A new, toothed ornithorhynchid monotreme from Two Trees Site in the Riversleigh World Heritage Area, northwestern Queensland, Australia, is described. This species is the largest known ornithorhynchid, fossil or extant, the fourth extinct platypus described, and the second species discovered at Riversleigh. It exhibits a unique molar morphology that significantly broadens understanding about disparity within this group of monotremes and challenges a previous presumption that fossil species of Obdurodon form an anagenetic lineage leading directly to the living dentally degenerate Platypus Ornithorhynchus anatinus. Apical cusp wear on its teeth suggests that it was crushing rather than cutting hard prey items. Its relatively derived features also adds to mounting evidence that the Two Trees deposit that contains several unique taxa may be younger than the surrounding middle Miocene fossil deposits, possibly late Miocene or even Pliocene in age, intervals of time previously unrepresented by ornithorhynchids.

Late Cretaceous vertebrate faunas of India are known predominantly from intertrappean deposits in the Deccan volcanic province of the central and western parts of the country. A thick and nearly continuous sequence of Early Cretaceous—Early Paleocene fossiliferous sediments exposed in the Cauvery Basin of South India has been comparatively poorly explored. Here, we present a preliminary description of a new fauna consisting of vertebrate fossils discovered from the continental Upper Cretaceous (late Maastrichtian) Kallamedu Formation. The Kallamedu Fauna includes ganoid fishes, amphibians, turtles, crocodiles, and dinosaurs, with many taxa suggesting Late Cretaceous biotic links between India and other Gondwanan landmasses. Teeth of abelisaurid dinosaurs, known previously from the Middle Jurassic of South America and the Late Cretaceous of Africa, Madagascar, and central and western India, support a pan-Gondwanan distribution for this group oftheropod dinosaurs. Of greatest significance, however, is the first discovery of a Simosuchus-like notosuchian crocodile outside of Madagascar. This report of the first Indian Simosuchus-like notosuchian crocodile further strengthens earlier evidence from other vertebrate groups for close biotic links between India and Madagascar in the Late Cretaceous, most likely through dispersal via the Seychelles block, Amirante Ridge, and Providence Bank.

The southern Saskatchewan mid-Miocene Wood Mountain Formation has been the basis of studies describing its mammalian and herpetofaunas; here we present the description of the fish material from the formation. The fauna, of probable Barstovian age, would have been isolated from the western side of the continent, in an area draining towards the northeast. Sixteen taxa are recognized to specific orders or lower taxonomic levels, although this number is approximate because some identifications are tentative. The fauna includes a lepisosteid (Lepisosteus), an amiine, a probable hiodontiform osteoglossomorph, a hiodontid (Hiodon), at least two unidentified cypriniforms and a leuciscine, three ictalurids (Ameiurus, Ictalurus, and cf. Noturus), an esocid Esox sp. more closely related to pikes than to pikerels, a possible moronid perciform, a centrarchid (cf. Pomoxis), two percids (including Stizostedion sp.), and an unidentified teleost. This fauna includes the earliest North American percids, the last occurrence of lepisosteid and amiine fossils in Canada west of the Great Lakes, and may constitute the earliest evidence of North American moronids. The assemblage is typical of well-oxygenated, lowland fluvial environments, and indicates a wide variety of substrates and flow strengths, as well as the presence of aquatic vegetation in the vicinity. Additionally, the fauna implies the nearby presence of turbid and deeper environments, suggesting that the area was an environmentally varied floodplain during deposition. The paleoenvironmental implications of this ichthyofauna are compatible with those of the herpetofauna: warm temperate to subtropical, with temperatures similar to those of northern Mississippi or southern Tennessee.

Two fossil fish were recently recovered from late Miocene freshwater deposits of the Muş Basin in Eastern Anatolia, Turkey. This area is in the collision zone of the Afro-Arabian and Eurasian plates, and therefore is a biogeographic contact zone or ecotone, where different biotas have been brought together. Only one fish was previously known from the area, the leuciscine cyprinid Leuciscus (Palaeoleuciscus) oeningensis. Renewed collecting at this locality provides the potential to determine much more information about the composition of the biogeographic contact zone. The two fishes described here are not named; one is placed in the family Clupeidae and the other is left as an indeterminate teleost. The fishes from the Muş Basin locality indicate that the fauna, or at least the fish portion, of the ecotone has an overall Eurasian origin, with little or no Afro-Arabian component.

Although morphological evidence alone appears insufficient to resolve the problem of extant amphibian ancestry, comparison of developmental processes and functional correlates of ontogenetic change may provide a basis for evaluating relationships among extinct and extant tetrapods. In the first allometric study of cranial and postcranial growth in any lepospondyl, I investigate skeletal development in the microsaurs Microbrachis pelikani and Hyloplesion longicostatum using traditional measurement-based and geometric morphometric analyses. Regression analyses against both skull and centrum lengths for M. pelikani indicate positive allometric scaling of the interclavicle plate length, pubis, and ilium, and negative scaling of the diameter of the orbit. Preliminary data for H. longicostatum support negative scaling of neural arch height and posterior centrum height. Results from geometric morphometrics suggest slight widening of the cheek in M. pelikani, rather than marked elongation. Overall, cranial and postcranial growth in both microsaurs was primarily isometric and comparison with allometric data from other Paleozoic taxa suggests that isometric growth is an ancestral feature of development in early tetrapods. All regression analyses for M. pelikani and H. longicostatum had a constant linear slope, indicating that ontogenetic trajectories were continuous, with gradual skeletal growth and no shift in feeding or locomotor function during ontogeny. The lack of morphological change suggests that these microsaurs did not undergo an extant amphibian-like metamorphosis that included reorganization of the skeleton. These data support the hypothesis that metamorphosis is a derived mode of development present only in extant amphibians and their closest relatives.

The Neotropical frog genus Leptodactylus is one of the most taxonomically diverse of all neobatrachian anurans. Despite the genus being highly diversified and widely distributed today, the fossil record is scanty and restricted to the Quaternary of the Neotropics. Here, we report and describe a new record of total group Leptodactylus from the Chapadmalalan (early Pliocene) of the South American Pampas. We evaluate both qualitative and quantitative characters and discuss the taxonomic value of body size in the context of living Leptodactylus. A number of features of the fossil elements suggests an affinity with the living species of the L. latrans species group and, particularly, with L. latrans. However, the lack of resolution of Leptodactylus interrelationships and, thus, the lack of osteological synapomorphies of the species groups and species within the genus conspire to force allocation of the fossils to crown Leptodactylus until they are studied in a rigorous phylogenetic context. In any case, the new material constitutes the oldest record of total group Leptodactylus and extends their stratigraphic range back to the early Pliocene.

New anatomical observations and reinterpretations of previously identified structures have resulted in new taxonomic diagnoses for the fossil hind-limbed marine snakes Pachyrhachis problematicus, Eupodophis descouensi, and Haasiophis terrasanctus. Among the most important conclusions of our study are the following: Haasiophis and Eupodophis show no evidence of possessing a laterosphenoid; Pachyrhachis and Eupodophis do retain a jugal; Haasiophis, like Eupodophis, has chevron bones in the caudal region; Haasiophis has a large number of unfused intercentra along the anterior portion of the precloacal column; the dentary of Pachyrhachis has numerous mental foramina (at least four); Pachyrhachis has at least one sacral vertebra with unfused sacral ribs. To test the effect of our new observations on the phylogenetic relationships of snakes, we ran three phylogenetic analyses using alternative outgroups to polarize the character transformations. The ingroup consisted of all well-preserved fossil snakes from the Cretaceous, the madtsoiids, and taxa that are representative of all major groups of extant snakes. The analyses yielded a series of most parsimonious trees that placed Pachyrhachis, Eupodophis, and Haasiophis either as a series of stem taxa at the base of the radiation of snakes (two analysis), or as members of a clade of fossil snakes that are the sister group of all living alethinopidians (one analysis).

The study of bone growth rate and metabolic rate evolution in archosaurs (crocodiles, dinosaurs including birds, and pterosaurs) and close outgroups has become a subject of major interest among paleontologists in recent years. In this paper, we estimate the bone growth rate of Euparkeria using a new statistical inference model for the humerus. We modified the taxonomic range of extant species used in previous studies, on which we performed quantitative measurements of histological features and bone growth rates. Bone growth rate values estimated for Euparkeria are crucial in understanding the ancestral condition for archosaurs because this taxon is considered the closest relative to the archosaur crown group. We obtained an instantaneous growth rate of 6.12 µm/day, suggesting that Euparkeria shared with other non-archosaurian archosauromorphs (Prolacerta, Proterosuchus, and Erythrosuchus) a condition of high growth rate compatible with endothermy. This derived state may have been inherited by some Triassic crurotarsans, as suggested by the high instantaneous bone growth rate (14.52 µm/day) estimated in this study for Postosuchus. Jurassic crurotarsans may have lost endothermy during the transition from terrestrial habitats and active predation to aquatic habitats and sit-and-wait predation behaviors, so that Cretaceous crocodiles may be secondarily ectothermic, as suggested by δ¹⁸O values. In conclusion, we provide new evidence for the hypothesis of an ancestral endothermic state for the last common ancestor of archosaurs, and show that non-archosaurian archosauromorphs and Triassic crurotarsans may have been characterized by a thermometabolism more similar to that of dinosaurs than to that of lepidosaurs and turtles.

We describe Katepensaurus goicoecheai, gen. et sp. nov., a diplodocoid sauropod dinosaur from the Bajo Barreal Formation (Upper Cretaceous: Cenomanian—Turonian) of south-central Chubut Province, central Patagonia, Argentina. The holotypic specimen is a closely associated partial axial skeleton that includes cervical, dorsal, and caudal vertebrae. The dorsal vertebrae of Katepensaurus exhibit the following distinctive characters that we interpret as autapomorphies: (1) internal lamina divides lateral pneumatic fossa of centrum; (2) vertical ridges or crests present on lateral surface of vertebra, overlying neurocentral junction; (3) pair of laminae in parapophyseal centrodiapophyseal fossa; (4) transverse processes perforated by elliptical fenestrae; and (5) well-defined, rounded fossae on lateral aspect of postzygapophyses. Based on the results of previous phylogenetic analyses, we regard the new taxon as a member of Rebbachisauridae; more specifically, it may pertain to Limaysaurinae, a rebbachisaurid subclade that, to date, is definitively known only from southern South America. As currently understood, the rebbachisaurid fossil record suggests that the clade achieved its greatest taxonomic diversity within a few million years of its extinction during the early Late Cretaceous.

Arenysaurus ardevoli is a lambeosaurine hadrosaurid from the late Maastrichtian of Arén (Huesca, northern Spain) that has recently been described. The holotype is the first and the most complete lambeosaurine with a braincase from Europe. In this paper, we present a complete description of the postcranial skeleton, which was poorly described when the taxon was named because it was partially unprepared, and new information on several cranial bones (jugal, maxilla, and dentition). A new phylogenetic analysis of Arenysaurus and the closely related Blasisaurus canudoi, also from the late Maastrichtian of Arén, places them inside the Parasaurolophini in a dichotomy with Parasaurolophus spp. Paleobiogeographically, the presence of Arenysaurus and its relationships with other lambeosaurines suggest at least one geodispersal event from Asia to Europe no later than the middle—late Campanian.

Ceratopsidae represents one of the last and best-known radiations of non-avian dinosaurs. Interspecific variation is well documented qualitatively with linear measurements, but little has been done to quantify shape differences in the frill that may indicate functional or evolutionary signals. In order to investigate shape change in the squamosal across Chasmosaurinae and Centrosaurinae, we applied geometric morphometrics to the outline of the squamosal for 155 specimens representing 27 ceratopsid species and Protoceratops spp. A Mantel test suggests that the shape of ceratopsid squamosals is highly constrained by phylogeny. MANOVA, ANOVA, and their phylogenetic versions suggest that an evolutionarily significant allometric signal exists between the two clades, but not within clades. Principal component analysis indicates that centrosaurines have a uniform squamosal shape, with the exceptions of Spinops and Diabloceratops. Even when accounting for phylogeny, the relationship between squamosal shape and size is significant. Mapping shape onto the phylogeny, we estimated ancestral shapes at nodes. The transition from the non-ceratopsid to ceratopsid condition is characterized by a squamosal with a wider angle between the infratemporal process and the caudoventral margin, and a more dorsoventrally elongated and caudally expanded blade. From root to tips, centrosaurine squamosals were found to be conservative, but exhibit a slight dorsoventral expansion and a narrow angle between the infratemporal process and the caudoventral margin in more derived taxa. Chasmosaurines, compared with centrosaurines, show a derived morphology, with a trend towards a blade that is strongly expanded dorsoventrally and with a narrower angle between the infratemporal process and the caudoventral margin.

Sinophoneus yumenensis and Stenocybus acidentatus are the only dinocephalians from China, and the latter taxon has been proposed to be a junior synonym of the former. Here I confirm this synonymy on the grounds that the differences between the two putative taxa are due to ontogenetic variation. The osteology of Sinophoneus yumenensis is described in detail based on both previously described specimens and several new ones from the same locality. Sinophoneus yumenensis differs from all other anteosaurs in having premaxillary dorsal processes that are separated by relatively long nasal anteromedial processes, and vomers without raised, elongated edges; from all other anteosaurs except Archaeosyodon praeventor in having distinct frontal posterolateral processes, and a wide intertemporal region formed partly by long posterior processes of the postfrontals that approach the posterior edge of the skull roof; and from Archaeosyodon praeventor in having a well-developed midline ridge on skull roof. A revised phylogenetic analysis including the new material recovers Sinophoneus as the most basal known anteosaurid.

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Here for the first time we use micro-computed tomography (µCT) scanning techniques to study dental replacement in the Early Triassic cynodont Thrinaxodon liorhinus.We analyzed five specimens ranging 37–87 mm in skull length using µCT scanning, which were supplemented by detailed anatomical analysis of 48 specimens with a basal skull length of 30–96 mm. Our results indicate that lower postcanines are more numerous and present amore complex morphology than the upper postcanines, even in the same individual; only the lower postcanines have more than three sectorial cusps and a cingular collar on the lingual margin. Complexity of the postcanines increases from the smallest individual to specimens with a skull length of 75 mm, but complexity decreases in larger specimens. Our results confirm the alternate replacement of the postcanines and the posterior migration of the postcanine series (including the loss without replacement of the anterior-most postcanines). Observations point to a posterior-to-anterior replacement wave in lower postcanines, but the evidence is not clear-cut for the upper series. The virtual extraction of functional and replacement teeth permitted us to conclude that in most of the cases the upper canines were replaced anteriorly, whereas lower canines were replaced posteriorly. The presence of two simultaneous replacements of the upper canine tooth was observed in two small juveniles, suggesting a higher rate of canine replacement at a younger age. Incisors also had a sequential replacement pattern, and more replacement teeth were present in medium-sized individuals.

Isolated bones of forelimb and pelvic girdle (two humeri, five ulnae, and an ilium) recovered from the Late Jurassic (Kimmeridgian) Guimarota coal mine in western central Portugal are attributed to the docodont Haldanodon exspectatus, dryolestoids, and a ?paulchoffatiid multituberculate. The larger of the two humeri is assigned to the dryolestid Dryolestes leiriensis based on size and shape. It clearly exhibits an incipient trochlea at the distal joint, suggesting that this derived character was well established among Late Jurassic dryolestidans, including Henkelotherium. Plesiomorphic characters are the prominent spherical radial condyle and the weakly developed ulnar condyle. An incipient medial keel is present in distal aspect of the humerus trochlea. The shallow olecranon fossa of the humerus corresponds to the small anconeal process of the radius. The smaller humerus with damaged distal joint is 50% smaller and cannot be assigned to a specific dryolestoid taxon. It is in the size range of the smaller Guimarota dryolestoids Krebsotherium, Drescheratherium, and Henkelotherium. One ulna differs from the dryolestoid ulnar shape by the nearly semicircular articular surface for the ulnar condyle of the humerus, the asymmetric olecranon with medial overhang, as well as the prominent anconeal process and is tentatively attributed to a paulchoffatiid multituberculate.

NewZealand's first pre-Pleistocene mystacinid bat fossils have been recovered from early Miocene sediments of the Manuherikia Group near St. Bathans, Central Otago. Mystacinidae, which belongs to the Gondwanan bat superfamily Noctilionoidea, is the only living mammalian family endemic to New Zealand, although its distribution included Australia in at least the Oligo-Miocene. The only member of the family definitely surviving is the peculiar walking bat Mystacinatuberculata. The St. Bathansmystacinid fossils consist of isolated teeth and postcranial fragments that appear to represent two new taxa of similar size and functional morphology (dental and wing) to Quaternary mystacinids. They suggest an Australasian mystacinid radiation now numbering at least eight species: four from New Zealand and four from Australia. The St. Bathans fossils demonstrate that mystacinids have been in New Zealand for at least 19–16 Ma and signal the longest fossil record for an endemic lineage of island bats anywhere in the world. They add to the list of endemic vertebrate lineages present in Zealandia by the early Miocene, including leiopelmatid frogs, sphenodontids, acanthisittid wrens, adzebills, moa, and kiwi.

New discoveries of numerous fossil femora from giant caviomorph rodents from the Miocene of Venezuela and a specimen of aMiocene giant rodent from Trinidad in the collections of the Naturhistorisches Museum in Basel made possible the first examination of taxonomic, ontogenetic, and functional variation in these animals. We provide comparisons of femoral shape, metrics, and growth (epiphyseal closure), finding that four morphotypes are distinguishable based largely on degrees of robustness or gracility. This indicates that the diversity of giant caviomorphs was larger than previously known; Phoberomys pattersoni was not the only giant caviomorph that inhabited the Miocene of the northern Neotropics. The study of cortical cross-sectional area of fossils serves to estimate the body mass for two giant caviomorphs at 420–580 kg. The first description of patterns of bone microstructure in three fossil giant caviomorph femora reveals similarities to extant rodents: absence of Haversian tissue and presence of layers of lamellar followed by reticular-like bone.

Recent field work in the late Cenozoic Zanda Basin in southwestern Tibetan Plateau has provided new fossil evidence of vertebrate faunas spanning the late Miocene to Pleistocene, which represents new occurrences hitherto unknown in that region of Asia. In this paper we describe a new species of the cursorial hyaenid Chasmaporthetes, C. gangsriensis, sp. nov., from the Zanda Basin. Chasmaporthetes gangsriensis is smaller than other Plio-Pleistocene Eurasian records of the genus,and retains relatively wide premolars that are underdifferentiated in size. The m1 talonid has a trenchant hypoconid typical of Chasmaporthetes, but with a trigonid length-to-width ratio lower than all specimens referred to the genus. Metatarsal and phalangealelements referred to C. gangsriensis are long and gracile, indicating cursorial abilities typical of Chasmaporthetes. With an age of early Pliocene (4.89–4.08 Ma), C. gangsriensis is morphologically the most basal Pliocene Chasmaporthetes in China,and is consistent with the ‘out of Tibet’ hypothesis for some Pleistocene megafauna. An analysis of nasal bone morphology revealed large intraspecific variation in extant spotted hyenas, showing that it is not a reliable criterion for species diagnosisin Chasmaporthetes. An evaluation of the biostratigraphic relationships among Asian and North American occurrences of Chasmaporthetes indicates that the genus first dispersed into the New World during the early Blancan North American landmammal age (NALMA) with likely ancestry close to the heterogeneous sample of C. lunensis in Eurasia. The possibility of a second dispersal is indicated by a mixed sample of specimens with significantly smaller p4/m1 length ratio than other Chasmaporthetes.

Eurygnathohippus is a genus of hipparionine horse that evolved in and was confined to the African continent from the late Miocene to Pleistocene interval. Eurygnathohippus woldegabrieli is a new species from Aramis, Ethiopia, dated between 4.4 and 4.2 Ma. The hypodigm is currently restricted to 157 specimens from 14 Aramis localities and one nearby Gona locality. We nominate a mandible as the type and a maxillary dentition and two complete metacarpal IIIs as paratypes. Our analysis reveals that Eurygnathohippus woldegabrieli is derived compared with late Miocene Eurygnathohippus feibeli in its overall size, cheek tooth crown height, mandibular symphysis length, and robusticity of distal limb elements. It is primitive in mandibular symphysis length and robusticity of distal limb elements compared with the more advanced medial Pliocene species Eurygnathohippus hasumense. A study of Eurygnathohippus woldegabrieli's paleodiet as measured by two mesowear methods, corroborated by carbon isotope studies, reveals that it was a dedicated grazer with a coarse C4 diet akin to that of modern zebras, wildebeests, and white rhinoceroses.

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