Sérgio P Ávila
email: avila@uac.pt

José M N Azevedo

Patrícia Madeira

Ricardo Cordeiro

Carlos S Melo

Lara Baptista

Paulo Torres

Markes E Johnson

Romain Vullo

Plio-Pleistocene actinopterygian fishes from Santa Maria Island (Azores: North-eastern Atlantic Ocean): palaeoecological and palaeobiogeographical implications

Keywords: Actinopterygii, Azores archipelago, glacial-interglacial cycles, sea-surface temperature, Sparisoma cretense, Labrodon pavimentatum, Sparidae

Fossil fish are among the rarest in volcanic oceanic islands, their presence providing invaluable data for the understanding of more general (palaeo)biogeographical patterns and processes. Santa Maria Island (Azores Archipelago) is renowned for its palaeontological heritage, with representatives of several phyla, including the Chordata. Herein, we report on the fossil fishes, resulting in an increase of the number of Pliocene fish from the Azores to 11 taxa: 7 Chondrichthyes and 4 Actinopterygii. The genus Sparisoma is reported for the first time in the fossil record. The presence of fossil remains of the parrotfish Sparisoma cretense in Last Interglacial outcrops is significant, because it posits a setback for the theory that most of the present-day Azorean marine species colonized the area after the last glacial episode. Our multidisciplinary approach combines palaeontological data with ecological and published genetic data, offering an alternative interpretation. We suggest that most of the Azorean shallow-water subtropical and temperate marine species living in the archipelago during the Last Interglacial were not affected by the decrease in sea surface temperatures during the last glacial episode. We also predict low genetic diversity for fish species presently living in the Azores and ecologically associated with fine sediments. These are viewed as post-glacial colonizers or as 'bottleneck' survivors from the Last Glaciation.

Introduction

Oceanic islands have long been considered as ideal places to study biogeographical patterns and processes, and to test evolutionary theories [START_REF] Darwin | On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life[END_REF][START_REF] Wallace | Island life, or, the phenomena and causes of insular faunas and floras: including a revision and attempted solution of the problem of geological climates[END_REF]. A detailed knowledge of an island's geological history and evolution is of paramount importance, influenced by the ontogenic state of the island as determined by a series of factors [e.g. geological age of the oldest subaerial lavas, terrestrial area, maximum altitude, latitude; see [START_REF] Whittaker | A General Dynamic Theory of Oceanic Island Biogeography: Extending the MacArthur-Wilson Theory to Accommodate the Rise and Fall of Volcanic Islands[END_REF]; [START_REF] Fernández-Palacios | Towards a glacial-sensitive model of island biogeography[END_REF]]. Such factors ultimately regulate and explain both the number of species that live on the island, as well as the functional composition of the biological assemblage itself. The marine fossil record for volcanic oceanic islands may be considered as rare or poor, especially when compared to that for vastly larger continentes (Ávila et al., 2018). However, the dating of an island's fossil fauna and flora when coupled with checklists validated by experts provides valuable insights for a number of disciplines such as palaeobiogeography, palaeoceanography, phylogenetic and climate-change studies (Ávila et al., 2019).

The remarkable marine fossil record of Santa Maria Island in the Azores Archipelago has been intensively studied over the last decades (for a review, see Ávila et al. (2018) and references therein). The result has been 204 Pliocene and 146 Pleistocene (Last Interglacial) species and 15-20 further ichnospecies reported for the island [START_REF] Santos | Role of environmental change in rock-boring echinoid trace fossils[END_REF][START_REF] Uchman | Vertically-oriented trace fossil Macaronichnus segregatis from Neogene of Santa Maria Island (Azores; NE Atlantic) records vertical fluctuations of the coastal groundwater mixing zone on a small oceanic island[END_REF][START_REF] Uchman | The trace fossil Diopatrichnus santamariaensis nov. isp. -a shell armoured tube from Pliocene sediments of Santa Maria Island, Azores (NE Atlantic Ocean)[END_REF][START_REF] Raposo | Comparing methods of evaluation of geosites: the fossiliferous outcrops of Santa Maria Island (Azores, NE Atlantic) as a case study for sustainable island tourism[END_REF]. The vast majority of specimens collected are invertebrates: molluscs [START_REF] Zbyszewski | La faune miocène de l'île de Santa Maria (Açores)[END_REF][START_REF] Ávila | Checklist of the Pleistocene marine molluscs of Prainha and Lagoinhas (Santa Maria Island, Azores)[END_REF], 2015a, 2015b, 2016;[START_REF] Janssen | Early Pliocene heteropods and pteropods (Mollusca, Gastropoda) from Santa Maria (Azores, Portugal): systematics and biostratigraphic implications[END_REF], brachiopods [START_REF] Kroh | Novocrania turbinata (Brachiopoda) from the Early Pliocene of the Azores (Portugal)[END_REF], crustacean balanids [START_REF] Winkelmann | Zullobalanus santamariaensis sp. nov., a new late Miocene barnacle species of the family Archeobalanidae (Cirripedia: Thoracica), from the Azores[END_REF], echinoderms [START_REF] Madeira | The fossil echinoids of Santa Maria Island, Azores (Northern Atlantic Ocean)[END_REF] and ostracods [START_REF] Meireles | Late Miocene marine ostracods from Santa Maria Island, Azores (NE Atlantic): Systematics, palaeoecology and palaeobiogeography[END_REF]. A small number of fossil vertebrate remains also have been studied, most notably cetaceans [START_REF] Estevens | Fossil whales from the Azores[END_REF]Ávila et al., 2015c) and sharks (Ávila et al., 2012). Fossil bony fishes are known from the island, but the last account for Santa Maria fossil Actinopterygii fishes' dates from the 1950's and 60's [START_REF] Zbyszewski | La faune miocène de l'île de Santa Maria (Açores)[END_REF][START_REF] Ferreira | A fauna miocénica da ilha de Santa Maria (Açores)[END_REF]. With few exceptions [START_REF] Ávila | Systematics, palaeoecology and palaeobiogeography of the Neogene fossil sharks from the Azores (Northeast Atlantic)[END_REF][START_REF] Betancort | Early Pliocene fishes (Chondrichthyes, Osteichthyes) from Gran Canaria and Fuerteventura (Canary Islands, Spain)[END_REF], the majority of the published palaeoecological and palaeobiogeographical studies on the marine fauna and flora of the Macaronesian archipelagos targeted sessile or low-motility species, such as the marine molluscs, echinoderms, bryozoans, barnacles, ostracods and algae [START_REF] Meco | Los Strombus Neogenos y Cuaternarios del Atlantico Eurafricano. (Taxonomia, Biostratigrafia y Palaeoecologia)[END_REF][START_REF] Meco | The Quaternary deposits in Lanzarote and Fuerteventura (Eastern Canary Islands, Spain): an overview[END_REF][START_REF] Meco | The Canary record of the evolution of the North Atlantic Pliocene: New 40 Ar/ 39 Ar ages and some notable palaeontological evidence[END_REF][START_REF] Meco | Early Pliocene tracer of North Atlantic and South Pacific sea surface currents: Janthina typica (Bronn, 1860) (Mollusca: Gastropoda)[END_REF]Ávila et al., 2008a, 2008b, 2009;2015a;[START_REF] Winkelmann | Zullobalanus santamariaensis sp. nov., a new late Miocene barnacle species of the family Archeobalanidae (Cirripedia: Thoracica), from the Azores[END_REF][START_REF] Madeira | The fossil echinoids of Santa Maria Island, Azores (Northern Atlantic Ocean)[END_REF][START_REF] Santos | Miocene intertidal zonation on a volcanically active shoreline: Porto Santo in the Madeira Archipelago, Portugal[END_REF]Santos et al., , 2012aSantos et al., , 2012b;;[START_REF] Meireles | Late Miocene marine ostracods from Santa Maria Island, Azores (NE Atlantic): Systematics, palaeoecology and palaeobiogeography[END_REF][START_REF] Ávila | Unravelling the patterns and processes of evolution of marine life in oceanic islands: a global framework[END_REF][START_REF] Baarli | What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands[END_REF][START_REF] Baarli | Miocene to Pleistocene transatlantic dispersal of Ceratoconcha coral-dwelling barnacles and North Atlantic island biogeography[END_REF][START_REF] Betancort | Mio-Pliocene crustaceans from the Carany Islands, Spain[END_REF][START_REF] Johnson | Miocene-Pliocene rocky shores on São Nicolau (Cape Verde Islands): Contrasting windward and leeward biofacies on a volcanically active oceanic island[END_REF][START_REF] Meireles | The Holocene to Recent ostracods of the Azores (NE Atlantic): systematics and biogeography[END_REF][START_REF] Rebelo | Rhodolith forming coralline algae in the Upper Miocene of Santa Maria Island (Azores, NE Atlantic): a critical evaluation[END_REF][START_REF] Tuya | Seagrass paleo-biogeography: Fossil records reveal the presence of Halodule cf. in the Canary Islands (eastern Atlantic)[END_REF]. Still largely unresolved, an interesting question is how the evolutionary patterns and processes inferred from these studies do relate with species' dispersal capabilities (Ávila et al., 2019). Therefore, this study aims to: 1) review and update the status of all existing Actinopterygii fossil material from Santa Maria Island; 2) use this new data to test previous statements by several authors (e.g., [START_REF] Briggs | Marine zoogeography[END_REF][START_REF] Santos | Marine research, resources and conservation in the Azores[END_REF][START_REF] Domingues | Historical population dynamics and demography of the eastern Atlantic pomacentrid Chromis limbata (Valenciennes, 1833)[END_REF][START_REF] Domingues | Tropical fishes in a temperate sea: evolution of the wrasse Thalassoma pavo and the parrotfish Sparisoma cretense in the Mediterranean and the adjacent Macaronesian and Cape Verde Archipelagos[END_REF] who concluded that the shallow littoral fauna of the Azores was extirpated during the Last Glacial episode; and 3) compare the palaeobiogeographical and palaeoecological patterns known from sessile and lowdispersive species (e.g. non-planktotrophic marine molluscs), with that of highly motile species such as fishes.

Geographical and Geological Setting

Azores Archipelago

The nine volcanic oceanic islands that form the Azores Archipelago are located in the north-eastern Atlantic Ocean (Fig. 1) and rise from a bathymetric anomaly (the Azores Plateau) with depths of about 2,000 m. The most distant islands (Flores, in the western group, and Santa Maria in the eastern group) are 615 km apart. Flores and Corvo belong to the North American tectonic plate, whereas the other seven islands are located around the most-studied area called the Azores Triple Junction [START_REF] Laughton | The Azores-Gibraltar plate boundary[END_REF], a place where three major tectonic plates, North American, Nubian and Eurasian, interact. The Azores Triple Junction is limited by the East Azores Fracture Zone to the south, the Mid-Atlantic Ridge (MAR) to the west and the Terceira's Rift and Gloria Fault to the northeast and east [START_REF] Searle | Tectonic pattern of the Azores spreading centre and triple junction[END_REF] (Fig. 1A). This area (i.e. the Azores Plateau, the Azores Triple Junction and the islands that compose the Azores Archipelago), was named the 'Azores Geosyndrome' [START_REF] Vogt | The "Azores Geosyndrome" and Plate Tectonics: Research History, Synthesis, and Unsolved Puzzles[END_REF], which is derived from a series of anomalies related to 'crustal thickness, rock composition, basement depth, plate boundary morphology, seismicity, gravity and geoid, and upper mantle seismic velocity structure'.

Santa Maria Island

This island has a complex geological history (see [START_REF] Ramalho | The emergence and evolution of Santa Maria Island (Azores) -the conundrum of uplifted islands revisited[END_REF] for a review). It is the oldest island of the Azores Archipelago, first rising above sea level at about 6 Ma, initially by Surtseyan activity (the Cabrestantes Formation), and then by subaerial, monogenetic volcanism associated to the Porto Formation. High rates of magma production formed a shield volcano (the Anjos volcanic complex, dating from 5.8 to 5.3 Ma), which substantially increased the area of the Santa Maria protoisland, as attested by the present-day insular shelf [START_REF] Ricchi | Marine terrace development on reefless volcanic islands: New insights from high-resolution marine geophysical data offshore Santa Maria Island (Azores Archipelago)[END_REF]. Although the entire volcanic edifice likely has undergone subsidence since extrusion of the first lavas of the submarine edifice, at around 5.3 Ma, a prolonged subsidence rate of about 100 m/myr lasted until 3.5 Ma [START_REF] Ramalho | The emergence and evolution of Santa Maria Island (Azores) -the conundrum of uplifted islands revisited[END_REF]. Volcanic activity associated with the Anjos shield volcano ceased at about 5.3 Ma and was followed by a period of about 1.2 myr with almost no volcanism, during which the protoisland nearly vanished due to erosion [START_REF] Ávila | Systematics, palaeoecology and palaeobiogeography of the Neogene fossil sharks from the Azores (Northeast Atlantic)[END_REF][START_REF] Ramalho | The emergence and evolution of Santa Maria Island (Azores) -the conundrum of uplifted islands revisited[END_REF], thus originating a large, flat, shallow seamount. The sediments of this unit (the Touril volcano-sedimentary complex, 5.30 to 4.13 Ma) are highly fossiliferous and correspond to early Pliocene outcrops formerly described in the literature as of Miocene in age (see [START_REF] Madeira | The marine fossils from Santa Maria Island (Azores, Portugal): an historical overview[END_REF] for a review). Volcanic activity initiated again at about 4.1 Ma, during the first rejuvenated stage, with eruptive foci associated with the Pico Alto volcanic successions, first submarine and later subaerial in nature [START_REF] Ramalho | The emergence and evolution of Santa Maria Island (Azores) -the conundrum of uplifted islands revisited[END_REF], thus originating the revival of Santa Maria as an island. This stage lasted to 3.5 Ma, when the subsidence trend was reversed, and the island's volcanic edifice initiated an uplift trend continuing to the present day. Initially, a rate of 59 m/myr occurred from 3.5 to 2.15 Ma, thereafter at a slower rate of 42 m/myr between 2.15 Ma and the present [START_REF] Ricchi | Marine terrace development on reefless volcanic islands: New insights from high-resolution marine geophysical data offshore Santa Maria Island (Azores Archipelago)[END_REF]. This uplift trend, coupled with Pleistocene glacio-eustatic sea-level fluctuations, produced a staircase of 10 subaerial and of 5 submerged marine terraces, the former particularly evident across the island's western sector at elevations ranging from 7-11 to 210-230 m [START_REF] Ramalho | The emergence and evolution of Santa Maria Island (Azores) -the conundrum of uplifted islands revisited[END_REF], and the latter on the shelf all around the island at depths ranging between -40/-50 and -120/-140 m [START_REF] Ricchi | Marine terrace development on reefless volcanic islands: New insights from high-resolution marine geophysical data offshore Santa Maria Island (Azores Archipelago)[END_REF]. A second rejuvenated stage occurred from 3.2 to 2.8 Ma, associated with monogenetic volcanism of the Feteiras Formation. Uplift has continued until today, but erosion became the dominant agent impacting the island's landscape during the last 2.8 myr [START_REF] Ramalho | The emergence and evolution of Santa Maria Island (Azores) -the conundrum of uplifted islands revisited[END_REF].

Institutional

Methods

Most of the 20 known fossiliferous outcrops on Santa Maria Island are early Pliocene in age, but scattered Last Interglacial deposits from the Pleistocene also are known from the north (Lagoinhas; Ávila et al., 2009a, 2009b) and southern shores (Prainha, Praia do Calhau and Vinha Velha outcrops (Ávila et al., 2002, 2015a; Fig. 1B). The fossil fish specimens reported, herein, were found in sedimentary layers from a total of eight outcrops (cf. Table 1). Six of these contain fauna that deposited during the early Pliocene: Cré [START_REF] Kroh | Novocrania turbinata (Brachiopoda) from the Early Pliocene of the Azores (Portugal)[END_REF]; Fig. 2A), Figueiral (Rebelo et al., 2016a;Ávila et al., 2018a; Fig. 2B), Malbusca (Rebelo et al., 2016b;[START_REF] Johnson | Intense hurricane transport sand onshore: example from the Pliocene Malbusca section on Santa Maria Island (Azores, Portugal)[END_REF]; Fig. 3A), West Fault of Malbusca (Uchman et al., 2017 Fig. 3B), Pedra-que-pica (Ávila et al., 2015b, 2018a;[START_REF] Uchman | Vertically-oriented trace fossil Macaronichnus segregatis from Neogene of Santa Maria Island (Azores; NE Atlantic) records vertical fluctuations of the coastal groundwater mixing zone on a small oceanic island[END_REF]Fig. 3C), and the yet undescribed Ponta dos Frades outcrop. The two remaining outcrops [Prainha (Fig. 2C) and Vinha Velha (Fig. 2D)] include faunas from the Last Interglacial period (c. 116-130 kyr), of which the warmest interval is known as MIS 5e (Marine Isotopic Stage 5e) (Ávila et al., 2015a). Figure 1B shows the geographical location of each outcrop and Figure 4 displays representative composite sections of the studied outcrops.

All specimens described were collected during fourteen fieldwork campaigns of the Palaeontology in Atlantic Islands workshops, held on Santa Maria Island from 2002 to 2017. In compliance with the legislation that rules the "PalaeoPark Santa Maria", all fossil specimens collected were deposited in the fossil collection at the Department of Biology of the University of the Azores (DBUA-F). Over 1,300 lots containing fossil specimens collected at Santa Maria Island were screened for fossil Actinopterygii fishes, yielding a total of 42 lots. Systematics for Actinopterygii conform to the World Register of Marine Species (WoRMS, 2018). As the oral and pharyngeal tooth plates are frequently well preserved in the fossil record and as they display diagnostic features [START_REF] Bellwood | A Review of the fossil record of the parrotfishes (Labroidei: Scaridae) with a description of a new Calotomus species from the middle Miocene (Badenian) of Austria[END_REF], direct comparisons of the fossil remains with fossil and recent remains (whenever available) were used to classify our material. The teeth terminology for Scaridae is in accordance with [START_REF] Day | Phylogenetic relationships of the Sparidae (Teleostei: Percoidei) and implications for convergent trophic evolution[END_REF].

All data generated or analysed during this study are included in this published article.

Results

Actinopterygian fish taxa were found in the fossilliferous sediments of Santa Maria Island: at least two extinct Sparidae species with a probable Mio-Pliocene temporal range (Fig. 5A-Q); Sparisoma cretense (Linnaeus, 1758) (Fig. 6), an extant Scaridae herein reported for the Pliocene and Pleistocene (Last Interglacial, MIS 5e) of the Azores; and Labrodon pavimentatum Gervais, 1857 (Fig. 7), an extinct Labridae with a Mio-Pliocene temporal range. In total, 54 teeth and several pharyngeal plates were 165-2, 204-2, 205-2, 250-1, 260, 286, 313, 344-2, 350, 382, 448, 460-1, 477-2, 508-1, 508-2, 595, 596, 597, 598, 599, 601, 647, 667, 668, 669, 671, 672, 673, 674, 966-2, 991, 1014, 1017, 1073, 1083. Cré, formerly also known as Pedreira dos Frades (2): MGM 11311, 11312 (one spheroidal and one oval molariform teeth, respectively); Santa Maria Island (4 teeth), no locality: MGM 11313.

Description-The 50 teeth examined from the DBUA collection represent three types of dentition: molariform, conical and incisiform teeth. We have examined a total of 39 molariform teeth, corresponding to the lingual series (36 spheroidal in shape (Fig. 5A-F, 5L), ranging from 2.87 to 17.34 mm in diameter; and 3 oval in shape, 5.89-11.51 mm), 9 conical teeth (Fig. 5G-K), corresponding to the labial series (2.41-7.93 mm in diameter) and 2 'spatulate' incisiform teeth (1.45-1.53 mm in diameter; DBUA-F 668, 671). Some of the largest spheroidal molariform teeth exhibit a central depression; these are considered to belong to the upper lingual series (Fig. 5A-C, 5F). Some of the largest teeth show radial grooves at the base of the crown. The general shape and size resemble some of the teeth described by [START_REF] Betancort | Early Pliocene fishes (Chondrichthyes, Osteichthyes) from Gran Canaria and Fuerteventura (Canary Islands, Spain)[END_REF].

The four teeth housed at MGM (Lisbon) that we examined are all lateral teeth, with a conical shape, and rounded, worn crowns (Fig. 5M-Q).

Remarks-this material represents at least two taxa, including a small one and a larger one (possibly Diplodus and Pagrus, respectively). Some of these teeth might also belong to Archosargus [START_REF] Cutwa | Intralocality variation in feeding biomechanics and prey use in Archosargus probatocephalus (Teleostei, Sparidae), with implications for the ecomorphology of fishes[END_REF]. However, any generic/specific assignment would be highly tentative without any additional osteological evidence.

Stratigraphic and geographic range-Extinct

Archosargus species are reported from the Miocene and Pliocene of the Mediterranean Sea [START_REF] Obrador | Nuevas localidades con fauna ictiológica para el Neógeno menorquín[END_REF][START_REF] Vicens | Vertebrats fòssils (Pisces i Reptilia) del Burdigalià de cala Sant Vicenç (Pollença, Mallorca)[END_REF][START_REF] Mas | Presència de Tomistoma cf. lusitanica (Vianna i Moraes, 1945) (Reptilia: Crocodylia) al Burdigalià inferior de Mallorca (Illes Balears, Mediterrània occidental). Implicacions paleoambientals[END_REF] and from the Miocene of France [START_REF] Gagnaison | Le site paléontologique du Grand Morier (Pont-Boutard, Indre-et-Loire, France): contexte géologique et détail biostratigraphique des formations cénozoïques à partir des assemblages de vertébrés fossiles[END_REF]. In the Atlantic, Archosargus species are reported from the Miocene of Portugal [START_REF] Zbyszewski | Os peixes miocénicos portugueses[END_REF][START_REF] Jonet | L'helvétien du Penedo et sa faune ichthyologique[END_REF] and Morocco [START_REF] Lecointre | Recherches sur le Néogène et le Quaternaire marin de la Côte Atlantique du Maroc, Tome 2 -Paléontologie[END_REF], the Pliocene of Canary Islands (Gran Canaria Island) [START_REF] Betancort | Early Pliocene fishes (Chondrichthyes, Osteichthyes) from Gran Canaria and Fuerteventura (Canary Islands, Spain)[END_REF] and from the Pliocene of the Azores (Santa Maria Island) [START_REF] Zbyszewski | Os peixes miocénicos portugueses[END_REF][START_REF] Ferreira | A fauna miocénica da ilha de Santa Maria (Açores)[END_REF][START_REF] Zbyszewski | La faune miocène de l'île de Santa Maria (Açores)[END_REF]Ávila et al., 2015b). The extinct species formerly known as D. jomnitanus is reported from the Miocene of France [START_REF] Gagnaison | Le site paléontologique du Grand Morier (Pont-Boutard, Indre-et-Loire, France): contexte géologique et détail biostratigraphique des formations cénozoïques à partir des assemblages de vertébrés fossiles[END_REF], Portugal [START_REF] Zbyszewski | Os peixes miocénicos portugueses[END_REF][START_REF] Jonet | L'helvétien du Penedo et sa faune ichthyologique[END_REF] and the Mediterranean Sea [START_REF] Vicens | Vertebrats fòssils (Pisces i Reptilia) del Burdigalià de cala Sant Vicenç (Pollença, Mallorca)[END_REF], and from the Pliocene of the Azores (Santa Maria Island) [START_REF] Zbyszewski | Os peixes miocénicos portugueses[END_REF][START_REF] Ferreira | A fauna miocénica da ilha de Santa Maria (Açores)[END_REF][START_REF] Zbyszewski | La faune miocène de l'île de Santa Maria (Açores)[END_REF]. Extinct Pagrus species are reported from Mio-Pliocene sediments from the Mediterranean Sea and from Europe [START_REF] Arambourg | Les poissons fossiles d'Oran. Matériaux pour la carte géologique de l´Algérie[END_REF][START_REF] Bauzá | Nuevas aportaciones al conocimiento de la ictiología del Neógeno catalano-balear[END_REF]Menesini, 1969;[START_REF] Bauzá | Contribución al conocimiento de la fauna ictiológica del Neógeno Catalano Balear[END_REF][START_REF] Jonet | Notes d'ichthyologie Miocene Portugaise[END_REF][START_REF] Antunes | Vertébrés (crocodiliens, poissons) du Miocène marin de l'Algarve occidentale[END_REF].

Family LABRIDAE Cuvier, 1816

Tribe SCARINI Rafinesque, 1810

Genus SPARISOMA Swainson, 1839

Sparisoma cretense (Linnaeus, 1758) Iberian shores and Senegal [START_REF] Abecasis | First record of the Mediterranean parrotfish, Sparisoma cretense in Ria Formosa (south Portugal)[END_REF][START_REF] Randall | Scaridae[END_REF].

Ecology-The parrotfish Sparisoma cretense is an omnivorous daytime feeder species with specialized pharyngeal bones and muscles [START_REF] Bullock | Myologie céphalique de deux poissons perroquets (Teleostei: Scaridae)[END_REF]. It is a sexually dimorphic species that lives on rocky bottoms covered by algae and sea grass beds, where it feeds on algae, sea grass and small invertebrates with its fused, beak-like jaw (Quignard & Pras, 1986;[START_REF] Abecasis | First record of the Mediterranean parrotfish, Sparisoma cretense in Ria Formosa (south Portugal)[END_REF]. This shallow-water species is common to about 50 m depth [START_REF] Guidetti | Spatio-temporal variability in abundance of the parrotfish, Sparisoma cretense, in SE Apulia (SE Italy, Mediterranean Sea)[END_REF].

Stratigraphic and geographic range-This extant species is presently reported from the Mediterranean Sea and from the eastern Atlantic shores of Portugal, the Azores, Madeira, Canary Islands, Cabo Verde and Senegal [START_REF] Abecasis | First record of the Mediterranean parrotfish, Sparisoma cretense in Ria Formosa (south Portugal)[END_REF][START_REF] Randall | Scaridae[END_REF].

A Description-The dentition of Labridae is characterized by subtriangular pharyngeal plates composed by small, contiguous, flattened teeth, which may be rounded or suboval in shape [START_REF] Jonet | Notes d'ichthyologie miocène portugaise. IV -Les Labridae[END_REF]. The two lower pharyngeal plates collected from the Pedraque-pica coquina in Santa Maria Island (Azores), as well as that deposited at MGM collection (Lisbon), conform with both the figures and the description provided by [START_REF] Betancort | Early Pliocene fishes (Chondrichthyes, Osteichthyes) from Gran Canaria and Fuerteventura (Canary Islands, Spain)[END_REF]. [START_REF] Cocchi | Monografia dei Pharyngodopilidae. Nuova famiglia di Pesci Labroidi[END_REF] was the first to describe pharyngeal plates similar to our samples, which were attributed to Labrodon multidens [START_REF] Sacco | Apparati dentali di Labrodon e di Chrysophrys del Pliocene italiano[END_REF], and to L.

pavimentatum [START_REF] Simonelli | Terreni e fossili dell'Isola di Pianosa nel Mar Tirreno[END_REF].

Stratigraphic and geographic range-This extinct species is reported from the Miocene of France [START_REF] Sauvage | Note sur le genre Nummopalatus et sur les espèces de ce genre trouvés dans les terrains tertiaires de la France[END_REF][START_REF] Gagnaison | Le site paléontologique du Grand Morier (Pont-Boutard, Indre-et-Loire, France): contexte géologique et détail biostratigraphique des formations cénozoïques à partir des assemblages de vertébrés fossiles[END_REF], Portugal [START_REF] Jonet | L'helvétien du Penedo et sa faune ichthyologique[END_REF], Poland [START_REF] Bellwood | A review of the fossil record of the Labridae[END_REF], and the Mediterranean [START_REF] Cocchi | Monografia dei Pharyngodopilidae. Nuova famiglia di Pesci Labroidi[END_REF][START_REF] Mas | Presència de Tomistoma cf. lusitanica (Vianna i Moraes, 1945) (Reptilia: Crocodylia) al Burdigalià inferior de Mallorca (Illes Balears, Mediterrània occidental). Implicacions paleoambientals[END_REF]. It is also reported from the western Atlantic, from the Miocene of Costa Rica [START_REF] Laurito | Ictiofauna del mioceno inferior de la localidad de Pacuare de Tres Equis, formación río Banano, provincia de Cartago, Costa Rica, y descripción de un nuevo género y una nueva especie de Scaridae[END_REF] and also from the Pliocene of Morocco [START_REF] Lecointre | Recherches sur le Néogène et le Quaternaire marin de la Côte Atlantique du Maroc, Tome 2 -Paléontologie[END_REF], France (de [START_REF] De Lumley | La stratigraphie du remplissage de la Grotte du Vallonnet[END_REF]) and the Azores (Santa Maria Island: [START_REF] Zbyszewski | Os peixes miocénicos portugueses[END_REF][START_REF] Ferreira | A fauna miocénica da ilha de Santa Maria (Açores)[END_REF][START_REF] Zbyszewski | La faune miocène de l'île de Santa Maria (Açores)[END_REF]this work).

Discussion

During the late Miocene, the once continuous and large tropical Miocene European-West African palaeobiogeographical molluscan province (Ávila et al., 2016) stretched between about 50° N to the equator and further south to Angola [START_REF] Baarli | Miocene to Pleistocene transatlantic dispersal of Ceratoconcha coral-dwelling barnacles and North Atlantic island biogeography[END_REF], at about 15° S (Fig. 8A). The waters around the Azores thus exhibited tropical temperatures during the late Miocene/early Pliocene, with mean annual sea surface temperatures (SSTs) estimated to be about 3.7-6.3°C higher than the present-day 20.6°C (Ávila et al., 2016). The extinct Pliocene fish species reported from the fossiliferous sediments of Santa Maria Island in the Azores (two Sparidae indet. and

Labrodon pavimentatum) add at least three more taxa to an increasing number of known thermophilic taxa that went extinct or locally disappeared from this volcanic oceanic island (as well as from other Atlantic islands/archipelagos) during the pronounced climatic cooling events that characterized the mid-Piacenzian stage, towards the end of the Pliocene at about 3.3-3.6 Ma (or sometime prior), consequence of a global glaciation (the MIS M2; see [START_REF] Lisiecki | A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O A Pliocene-Pleistocene stack of 57 globally distributed benthic δ 18 O records[END_REF]Fig 8B).

Several warm-water species are also known to have disappeared from the Canary Islands at about 4.2-4.1Ma [START_REF] Meco | Evidence for long-term uplift on the Canary Islands from emergent Mio-Pliocene littoral deposits[END_REF]. As a direct consequence of the MIS M2 glaciation, a southward geographical range contraction of the biogeographical provinces took place (Ávila et al., 2016; Fig. 8B). Island across a wide spectrum of phyla: molluscs (5 bivalves, 1 benthic macrogastropod, 1 neustonic gastropod and 4 holoplanktonic gastropods; [START_REF] Janssen | Early Pliocene heteropods and pteropods (Mollusca, Gastropoda) from Santa Maria (Azores, Portugal): systematics and biostratigraphic implications[END_REF][START_REF] Beu | Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae)[END_REF]Ávila et al., 2015, 2016, 2018a), 4 echinoderms [START_REF] Madeira | The fossil echinoids of Santa Maria Island, Azores (Northern Atlantic Ocean)[END_REF], 1 brachiopod [START_REF] Kroh | Novocrania turbinata (Brachiopoda) from the Early Pliocene of the Azores (Portugal)[END_REF], 1 barnacle [START_REF] Winkelmann | Zullobalanus santamariaensis sp. nov., a new late Miocene barnacle species of the family Archeobalanidae (Cirripedia: Thoracica), from the Azores[END_REF] and5 sharks (Ávila et al., 2012). This pattern of extinctions/extirpations from volcanic oceanic islands during the late Pliocene also is reported for other Atlantic archipelagos, such as Madeira (Santos et al., 2012), Canary Islands [START_REF] Meco | Evidence for long-term uplift on the Canary Islands from emergent Mio-Pliocene littoral deposits[END_REF][START_REF] Meco | The Canary record of the evolution of the North Atlantic Pliocene: New 40 Ar/ 39 Ar ages and some notable palaeontological evidence[END_REF][START_REF] Meco | Early Pliocene tracer of North Atlantic and South Pacific sea surface currents: Janthina typica (Bronn, 1860) (Mollusca: Gastropoda)[END_REF][START_REF] Baarli | Miocene to Pleistocene transatlantic dispersal of Ceratoconcha coral-dwelling barnacles and North Atlantic island biogeography[END_REF] and Cabo Verde [START_REF] Baarli | Miocene to Pleistocene transatlantic dispersal of Ceratoconcha coral-dwelling barnacles and North Atlantic island biogeography[END_REF]. flood [START_REF] Blanc | The opening of the Plio-Quaternary Gibraltar Strait: assessing the size of a cataclysm[END_REF]. As attested by the fossil record of their geographical distribution, most of the Actinopterygii (this work) and Chondrichthyes fishes (Ávila et al., 2012) reported from the Pliocene of the Azores are also reported from Pliocene deposits in the northeast Atlantic and the Mediterranean Sea, with some species being reported as well from Pliocene sediments along the north-western shores of Africa, and no

Western Atlantic species reported. This predominantly eastern Atlantic pattern of biogeographical relationships for the Azorean Pliocene marine fauna derives from the sea surface currents set in place by the easterly trade winds that facilitated dispersal of marine species from European shores towards the western Atlantic, a few reaching and colonizing American Atlantic shores [START_REF] Harzhauser | Circum-Mediterranean Oligo-Miocene biogeographic evolution -the gastropods' point of view[END_REF][START_REF] Baarli | Miocene to Pleistocene transatlantic dispersal of Ceratoconcha coral-dwelling barnacles and North Atlantic island biogeography[END_REF] and even the Pacific [START_REF] Meco | Early Pliocene tracer of North Atlantic and South Pacific sea surface currents: Janthina typica (Bronn, 1860) (Mollusca: Gastropoda)[END_REF].

The final closure of the Central American Seaway, caused by re-emergence of the Panamanian land bridge [START_REF] Briggs | Global Biogeography[END_REF] at about 2.8 Ma [START_REF] O'dea | Formation of the Isthmus of Panama[END_REF], and the associated strengthening of the Gulf Stream, altered the north Atlantic system of sea surface circulation. The effect of a stronger Gulf Stream is testified by the shallowwater (<50 m depth) marine molluscs of the Azores, which show a gradual increase in the number of Western-Atlantic related species from 10.0% to 12.3%, when Last Interglacial (MIS 5e) checklists of fossil marine molluscs from the Azores (Ávila et al., 2002, 2009a, 2009b, 2015a) are compared to recent checklists available from this archipelago [START_REF] Ávila | Shallow-water marine molluscs of the Azores: biogeographical relationships[END_REF][START_REF] Cordeiro | Checklist of the littoral gastropods (Mollusca: Gastropoda) from the Archipelago of the Azores (NE Atlantic)[END_REF]; Fig. 8C).

Intensification of the Pleistocene glacial episodes clearly impacted the Azorean fish pool in a similar manner to that described for the marine molluscs (Ávila et al., 2008a, 2008b, 2009a). We here expand on those conclusions, which were based on the MIS 5e mollusc fossil record from Santa Maria Island, and we postulate that range expansions of tropical and subtropical fishes with a Cabo Verdean origin probably occurred during 'windows of opportunity' towards the end of glacial Terminations (i.e.

the short periods of time, c. 6 kyr, between the end of a glacial episode and the inception of a full interglacial episode). During those intervals, some fish species might have been able to reach, colonize and establish viable populations in the Canaries, Madeira and, in less numbers, the Azores Archipelago (Fig. 8D). We further hypothesize that, again in a similar manner to the marine molluscs (Ávila et al., 2008a, 2008b, 2009a), during the subsequent glacial episode, (1) all tropical species with a Cabo Verdean provenience that became established in the northern archipelagos (Azores, Madeira and Canaries) during the previous interglacial were extirpated (Ávila et al., 2019; Fig. 8E), and (2) shallow-water fish species associated with fine sediments were functionally extirpated (i.e. locally disappeared from most volcanic oceanic islands) or their insular populations passed through a 'bottleneck' effect, resulting in a substantial net decrease in population size. The latter event occurs because the finesand habitat is mostly lost whenever sea level falls below the erosive edge of the insular shelf during glacial episodes (Ávila et al., 2008b, 2015a; Fig. 8G-I). The trigger for this outcome resides with the slope of the insular volcanic edifice being so steep below the erosive shelf edge, that it no longer becomes possible to physically retain fine sediments around the island, ultimately being lost to the abyssal depths (Fig. 8H).

Either way, be it post-glacial colonizers or 'bottleneck' glacial survivors, we predict lower genetic diversity of the populations of shallow-water insular fish species associated with sandy bottoms [e.g. the following extant species in the Azores: the European finless eel Apterichtus caecus (Linnaeus, 1758); the wide-eyed flounder Bothus podas (Delaroche, 1809); the striped red mullet Mullus surmuletus Linnaeus, 1758; the Atlantic lizard fish Synodus saurus (Linnaeus, 1758); the greater weever Trachinus draco Linnaeus, 1758; and the pearly razorfish Xyrichtys novacula (Linnaeus, 1758)], when compared with continental populations. This prediction can be tested using molecular tools.

In contrast, fish species associated with algae-covered rocky shores, such as the omnivorous parrotfish Sparisoma cretense, were not affected by the drop in SSTs associated with the inception of glacial episodes, which was estimated at about 2-3°C [START_REF] Crowley | Temperature and circulation changes in the eastern North Atlantic during the last 150,000 years: Evidence from the planktonic foraminiferal record[END_REF] in the region of the Azores. The lineage that led to the two eastern Atlantic species, S. cretense (presently reported from the Mediterranean Sea and from the eastern Atlantic shores of mainland Portugal, the Azores, Madeira, Canaries, Cabo Verde and Senegal; cf. Table 2), and S. strigatum (Günther, 1862) (endemic to Saint Helena and Ascension islands; Table 2), originated at about 10 Ma from a West Atlantic ancestor [START_REF] Bernardi | Molecular systematics, zoogeography, and evolutionary ecology of the Atlantic parrotfish genus Sparisoma[END_REF]. The oldest known fossil specimens of S. cretense were collected in two Pliocene outcrops from Santa Maria Island (Pedra-que-pica and Ponta dos Frades) and dated as 4.78±0.13 to 4.13±0.19 myr in age (Table 1), thus our data are in agreement with the estimates of Bernardi and colleagues (2000).

Last interglacial (MIS 5e) fossils of S. cretense were also collected from a

Pleistocene outcrop (Vinha Velha; cf. Table 1). Today, S. cretense lives as far north as the eastern Atlantic shores of mainland Portugal, where it breeds during the summer, from July to September [START_REF] Abecasis | First record of the Mediterranean parrotfish, Sparisoma cretense in Ria Formosa (south Portugal)[END_REF]Froese & Pauly, 2018), with mean SSTs varying from 17 to 19°C. The present average SSTs range in the Azores from 15° C in the winter, to about 23-24°C in the summer (Ávila et al., 2008c). The gonadosomatic index of S. cretense (which is closely associated with mean temperature) increases in the Azores from June to August and then drops to a minimum in November [START_REF] Afonso | Spatial patterns in reproductive traits of the temperate parrotfish Sparisoma cretense[END_REF]. Hence, although it mainly breeds from mid-July to mid-September, it is possible that this species extends its reproductive activity through October [START_REF] Afonso | Spatial patterns in reproductive traits of the temperate parrotfish Sparisoma cretense[END_REF]. Therefore, in our opinion, neither temperature nor habitat shift were an impediment for the survival of this species in the Azores throughout the last glacial episode. Our view differs from that of previous authors, who suggested that 'the drop of sea temperatures (…) that occurred during the Pleistocene probably resulted in mass extinctions' (of fishes) and so 'most of the organisms now present would have reached the Azores in the last 17,000 years' [START_REF] Santos | Marine research, resources and conservation in the Azores[END_REF]. Our reasoning also contradicts the conclusions of [START_REF] Domingues | Tropical fishes in a temperate sea: evolution of the wrasse Thalassoma pavo and the parrotfish Sparisoma cretense in the Mediterranean and the adjacent Macaronesian and Cape Verde Archipelagos[END_REF], who stated that 'persistence of (…) S. cretense in the Azores archipelago during the Pleistocene glaciations is difficult to admit'. Moreover, the very abundant and well-studied MIS 5e (i.e. Last Interglacial)

fossil record from Santa Maria Island disproves the conclusions of these former authors.

The finding of fossil pharyngeal plates belonging to S. cretense in MIS 5e sediments does not necessarily exclude the hypothesis that this species locally disappeared during the Last Glaciation, only to recolonize the archipelago postglacially. Nevertheless, we consider it more plausible to argue that such extirpation did not happen, taking in consideration the following: (1) detailed studies on the Azorean MIS 5e and recent marine molluscs showed that the drop of the SSTs during the Last Glaciation only affected two groups of species: the tropical species that reached the Azores probably during a 'window of opportunity' associated with the final phase of Termination 2, and bivalve species associated to fine-sand sediments; both groups were extirpated (Ávila et al., 2008a, 2008b, 2009b, 2015a); (2) as temperature is known to play a key role on marine fish species biology [START_REF] Pepin | Effect of temperature and size on development, mortality, and survival rates of the pelagic early life history stages of marine fish[END_REF][START_REF] Van Der Kraak | Temperature effects on the reproductive performance of fish[END_REF][START_REF] Pankhurst | Cold and dark or warm and light: variations on the theme of environmental control of reproduction[END_REF][START_REF] Dolomatova | Role of temperature in regulation of the life cycle of temperate fish[END_REF][START_REF] Poloczanska | Responses of Marine Organisms to Climate Change across Oceans[END_REF] and in light of the premises pointed above, the drop of SSTs was not sufficient enough to severely affect the survival, growth and reproduction of the temperate parrotfish S. cretense in the Azores during the Last Glacial episode; (3) finally, if S. cretense was a post-glacial colonizer of the Azores, the genetic diversity of the Azorean populations should be low, in comparison with southern Madeiran populations (postulated to have not been affected by the drop of SSTs), but that is not the case, as pointed out by [START_REF] Domingues | Tropical fishes in a temperate sea: evolution of the wrasse Thalassoma pavo and the parrotfish Sparisoma cretense in the Mediterranean and the adjacent Macaronesian and Cape Verde Archipelagos[END_REF]. Thus, combining our palaeontological data with ecological and genetic data from other authors [START_REF] Abecasis | First record of the Mediterranean parrotfish, Sparisoma cretense in Ria Formosa (south Portugal)[END_REF][START_REF] Afonso | Spatial patterns in reproductive traits of the temperate parrotfish Sparisoma cretense[END_REF][START_REF] Domingues | Tropical fishes in a temperate sea: evolution of the wrasse Thalassoma pavo and the parrotfish Sparisoma cretense in the Mediterranean and the adjacent Macaronesian and Cape Verde Archipelagos[END_REF], we believe the most plausible scenario is the survival of most (if not all) temperate and subtropical fish species in the Azores during the Last Glacial episode, so long as their ecological traits are not tied on sandy habitats.

This contribution expands the number of Pliocene fishes reported from the Azores to at least 11 taxa: seven taxa of Chondrichthyes (Ávila et al., 2012)

Conclusions

The genus Sparisoma Swainson, 1839 is reported, herein, for the first time in the fossil record. The discovery of several pharyngeal plates of S. cretense on Pliocene and on MIS 5e sediments (Last Interglacial) of Santa Maria Island challenges former authors [START_REF] Briggs | Marine zoogeography[END_REF][START_REF] Santos | Marine research, resources and conservation in the Azores[END_REF][START_REF] Domingues | Historical population dynamics and demography of the eastern Atlantic pomacentrid Chromis limbata (Valenciennes, 1833)[END_REF][START_REF] Domingues | Tropical fishes in a temperate sea: evolution of the wrasse Thalassoma pavo and the parrotfish Sparisoma cretense in the Mediterranean and the adjacent Macaronesian and Cape Verde Archipelagos[END_REF] who argued that mass extinctions affected the shallow-water marine fauna of the Azores during the course of the Last Glaciation and that, as a consequence, most of the present Azorean marine species colonized the area during the last 17-18 kyr. A multidisciplinary approach, merging our palaeontological data with ecological and genetic data, offers an alternative, more plausible explanation, suggesting that most (if not all) of the Azorean shallow-water subtropical and temperate marine species living in the archipelago during the Last Interglacial (and probably in previous interglacials as well) and associated to non-mobile sediments (e.g., rocky shores, covered or not by algae), were not affected by the drop of the SSTs during the Last Glacial episode.

Finally, we also predict that the only marine fish species that were extirpated from the Azores during the course of the Last Glaciation were those associated with fine sand (Fig. 8G-I), and the thermophilic species that colonized the archipelago during the Last Interglacial/Termination 2 'window of opportunity' (Fig. 8D-F).

Whether fish species ecologically associated with fine sediments and presently living in the Azores are post-glacial colonizers or 'bottleneck' survivors from the Last Glaciation should be assessed by genetic tools, as we anticipate low genetic diversity of the Azorean populations, when compared with continental counterparts. coquina ever described from a volcanic oceanic island, with a total estimated area of >23,400 m 2 and a total thickness for the sediments of 10-11 m (Ávila et al., 2015b).

[Intended for page width]. (Rebelo et al., 2016a;[START_REF] Uchman | The trace fossil Diopatrichnus santamariaensis nov. isp. -a shell armoured tube from Pliocene sediments of Santa Maria Island, Azores (NE Atlantic Ocean)[END_REF], Figueiral (Ávila et al., 2018), Pedra-que-pica (Ávila et al., 2015b), West fault of Malbusca [START_REF] Uchman | The trace fossil Diopatrichnus santamariaensis nov. isp. -a shell armoured tube from Pliocene sediments of Santa Maria Island, Azores (NE Atlantic Ocean)[END_REF], Cré [START_REF] Janssen | Early Pliocene heteropods and pteropods (Mollusca, Gastropoda) from Santa Maria (Azores, Portugal): systematics and biostratigraphic implications[END_REF], Prainha and Vinha Velha (Ávila et al., 2010, 2015a). [Intended for page width]. Interglacial, a subset of marine subtropical species expands their geographical ranges towards higher latitudes (red arrow), reaching temperate archipelagos and establishing viable populations in those islands (e.g. small red star in D). In a similar way, a subset of marine temperate species expands their geographical ranges towards higher latitudes, reaching boreal/arctic archipelagos and establishing viable populations as well (blue arrow). E: During the course of the Last Glacial episode, the thermophilic species that established on temperate islands are extirpated and it is expected that a subset of marine temperate species (small blue circles), adapted to cool temperatures may expand their geographical ranges towards lower latitudes, reaching subtropical archipelagos and establishing viable populations. F: the subsequent episode of global warming that led to the present interglacial, extirpates the cold-adapted species that reached subtropical islands during the previous glacial episode, and range expansion of species towards higher latitudes is documented. G-I:

Mobile sediment response to glacio-eustatic sea level fluctuations (Ávila et al., 2008b, 2010). G: During the Last interglacial (MIS 5e), as a result of marine and fluvial erosion, sediments are transported to the island shelf where they accumulate between the shoreline angle (i.e., the angle between the cliff of the island and the shore platform)

and the erosive shelf edge. H: The inception of sea-level lowstands during the Last Glacial episode, promotes the remobilization and transport downslope of sediments

  Abbreviations DBUA-F: fossil collection of the Department of Biology of the University of the Azores (Portugal). LAQ-F: fossil collection of the Liceu Antero de Quental, Ponta Delgada, São Miguel Island (Azores, Portugal). MGM: fossil collection of the former Museu Geológico e Mineiro, now Museu Geológico, LNEG, Lisbon (Portugal).

Figure

  Figure 5A-Q

Figure 6

 6 Figure 6

Figure 7

 7 Figure 7

  Between 5.3 and 4.13 Ma, the protoisland of Santa Maria probably was entirely destroyed, originating a large seamount where marine sediments rich in organic debris were deposited. In a broader palaeoceanographical context, the pattern of sea surface and bottom circulation in the area should have been different from the present day, as the connection between the Atlantic and the Pacific oceans was still open at the Central American Seaway[START_REF] Garcia-Castellanos | Catastrophic flood of the Mediterranean after the Messinian salinity crisis[END_REF], and the Gibraltar Seaway had just reopened at 5.33 Ma, in an event known as the Zanclean or post-Messinian

Figure 1 .

 1 Figure 1. A: Location of the Azores Archipelago in the NE Atlantic, and location and

Figure 2 .

 2 Figure 2. Aerial (drone) views of the fossiliferous outcrops from Santa Maria Island. A-

Figure 3 .

 3 Figure 3. Aerial (drone) views of the Pliocene fossiliferous outcrops from Santa Maria

Figure 4 .

 4 Figure 4. Stratigraphic columns of the studied outcrops: Malbusca (Rebelo et al.,

Figure 5 .

 5 Figure 5. Actinopterygian fishes from Early Pliocene deposits of Santa Maria Island

Figure 6 .FiguresFigure 1 .

 61 Figure 6. Actinopterygian fishes from Early Pliocene (DBUA-F 825, 1069, 1214) and Late

Figure 2 .

 2 Figure 2. Aerial (drone) views of the fossiliferous outcrops from Santa Maria Island. A-

Figure 3 .Figure 4 .

 34 Figure 3. Aerial (drone) views of the Pliocene fossiliferous outcrops from Santa Maria

Figure 8 .

 8 Figure 8. A-C: NE Atlantic Biogeographic Molluscan Provinces from late Miocene to

  Sparisoma in the Atlantic Ocean and the Mediterranean Sea (Table2). Of these, only 3 species are reported for the Eastern Atlantic: two tropical species (Sparisoma choati Rocha, Brito & Robertson, 2012, reported for Cabo Verde, São Tomé and Príncipe and to the tropical west African shores; S. frondosum (Agassiz, 1831), endemic to Cabo Verde); and the eurythermic S. cretense, with a wider geographical distribution, occurring in all the Macaronesian archipelagos, the Mediterranean Sea,

	(DBUA-F 1030), 2.82 cm (DBUA-F 1214-1), 2.84 cm (DBUA-F 1214-2) and an inferred 3.82
	cm (DBUA-F 825 broken specimen measuring 2.84 cm). The fragmentary tooth plate
	collected at Pedra-que-pica (DBUA-F 1069) measures 1.22 cm.
	Today, there are 15 species of

). Its lower pharyngeal plate was 4.11 cm wide, which compares with those from fossil material, which measured 2.62 cm wide

  search for fossil Sparisoma species on the PaleoBiology Database and on[START_REF] Bellwood | A review of the fossil record of the Labridae[END_REF] yielded no occurrences. With the exception of otolithes from the Late Eocene of France referred to Sparisoma[START_REF] Nolf | Les otolithes de téléosténs éocènes d'Aquitaine (sud-ouest de la France) et leur intérêt stratigraphique[END_REF] but see remarks by[START_REF] Bellwood | A review of the fossil record of the Labridae[END_REF], is herein reported from the Pliocene (Pedra-que-pica and Ponta dos Frades outcrops) and Pleistocene (Vinha Velha outcrop; Last Interglacial, MIS 5e) of Santa Maria

	Island, Azores.
	Tribe HYPSIGENYINI Günther, 1861
	Genus LABRODON Gervais, 1857
	† Labrodon pavimentatum Gervais, 1857

in whose opinion these otoliths are not secure evidence of Sparisoma], this genus is reported herein for the first time from the fossil record based on dental remains. S. cretense

:

  Carcharias acutissima (Agassiz, 1833), Carcharhinus cf. leucas (Valenciennes, 1839 in Müller and Henle, 1839-1841), Cosmopolitodus hastalis (Agassiz, 1833), Isurus oxyrinchus

	archipelagos over 1,100 km apart is understandable if it is taken into consideration
	that during the Pliocene both archipelagos were part of the same Atlantic
	biostratigraphic molluscan province [the Pliocene Mediterranean-West African
	Province of Ávila et al. (2016); see Fig.8B] sharing similar tropical palaeoclimatic
	conditions.

Rafinesque, 1810, Otodus (Megaselachus) megalodon (Agassiz in Charlesworth, 1837), Notorynchus primigenius (Agassiz, 1833) and Paratodus benedenii (Le Hon, 1871); and four of Actinopterygii (this work): at least two Sparidae indet. taxa, Labrodon pavimentatum and Sparisoma cretense. Most of these are also reported for the Pliocene of Canaries (Betancort et al., 2016), the exceptions being Carcharhinus cf. priscus (Agassiz, 1843), Diodon scillae Agassiz, 1843 and Galeocerdo cf. aduncus Agassiz, 1843, only reported for Canary Islands; and Sparidae indet., N. primigenius and S. cretense, only reported for the Azores. The high number of shared species on

Table 1 .

 1 Relative age of the outcrops (in millions of years) from Santa Maria Island (Azores) containing fossil remains of Actinopterygii fishes.

	Outcrop	Age (Ma)	Bed	Inferred depth of deposition (m)	Number of teeth/pharyngeal plates per species Sparisoma Labrodon Sparidae cretense pavimentatum
	Cré	4.78 ± 0.13 to 4.13 ± 0.19 Sandstone	?	4
	Figueiral	4.78 ± 0.13 to 4.13 ± 0.19 Sandstone	?	1
	Ponta dos Frades	4.78 ± 0.13 to 4.13 ± 0.19 Sandstone	?		6
	Pedra-que-pica	4.78 ± 0.13 to 4.13 ± 0.19 Coquina	-40	26	1	2
	Malbusca	4.32 ± 0.06 to 4.02 ± 0.06 Sandstone	-60	17
	West fault of Malbusca	4.32 ± 0.06 to 4.02 ± 0.06 Sandstone	-60	2
	Vinha Velha	Last Interglacial (MIS 5e) Sand		+1 to +2		1

Table 2 .

 2 Present geographical distribution of the genus Sparisoma in the Atlantic Ocean and the Mediterranean Sea. AZO -Azores Archipelago; 1101 MAD -Madeira Archipelago; SEL -Selvagens Archipelago; CAN -Canaries Archipelago; CAB -Cabo Verde Archipelago; STP -São Tomé and 1102 Príncipe Archipelago; IBE -Atlantic Iberian shores from Finisterra south to the Straits of Gibraltar; MED -Mediterranean Sea; TWAF -Tropical 1103 west African shores, from Cape Blanc (Senegal) south to Angola; NWA -Atlantic coast of Northwest Africa, from the Straits of Gibraltar south 1104 to Senegal; ASC -Ascension Island; STH -Saint Helena Island; SWA -Southwest Atlantic, including Brazil and its oceanic islands; WAT -1105 Western Atlantic, including the Caribbean Sea. 1106

Table 3 .

 3 Taxa/species reported from the Pliocene sediments of Santa Maria Island and that are presently extinct or were extirpated (local disappearances) from the marine fauna of the island during the global climate deterioration that characterizes the late

	Pliocene.
	Phylum	Taxa

Acknowledgments

We thank Direcção Regional da Ciência e Tecnologia (Regional Government of the Azores), FCT (Fundação para a Ciência e a Tecnologia) of the Portuguese Government, and Câmara Municipal de Vila do Porto for financial support, and acknowledge the field assistance of Clube Naval de Santa Maria and Câmara Municipal de Vila do Porto.

We are grateful to the organizers and participants of all editions of the International Workshop Palaeontology in Atlantic Islands who helped with fieldwork (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017).

We thank F. Couto (Hobby Factor) for the aerial/drone photos. We thank M. Ramalho and J. Anacleto (Museu Geológico, LNEG, Lisbon), for allowing access to their historical collections. SPA acknowledges his research contract (IF/00465/2015) funded by the Portuguese Science Foundation (FCT). LB acknowledges her PhD Grant from FCT (SFRH/BD/135918/2018). CSM is benefiting from a PhD grant M3.1.a/F/100/2015 from Fundo Regional para a Ciência e Tecnologia (FRCT). This research also received substantial support from the SYNTHESYS Project (http://www.synthesys.info/), which is financed by the European Community Research Infrastructure Action under the FP7 'Capacities' Program: SPA studied fossil collection at the Museum für Naturkunde, Berlin (DE-TAF-1071). This work also was supported by FEDER funds through the Operational Programme for Competitiveness Factors -COMPETE, and by National Funds through FCT under the UID/BIA/50027/2013, POCI-01-0145-FEDER-006821 and under DRCT-M1.1.a/005/Funcionamento-C-/2016 (CIBIO-A) project from FRCT. This work was also supported by FEDER funds (in 85%) and by funds of the Regional Government of the Azores (15%) trough Programa Operacional Açores 2020, in the scope of the project "AZORESBIOPORTAL -PORBIOTA": ACORES-01-0145-FEDER-000072.

Author Contributions

S.P.A and R.V. designed the research plan. S.P.A., P.M., R.C. and R.V. collected the fossil material. C.S.M. constructed all figures. S.P.A., M.E.J and R.V. wrote the manuscript, with input from all authors, who discussed and commented on the manuscript.

Additional Information

Competing Interests: The authors declare no competing interests.


Haifeng Li

Arnaud J Perez

Beata Taudul

Teak D Boyko

John W Freeland

Marie- Liesse Doublet

Jean-Marie Tarascon

Jordi Cabana

Elucidation of active oxygen sites upon delithiation of Li 3 IrO 4

Transformational increases in the storage capacity of battery cathodes could be achieved by tapping into the redox activity at oxide ligands in addition to conventional transition metal couples. Yet the key signatures that govern such lattice oxygen redox (LOR) have not been ascertained. Li 3 IrO 4 has the largest reversible LOR, rendering it a unique model system. Here, Xray spectroscopy and computational simulations reveal that LOR in Li 3 IrO 4 is selectively compensated via O sites with 3 lone pairs, which are activated by Li/Ir disorder. The 2-electron LOR can be reversed to regenerate the initial state without unlocking competing bulk reactions observed in many other compounds. We uncover an intricate interplay between stoichiometry, O coordination and non-bonding states in LOR and pinpoint spectroscopic signatures. This interplay is indispensable to design materials with 3d metals that fulfill the promise of LOR to overcome the bottlenecks of current cathodes for future implementation in practical batteries.

The manipulation of the redox chemistry of the transition metal (TM)oxide bond in solids enabled the advent and dominance of Li-ion batteries as storage devices in the wireless revolution and as rapidly expanding alternative in transportation and the grid, [START_REF] Dunn | Electrical Energy Storage for the Grid: A Battery of Choices[END_REF] propelling our push away from the fossil fuel paradigm. Ironically, the redox processes of layered Li[TM]O 2 (TM = Co, Ni, Mn, among others) cathodes, concurrent with Li (de)intercalation, also determine the current roadblocks to transformational energy density that could lead them to rule these mass markets as well. [START_REF] Goodenough | Challenges for Rechargeable Li Batteries[END_REF] Full delithiation cannot be achieved without severely compromising stability, [START_REF] Mizushima | Li x CoO 2 (0 < x < -1): A new cathode material for batteries of high energy density[END_REF][START_REF] Lu | Layered Li[Ni x Co 1-2x Mn x ]O 2 Cathode Materials for Lithium-Ion Batteries[END_REF][START_REF] Tsutomu | Layered Lithium Insertion Material of LiCo 1/3 Ni 1/3 Mn 1/3 O 2 for Lithium-Ion Batteries[END_REF][START_REF] Yoshizawa | An application of lithium cobalt nickel manganese oxide to high-power and high-energy density lithium-ion batteries[END_REF] because the covalent TM-O bond, conventionally labeled as the formal oxidation state of TM, becomes too oxidized. To disrupt the constraints of such "cationic redox" (CR, involving TM nd-O 2p mixed states), researchers have sought to tap into the redox activity of oxide anions. In particular, layered oxides with an over-stoichiometry of Li, Li[Li x TM 1-x ]O 2 , have attracted considerable excitement because their capacities approach 300 mAhg -1 . [START_REF] Lu | Layered Cathode Materials Li[END_REF][START_REF] Johnson | The significance of the Li 2 MnO 3 component in 'composite' xLi 2 MnO 3 •(1-x)LiMn 0.5 Ni 0.5 O 2 electrodes[END_REF][START_REF] Thackeray | Comments on the structural complexity of lithium-rich Li 1+x M 1-x O 2 electrodes (M = Mn, Ni, Co) for lithium batteries[END_REF][START_REF] Thackeray | Li 2 MnO 3 -stabilized LiMO 2 (M = Mn, Ni, Co) electrodes for lithium-ion batteries[END_REF][START_REF] Johnson | Synthesis, Characterization and Electrochemistry of Lithium Battery Electrodes: xLi 2 MnO 3 •(1x)[END_REF] This vertical step in performance is proposed to stem from combining CR and participation of non-bonding states of O (termed as "lattice O redox", LOR). [START_REF] Rozier | Review-Li-Rich Layered Oxide Cathodes for Next-Generation Li-Ion Batteries: Chances and Challenges[END_REF][START_REF] Oishi | Direct observation of reversible oxygen anion redox reaction in Li-rich manganese oxide, Li 2 MnO 3 , studied by soft X-ray absorption spectroscopy[END_REF] Despite their enhanced electrochemical activity, these cathode materials suffer from unacceptable energy efficiency and degradation. [START_REF] Luo | Charge-compensation in 3d-transitionmetal-oxide intercalation cathodes through the generation of localized electron holes on oxygen[END_REF][START_REF] Yabuuchi | Detailed Studies of a High-Capacity Electrode Material for Rechargeable Batteries[END_REF][START_REF] Jacquet | Charge Transfer Band Gap as an Indicator of Hysteresis in Li-Disordered Rock Salt Cathodes for Li-Ion Batteries[END_REF][START_REF] Assat | Fundamental interplay between anionic/cationic redox governing the kinetics and thermodynamics of lithium-rich cathodes[END_REF] The most reversible cases involve heavy metals, such as Ir [START_REF] Mccalla | Visualization of O-O peroxo-like dimers in high-capacity layered oxides for Li-ion batteries[END_REF][START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF][START_REF] Pearce | Evidence for anionic redox activity in a tridimensional-ordered Li-rich positive electrode β-Li 2 IrO 3[END_REF] which are not economically viable for use in a battery.

It is imperative to achieve a holistic understanding of LOR to design materials containing base metals with high storage capacity that is efficient and reversible. In terms of electronic structure, a key descriptor is an O/TM ratio greater than 2, [START_REF] Seo | The structural and chemical origin of the oxygen redox activity in layered and cation-disordered Li-excess cathode materials[END_REF][START_REF] Saubanère | The intriguing question of anionic redox in high-energy density cathodes for Li-ion batteries[END_REF] which generates O 2p states that are only connected to Li through electrostatic interactions, rendering them essentially nonbonding. Hong et al. proposed that additional active non-bonding states must be generated in

Li 2 TMO 3 (Li[Li 1/3 TM 2/3 ]O 2
) by the creation of in-plane defects [START_REF] Gent | Coupling between oxygen redox and cation migration explains unusual electrochemistry in lithium-rich layered oxides[END_REF] through out-of-plane cationic migration [START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF] Xie et al. further predicted that the greatest enhancement could be achieved in [START_REF] Xie | Requirements for reversible extra-capacity in Lirich layered oxides for Li-ion batteries[END_REF] Indeed, the most striking activity was accomplished with Li 3 IrO 4 (Li[Li 1/2 Ir 1/2 ]O 2 ), with reversible cycling of 2 mol Li to form a very highly oxidized phase which does not fit conventional CR, [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] the highest extent of LOR per mol TM of any known compound.

Li 3 TMO 4 (Li[Li 1/2 TM 1/2 ]O 2 ).
Prior evidence indicates that no out-of-plane migration of Ir occurs [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] because it faces a high barrier in a layered structure. [START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF] Consequently, the reasons that make Li 3 TMO 4 in general, and Ir in particular, so special remain to be elucidated. Since the number of holes per O site is critical to define reactivity, [START_REF] Ben Yahia | Unified picture of anionic redox in Li/Na-ion batteries[END_REF] it is important to experimentally ascertain whether key O states underpin the unique ability of Li 3 IrO 4 to undergo LOR.

Having established the redox inactivity of Ir earlier, [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] here, we follow the changes of O in the highly oxidized states reached via deintercalation of Li 3 IrO 4 . A combination of X-ray spectroscopy (Figure 1) and computational modeling uncovered the existence of two nonequivalent O sites showing different involvement in the reaction, with a critical role of the site with 3 lone pairs. Reintercalation reproduces the initial electronic structure, contributing to low voltage hysteresis. Li 3 IrO 4 reacts through LOR without producing the RIXS signatures commonly associated with it, [START_REF] Gent | Coupling between oxygen redox and cation migration explains unusual electrochemistry in lithium-rich layered oxides[END_REF][START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF][START_REF] Xu | Elucidating anionic oxygen activity in lithium-rich layered oxides[END_REF][START_REF] Yang | Anionic and cationic redox and interfaces in batteries: Advances from soft X-ray absorption spectroscopy to resonant inelastic scattering[END_REF] suggesting that multiple possible pathways of LOR may exist. The findings solidify our understanding of unconventional, yet chemically reversible ligand reactivity transcending classical CR paths.

Electrochemistry and spectroscopy of the pristine state. Li 3 IrO 4 can be oxidized to, nominally, Li 1 IrO 4 through a long plateau at 3.9-4.0 V vs Li + /Li 0 (Figure 1a), a process with high electrochemical reversibility. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] Further oxidation to 4.5 V induces amorphization to "a-IrO 3 ", an irreversible step inducing notable voltage hysteresis and capacity loss upon subsequent reduction. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] Perez et al. reported a minor shift of the Ir L III -edge XAS to high energy in the initial stages of deintercalation, with the position staying largely constant thereafter, [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] indicating the involvement of O in the charge compensation. To evaluate this hypothesis, electrodes were harvested at representative states (Figure 1a).

The O K-edge X-ray absorption spectroscopy (XAS) of Li 3 IrO 4 (Figure 1c) exhibits three features at 527.9, 529.1, and 531.7 eV, corresponding to transitions to unoccupied O 2p-Ir 5d hybridized states (Supplementary Note 1). The broad features above 535 eV arise from O 2p-Ir 6s, p states and the multiple scattering events upon photoionization. The spectrum was measured in partial fluorescence yield (PFY) to maximize signals from the interior of the electrode because the surface signals (total electron yield, TEY) were dominated by a peak at ~533.7 eV (Figure S2) ascribed to Li 2 CO 3 impurities. [START_REF] Qiao | Soft x-ray irradiation effects of Li 2 O 2 , Li 2 CO 3 and Li 2 O revealed by absorption spectroscopy[END_REF] The surface showed a notable sensitivity to air, with batches where contamination was enough to produce these signals, albeit at much lower relative intensity, even in fluorescence yield measurements (Figure S2).

The O pre-edge (< 535 eV) signals reflect a splitting of the O 2p-Ir 5d states in a distorted octahedral ligand field, with π and σ interactions appearing below and above 530 eV, respectively. These interactions would give rise to t 2g and e g states, respectively, in an undistorted octahedral field; they will be labelled as such for brevity. The qualitatively lower pre-edge intensity below than above 530 eV reflects the ratio of unoccupied states in the lowspin d 4 configuration of Ir(V) and differences in the extent of overlap between Ir 5d and O 2p states. Measurements of zero-field cooled magnetization between 25 and 300 K showed weak paramagnetism with μ eff = 0.84 μ B /Ir (Figure S1b), similar to other Ir(V) phases (Supplementary Note S4) [START_REF] Cao | Novel Magnetism of Ir 5+ (5d 4 ) Ions in the Double Perovskite Sr 2 YIrO 6[END_REF][START_REF] Terzic | Evidence for a low-temperature magnetic ground state in double-perovskite iridates with Ir 5+ (5d 4 ) ions[END_REF] and consistent with previous EPR measurements. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] The additional splitting observed in the O pre-edge, around 1.2 eV, appeared to be beyond the range expected from spin-orbit coupling, which has been reported as frustrated in other Ir(V) oxides. [START_REF] Terzic | Evidence for a low-temperature magnetic ground state in double-perovskite iridates with Ir 5+ (5d 4 ) ions[END_REF] Its origin was probed by X-ray emission spectroscopy (XES) through selective excitations at 527.85 and 529.05 eV (Figure 1b). XES probes transitions from occupied O 2p states to fill the 1s core-hole (Supplementary Note 2). Excitation at 529.05 eV induced a blueshift of 0.6 eV on the main emission peak compared to 527.85 eV excitation, accompanied by a broadening of the shoulder at higher energy (Figures 1b andS3). This behavior indicates the existence of two different non-equivalent sites for O in the crystal structure, connected to two and one distorted IrO 6 octahedra. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] The blueshift was much smaller than the splitting of the two corresponding pre-edge peaks, reflecting a different core-hole screening for the two sites.

Excitations at higher energy only induced subtle shifts reflecting the balance between exciting the two O sites with different binding energy.

Two and three localized electron lone pairs, respectively, were revealed by the computed Electron Localization Functions (ELF) of the two O sites (O 2LP and O 3LP , hereafter, where LP = electron lone pairs, Figure 2a), in line with the octet rule (Figure S4). [START_REF] Ben Yahia | Unified picture of anionic redox in Li/Na-ion batteries[END_REF] The lone pairs of O 3LP lie higher than O 2LP in the computed density of states of Li 3 IrO 4 (Figure 2b), in agreement with their computed Madelung potentials (

). The simulated XAS, assuming a structure with Li/Ir ordering in the transition metal layers, qualitatively reproduced the three main regions observed experimentally (Figure 2c). The significant splitting of the hybridized t 2g states could only be obtained when the core-level shift was included in the calculations, and became even more pronounced when Li/Ir intralayer disorder was introduced, according to the experimentally observed structure. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] Such disorder affects the distribution of O 2LP and O 3LP in each IrO 6 octahedron (Table S1), which splits the bands and shrinks the band gap (Figure 2b). All in all, the XAS spectrum can be viewed as the sum of the individual spectra of O 3LP and O 2LP , with the former being responsible for the features at lower energy, in perfect agreement with its higher electronic charge (i.e. less covalent bonds to Ir). increased from pristine to x = 2 (Figure 1e), but remained comparatively unchanged between x = 2 and x = 1 (Figure 1e). Above 530 eV, the onset of the third pre-edge peak was static (Figures 1c and1d), but its area progressively increased through a significant broadening toward higher energy (Figure 1c). The net result was a rather proportional increase in its integrated intensity with delithiation (Figure 1f). These observations indicate an increase in unoccupied states with O character upon oxidation.

Changes at O states upon

Computational analysis of the changes in O K-edge XAS (Figure 3) revealed that, upon oxidation from pristine to x = 2, the existence of Li/Ir intralayer disorder shifts the charge compensation from only depleting O 2p-Ir 5d states (i.e., classical formal oxidation of cations, CR) in the ideal lattice to also significant involving one of the three lone pairs of O 3LP (Figure S6). This prediction is consistent with CR only being observed up to Li 2.5 IrO 4 via Ir L III -edge XAS. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] This effect can be visualized in the ELFs of one of the possible disordered structures of shorten their Ir-O length upon lone-pair depletion, to below 1.9 Å, [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] most likely leading to a higher bond order, as previously proposed for Li 2-x Ir 1-y Sn y O 3 . [START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF] The collapse of the two signals below 530 eV is ascribed to all O becoming electronically equivalent (Figure 3). The remaining shoulder at low energy in the experimental spectra could arise from the incomplete oxidation of the electrode to x = 1, since the experimental cut-off was set assuming a faradaic efficiency of 100%.

The O K-edge XAS of the electrode oxidized to 4.5 V, associated with the irreversible transition to amorphous IrO 3 , 19 possessed a single peak at 528.6 eV, with no shoulders at lower energy and a significant asymmetry spanning toward 530 eV (Figure 1c). The integrated (relative) area under this single signal was slightly greater than x = 1 (~2.4%, Figure 1e). Similarly, the centroid of the feature between 530 and 535 eV blue shifted by 0.3 eV with an increase in the integrated area that qualitatively followed the trend starting from x = 3 (Figure 1f). Blueshifts with respect to x = 1 were also observed in both the inflection point in the main absorption edge (Figure S5) and all O Kα emission spectra (Figure 1b). These changes indicate a shift of the O 1s level to lower energy, signifying an increased Z eff , [START_REF] Shadle | Ligand K-Edge X-ray Absorption Spectroscopy as a Probe of Ligand-Metal Bonding: Charge Donation and Covalency in Copper-Chloride Systems[END_REF][START_REF] Solomon | Ligand K-edge Xray absorption spectroscopy: covalency of ligand-metal bonds[END_REF] consistent with the strong participation of the anions in the compensation of the process of oxidation. Overall, all spectra became broader at this high state of charge, as expected from amorphization. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] Chemical reversibility of LOR. While other oxides have conclusively been shown to display unconventional LOR activity upon delithiation, many display chemical hysteresis, whereby subsequent reduction does not return the compound to its original crystal and/or electronic structure. [START_REF] Jacquet | Charge Transfer Band Gap as an Indicator of Hysteresis in Li-Disordered Rock Salt Cathodes for Li-Ion Batteries[END_REF][START_REF] Assat | Fundamental interplay between anionic/cationic redox governing the kinetics and thermodynamics of lithium-rich cathodes[END_REF][START_REF] Oishi | Charge compensation mechanisms in Li 1[END_REF][START_REF] Yabuuchi | High-capacity electrode materials for rechargeable lithium batteries: Li 3 NbO 4 -based system with cation-disordered rocksalt structure[END_REF][START_REF] Li | Li 3 RuO 4 Polymorphs[END_REF][START_REF] Hu | Evolution of redox couples in Li-and Mn-rich cathode materials and mitigation of voltage fade by reducing oxygen release[END_REF] Since the final step of O 2 loss is irreversible, [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] we will only elaborate on the reduction of an electrode charged to x = 1, or LiIrO 4 . Its reduction to 2.6 V produced a capacity equivalent to 1.5 mol of Li, and almost completely restored the O K-edge XAS and O Kα XES to the pristine state (Figure 1). A shoulder at high energy in the XES, which vanished gradually upon delithiation, became prominent again after, suggesting that it is correlated to the (de)intercalation process. All in all, the O p states before and after a full cycle were almost identical.

Implications for the existence and mechanism of LOR. The evolution of the O spectra

clearly demonstrates the participation of ligand states in the charge compensation of the delithiation of Li 3 IrO 4 . In particular, the results reveal the shifting contribution from O 3LP , which are at higher energy in the pristine state, to O 2LP as the delithiation progressed beyond 1 mol of Li. In the preceding study by Perez et al., Ir L III -edge XAS of the same states revealed only a minor change in the early stages of the reaction, which was essentially arrested after about 0.5 mol of Li were removed from Li 3 IrO 4 . [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] Our DFT calculations show that this effect is related to the statistical Li/Ir disorder within the transition metal layer of the oxide. Since O 2 loss does not occur when the oxidation is limited to x = 1, [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] we can indisputably ascribe the behavior of Li 3 IrO 4 -Li 1 IrO 4 to LOR, beyond the bounds of CR. [START_REF] Li | Li 3 RuO 4 Polymorphs[END_REF] Interestingly, although evolution of O 2 accompanied by amorphization is induced when the last 1/3 of Li are removed, the O spectra indicate that ligands in a-IrO 3 remained highly oxidized despite the evolution of O 2 . [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] In other Li-rich transition metal oxides, LOR is most often associated with the onset of a sharp feature in resonant inelastic X-ray scattering (RIXS) maps, located at ~523 eV emission when the excitation was at ~531 eV. [START_REF] Gent | Coupling between oxygen redox and cation migration explains unusual electrochemistry in lithium-rich layered oxides[END_REF][START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF][START_REF] Xu | Elucidating anionic oxygen activity in lithium-rich layered oxides[END_REF][START_REF] Yang | Anionic and cationic redox and interfaces in batteries: Advances from soft X-ray absorption spectroscopy to resonant inelastic scattering[END_REF] RIXS maps were also measured for Li x IrO 4 (Figure 4), with an estimated flux (5 x 10 10 -1 x 10 11 photons/s), below the reported threshold of sample damage reported in the literature. [START_REF] Lebens-Higgins | Distinction between Intrinsic and X-ray-Induced Oxidized Oxygen States in Li-Rich 3d Layered Oxides and LiAlO 2[END_REF] There was an increase in the dispersion of emitted states (x axis in Figure 4), as well as the relative intensity of the elastic peak for all oxidized phases. This enhancement has been associated in very recent work to  1 -O 2 units. [START_REF] House | Superstructure control of first-cycle voltage hysteresis in oxygen-redox cathodes[END_REF][START_REF] House | First-cycle voltage hysteresis in Lirich 3d cathodes associated with molecular O 2 trapped in the bulk[END_REF] Furthermore, delithiation from Li 3 IrO 4 did not produce any features at ~523 eV emission for a ~531 eV excitation. This feature was concurrent with the existence of out-of-plane Sn migration in layered Li 2-x Ir 1-y Sn y O 3 , which only displays LOR at y > 0. [START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF][START_REF] Li | Probing Electrochemically-Induced Structural Evolution and Oxygen Redox Reactions in Layered Lithium Iridate[END_REF] It has recently been specifically ascribed to the formation of short O-O bridges between Ir atoms when these defects are introduced. [START_REF] Gent | Design Rules for High-Valent Redox in Intercalation Electrodes[END_REF] Most importantly, it is also observed in conventional layered oxides, [START_REF] Lebens-Higgins | Revisiting the charge compensation mechanisms in LiNi 0.8 Co 0.2-y Al y O 2 systems[END_REF][START_REF] Li | Unraveling the Cationic and Anionic Redox Reactions in a Conventional Layered Oxide Cathode[END_REF] where the charge compensation could formally be accounted by conventional CR. In that case, the appearance of the loss feature at 523 eV correlates with the collapse of the interlayer distance, concurrent with a deformation of the octahedral coordination of the transition metals. [START_REF] Lebens-Higgins | Revisiting the charge compensation mechanisms in LiNi 0.8 Co 0.2-y Al y O 2 systems[END_REF] No evidence of Ir migration exists for Li x IrO 4 before amorphization, [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] consistent with a predicted low driving force. [START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF] Formation of short peroxo (O-O) bridges between Ir 24 is also not predicted by our models. Lastly, the change in the interlayer distance is very small up to x = 1. [START_REF] Perez | Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li 3 IrO 4[END_REF] Therefore, our work indicates that: i) LOR is not uniquely associated with specific loss features in the RIXS maps, ii) spectroscopic evaluation of both metals and ligands is required to determine its existence, and iii) different processes may fall under the umbrella of LOR with subtle differences in structural and electronic features.

The DFT calculations presented here indicate that delithiation is compensated by O 2p states that are initially non-bonding. The IrO 6 octahedra are predicted to distort to form short Ir-O bonds, [START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF] and introduce O-O distances at ~2.4 Å, characteristic of the so-called reductive coupling mechanism. [START_REF] Xie | Requirements for reversible extra-capacity in Lirich layered oxides for Li-ion batteries[END_REF][START_REF] Sathiya | Reversible anionic redox chemistry in high-capacity layered-oxide electrodes[END_REF] The principle by which LOR occurs in Li 3 IrO 4 is consistent with Li [START_REF] Xie | Requirements for reversible extra-capacity in Lirich layered oxides for Li-ion batteries[END_REF] Therefore, it does not require out-of-plane migration of heavy cations like Sn(IV), [START_REF] Hong | Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides[END_REF] a prominent driver of voltage hysteresis and irreversibility. [START_REF] Gent | Design Rules for High-Valent Redox in Intercalation Electrodes[END_REF][START_REF] Sathiya | Origin of voltage decay in high-capacity layered oxide electrodes[END_REF] The LOR is extremely reversible if delithiation is stopped at Li 1 IrO 4 , with the material returning to its initial state. This behavior distinguishes Li 3 IrO 4 from other lithiated oxides where LOR unlocks a different pathway involving conventional CR, [START_REF] Assat | Fundamental interplay between anionic/cationic redox governing the kinetics and thermodynamics of lithium-rich cathodes[END_REF][START_REF] Oishi | Charge compensation mechanisms in Li 1[END_REF][START_REF] Yabuuchi | High-capacity electrode materials for rechargeable lithium batteries: Li 3 NbO 4 -based system with cation-disordered rocksalt structure[END_REF][START_REF] Hu | Evolution of redox couples in Li-and Mn-rich cathode materials and mitigation of voltage fade by reducing oxygen release[END_REF][START_REF] Rana | Quantifying the Capacity Contributions during Activation of Li 2 MnO 3[END_REF] including parent Li 3 RuO 4 . [START_REF] Li | Li 3 RuO 4 Polymorphs[END_REF][START_REF] Jacquet | Competition between Metal Dissolution and Gas Release in Li-Rich Li 3 Ru y Ir 1-y O 4 Model Compounds Showing Anionic Redox[END_REF] This report clearly pinpoints the O states that enable the shift of the redox centers to the ligands. While α-Li 2 IrO 3 also possesses two non-equivalent O sites, similar measurements did not find any significant difference in their contribution to charge compensation. [START_REF] Li | Probing Electrochemically-Induced Structural Evolution and Oxygen Redox Reactions in Layered Lithium Iridate[END_REF] transition metal is crucial, as it allows hybridization that stabilizes the structure and renders it reversible. We have also proposed [START_REF] Saubanère | The intriguing question of anionic redox in high-energy density cathodes for Li-ion batteries[END_REF][START_REF] Xie | Requirements for reversible extra-capacity in Lirich layered oxides for Li-ion batteries[END_REF][START_REF] Ben Yahia | Unified picture of anionic redox in Li/Na-ion batteries[END_REF]

  delithiation. Deintercalation of the first 2 mol of Li from Li 3 IrO 4 induced minor changes in μ eff , to 0.595 and 1.178 μ B /Ir at x = 2 and 1 (in Li x IrO 4 , Figures S1c and S1d), reflecting a relatively weak paramagnetism that does not quite reach values expected even for S = 1/2. The fine structure of the O K-edge XAS above 535 eV was modified, with the centroid shifting toward high energy compared to the pristine state (Figures 1c and S5). The centroid of the XES showed also blueshifted at all excitations except 528.55 eV. The changes were most pronounced with the first Li removal. All these changes were assigned to the lowering of the energy of the O 1s states due to an increase in average Z eff (effective nuclear charge) resulting from depletion of electron density of O. The most drastic changes in the O K-edge XAS took place below 530 eV. There was a dominant peak at 528.5 eV showing a shoulder at 527.7 eV in both x = 2 and x = 1 (Figure 1c), a change in both position and, especially, relative intensity of the maxima compared to the pristine state. Their increased overlap prevented selective excitation of O 2LP and O 3LP in the XES (Figure 1b). Overall, the integrated intensity under the pre-edge XAS signals below 530 eV significantly

Li 2

 2 IrO 4 (Figure3). Similar results were obtained for other patterns of Li/Ir disorder, with O 2LP systematically participating to a much lesser extent than O 3LP (FigureS6), consistent with the relative positioning of their lone-pair states in the pDOS (Figure2). This change in electronic structure perfectly reproduces the change in the ratio of intensity below 530 eV in the XAS spectrum of Li 2 IrO 4 (Figure3), as the newly depleted O 3LP  2LP states (orange O connected to 1 Ir) showed similar energy to O 2LP (red O connected to 2 Ir). Upon further oxidation to x = 1, the initial O 2LP states in Li 3 IrO 4 became more involved, yet still to a lower extent than O 3LP . The computations revealed that the oxidation of the two O 2LP between two IrO 6 octahedra (red oxygens in Figures2 and 3) decreased their bond length toward 2.4 Å. In contrast, O 3LP tended to

Figure 1 .

 1 Figure 1. (a) Voltage-composition profile of Li 3 IrO 4 . The states of interest for ex situ analysis

Figure 2 .

 2 Figure 2. (a) Electron localization Function (ELF), computed by DFT, for Li 3 IrO 4 , showing 2

Figure 3 .

 3 Figure 3. (left) Simulated vs. experimental XAS spectra for Li x IrO 4 (x = 3, 2, 1), showing that

Figure 4 .

 4 Figure 4. Ex situ O K-edge RIXS maps of Li 3 IrO 4 at the different electrochemical states

  2-x Ir 1- y Sn y O 3 : 24 it involves a high density of uncoordinated O 2p states, or lone pairs. However, unlike Li 2-x Ir 1-y Sn y O 3 , the high O/Ir ratio of Li 3 IrO 4 generates sufficient non-bonding states in its pristine state, as originally predicted by Xie et al.

  . This fact convincingly reinforces that LOR requires O sites like O 3LP , namely with connectivity to only one transition metal, to avoid cation migration, which is not favorable for Ir. These sites are present in Li 3 IrO 4 , but not α-Li 2 IrO 3 ,[START_REF] Kobayashi | Structure, and magnetic and electrochemical properties of layered oxides, Li 2 IrO 3[END_REF] or similar honeycomb oxides. At the same time, comparison with other Li 3 TMO 4 (TM = Nb or V) emphasizes that connectivity to a d n (n > 0)

  that oxides having no empty d-orbitals to enable rehybridization should undergo irreversible reactions with O 2 release. Further disentangling the role of Ir, in contrast to other d n metals such as Ru,[START_REF] Li | Li 3 RuO 4 Polymorphs[END_REF] as enabling effective rehybridization[START_REF] Ben Yahia | Unified picture of anionic redox in Li/Na-ion batteries[END_REF] and/or preventing the formation of defects[START_REF] Gent | Design Rules for High-Valent Redox in Intercalation Electrodes[END_REF] is indispensable if this reversible reactivity is to be mimicked with base metals, a required step for this concept to have technological impact in highenergy Li-ion batteries.

Acknowledgements

This material is based upon work supported by the National Science Foundation under Grant No. DMR-1809372. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Part or all of the research described in this paper was performed at the Canadian Light Source, a national research facility of the University of Saskatchewan, which is supported by the Canada Foundation for Innovation (CFI), the Natural Sciences and Engineering Research Council (NSERC), the National Research Council (NRC), the Canadian Institutes of Health Research (CIHR), the Government of Saskatchewan, and the University of Saskatchewan.

Methods

See the Supplementary Information for details of the materials and methods.