MuseumLab - Evolutionary history of bony fish

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This study conducted a spatiotemporal review of the coelacanth fossil record and explored its distribution and diversity patterns. Coelacanth research can be divided into two distinct periods: the first period, which is based solely on the fossil record, and the second period following the discovery of extant taxa, significantly stimulating research interest. The distribution and research intensity of coelacanth fossils exhibit marked spatial heterogeneity, with Europe and North America being the most extensively studied regions. In contrast, Asia, South America, and Oceania offer substantial potential for future research. Temporally, the coelacanth fossil record also demonstrates significant variation across geological periods, revealing three diversity peaks in the Middle Devonian, Early Triassic, and Late Jurassic, with the Early Triassic peak exhibiting the highest diversity. With the exception of the Late Devonian, Carboniferous, and Late Cretaceous, most periods remain understudied, particularly the Permian, Early Jurassic, and Middle Jurassic, where the record is notably scarce. Integrating the fossil record with phylogenetic analyses enables more robust estimations of coelacanth diversity patterns through deep time. The diversity peak observed in the Middle Devonian is consistent with early burst models of diversification, whereas the Early and Middle Triassic peaks are considered robust, and the Late Jurassic peak may be influenced by taphonomic biases. The low population abundance and limited diversity of coelacanths reduce the number of specimens available for fossilization. The absence of a Cenozoic coelacanth fossil record may be linked to their moderately deep-sea habitat. Future research should prioritize addressing gaps in the fossil record, particularly in Africa, Asia, and Latin America; employing multiple metrics to mitigate sampling biases; and integrating a broader range of taxa into phylogenetic analyses. In contrast to the widespread distribution of the fossil record, extant coelacanths exhibit a restricted distribution, underscoring the urgent need to increase conservation efforts.

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The discovery in 1938 of a living coelacanth, Latimeria chalumnae, triggered much research and discussion on the evolutionary history and phylogeny of these peculiar sarcopterygian fishes. Indeed, coelacanths were thought to represent the 'missing link' between fishes and tetrapods, a phylogenetic position which is now dismissed. Since the first analyses using a phylogenetic approach were carried out three decades ago, a relatively similar data matrix has been consistently used by researchers for running analyses, with no significant changes aside from the addition of new taxa and characters, and minor corrections to the states' definition and scorings. Here, we investigate the phylogeny of Actinistia with an updated data matrix based on a list of partially new or modified characters. From the initial list of characters available in the most recent studies, we removed 16 characters, modified 16 other characters' definition and added 18 new characters, resulting in a list of 112 characters. We also revised the data matrix by correcting 171 miscoding found for 37 taxa. Based on the new phylogeny, we propose a new classification of coelacanths including 46 coelacanth genera, part of them allocated within nine families and four sub-families. Most of these groups were already named but were not recognised as clades, or poorly or not diagnosed in previous phylogenetic analyses. We provide several new or emended diagnoses for each clade. For the first time, a set of Palaeozoic coelacanth genera are found gathered within a clade, namely the Diplocercidae. All Mesozoic coelacanths, including extant Latimeria, are resolved as members of the order Coelacanthiformes, a clade that arose in the Permian, with Coelacanthus diverging first. We also found that most Mesozoic coelacanths are gathered into a clade, the Latimerioidei, itself divided into the Latimeriidae and the Mawsoniidae, each of which is divided into two subfamilies. Although these important changes, the new phylogeny of the Actinistia shows no significant alteration, and it remains relatively similar compared to previous studies. This demonstrates that the coelacanth phylogeny is now rather stable despite the weak support for most nodes in the phylogeny, and despite the difficulty of defining relevant morphological characters to score in this relatively slowly evolving lineage.

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Libanissus bkassinensis Azar, Maksoud & Nel, gen. et sp. nov. is illustrated and described from the Lower Cretaceous dysodile (oil papershales) of Bkassine, South Lebanon, and its taxonomic position discussed. Libanissus bkassinensis Azar, Maksoud & Nel, gen. et sp. nov. is characterized by its banded legs and body, a hind wing with two lobes, RA and RP very short, M with only two very short apical branches, CuA with two branches, and a small but distinct apical furcation of PCu close to the incision of the wing margin. Libanissus bkassinensis Azar, Maksoud & Nel, gen. et sp. nov. represents the earliest record (lower Barremian) of the Issidae. Prior to this discovery, the oldest known record was from the Paleocene of France.

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Although the split of coelacanths from other sarcopterygians is ancient, around 420 million years ago, the taxic diversity and the morphological disparity of the clade have remained relatively low, with a few exceptions. This supposedly slow evolutionary pace has earned the extant coelacanth Latimeria the nickname "living fossil". This status generated much interest in both extinct and extant coelacanths leading to the production of numerous anatomical studies. However, detailed descriptions of extinct taxa are made difficult due to the quality of the fossil material which generally prevents fine comparisons with the extant Latimeria. Here we describe a new genus and species of coelacanth, Graulia branchiodonta gen. et sp. nov. from the Middle Triassic of Eastern France, based on microtomographical imaging using synchrotron radiation. Through exquisite 3D preservation of the specimens, we reconstructed the skeletal anatomy of this new species at an unprecedented level of detail for an extinct coelacanth, and barely achieved for the extant Latimeria. In particular, we identified a well-developed trilobed ossified lung whose function is still uncertain. The skeletal anatomy of G. branchiodonta displays the general Bauplan of Mesozoic coelacanths and a phylogenetic analysis resolved it as a basal Mawsoniidae, shedding light on the early diversification of one of the two major lineages of Mesozoic coelacanths. However, despite its exquisite preservation, G. branchiodonta carries a weak phylogenetic signal, highlighting that the sudden radiation of coelacanths in the Early and Middle Triassic makes it currently difficult to detect synapomorphies and resolve phylogenetic interrelationships among coelacanths in the aftermath of the great Permo-Triassic biodiversity crisis.

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The lungfish, the extant sister group of the tetrapods, have an evolutionary history illustrated by a fossil record extending for ∼420 million years. The post-Paleozoic fossil record of the clade is almost exclusively restricted to sediments deposited in freshwater paleoenvironments and is characterized by an abundance of highly mineralized tooth plates, whereas cranial and postcranial remains are scarce. Here, we report a sample of isolated tooth plates found in the Upper Triassic Pebbly Arkose Formation of the Mid-Zambezi Basin, Zimbabwe. It consists of pterygoid and prearticular tooth plates from adult individuals, plus some dental plates referred to juvenile individuals, which we refer to a new species of Ferganoceratodus. This discovery provides an opportunity to review briefly the tooth plates of the ‘ptychoceratodontid morphotype’ reported from around the world. We discuss how various occurrences previously referred to Ptychoceratodus may be more appropriately referred, with caution, to Ferganoceratodus. We also describe the histology of the tooth plates of the new species and note similarities with other Mesozoic taxa. The scarcity of histological data for Mesozoic lungfish tooth plates compounds the problem of assigning isolated tooth plates to genus and species level. Ferganoceratodus and closely related taxa arose in the Early Triassic in southern Gondwana and diversified worldwide in the Late Triassic. The genus then became more common in Laurasia during the Jurassic and Early Cretaceous and declined thereafter with relict Late Cretaceous occurrences in Madagascar and South America.

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Fossil evidence suggests that ray-finned fishes (Actinopterygii) diversified greatly after the largest mass extinction event at the Permian–Triassic boundary. This radiation resulted in a diversity peak in the Middle Triassic, which is manifested in diverse feeding specializations, especially among small-bodied Neopterygii. We present new material from an early Spathian (Early Triassic) outcrop in northern Dobrogea, southeast Romania. The material includes isolated jaw and palatal bones that evidently belong to a single individual, a durophagous actinopterygian, and isolated scales referred to the same taxon. A systematic evaluation of this material indicates affinities with †Polzbergiidae, and provides a first glimpse of internal aspects of the feeding apparatus of that group. A pair of ectopterygoids with crushing dentition show a well-developed lateral process, a feature that was previously proposed to be a synapomorphy uniting Cladistia (bichirs) with the Triassic †Scanilepiformes. The recognition of this structure in various Triassic ray-fins (summarized herein) indicates that it was probably widespread among stem neopterygians. The new material belongs to a large individual with a heterodont dentition, therefore representing the earliest large, specialized, durophagous neopterygian. It increases the group's morphological diversity in the Spathian, and hints at an earlier trophic diversification after the mass extinction. Based on new data, we analyse changes in body size of bony fishes through the Early and Middle Triassic. Current evidence suggests that body size distribution remained skewed towards larger sizes in the late Early Triassic, and that the diversification of small-bodied stem neopterygians had not yet been in full swing.

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This work presents the first record of bony fish from the Maastrichtian of the Marília Formation (Bauru Group) in Goiás State, Brazil. A fragment of a pectoral spine, recovered by screen-washing, clearly represents an important catfish (Siluriformes) record from the Late Cretaceous of South America. The material possesses similarities with forms from the Campanian - early-Maastrichtian of the Adamantina Formation and the Maastrichtian of the Marília (São Paulo State) and El Molino (Bolivia) formations. Inclusion of the new material from Goiás in the dataset for the aforementioned areas within a paleoenvironmental setting provides evidence that Late Cretaceous catfish had a wider distribution than previously known.

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The vertebrate skull varies widely in shape, accommodating diverse strategies of feeding and predation. The braincase is composed of several flat bones that meet at flexible joints called sutures. Nearly all vertebrates have a prominent 'coronal' suture that separates the front and back of the skull. This suture can develop entirely within mesoderm-derived tissue, neural crest-derived tissue, or at the boundary of the two. Recent paleontological findings and genetic insights in non-mammalian model organisms serve to revise fundamental knowledge on the development and evolution of this suture. Growing evidence supports a decoupling of the germ layer origins of the mesenchyme that forms the calvarial bones from inductive signaling that establishes discrete bone centers. Changes in these relationships facilitate skull evolution and may create susceptibility to disease. These concepts provide a general framework for approaching issues of homology in cases where germ layer origins have shifted during evolution.

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Only few candidates of Mesozoic fishes with a similar body plan and ecological niche to the modern billfishes are suggested as their analogues. Several specimens were recovered from Cenomanian deposits in Germany and Lebanon and display a billfish-like fusiform body with elongated premaxillae. They are found close to the plethodids and show a unique combination of characters (rostrum pointed and extremely elongated, double articular head of the quadrate, anteroposteriorly elongated abdominal centra indicating a slender body and different types of scales on the body) allowing their inclusion in a new genus. Two 'Protosphyraena' species are also assigned to this new genus. This fish can be considered as an ecological analogue to the extant xiphioids sharing their feeding habits. This fish was abundant and roamed, as an apex predator, the Central Tethys and the Boreal realms during the Cenomanian.

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The first discovery of a dinosaur bone from the Kingdom of Cambodia is reported in this paper. It consists of a sauropod fibula from a sandstone layer on Koh Paur island, in Koh Kong province, in south-western Cambodia. The dinosaur-bearing bed belongs to the non-marine Grès Supérieurs series and is apparently of Early Cretaceous age. On the basis of various characters, notably the development of the anteromedial crest, the dinosaur fibula from Koh Paur is referred to a euhelopodid titanosauriform. This first dinosaur discovery in Cambodia suggests that the thick non-marine formations which cover vast areas in the south-western part of the country are potentially an important source of continental Mesozoic vertebrates.

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Coelacanths form today an impoverished clade of sarcopterygian fishes, which were somewhat more diverse during their evolutionary history, especially in the Triassic. Since the first description of the coelacanth Ticinepomis peyeri from the Besano Formation of the UNESCO World Heritage Site of Monte San Giorgio (Canton Ticino, Switzerland), the diversity of coelacanths in the Middle Triassic of this area of the western Paleo-Tethys has been enriched with discoveries of other fossil materials. At Monte San Giorgio, two specimens of Heptanema paradoxum and several specimens of the unusual coelacanth Rieppelia heinzfurreri, have been reported from the Meride Limestone and the Besano Formation, respectively. Another unusual coelacanth, Foreyia maxkuhni, and two specimens referred to Ticinepomis cf. T. peyeri have been described from the isochronous and paleogeographical close Prosanto Formation at the Ducanfurgga and Strel sites (near Davos, Canton Graubünden). In the framework of the revision of the coelacanth material from the Besano Formation kept in the collection of the Paläontologisches Institut und Museum der Universität Zürich (Switzerland), we reviewed the genus Ticinepomis on the basis of the holotype and four new referred specimens. Several morphological traits that were little and/or not understood in T. peyeri are here clarified. We re-evaluate the taxonomic attribution of the material of Ticinepomis cf. T. peyeri from the Prosanto Formation. Morphological characters are different enough from the type species, T. peyeri, to erect a new species, Ticinepomis ducanensis sp. nov., which is shown to be also present in the Besano Formation of Monte San Giorgio, where it is represented by fragmentary bone elements. The recognition of a new coelacanth species indicates that the diversity of this slow-evolving lineage was particularly high in this part of the Western Tethys during the Middle Triassic, especially between 242 and 240 million years ago.

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Since the split of the coelacanth lineage from other osteichthyans 420 million years ago, the morphological disparity of this clade has remained remarkably stable. Only few outliers with peculiar body shape stood out over the evolutionary history, but they were phylogenetically and stratigraphically independent of each other. Here, we report the discovery of a new clade of ancient latimeriid coelacanths representing a small flock of species present in the Western Tethys between 242 and 241 million years ago. Among the four species, two show highly derived anatomy. A new genus shows reversal to plesiomorphic conditions in its skull and caudal fin organisation. The new genus and its sister Foreyia have anatomical modules that moved from the general coelacanth Bauplau either in the same direction or in opposite direction that affect proportions of the body, opercle and fins. Comparisons with extant genetic models shows that changes of the regulatory network of the Hedgehog signal gene family may account for most of the altered anatomy. This unexpected, short and confined new clade represents the only known example of a burst of morphological disparity over the long history of coelacanths at a recovery period after the Permian-Triassic Mass Extinction.

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Teleosts form the largest clade among the extant actinopterygians, some extinct forms of which are still poorly positioned in the phylogeny. The Tselfatiiformes and Araripichthyidae are such examples. A newly discovered genus and species from the Cenomanian of Haqel, Lebanon, is described, and its systematic affinities are discussed. It shares several characteristics (deep and compressed body with elongated and high dorsal and anal fins, edentulous maxilla, and sinusoidal vertebral column) with both the Tselfatiiformes and Araripichthys, making it difficult to place within the teleosts. It shares with Abisaadichthys, among the tselfatiiforms’ family Protobramidae, an autogenous retroarticular, and with Araripichthys premaxillae with a long ascending process, well-developed maxillary articular condyle and two supramaxillae. Moreover, it shows some unique characteristics (a thin maxilla with two large supramaxillae, fused articular and angular bones, mandibular sensory canal opening on the external side of the anguloarticular, first dorsal pterygiophore having the same enlarged semi-circular plate as the first anal pterygiophore) justifying its generic status. Comments on some of the protobramids are presented, and the necessity for phylogenetic analysis to place the Tselfatiiformes, Araripichthys and Ypsiloichthys within the teleosts is outlined.

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The extant Amiiformes are represented by a single living freshwater genus Amia (bowfin) with recent phylogenomic analysis indicating the presence of multiple species. However, they have a more extensive fossil record first appearing in the Early Jurassic and are recorded as occurring on all continents, except Antarctica and Australia. Here, we describe fossil amiid fishes Calamopleurini? (Halecomorphi, Amiiformes) from the Cretaceous (Albian—Cenomanian) Griman Creek Formation, Lightning Ridge, New South Wales, Australia, representing the first record, extinct or extant, of the amiids in Australia. The material comprises jaw elements that have been replaced by opal. This new record from Australia adds to previously documented Cretaceous Western Gondwanan occurrences from South America and Africa and further supports a distinct southern “Gondwanan” fish population in the seas surrounding the fragmenting Gondwanan landmasses during the ‘mid’ — Late Cretaceous.

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The Sinamiidae are a family of halecomorph fishes (Holostei) stratigraphically limited to the Lower Cretaceous and confined to East Asia. The first species of sinamiids were discovered in China, and then new occurrences were recorded in Thailand and Japan. The three recognized genera, Sinamia, Siamamia and Ikechaoamia, are notably characterized by an unpaired parietal. Here, we describe a new genus and species of sinamiid based on material from the Aptian Khok Kruat Formation of Ban Krok Duean Ha, Nakhon Ratchasima, Thailand. The new taxon known from preserved specimens in 3D is characterized by four pairs of extrascapular and tall cylindrical teeth with a conical enamel stalk topped by an arrowhead-shaped acrodine cap, among other characters. A phylogenetic analysis of the halecomorph fishes shows that the new taxon is the sister of the other Thai species, Siamamia naga, and that the two are grouped with two Chinese genera in a strongly supported clade, the Sinamiinae. This subfamily is here grouped with the Amiinae that contained the extant Amia. This new discovery is a clue that Southeast Asia may have been a center of diversification for this fish clade, and the phylogenetic analysis reveals that amiines may have originated somewhere in Asia during the Cretaceous before they spread throughout the northern hemisphere.

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Mawsoniidae is a family of coelacanths restricted to the Mesozoic. During the Cretaceous, mawsoniids were mainly represented by the Mawsonia/Axelrodichthy complex, long known to be from western Gondwana only (South America and Africa). This apparent biogeographical distribution then faded following the discovery of representatives in the Late Cretaceous of Laurasia (Europe and North America). We report here the presence, in the Lower Cretaceous site of Kham Phok, NE Thailand, of an angular bone referred to the Mawsonia/Axelrodichthys complex. A comparison with angulars referring to both genera found in various regions of the world between the Late Jurassic and the Late Cretaceous indicated that the distinctions between these genera, and even more so between their constituent species, are unclear. This discovery is further confirmation of the very slow morphological evolution within this lineage, which may explain why their evolutionary history appears to be disconnected, at least in part, from their geographical distribution over time.

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Coelacanths form a clade of sarcopterygian fish represented today by a single genus, Latimeria. The fossil record of the group, which dates back to the Early Devonian, is sparse. In Switzerland, only Triassic sites in the east and southeast of the country have yielded fossils of coelacanths. Here, we describe and study the very first coelacanth of the Jurassic period (Toarcian stage) from Switzerland. The unique specimen, represented by a sub-complete individual, possesses morphological characteristics allowing assignment to the genus Libys (e.g., sensory canals opening through a large groove crossed by pillars), a marine coelacanth previously known only in the Late Jurassic of Germany. Morphological characters are different enough from the type species, Libys polypterus, to erect a new species of Libys named Libys callolepis sp. nov. The presence of Libys callolepis sp. nov. in Lower Jurassic beds extends the stratigraphic range of the genus Libys by about 34 million years, but without increasing considerably its geographic distribution. Belonging to the modern family Latimeriidae, the occurrence of Libys callolepis sp. nov. heralds a long period, up to the present day, of coelacanth genera with very long stratigraphic range and reduced morphological disparity, which have earned them the nickname of 'living fossils'.

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Darwin pointed out that “species of different genera and classes have not changed at the same rate” (Darwin, 1859, chapter X). Besides, he coined the expression “living fossils” for lineages whose “new forms will have been more slowly formed, and old forms more slowly exterminated” (chapter IV), among other characteristics. This expression has become popular, but has sometimes been misunderstood as meaning that some organisms do not evolve. It has also been commonly used by paleontologists and evolutionary biologists to describe a general pattern of relative stasis in morphological evolution in some lineages. Darwin's definition of the concept was imprecise and he considered that “species and groups of species, which are called aberrant, and which may fancifully be called living fossils, will aid us in forming a picture of the ancient forms of life” (Darwin, 1859, Chapter XIV). For more than 200 years, nevertheless, debates have raged on the definition of the concept (e.g., Bennett et al., 2017, 2018; Lidgard and Love, 2018; Turner, 2019), and more generally on the merits of its use in the life sciences (e.g., Casane and Laurenti, 2013; Naville et al., 2015). Although Darwin (1859) cited several taxa of fish as examples of “living fossils,” he did not mention the coelacanths, or actinistians, which were only known as fossils at his time. Huxley, however, soon after (1866) noticed the low anatomical disparity of coelacanths throughout their history. Since that time, and especially after the discovery of the living Latimeria in 1938 (Smith, 1939), the coelacanth has become an iconic symbol of the “living fossil” due to the slow morphological evolution illustrated by the fossil record of the clade, and its supposed affinities with tetrapods. Only the question of evolutionary rate is addressed here, not the question of ancestral status or other “living fossil” characteristics attributed to coelacanths. The low rate of evolution based on a lasting generalist morphological Bauplan has been confirmed by most subsequent authors who have worked on the group (Schaeffer, 1952; Cloutier, 1991; Forey, 1998; Schultze, 2004; Zhu et al., 2012; Cavin and Guinot, 2014), knowing that there are also exceptions to this general Bauplan (e.g., Friedman and Coates, 2006; Wendruff and Wilson, 2012; Cavin et al., 2017). However, part of the community of researchers working on fossil and living coelacanths avoids using this expression.

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The global body-fossil record of marine 'fishes' from the time interval immediately preceding the Cretaceous-Paleogene Extinction is markedly poor. This deficiency appears to be further exacerbated with regards to offshore and deep-water taxa, obscuring our understanding of the state and composition of corresponding vertebrate faunas at the onset of this major extinction event. Recent fieldwork in the mid-late Maastrichtian exposures of the Pindos Unit in Gavdos Island, Greece, yielded a small but informative sample of fossil 'fishes', which inhabited the Tethys approximately three to four million years before the extinction. In this work we describe this sample, which comprises between eight and nine discrete morphotypes of various size classes, belonging to †Ichthyodectoidei, Aulopiformes (†Dercetidae, †Enchodontidae, †Ichthyotringidae), cf. †Sardinioididae, as well as the hexanchid shark †Gladioserratus sp. The new material expands the faunal list for the Maastrichtian of Gavdos Island, and the Pindos Unit as a whole, and further allows for the description of a new genus and species of †Enchodontidae and a new species of †Ichthyotringidae. The two new taxa are found to be widespread in the Maastrichtian of the Pindos Unit. The overall character of the assemblage agrees with previous interpretations of an offshore and rather deep depositional environment for the fossiliferous horizons. Furthermore, it exhibits a higher diversity than, and little taxonomic overlap with penecontemporaneous teleost assemblages from the Tethys, and informs on the otherwise poorly known Maastrichtian offshore and deep-water marine ichthyofaunas of the region.

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Today, the only living genus of coelacanth, Latimeria is represented by two species along the eastern coast of Africa and in Indonesia. This sarcopterygian fish is nicknamed a "living fossil", in particular because of its slow evolution. The large geographical distribution of Latimeria may be a reason for the great resilience to extinction of this lineage, but the lack of fossil records for this genus prevents us from testing this hypothesis. Here we describe isolated bones (right angular, incomplete basisphenoid, fragments of parasphenoid and pterygoid) found in the Cenomanian Woodbine Formation in northeast Texas that are referred to the mawsoniid coelacanth Mawsonia sp. In order to assess the impact of this discovery on the alleged characteristic of "living fossils" in general and of coelacanths in particular: 1) we compared the average time duration of genera of ray-finned fish and coelacanth in the fossil record; 2) we compared the biogeographic signal from Mawsonia with the signal from the rest of the vertebrate assemblage of the Woodbine formation; and 3) we compared these life traits with those of Latimeria. The stratigraphical range of Mawsonia is at least 50 million years. Since Mawsonia was a fresh, brackish water fish with probably a low ability to cross large sea barriers and because most of the continental components of the Woodbine Fm vertebrate assemblage exhibit Laurasian affinities, it is proposed that the Mawsonia's occurrence in North America is more likely the result of a vicariant event linked to the break-up of Pangea rather than the result of a dispersal from Gondwana. The link between a wide geographic distribution and the resilience to extinction demonstrated here for Mawsonia is a clue that a similar situation existed for Latimeria, which allowed this genus to live for tens of millions of years.

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The positive correlation between speciation rates and morphological evolution expressed by body size is a macroevolutionary trait of vertebrates. Although taxic diversification and morphological evolution are slow in coelacanths, their fossil record indicates that large and small species coexisted, which calls into question the link between morphological and body size disparities. Here, we describe and reassess fossils of giant coelacanths. Two genera reached up to 5 m long, placing them among the ten largest bony fish that ever lived. The disparity in body size adjusted to taxic diversity is much greater in coelacanths than in ray-finned fishes. Previous studies have shown that rates of speciation and rates of morphological evolution are overall low in this group, and our results indicate that these parameters are decoupled from the disparity in body size in coelacanths. Genomic and physiological characteristics of the extant Latimeria may reflect how the extinct relatives grew to such a large size. These characteristics highlight new evolutionary traits specific to these "living fossils"

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The Late Jurassic Allosaurus is one of the better-studied dinosaurs. A histological and geochemical study of a tibia and a femur of A. fragilis recovered in the Upper Jurassic Cleveland-Lloyd Dinosaur Quarry, Utah, United States has been done in order to address growth characteristics of this species. The two bones, probably belonging to separate individuals, are among the largest known for this species, which make them suitable to address such issues. The inclusion of our data on femur growth markings in the previously published data reflects a range of growth variability rather than two distinct growth strategies. The tibia has a well-developed external fundamental system indicating somatic maturity achievement. Using a quantitative method of superimposition to retrocalculate missing lines of arrested growth, the tibia appears to correspond to an individual that reached its skeletal maturity at 22 years and died at approximately 26 years. In the tibia, the concentration of zinc, a potential biomarker associated with bone formation, displays a higher concentration in zones of rapid growth compared to annuli. There is no direct relationship between the values of δ18Op and the lines of arrested growth distribution. The absence of relations between the histological organization and an enrichment in REE of the bone, indicates that the variations of δ18Op likely represent a diagenetic process rather than a primordial, biologic composition. However, the geochemical composition of the bones is not homogeneous along the sections, indicating that the signal variations have not been completely erased by diagenesis.

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The Recent re-/discovery of unusual Lower Cretaceous continental deposits (dysodiles) brings important and exceptional paleontological assets. Dysodile beds are found in many localities across Lebanon and are characterized by their high organic matter content and their richness in exceptionally well-preserved fossils. We focus our study on five sampling localities in the lower Barremian sandstone beds, deposited when Lebanon was located in the north-eastern part of the Gondwana supercontinent. The localities are found associated with volcanic deposits suggesting a close relation between volcanism and their deposition and/or preservation. The present study provides, for the first time, insights on the fossil assemblages found in the dysodiles, including fishes, turtles, gastropods, insects, plant debris (macroflora and palynomorphs), ostracods and coprolites. We provide a preliminary reconstruction of the depositional environment that is common to the five sampling localities. It was a freshwater lake or possibly a series of interconnected lakes, in the vicinity of volcanic edifices, surrounded by a typical Lower Cretaceous flora (open forest environment), and inhabited by basal actinopterygian fishes and teleosts that will constitute the core of subsequent freshwater assemblages. The Lebanon localities have important implications for local palaeoenvironments as well as worldwide biogeography. In addition, the fossil assemblages show some taxonomic and taphonomic differences between the sampling sites, suggesting local differences in environmental conditions during deposition.

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New and well-preserved fossil fish material from the Upper Cretaceous (Cenomanian) of Haqel, Lebanon, is assigned to Spathiurus dorsalis Davis, 1887. Spathiurus dorsalis and Amphilaphurus major are found to be synonymous. A complete re-description of this taxon is provided and delivers new recognized anatomical information, mainly cranial features. Spathiurus dorsalis displays diagnostic characters of ionoscopids and consequently is designated as a new member of this family. A phylogenetic analysis was performed to place this taxon within the Halecomorphi. The studied taxon was recovered as the sister genera of Ionoscopus petrarojae, both derived compared to ‘Ionoscopus’ cyprinoides, suggesting that the latter should be placed in a distinct genus. The validated placement of Spathiurus within the Ionoscopidae extends the stratigraphic range of this family from the Albian to the Cenomanian and becomes the first record of an ionoscopiform from the Upper Cretaceous and from the Middle East.

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Coelacanths are iconic fishes represented today by a single marine genus. The group was a little bit more diversified in the Mesozoic, with representatives in marine and continental environments in the Late Cretaceous. Here we describe isolated skull bones of the last know freshwater coelacanths found in several fossil sites from the Early Campanian to the Early Maastrichtian of Southern France (in the Departments of Aude, Bouches-du-Rhône, Hérault, and Var). The sample does not allow distinguishing different species, and all material is referred to Axelrodichthys megadromos Cavin, Valentin, Garcia originally described from the locality of Ventabren in Southern France. A reconstruction of the skull is proposed. Previously unrecognized features are described, including parts of the postparietal portion of the skull, of the suspensorium and of the mandible. The new data confirm the assignation of the species to the mawsoniids, and more specifically to Axelrodichthys. A cladistic analysis scoring new character states provides a similar topology than a previous analysis, i.e. A. megadromos is placed in a polytomy with Axelrodichthys araripensis and Lualabaea lerichei, two species from the Early Cretaceous of Brazil and from the Late Jurassic of the Democratic Republic of the Congo, respectively. A. megadromos appears to have been restricted to freshwater environments, to the contrary of oldest Western Gondwanan representatives of the family that were able to live in brackish and marine waters. A. megadromos is the last representative of the mawsoniids and its occurrence in Europe is probably the result of a dispersal event from Western Gondwana that happened somewhen in the Cretaceous. Based on the available data, the mawsoniids went extinct in the mid-Maastrichthian, i.e. before the end-Cretaceous mass extinction. But it is possible that the fossil record of this family, which has been only recently recognized in Late Cretaceous European deposits, will geographically and stratigraphically widen with further discoveries.

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The Australian Mesozoic fish fauna is considered to be depauperate in comparison with fish faunas in the Northern Hemisphere. However, due to its geographical location as a potential radiation center in the Southern Hemisphere, Australia’s Mesozoic fish fauna is important for understanding fish radiations. Most of the modern fish groups originated during the Mesozoic, but the first records of a modern fish fauna (freshwater and marine) in Australia does not occur until the lower Paleogene. Here, we review all known fossil fish-bearing localities from the Mesozoic of Australia, to improve the understanding of the record. The apparent low Australian Mesozoic fish diversity is likely due to its understudied status of the constituent fossils rather than to a depauperate record. In addition, we review recent work with the aim of placing the Australian Mesozoic fish fauna in a global context. We review the taxonomy of Australian fossil fishes and conclude that the assignments of many actinopterygians need major revision within a modern phylogenetic context. The vast majority of chondrichthyans are yet to be formally described; to the contrary all of the known lungfish specimens have been described. This study considers the microscopic and fragmented remains of Mesozoic fish already found in Australia, allowing a more complete view of the diversity of the fishes that once inhabited this continent.

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The Mesozoic sedimentary cover of the Aiguilles Rouges Massif straddling the Swiss-French border has yielded several archosaur footprint sites dated to the Early or Middle Triassic and composed of mostly poorly preserved footprints lacking any orderly arrangement and resting on a megatracksite level. Here we describe two short archosaur trackways attributed to Isochirotherium herculis and located at ca. 2400 m asl in two distinct small valleys separated from each other by a linear distance of 6.4 km. Projection of both trackways onto the same plane showed that they were aligned with a deviation angle of only 3°. These aligned trackways are interpreted as remnants of a straight and narrow walking route taken by a single trackmaker species. It is possible that both trackway segments were made by the same individual. In the present landscape, the Triassic outcrops are small and scattered along a roughly straight NE-SW line. The orientation of the trackways agrees with the general orientation of the outcrops, which is very unlikely to be caused by chance only. We explain this apparent coincidence as resulting from the structural inheritance of a general NE-SW Paleozoic shear zone that controlled the orientation of the Vindelician High on which the archosaurs walked, then that defined the axis of the much later Massif uplift, and eventually affected the general orientation of the erosion that uncovered the trackways.

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Both biotic and abiotic factors likely played a role in influencing the diversification patterns of clades. Although the role of environmental forcing on the long-term evolution of biodiversity has been explored for invertebrate clades, little is known about how vertebrate groups responded to environmental changes. Among vertebrates, fishes (ray-finned fishes and elasmobranchs) have a long, rich, and complex evolutionary history comprising numerous diversification and extinction events. Yet, knowledge on the causes for the diversity fluctuations of these most speciose aquatic vertebrate clades in modern marine and continental ecosystems were restricted to qualitative interpretations. Here we use multiple regression methods to quantitatively examine the role of six abiotic parameters over the long-term variations of elasmobranch and actinopterygian genus-level diversity. We find that marine actinopterygian diversity is mainly controlled by temperature while continental fragmentation is the primary driver of the diversity fluctuations of elasmobranchs. Sea-level variations correlate positively with the diversity variations of both marine groups, whereas none of the tested proxies explains the diversity variation of freshwater ray-finned fishes. Our results indicate that such contrasting responses are mainly due to ecological and life-history trait differences between these groups.

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Tooth replacement in vertebrates is extremely diverse, and its study in extinct taxa gives insights into the evolution of the different dental renewal modes. Based on μ-CT scans of a left lower jaw of the extinct fish †Scheenstia (Actinopterygii, Lepisosteiformes), we describe in detail a peculiar tooth replacement mode that is, as far as we could ascertain from the literature, unique among vertebrates. The formation of the replacement teeth comprises a 180° rotation of their acrodin cap that occurs intraosseously within bony crypts, and their setting up appears to be synchronous. We propose a model for the dental renewal process and identify complementary anatomical features visible in the tomography such as the junction between the different tooth-bearing bones (prearticular–coronoid and dentary), as well as cavities corresponding to intraosseous crypts, nervous and/or vascular canals. The location of the cavities and their subsequent identification (e.g. Meckel's cavity, mandibular sensory canal) help us to identify the function of pores visible on the bone surface and understand their relation to internal anatomical features. Finally, recognition of this tooth replacement mode raises the question of whether it is specific to †Scheenstia or related to a particular dentition type and thus potentially occurs in other lineages.

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Lepidotes bernissartensis is a species of holostean ray-finned fish from the Barremian–Aptian of Bernissart, Belgium, described by Traquair in 1911. We provide here a revision of its anatomy, which led us to include this species in the genus Scheenstia, and to consider L. brevifulcratus and L. arcuatus, both from the same site, synonymous with S. bernissartensis. We performed two cladistic analyses in order to assess the phylogenetic position of S. bernissartensis and to do an updated appraisal of the evolutionary history of the ginglymodians. Scheenstia is included in the Lepidotidae, and placed in a pectinated position between the basal genus Lepidotes and the more derived members of the family (other species of Scheenstia, Isanichthys and Camerichthys). The nodes within the lepidotids are weakly supported. Although S. bernissartensis is not directly related to S. mantelli from the Wealden of Europe, the two species have similar palaeoenvironments and stratigraphical ranges. Taken as a whole, the ginglymodians experienced several episodes of diversification that are spatially and temporally restricted. The oldest episode involved basal ginglymodians and occurred in the Middle Triassic, in marine environments along the northern margin of the Tethys. A second episode affected the Semionotidae and occurred in freshwater environments of North America and Europe in the Late Triassic and Early Jurassic. The remaining Semionotiformes, Macrosemiidae and Callipurbeckidae, ranged from the Triassic to the Early Cretaceous and were mostly marine. Among the Lepisosteiformes, two clades, the Lepidotidae and the Lepisosteoidi, show episodes of diversification, first in marine and then in freshwater environments.

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Dugaldia emmilta is a teleostean fish found in the late Albian Toolebuc Formation in Queensland, Australia. In the original description, D. emmilta was attributed to the Neoteleostei because of the presence of a tripartite occipital condyle, and the species was postulated to have a basal position among neoteleosteans because of the presence of several plesiomorphic characters. A reexamination of the holotype, together with the description of two new specimens, indicates that D. emmilta is an ichthyodectiform fish. A phylogenetic analysis resolves this species as the sister to Ogunichthys + Ichthyodectoidei. This species shows unusual features for an ichthyodectiform, in particular the shape of the mandible and the arrangement of the teeth on the lower jaw. Jaw mechanics in ichthyodectiforms are peculiar because they allow a significant lateral enlargement. In Dugaldia, a similar disposition is present but is exaggerated by specific features of the maxilla and the mandible. Comparisons with the sarcastic fringehead (Neoclinus blanchardi), a living blenny that shows a ‘gaping display,’ reveal that Dugaldia was likely able to exhibit extreme lateral mouth enlargement.

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Ichthyoliths (fossil fish microremains) from geological core samples are commonly recorded and where present allow dating and contribute to the knowledge of the evolution of fish faunas through time (see, for instance, Sibert et al., Citation2014; Sibert and Norris, Citation2015, for the Ocean Drilling Program). However, reports of articulated fish specimens in cores are much rarer due to the limited chance of a core drill returning a small-diameter cylinder of rock encompassing the fossil to the surface. Examples of articulated fishes described from cores include specimens of Permo-Carboniferous actinopterygians near the city of Zurich, Switzerland (Bürgin, Citation1990), as well as a new taxon of a Cenomanian ellimmichthyiform from Alberta, Canada (Hay et al., Citation2007), and two new Eocene cypriniform fishes from Guangdong and Henan, China (Liu, Citation1957; Zhou, Citation1990; Chang and Chen, Citation2008). In this paper, we report the discovery of an ichthyodectiform fish fossil collected during re-evaluation of a core from DSDP Leg 41 Site 367 at the IODP Bremen Core Repository, Germany ( ). The core was recovered from a well drilled in the Cape Verde Basin, ca. 400 km offshore from the West African Atlantic Margin, to test the early basin evolution of the Central Atlantic region (Lancelot et al., Citation1977). The fossil fish was discovered in core 21 section 6 at 699.9 m measured depth, preserved on the bedding surface of a bituminous marl. Reports from the DSDP expedition had previously recorded fish vertebrae in the same subunit, suggesting abundance and/or high preservation rate of fish remains in Central Atlantic waters during the Albian to Cenomanian period (Lancelot et al., Citation1977:fig. 6). Associated calcareous nannofossils indicate an earliest Cenomanian age for the cored interval containing this specimen ().

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Fishes are characterized by their capacity to occupy all aquatic environments and by their amazing range of size and morphology. While it is known that habitat influenced the diversity dynamics of fish clades, studies on environmental colonization events through the evolutionary history of ray-finned fishes have yielded conflicting results as to the origin of modern clades and preferential directions of shifts. The effects of habitat over morphological evolution such as body size remain poorly known in vertebrates. However, body size evolution is more frequently addressed in terms of variation through time and numerous studies have demonstrated that successive taxa within a clade tend to increase in size through time (Cope's or Depéret's rule). We use phylogenetic comparative methods on a genus-level actinopterygian super-tree based on extant and fossil data covering the Late Jurassic-Paleogene interval. Results indicate marine ancestry for freshwater lineages and a dominance of colonizations from marine clades towards other habitats. Similar trends in environment occupancy among different ray-finned clades are explored. Three main trends affecting non-closely-related clades are recognized: (i) the freshwater invaders, (ii) the predominantly marine dwellers and (iii) the environmentally labile fishes. Habitat effects on body size evolution are not statistically supported, but most actinopterygian subclades originate from small-sized ancestors and tend to increase in size in the course of their evolutionary history. This trend is clear for lineages restricted for long periods of time in the same environments, either marine or freshwater, but it is not observed in environmentally labile fish lineages.

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A new genus and new species of ginglymodian is described from the Aptian Grès supérieurs Formation of the Savannakhet Basin, Laos (Lao People's Democratic Republic), found at the Ban Lamthouay locality. The fish is known from a single isolated head, which shows enough diagnostic characters to characterize a new taxon. It represents the first named actinopterygian fish from the Mesozoic of Laos. Among the derived characters are a very short and deep head, a series of very deep anterior infraorbitals, and a mosaic arrangement of the suborbitals. Recognition of this new form led us to identify isolated bones previously found in the Thai Khok Kruat Formation in Thailand, a lateral equivalent of the Grès supérieurs Formation. Two localities, Ban Saphan Hin and Khok Pha Suam, have yielded remains, in particular bones of the skull roof and of the circumorbital series as well as a partial postcranial body, assignable, with caution, to the new genus. When included in a cladistic analysis, the new taxon is placed at the base of the lepisosteoid lineage, together with Isanichthys known from an older formation in Thailand. The phylogenetic pattern obtained differs in some details from previous analyses and points out the pivotal role that some taxa play in the reconstruction of the phylogenies of ginglymodians. This new taxon enriches the diverse Late Jurassic–Early Cretaceous ginglymodian assemblage in South-east Asia, which surprisingly shows no evidence of teleosts.

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Genomic GC content can vary locally, and GC-rich regions are usually associated with increased DNA thermostability in thermophilic prokaryotes and warm-blooded eukaryotes. Among vertebrates, fish and amphibians appeared to possess a distinctly less heterogeneous AT/GC organization in their genomes, whereas cytogenetically detectable GC heterogeneity has so far only been documented in mammals and birds. The subject of our study is the gar, an ancient "living fossil" of a basal ray-finned fish lineage, known from the Cretaceous period. We carried out cytogenomic analysis in two gar genera (Atractosteus and Lepisosteus) uncovering a GC chromosomal pattern uncharacteristic for fish. Bioinformatic analysis of the spotted gar (Lepisosteus oculatus) confirmed a GC compartmentalization on GC profiles of linkage groups. This indicates a rather mammalian mode of compositional organization on gar chromosomes. Gars are thus the only analyzed extant ray-finned fishes with a GC compartmentalized genome. Since gars are cold-blooded anamniotes, our results contradict the generally accepted hypothesis that the phylogenomic onset of GC compartmentalization occurred near the origin of amniotes. Ecophysiological findings of other authors indicate a metabolic similarity of gars with mammals. We hypothesize that gars might have undergone convergent evolution with the tetrapod lineages leading to mammals on both metabolic and genomic levels. Their metabolic adaptations might have left footprints in their compositional genome evolution, as proposed by the metabolic rate hypothesis. The genome organization described here in gars sheds new light on the compositional genome evolution in vertebrates generally and contributes to better understanding of the complexities of the mechanisms involved in this process.

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A bizarre latimeriid coelacanth fish from the Middle Triassic of Switzerland shows skeletal features deviating from the uniform anatomy of coelacanths. The new form is closely related to a modern-looking coelacanth found in the same locality and differences between both are attributed to heterochronic evolution. Most of the modified osteological structures in the new coelacanth have their developmental origin in the skull/trunk interface region in the embryo. Change in the expression of developmental patterning genes, specifically the Pax1/9 genes, may explain a rapid evolution at the origin of the new coelacanth. This species broadens the morphological disparity range within the lineage of these 'living fossils' and exemplifies a case of rapid heterochronic evolution likely trigged by minor changes in gene expression.

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Remains of a coelacanth specimen are described from Rhaetian deposits of the Var Department, southeastern France. They comprise the lower part of a branchial apparatus associated with a left lower jaw and a basisphenoid. Osteological features of the angular and basisphenoid and the teeth ornamentation allow the inclusion of the specimen in the mawsoniid family, genus and species indeterminate. Mawsoniids are known in freshwater environments from the Triassic of North America and from the Cretaceous of Western Gondwana and Europe, as well as from Late Jurassic marine environments from Europe. The new discovery here reported represents the first coelacanth from the marine Triassic of France and improves the understanding of the palaeobiogeography of the Mawsoniidae.

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The extinct group of the Pycnodontiformes is one of the most characteristic components of the Mesozoic and early Cenozoic fish faunas. These ray-finned fishes, which underwent an explosive morphological diversification during the Late Cretaceous, are generally regarded as typical shell-crushers. Here we report unusual cutting-type dentitions from the Paleogene of Morocco which are assigned to a new genus of highly specialized pycnodont fish. This peculiar taxon represents the last member of a new, previously undetected 40-million-year lineage (Serrasalmimidae fam. nov., including two other new genera and Polygyrodus White, 1927) ranging back to the early Late Cretaceous and leading to exclusively carnivorous predatory forms, unique and unexpected among pycnodonts. Our discovery indicates that latest Cretaceous-earliest Paleogene pycnodonts occupied more diverse trophic niches than previously thought, taking advantage of the apparition of new prey types in the changing marine ecosystems of this time interval. The evolutionary sequence of trophic specialization characterizing this new group of pycnodontiforms is strikingly similar to that observed within serrasalmid characiforms, from seed- and fruit-eating pacus to flesh-eating piranhas.

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The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to 'Stromerichthys' from coeval deposits in Egypt. The ginglymodians were diversified with a large 'Lepidotes' plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

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Several attempts to include post-Devonian lungfish in phylogenies of dipnoans have been made, but are hampered by the poor preservation of most Mesozoic and Cenozoic lungfish, and by the paucity of the occurrences of these taxa. This contribution has made use of the few post-Devonian fossils that are known from cranial, dental and post-cranial remains, to compare them with Devonian material and with living lungfish. Characters have been chosen to cover the best preserved structures of the Mesozoic and Cenozoic fossils, and the resulting phylogeny has been discussed in relation to previous analyses. The post-Devonian phylogeny has been anchored to a published phylogeny of Devonian taxa and a phylogenetic diversity curve has been computed. Based on this phylogeny rates of origination and extinction have been calculated, and environmental transfers and trends in body size changes have been detected. Our analyses show that the Permian gnathorhizodontids and the extant lepidosirenids are closely related, that lungfishes have experienced two phases of taxic diversification, a marine one in the Devonian and a freshwater one in the Permian. Major negative size shifts occurred during the marine phase and major positive size shifts occurred during the freshwater phase. A new classification of post-Devonian dipnoan families is also presented.

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Freshwater fi shes are supposedly good case studies to test palaeobiogeographical models because they are attached to land masses, at least primary freshwater fi shes, which are unable to cross marine barriers. In this study, I review the literature about the fossil record and about the phylogeny of various freshwater fi sh groups in order to address, in a qualitative way, the biogeographic scenarios proposed to explain their modern distribution. At the intercontinental scale, vicariant events seem to have played a minor role in the distribution of main freshwater fi sh clades, except for some during the fi rst phases of the break-up. Most of the biogeographical events that shaped the modern distribution of freshwater fi sh clades are likely dispersals events that occurred in the Late Cretaceous and in the Palaeogene.

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Environmental drivers shape freshwater alpha-diversities. The Khorat Group in northeasternThailand is a succession of five continental formations ranging from the Middle? Jurassic with thelower part of the Phu Kradung to the Aptian with the Khok Kruat Formation. In order to identifyecological traits of the palaeocenoses, we focus here on biological and taphonomical features ratherthan on the sedimentological context of each assemblage. The major distinction that can be made inthe succession of bony fi sh assemblages within the Khorat Group is between the Late Jurassic basalCretaceous Phu Kradung Formation on the one hand and the Early Cretaceous Sao Khua and KhokKruat formations on the other hand.

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Latimeria chalumnae (Actinistia) was regarded as the 'ancestor of the four-legged vertebrates' and rapidly became the iconic example of a 'living fossil'. Although its evolutionary position close to the origin of tetrapods is now dismissed, the question of its evolutionary pace is still a matter of debate. The UNESCOs' World Heritage Monte San Giorgio Triassic site, spanning the border between Italy and Switzerland in the Southern Alps, has yielded one of the major marine vertebrate assemblages of the Middle Triassic worldwide. This general overview of the Middle Triassic coelacanths from Switzerland heralds a project that will be conducted in the following years. The project consists firstly to prepare, describe and compare the coelacanth material from the Besano Formation housed in the collection of the University of Zurich.

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The Cretaceous locality of Bernissart, Belgium, is well known for the Iguanodon remains it yielded. Fossils were collected during coalmine exploitation at the end of the 19th century. In the frame of the ColdCase project, which aims to understand the ecological and geological conditions in the Bernissart lake/swamp during the Barremian, a revision of the actinopterygian fauna from Bernissart, found alongside Iguanodons, has been launched. The revision of the ichtyofauna has started with taxa, unstudied since 1911: Coccolepis macroptera, Lepidotus bernissartensis, L. brevifulcratus and L. arcuatus. The study shows that the material attributed to both genera could likely be attributed to other genera and that the reduced actinopterygian taxic diversity found at Bernissart coni rms the lacustrine to swampy environment

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On the basis of nine lithostratigraphical profiles, 23 cephalopods taxa (nautilus and ammonites) are described from the Preafrican Trough and the Kem Kem region. Among them, a new species is proposed: Spathites (Jeanrogericeras) asflaensis nov. sp. This fauna is placed in its biostratigraphical framework and correlated with the standard zonation of the late Cenomanian–early Turonian. Moreover, stratigraphic correlations are proposed for the whole Maghreb from the Tarfaya Basin in the west to central Tunisia in the east. Selected taxa reveal the paleogeographical context of the western Tethys; a complex distribution of emerged areas and epicontinental seas impacted by an important marine trangression that constantly modified the costaline.

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A new ginglymodian fish, Khoratichthys gibbus, gen. et sp. nov., is described based on the impression of a single articulated fish preserved on a sandstone slab from the Late Jurassic–Early Cretaceous Phu Kradung Formation, northeastern Thailand. Khoratichthys gibbus is characterized by a distinct humpbacked body with elongate posterior spines on the dorsal ridge scales; the cheek is completely covered by bone; it has few infraorbitals, the elongate anterior-most one shows a tiny contact with the orbit, and six suborbitals arranged in one row; the opercule is rectancular in shape; the preopercule is narrow and regularly curved; and the interopercule large. A cladistic analysis including the type species of 25 ginglymodian genera indicates that Khoratichthys is the basal-most Lepisosteiformes, in an unresolved position with Neosemionotus and Lophionotus. This taxon provides a new evidence of the high diversity of ginglymodian fishes in the Phu Kradung Formation. A high taxic diversity of ginglymodians in Middle Jurassic–Early Cretaceous of southern Asian (excluding India) freshwater environments is observed, indicating that this clade occupied a major position in freshwater fish assemblages.

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Spinosaurs represent a group of peculiar theropod dinosaurs that have often been described as “crocodile-mimic”, predominantly fish-eating predators, and recently claimed to have been semi-aquatic animals. Here we report a suite of craniodental characters unexpectedly shared by spinosaurs and pike conger eels. Pike conger eels are predatory, mainly piscivorous bottom-dwelling anguilliform fishes that inhabit marine and brackish environments. These two groups of dinosaurs and fishes show a mediolaterally compressed, elongated rostrum, a terminal “rosette” bearing enlarged teeth in both upper and lower jaws, and a notch posterior to the premaxillary “rosette” characterized by the presence of reduced teeth. The morphological convergence observed in the jaws of these two distantly related groups of vertebrates may result from similar feeding behaviours. This typical jaw morphology likely represents an effective biomechanical adaptation for biting and grabbing elusive prey items in low-light aquatic environments. Associated with this specialized snout morphology, numerous integumentary mechanoreceptors involved in prey detection are present in both spinosaurs and pike congers. Our new observations provide an additional convincing argument regarding the decades-long and widely debated lifestyle of spinosaurs.

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In 1963, N. Tabaste described disconnected fossil material from the Saharan Cenomanian site of Gara Tabroumit, and especially three sets of isolated scales that she all referred to the genus Lepidotes. Although the rhomboid shape and overall morphology of one set of scales allow regarding them as ganoid scales, the external aspect of the ganoine is not as regularly smooth and shiny as it is in most lepidosteoid scales commonly referred to ginglymodian (“semionotiform”) fishes. A photonic microscopic study of scale ground sections definitively excludes the allocation of these scales to the genus Lepidotes, or to closely related genera, because of an interrupted ganoine layer, and, more generally to ginglymodians: i) the bony basal plate is deprived of Wil- liamson's canaliculi, which characterized holostean scales; ii) the basal plate is well vascularised and overlaid by a thick layer of dentine; iii) there is an elasmodine layer between dentine and the basal plate. These various histomorphologic characters allow us to consider these ridged scales as belonging to a polypteriform fish, probably Bawitius. The histological specificities of the two other scale series allow their allocation to holostean taxa, respectively to “Lepidotes”pankowskii and to Obaichthys africanus. A new generic name, Adrianaichthys, is coined for “Lepidotes” pankowskii.

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Two theoretical models have been proposed to describe long-term dynamics of diversification: the equilibrium model considers the Earth as a closed system with a fixed maximum biological carrying capacity, whereas the expansion model hypothesizes a continuously increasing diversification of life. Based on the analysis of the fossil record of all organisms, Benton suggested contrasting models of diversity dynamics between marine and continental realms. Diversity in marine environments is characterized by phases of rapid diversification followed by plateaux, i.e., an equilibrium model directly derived from insular biogeography theories, whereas diversity in continental environments is characterized by exponential growth. Previous studies that aimed at testing these models with empirical data were based on datasets extracted directly from the reading of the vagaries of the raw fossil record, without correcting for common fossil record biases (preservation and sampling). Although correction of datasets for the incompleteness of the fossil record is now commonly performed for addressing long-term biodiversity variations, only a few attempts have been made to produce diversity curves corrected by phylogenetic data from extant and extinct taxa. Here we show that phylogenetically corrected diversity curves for "fish" (actinopterygians and elasmobranchs) during the last 200 million years fit an equilibrium model in the marine realm and an expansion model in the freshwater realm. These findings demonstrate that the rate of diversification has decreased for marine fish over the Cenozoic but is in sharp expansion for freshwater fish.

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The vertebrate assemblage from the Early Cretaceous non-marine Xinlong Formation of the Napai Basin, in the south-western part of Guangxi Zhuang Autonomous Region (southern China), is reviewed. The assemblage includes chondrichthyans (at least six species of hybodont sharks including Hybodus, Thaiodus, Heteroptychodus and Acrorhizodus), actinopterygians (Halecomorphi and Ginglymodi), turtles (the adocid Shachemys and the carettochelyid Kizylkumemys), crocodilians (cf. Theriosuchus) and dinosaurs (the sauropods Fusuisaurus and Liubangosaurus, carcharodontosaurid and spinosaurid theropods, iguanodontians and a possible psittacosaurid). This assemblage shows many similarities to those from non-marine formations of the Khorat Group of north-eastern Thailand. It seems to be particularly close to that from the Khok Kruat Formation, considered as Aptian in age, as shown especially by sharks and turtles and by the presence of iguanodontians. An Aptian age is therefore proposed for the Xinlong Formation. A study of the stable oxygen and carbon isotope compositions of reptile apatite suggests that this part of South China experienced subtropical arid conditions during the deposition of the Xinlong Formation. In its composition, the vertebrate fauna from the Xinlong Formation seems to be more similar to coeval faunas from SE Asia than to assemblages from northern China (including the Jehol Biota). Although this may partly reflect different depositional and taphonomic environments (fluvial for the Xinlong Formation versus lacustrine for the Jehol Biota) it seems likely that, during Early Cretaceous time, southern China and SE Asia were part of a distinct zoogeographical province, different from that corresponding to northern China. This may be the result of both climatic differences (with relatively cool climates in northern China versus a subtropical climate in the south) and geographical barriers such as mountain chains.

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Actinopterygii (ray-finned fishes) and Elasmobranchii (sharks, skates and rays) represent more than half of today's vertebrate taxic diversity (approximately 33000 species) and form the largest component of vertebrate diversity in extant aquatic ecosystems. Yet, patterns of 'fish' evolutionary history remain insufficiently understood and previous studies generally treated each group independently mainly because of their contrasting fossil record composition and corresponding sampling strategies. Because direct reading of palaeodiversity curves is affected by several biases affecting the fossil record, analytical approaches are needed to correct for these biases. In this review, we propose a comprehensive analysis based on comparison of large data sets related to competing phylogenies (including all Recent and fossil taxa) and the fossil record for both groups during the Mesozoic-Cainozoic interval. This approach provides information on the 'fish' fossil record quality and on the corrected 'fish' deep-time phylogenetic palaeodiversity signals, with special emphasis on diversification events. Because taxonomic information is preserved after analytical treatment, identified palaeodiversity events are considered both quantitatively and qualitatively and put within corresponding palaeoenvironmental and biological settings. Results indicate a better fossil record quality for elasmobranchs due to their microfossil-like fossil distribution and their very low diversity in freshwater systems, whereas freshwater actinopterygians are diverse in this realm with lower preservation potential. Several important diversification events are identified at familial and generic levels for elasmobranchs, and marine and freshwater actinopterygians, namely in the Early-Middle Jurassic (elasmobranchs), Late Jurassic (actinopterygians), Early Cretaceous (elasmobranchs, freshwater actinopterygians), Cenomanian (all groups) and the Paleocene-Eocene interval (all groups), the latter two representing the two most exceptional radiations among vertebrates. For each of these events along with the Cretaceous-Paleogene extinction, we provide an in-depth review of the taxa involved and factors that may have influenced the diversity patterns observed. Among these, palaeotemperatures, sea-levels, ocean circulation and productivity as well as continent fragmentation and environment heterogeneity (reef environments) are parameters that largely impacted on 'fish' evolutionary history, along with other biotic constraints.

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The vertebrate-bearing beds of the Laño quarry (Condado de Treviño) are among the most relevant sites from the Late Cretaceous of Europe. Geologically, Laño and the adjacent region are set on the southern limb of the South-Cantabrian Synclinorium (SE Basque-Cantabrian Region, northern Iberian Peninsula). The Laño sites were discovered in 1984; thousands of bones and teeth, including microfossils, have been collected during the prospection in the field and excavation campaigns. The vertebrate remains occur at two different stratigraphic horizons within a continental to shallow marine succession of Late Campanian-Maastrichtian age. The lower horizon contains the Laño 1 and Laño 2 sites, whereas the upper horizon contains the Albaina site. In the Laño sites, three fossiliferous beds (called L1A, L1B and L2) are known within an alluvial system composed mainly of fluvial sands and silts. The sedimentary structures are consistent with channel areas within an extensive braided river system. Based mainly on stratigraphic correlations, the fluvial beds of Laño are regarded as Late Campanian to Early Maastrichtian in age. These deposits have yielded a very diverse vertebrate assemblage, which consists of nearly 40 species, including actinopterygians, lissamphibians, lepidosaurs, turtles, crocodyliforms, dinosaurs, pterosaurs, and mammals. Seven genera and ten species have been erected to date in Laño. With reference to the marine vertebrate association of Albaina, it consists of at least 37 species, including sharks and rays, actinopterygians, mosasaurids, and plesiosaurs. Two genera and species of rhinobatoids (family indet.) and two new species of rhinobatids have been erected in Albaina. The fossil association indicates a Late (but not latest) Maastrichtian age. Recently, isolated turtle and dinosaur fossils have been discovered in the sublittoral beds of Albaina. The Laño quarry is one of the most noteworthy Campanian-Maastrichtian vertebrate localities of Europe by its taxonomic diversity, and provides useful information about the composition and affinities of both continental and marine vertebrate faunas from the latest Cretaceous of southwestern Europe.

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The available data concerning the environmental changes and faunal replacements that occurred during the Cenomanian marine transgression in the North of Iberia are integrated and discussed on the basis of new evidence from the invertebrate and vertebrate fossil record. New stratigraphical data and the reassessment of known stratigraphic sections support the correlation of the Cenomanian carbonate-ramp successions from the Iberian margin to the centre of the Basque-Cantabrian Basin during a major transgressive episode. This new stratigraphical framework is the key to understand the changing oceanographic conditions in the area that resulted from a progressive inundation of the Iberian continental platform. This transgression seems to have triggered major faunal replacements in this particular geographic area, starting out around the Albian-Cenomanian transition. Ammonite faunal replacement led to a new radiation of this group that spread out rapidly until their new decline around the Cenomanian-Turonian boundary. A new record of Calycoceras (Newboldiceras) asiaticum spinosum and the first record of a Pachyrhizodontidae indet. (Actinopterygii, Teleostei, Crossognathiformes) from the Iberian Peninsula are reported here from the Cenomanian basal units of the major Late Cretaceous transgressive episode. The two new specimens come from the same level in an outer marine ramp succession near Amurrio, Basque Country, northern Spain, and are representatives of the Cenomanian faunal turnover. The new record of a pachyrhizodontoid fish from the Cretaceous of Iberia is an indication of the ichthyofaunal replacement in this part of the world. The relict fish faunas from the Early Cretaceous of the former island of Iberia were mostly formed by basal neopterygian taxa closely related to those of the marine Jurassic of other parts of Europe. During the Early-Late Cretaceous transition they were replaced by the teleostean-based new stock that constitutes the basis of the Late Cretaceous, Cenozoic, and Recent faunas.

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Since its usage by Darwin (1859), the concept of “living fossil” has undergone multiple definitions and has been much discussed and criticized. Soon after its discovery in 1938, the coelacanth Latimeria was regarded as the iconic example of a “living fossil.” Several morphological studies have shown that the coelacanth lineage (Actinistia) has not displayed critical morphological transformation during its evolutionary history and molecular studies have revealed a low substitution rate for Latimeria, indicating a slow genetic evolution. This statement, however, has been recently questioned by arguing that the low substitution rate was not real, and that the slow morphological evolution of actinistians was not supported by paleontological evidence. The assessment of morphological transformation among three vertebrate lineages during a time interval of circa 400 million years shows that the morphological disparity of coelacanths is much more reduced than the morphological disparity of Actinopterygii and Tetrapoda. These results support the idea that living coelacanths are singular organisms among the living world.

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The Early Triassic witnessed the highest taxic diversity of coelacanths (or Actinistia), a clade with a single liv- ing genus today. This peak of diversity is accentuated here with the description of a new coelacanth discovered in the lower Spathian (Upper Olenekian, Lower Triassic) cropping out in the Tulcea Veche (Old Tulcea) promon- tory, in the city of Tulcea, in North Dobrogea, Romania. The bone remains were preserved in a block of limestone, which was chemically dissolved. The resulting 3D and matrix-free ossifications correspond mostly to elements of the skull and branchial apparatus. Posterior parietals, postparietal with associated prootic and basisphenoid allow a precise description of the neurocranium. Ossifications of the lower jaw, together with branchial and pec- toral elements, complete the description of this coelacanth and support the coining of a new generic and specific name, Dobrogeria aegyssensis. A phylogenetic analysis of actinistians with the new species recovers clades which were found in most recent analyses, i.e. the Sasseniidae, the Laugiidae, the Coelacanthiformes, the Latimerioidei, the Mawsoniidae and the Latimeriidae, and identifies the new taxon as a non-latimerioid coelacanthiform.

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A new ginglymodian fish, Isanichthys lertboosi, is described from the Phu Kradung Formation, north-eastern Thailand, a freshwater deposit of probable Late Jurassic age. The species is represented by four specimens, from the Phu Noi locality, associated with a rich fauna of sharks, turtles, crocodiles, and theropod and sauropod dinosaurs. One specimen is an isolated braincase, which provides characters rarely observed in extinct ginglymodians. The species is referred to the genus Isanichthys, a taxon originally described on the basis of a single specimen from the Phu Nam Jun locality, a slightly younger site approximately 75 km from Phu Noi. Isanichthys is mainly distinguished by frontals slightly narrower anteriorly than posteriorly, two anterior infraorbitals not in contact with the orbit, reduced preorbital region, and a small orbit and a cheek region completely covered by bones. The new species is characterized, among other characters, by a dermal component of the sphenotic visible on the cheek, one pair of extrascapulars plus a small median one, the presence of few suborbitals (ca. 4 or 6) arranged in one row, and a median dorsal row of scales with spine. Comparisons with other ginglymodian taxa and a cladistic analysis indicates that Isanichthys (Lepidotes) latifrons from the Late Jurassic of England, as well as probably Isanichthys (Lepidotes) luchowensis from the Early or Middle Jurassic of Sichuan, China, form a clade with both Thai species of Isanichthys. The new species provides evidence of the high diversity of ginglymodian fishes in the Phu Kradung Formation and suggests a new hypothesis of phylogenetic relationships among extinct ginglymodians.

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Professor Jean-Pierre Berger joined the Fribourg University (Switzerland) in 1989 as a lecturer (chargé de cours), quickly rising to the rank of head assistant with a postdoctoral lecture qualification in 1992, and becoming Associate Professor for palaeontology in 1997. Fribourg, Lausanne, Tübingen and Munich were important places in his professional career.

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New coelacanth material from the Middle Triassic Prosanto Formation of the Ducan and Landwasser area near Davos in eastern Switzerland, Canton Graubünden, is described. A sub-complete individual is visible in ventral view, and shows details of its branchial apparatus. In particular, it possesses relatively large teeth on the ceratobranchials, and possible ossified hypobranchials. Few diagnostic characters are observable, and most of them are visible on the mandibles preserved in lateral view. This specimen shares characters with Ticinepomis peyeri, a smaller form from the Middle Triassic of Monte San Giorgio, whose holotype is re-described in part here. A second specimen, a fragmentary caudal skeleton shows the typical supplementary lobe of coelacanths, and meristic characters indicating probable close affinities with T. peyeri. We refer this material to Ticinepomis cf. T. peyeri. Because the new specimen is larger than the holotype, we refute the possible juvenile status of the small specimen from Monte San Giorgio. The new material of Ticinepomis from Canton Graubünden shows anatomical features not preserved on the holotype and allows the addition of new characters to a previously published data matrix of actinistians. A phylogenetic analysis is performed, which supports that Ticinepomis is nested among the Latimeriidae. The diversity of post-Palaeozoic coelacanths is assessed. The taxic diversity of observed occurrences shows a peak in the Early Triassic and a peak in the Late Jurassic, as detected in previous studies. When ghost lineages are included in the computation, the Late Jurassic peak is smoothened. By comparing the taxic diversity curves with the curve of average ghost lineage duration, we conclude that the Early Triassic peak of diversity was probably caused by a biological radiation, whereas the Late Jurassic peak of observed diversity is probably the result of a Lagerstätten effect.

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A recently discovered fish assemblage from the “Schistes à Meletta” facies (Lower Oligocene) of the Glières Plateau, Bornes Massif, Haute–Savoie, eastern France is described. The assemblage, comprising specimens ranging from fully-articulated skeletons to isolated scattered ossifications, is composed of Anenchelum cf. glarisianum, Pristigenys sp., Fistularia sp., Caranx cf. glarisianus alongside indeterminate teleosts. This new assemblage greatly increases the fish diversity previously known from the “Schistes à Meletta” of this area. The fauna shows biogeographic affinities with assemblages from the Peritethys domain, in particular from the Helvetic molassic basin and from the Paratethys. The genera identified at the Glières locality are represented today by species living in tropical nearshore environments together with species from the open sea. A possible explanation is that the environment of deposition was rather deep, and that shallow-water fishes were brought in by turbidity currents.

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Cladodontomorph sharks are Palaeozoic stem chondrichthyans thought to go extinct at the end-Permian mass extinction. This extinction preceded the diversification of euselachians, including modern sharks. Here we describe an outer-platform cladodontomorph shark tooth assemblage from the Early Cretaceous of southern France, increasing the fossil record of this group by circa 120 million years. Identification of this material rests on new histological observations and morphological evidence. Our finding shows that this lineage survived mass extinctions most likely by habitat contraction, using deep-sea refuge environments during catastrophic events. The recorded gap in the cladodontomorph lineage represents the longest gap in the fossil record for an extinct marine vertebrate group. This discovery demonstrates that the deep-sea marine diversity, poorly known during most of the fish evolutionary history, contains essential data for a complete understanding of the long-term evolution of marine fish paleobiodiversity.

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The osteology of Thaiichthys buddhabutrensis, nov. gen., from the Late Jurassic – Early Cretaceous of Thailand is described on the basis of a collection of well-preserved specimens. The mode of preservation of the material allows describing the external anatomy, as well as some elements of the internal anatomy (braincase, elements of the vertebral column). Most of the cranial and postcranial skeleton shows a rather conservative anatomy for ‘semionotiformes’, but the jaw apparatus displays specializations. Variations observed in the ossification pattern of the skull roof and of the cheek, in the morphology of the median dorsal scales and in fin rays’ count indicate that caution should be applied when these characters are used in diagnoses and in phylogenetic analyses. A phylogenetic analysis including a set of gars, of ‘semionotiformes’, of Macrosemiiformes and of Halecomorphi shows the following features: (1) the monophyly of Holostei; (2) sister-pair relationships between Tlayuamichin/Semiolepis, Isanichthys/’Lepidotes’ latifrons and Araripelepidotes/Pliodetes; (3) the latter pair, together with Thaiichthys and possibly ‘Lepidotes’ mantelli, are resolved as stem Lepisosteiformes; and (4) the ‘semionotiformes’ (a group gathering species of Semionotus and Lepidotes) do not form a clade.

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Two fish fragments from the Middle to Late Maastrichtian of the Island of Gavdos, Greece, are described. One is a caudal portion of an Ichthyodectoidei incertae sedis, which shows some affinities with Saurodon elongatus from the Late Campanian – Early Maastrichtian of Nardo, southern Italy. The other specimen is an isolated skull referred to Enchodus cf. dirus, which is well preserved enough to be included into a phylogenetic analysis of species referred to the genus Enchodus, and subsequently to analyse the biogeograhic signal provided by the cladogram. E. dirus is known in the Late Cretaceous of North America, both in the Western Interior Seaway and on the eastern coast. The occurrence of this lineage is western Tethys and central Tethys is regarded as the result of a vicariant event. Other vicariant events occurred in the Cretaceous between Enchodus species occurring in western and central Tethys respectively. On the other hand, the geographic distribution of several Enchodus species shows ranges extending along North-South axes.

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The osteology of the ichthyodectiform Eubiodectes libanicus (Pictet & Humbert, Citation1866) from the Cenomanian of Lebanon is described on the basis of acid-prepared specimens. For comparative purposes, the osteology of other putative ichthyodectiforms is described or discussed. We focus on the description of hitherto poorly described species such as Chiromystus mawsoni Cope, Citation1885, Ghrisichthys bardacki (Cavin, Citation1997a), ‘Saurodon' intermedius (Newton, Citation1878) and Thrissops sp. from Kimmeridge, England. Sixty-nine morphological characters are defined and analysed to infer the phylogenetic relationships within ichthyodectiforms. The main results are: (1) exclusion of Ascalabothrissops and Pachythrissops from the ichthyodectiforms; (2) redesignation of ‘Ichthyodectes' bardacki, from the Turonian of Morocco, to Ghrisichthys gen. nov.; (3) resolution of a monophyletic family Cladocyclidae grouping mid-Cretaceous ichthyodectiforms that lived mainly along the southern margin of Tethys (Chirocentrites, Cladocyclus, Eubiodectes, Chiromystus); (4) resolution of a Late Cretaceous family Ichthyodectidae containing Ichthyodectes, Ghrisichthys and Xiphactinus from mid-northern latitude seas; and (5) a better resolved Late Cretaceous family Saurodontidae in the northern hemisphere, that includes the genus Gillicus.

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