis (LD; Formas et al. 2006); T. cirrhacelis (LD; Trueb 1979); T. culeus, USNM:Amphibians & Reptiles:281587 (CT, ark:/87602/m4/423141); T. degener, UF:herp:39736 (CT, doi:10.17602/M2/M99912) (LD; Wiens 1993); T. fronteriensis (LD; Benavides et al. 2002); T. halli (LD; Formas et al. 2003); T. hauthali, FCEN 320 (DS), FML 3315 (DS); T. huayra (LD; Lavilla & Ergueta Sandoval 1995); T. ignavus (LD; Wiens 1993); T. laticeps, CAS:sua:11270 (CT, ark:/87602/m4/M49875); T. latirostris (LD; Wiens 1993); T. macrostomus, FCEN 1208-1 (DS); T. marmoratus, CAS:herp:152217 (CT, ark:/87602/m4/M49889), KU:kuh 164079, 164080 (DS); T. mendelsoni (LD; De la Riva et al. 2012); T. necopinus (LD; Wiens 1993); T. niger (LD; Trueb 1979); T. oxycephalus, FML 2867-II (CS), (LD; Barrionuevo 2013, 2016, 2018); T. philippii (LD; Cuevas & Formas 2002); T. rubigo (LD; Barrionuevo & Baldo 2009; Barrionuevo 2016, 2018); T. schreiteri, FML 541 (DS); T. scrocchii, FML 1515 (DS); T. sibiricus (LD; De la Riva & Harvey 2003); T. thompsoni, UF:herp:39734 (CT, doi:10.17602/M2/M20345) (LD, Wiens 1993); T. truebae (LD; Wiens 1993); T. vellardi (LD;

DATA ARCHIVING STATEMENT

Phylogenetic data for this study are available in Morpho-Bank (O'Leary & Kaufman 2012): https://doi.org/10.7934/P2723; https://doi.org/10.7934/P4531. This published work and the nomenclatural acts it contains have been registered with ZooBank: https://zoobank.org/References/ 6888D20A-7FF8-409F-9C1F-7E760575A74F Editor. Marcello Ruta

Andean geology and tectono-sedimentary history. Fieldwork in the Bolivian Altiplano has been carried out in the framework of an ongoing cooperation agreement (N•864/2014) between the MNHN-Bol (La Paz, Bolivia), the Institut des Sciences de l'Évolution de Montpellier (France) and the CCT-CONICET (Mendoza, Argentina). This research was also supported by the National Geographic Society (NGS EC-44712R-18 [AB] and NGS 9971-16 [FP]), the ECOS-SUD/FONCyT international program (2015-2017; FP and POA), an "Investissements d'Avenir" grant managed by the French Agence Nationale de la Recherche (ANR) in the framework of the LabEx CEBA (ANR-10-LABX-25-01; POA and LM). This is a contribution of the Paltiplano project that has received financial support from the French Centre National de la Recherche Scientifique (CNRS) through the Mission pour les initiatives transverses et interdisciplinaires (MITI) program (SF and LM). We thank the Willi Hennig Society for the free access to the TNT software package. We acknowledge the continued support of Universidad de Buenos Aires and CONICET. We also thankfully acknowledge the contribution of the editors, J. Gardner (Royal Tyrrell Museum of Palaeontology), and an anonymous reviewer for their valuable comments and suggestions.

SUPPORTING INFORMATION

Additional Supporting Information can be found online (https://doi.org/10.1002/spp2.1543): S1).

Appendix

Abbreviations: CS, cleared and stained; CT, micro CT-scan data on MorphoSource (www.morphosource.org); DS, dry skeleton; LD, data taken from literature.

Institutional abbreviations: AMNH, American Museum of Natural History, New York, USA; CAS, California Academy of Sciences, San Francisco, USA; CBF, Colección Boliviana de Appendix S2: Character scoring of Telmatobius achachila.

T. achachila on dataset B17 from Barrionuevo (2017) ???011[01]?0?0?000???[12]0???1?1?11100011011????20???1?1?0110???????????????????? ??????????????????????

T. achachila on dataset GT21 from Gómez & Turazzini (2021) 00??10?00?0001001020??????1?1000011??100??1?01200000[01]00??0?0??????130??1???? ??21?????210111?[12]1??????????0100012112?1??2??11??101201[01]1?00????????[01]?0? 0?????000????1????00?????10?00?[01]?11?01?11210010?????101100?0???00?0?1?2??0??? ???????3?10101??11111111100??10 Strict consensuses obtained in the phylogenetic analyses of datasets B17 and GT21. See material and method for details. In GT21, the Telmatobius bolivianus species group is represented by T. oxycephalus, T. hauthali, and T. scrocchii. Abbreviations: B17, derived from that of Barrionuevo (2017); CI, Consistency Index; GT21, derived from that of Gómez & Turazzini (2021); MPTs, most parsimonious trees; RI, Retention Index.