The Madtsoiidae are an extinct lineage of snakes known from the Late Cretaceous to the Late Pleistocene, with a rich fossil record distributed mainly across Gondwanan landmasses. However, only a few taxa are represented by cranial or articulated remains, and most madtsoiids are known only by isolated vertebrae. The unambiguous record of Madtsoiidae from the Cenozoic in South America had been restricted to the genus Madtsoia from Eocene and Oligocene deposits of Patagonia and Brazil. Here, we describe a new madtsoiid taxon, Powellophis andina gen. et sp. nov., based on an articulated postcranial skeleton from the Mealla Formation (middle–late Paleocene) in northwestern Argentina. The new taxon is estimated to be around 3 meters long, with a vertebral morphology sharing similar features with other mid-to-large forms. Its inclusion in a recent analysis of madtsoiid relationships recovers Powellophis as an early member of a clade formed by mostly large bodied and gigantic taxa. Its presence in the Paleocene of northwestern Argentina fills the gap between the diverse Late Cretaceous and Eocene–Oligocene records of madtsoiids in South America, confirms their presence in northern Gondwana by the early Paleogene, and expands the diversity of the group.

Fossil remains of extinct mylodontine sloths have been discovered in numerous localities throughout the American supercontinent, but knowledge of them is still mainly centered on the Pleistocene forms rather than their Neogene relatives. In this contribution, previously unpublished cranial and postcranial materials herein ascribed to Glossotherium chapadmalense (Kraglievich), coming from the Pliocene Chapadmalal Formation (Province of Buenos Aires, Argentina), are presented. These remains are described and compared with those of other mylodontine species from South and North America, providing an exhaustive characterization of cranial morphology in G. chapadmalense and some preliminary insights into its postcranial anatomy. The results have revealed a unique combination of differences and similarities of this enigmatic species with the larger-sized representatives of Glossotherium. In addition, these materials allowed shedding light on the long-standing uncertainties regarding its taxonomic status, as this form has been alternately considered to belong to the genera Glossotherium or Glossotheridium over the last century. As a result, the genus Glossotherium was present, at least, at the Early–Late Pliocene transition in the Pampean region of Argentina, and is recorded by the Upper Pleistocene throughout the entire South American continent. The radiation of the Pleistocene species is associated with a consistent body mass increase that was probably a response to the cooling temperatures and higher predation pressure in South America during the Late Pliocene–Early Pleistocene. These phenomena were probably driven by the stable emergence of the Panamanian Isthmus around 3 Ma and the successive faunal turnover pulses of the Great American Biotic Interchange.

Rhabdodontid dinosaurs were a group of medium-sized iguanodontian ornithopods from the Late Cretaceous of Europe. The uppermost Cretaceous continental deposits from the Haţeg Basin of western Romania yielded a very rich assemblage of vertebrates including abundant rhabdodontid remains, which have been exclusively referred to the genus Zalmoxes thus far. Here we describe a new rhabdodontid dinosaur, Transylvanosaurus platycephalus gen. et sp. nov., from the uppermost Cretaceous of the Haţeg Basin. The holotype of the new taxon was discovered in early–late Maastrichtian strata near Pui in the eastern part of the basin and comprises the articulated basicranium and both frontals. Transylvanosaurus differs from all previously reported rhabdodontids in having particularly wide and crested frontals, elongated and straight paroccipital processes that make only a gentle lateral curve and project mostly posterolaterally, prominent and massive prootic processes that extend mainly anterolaterally and ventrally, wide and crest-like basal tubera that meet the long axis of the braincase at a very flat angle, widely splayed basipterygoid processes that extend mainly ventrolaterally and slightly anteriorly, as well as a well-developed notch on the lateral side of the basicranium that is continuous, straight, and inclined anteroventrally. Phylogenetic analyses employing two different datasets consistently recovered the new taxon within the Rhabdodontidae, at the base of the iguanodontian radiation. Based on the morphological comparisons presented herein, we propose a particularly close relationship between Transylvanosaurus and Rhabdodon from southern France, which in turn provides evidence for a more complex biogeographic history of the Rhabdodontidae than previously thought.

The Zaysan Basin in Central Asia has a long geological history, and it has therefore seen major climatic and evolutionary transformations. The Miocene fossil record of this locality is remarkably rich representing all groups of vertebrates. A revision of fish remains has been carried out and new records of fishes, reptiles, and mammals recovered from Miocene deposits of the Zaysan Basin have been described. The study of fossils has revealed the existence of a quite diverse vertebrate assemblage in the basin during the Miocene. Representatives of the Percidae and Amiinae, and the species †Leobergia zaissanica predominated among fishes, whereas reptiles were supposedly represented in the assemblage by pan-trionychid turtles and crocodiles. No amphibians have been revealed, while the only mammalian taxa in the studied sample is a fossorial rodent of the genus †Tachyoryctoides. In contrast to previous views regarding the Middle Miocene age of the Zaysan Formation, the analysis of fish and mammal remains recovered from this locality strongly suggests an Early Miocene age. Findings of bowfin remains in the Zaysan Basin confirm that this group had existed outside of North America beyond the Paleogene/Neogene transition, and, at the same time, these specimens are the last known occurrences of the taxa Amiidae, Amiiformes, and Halecomorphi outside of North America. Data also indicate the existence of a lacustrine ecosystem in the Zaysan Basin during the Miocene with a taxonomically rich vertebrate assemblage and diverse trophic relations being an important center of biodiversity in the Miocene of Central Asia.

The earliest Eocene (Ypresian) Fur Formation (Denmark) is globally renowned for its exceptionally well-preserved fossils, including birds, sea turtles, insects, plants, and fishes. Fishes, albeit abundant and diverse, however, are only superficially known and very few detailed, taxonomic studies have been realized to date. A new polymixiiform fish, Polyspinatus fluere gen. et sp. nov., from the Fur Formation is described based on seven well-preserved, nearly complete specimens. All the specimens were studied by traditional stereomicroscopy, and by micro-X-ray fluorescence-element mapping. Digital 2D-element images of strontium-, phosphorus-, and calcium distributions of each specimen were directly applied for the taxonomic descriptions presented herein. Polyspinatus fluere gen. et sp. nov. is the first known Eocene record of the family Polymixiidae based on articulated skeletal remains. Polyspinatus gen. nov. exhibits a unique combination of characters that support its recognition as a new genus of the Polymixiidae. Its specialized hyoid apparatus with the first and second branchiostegal rays being sinuous and parallel to each other, and the third being wide and plate-like, followed by four saber-like elements, is strikingly similar to that of Polymixia, supporting a possible sister-group relationship with extant beardfishes.

Gut contents are extremely important for inferring trophic interactions between extinct species. These are, however, very rare in the fossil record and it is not always possible to accurately identify both the carnivore and the consumed organisms. Here we describe the remains of a small fossil mammal foot preserved inside the body cavity of the holotype specimen of the small feathered dinosaur Microraptor zhaoianus. This adds to the known diversity of diet for this genus, which also consumed birds, fish, and lizards. Previous interpretations that Microraptor was an arboreal hunter of birds and adept hunter of fish are not supported. Although the various known stomach contents would be plausible prey items based on size, there is no clear evidence that any of them were predated rather than scavenged, and Microraptor likely did both and foraged in multiple habitats.

We provide a detailed histological report of the dorsal blades of the Permo-Carboniferous dissorophid Platyhystrix rugosus. The blades, originally interpreted as hyperelongated neural spines, show compelling histological evidence of a dermal contribution that includes mineralized fibers and plywood-like tissue remarkably similar to extant osteoderm-bearing ceratophryid frogs and trionychid turtles. Their fusion to the vertebrae suggests homology with the osteoderm series of related Permian dissorophids. Although the mode of ossification is difficult to ascertain, both dermal ossification and metaplasia of the surrounding fibrous connective tissue (such as ligaments interconnecting the blades) likely combined to produce the fused blades observed in the closely allied Carboniferous platyhystricine Astreptorhachis. These represent the oldest examples of the phenomenon of dermal-endochondral co-ossification of osteoderms and vertebrae in the postcranial skeleton of a Paleozoic tetrapod. Our findings also highlight the adoption of different developmental mechanisms to produce convergent ecomorphology in sail-backed Paleozoic dissorophid amphibians (dermal blades derived from osteoderms) versus contemporary synapsids (hyperelongated neural spines). Future histological studies should sample additional dissorophid taxa to map the development of osteoderms within a broader phylogenetic context and to better understand their functional diversity.

Theropod dinosaurs likely radiated in the wake of the End-Triassic Extinction, but the early history of their diversification remains obscure. The Elliot Formation (EF) and its lateral equivalents in southern Africa preserves abundant continental Late Triassic and Early Jurassic vertebrate fossils, representing an opportunity to study the early phases of theropod evolution. However, Elliot Formation theropod remains are scarce relative to other dinosaurian groups, and most of the South African record pertains to a single taxon, Megapnosaurus rhodesiensis. We present morphological and osteohistological data on two theropod distal tibiae from South Africa's upper EF. The two new tibiae are larger than any known specimens of M. rhodesiensis, and they show a fast-growing woven-parallel complex (WPC). One of the specimens bears a line of arrested growth, but neither shows outer circumferential lamellae. These observations suggest that both specimens are immature and distinguishable from M. rhodesiensis based on osteohistology. Comparative anatomical observations, including body mass comparisons, further support this distinction. We cannot rule out an identification for one of our tibiae as Dracovenator regenti, the only other valid EF theropod taxon known from body fossils. Our observations indicate that there is likely at least one additional, relatively large-bodied upper EF theropod species that remains unknown from adequate skeletal material.

†Araripichthys castilhoi belongs to the paleo-ichthyofauna from the Aptian calcareous concretions of Romualdo Member, Santana Formation, Araripe Basin, northeast Brazil. It was originally placed within Beryciformes (Acanthomorphata) by a combination of plesiomorphic and apomorphic characters. Later, an anatomical review of †Araripichthys demonstrated the presence of several primitive characters (cf. presence of fin spines, orbitosphenoid, two supramaxillae, seven hypurals, autogenous hypurals 1 and 2, second ural centrum and first uroneural not fused, and cycloid scales) and aligned it with Clupeocephala. †Araripichthys was also considered closely related to †Acanthichthys (primitive Acanthomorphata), basically by the body shape resemblance. Other included †Araripichthys in †Protobramoidei (basal Clupeocephala) based on the absence of pelvic fins, presence of stout neural spines and scales partially covering the dorsal fin. The odd taxonomic history of †Araripichthys is directly related to its scarce number of available well-preserved specimens and concurrently its absence in a comprehensive phylogenetic analysis. Here we present a paleohistological study, an efficient tool to precise the taxonomic position of fossil fishes, especially in cases like that of †Araripichthys. Its paleohistology presents pseudolamellar bony tissues with stellate lacunae, filled by osteocytes with ramified cytoplasmic extensions. The star-shaped osteocytes of †Araripichthys are clearly characteristic of basal teleosts. Conversely, in the scarce Acanthopterygii taxa with cellular bone the osteocytes morphology is clearly distinct since their canaliculi are not regularly localized around these cells. The currently accepted synapomorphies for Elopomorpha, Clupeocephala, Acanthopterygii, and the already known anatomical data for †Araripichthys together with its paleohistology, corroborate its incertae sedis position within basal Teleostei.

We here describe fossil remains from three Lower and Middle Miocene localities of Anatolia, which we tentatively refer to chamaeleonids. The material comprises isolated tooth-bearing bones from the Early Miocene (MN 3) of Sabuncubeli (western Anatolia), the Early Miocene (MN 4) of Dededağ (western Anatolia), and the Middle Miocene (MN 5) of the world-renowned hominoid locality of Paşalar (northwestern Anatolia). If our identifications are correct, these specimens would represent the only fossil record of this group from Anatolia as well as the oldest occurrences of chameleons from Asia. Moreover, the recovery of these specimens across different Lower and Middle Miocene localities, suggest that these animals were a typical element of the Anatolian herpetofaunas of the early Neogene. Differences among the specimens from the three localities point to a higher taxonomic diversity of Miocene Anatolian chamaeleonids, however, based on such limited material, intraspecific or ontogenetic variation cannot be ruled out. The oldest among these occurrences, the Sabuncubeli material, coincides chronologically with the oldest chameleons, which had been previously described from Central Europe (MN 3). As such, this supports the recently suggested biogeographic scenario, according to which chamaeleonids dispersed from Afro-Arabia to Europe during the Burdigalian, via the “Gomphotherium Landbridge,” through Anatolia and the Balkans. Finally, a few additional lizard and snake remains from the locality of Dededağ are described, adding to the poorly known fossil herpetofaunas of Anatolia.

The Salla Beds of Bolivia reveal a rich, late Oligocene (Deseadan, South American Land Mammal “Age”) fauna composed of at least 50 mammalian species. Many taxa (e.g., rodents and typotherian notoungulates) are represented by dozens to hundreds of specimens. Litopterns are much less common but are represented by one macraucheniid and two adianthid species. Until now, only fragmentary postcrania of proterotheriids have been described from Salla. The recent discovery of a maxillary fragment with two molars, examination of previously recovered mandibular fragments, and a phylogenetic analysis, allow us to recognize Promylophis cifellii gen. et sp. nov. It is characterized by small size, absence of a metaconule on M1–2, and lower molars with a short “paracristid” and reduced or absent “paraconid.” Postcranial elements referred to cf. P. cifellii resemble geologically younger (e.g., Miocene) proterotheriids by way of anatomically tridactyl, but functionally monodactyl pes, and distal femora with a supra-trochlear fossa that forms a “patellar pit” that appears to function as a passive stay apparatus for the knee joint. Such a mechanical means of diverting forces from muscle to bone and sinew could save biologically significant amounts of metabolic energy in long-standing animals.

For the first time, a specimen of Pelophylax pueyoi Navás, 1922a has been recovered in situ, about 600 meters from the main entrance inside the Libros II mine (Teruel, Spain). The fossil comes from the Libros Gypsum Unit (Late Miocene), and represents a nearly complete articulated adult frog exposed in ventral view, with partial preservation of soft tissues. The only apomorphic character diagnosing the family Ranidae is the presence of cylindrical sacral diapophyses. Other characteristics congruent with that of the family Ranidae can be observed: sphenethmoid fused medially, large and oval orbital fossa, well-developed pterygoids without alar expansion and the inner ramus clearly shorter than the posterolateral ramus, transverse processes of presacral vertebrae and sacral diapophyses of subequal length, sacrum unfused with the urostyle, probable bicondylar sacro-urostylar articulation, transverse processes of the urostyle lacking, absence of ribs, and elongated hind limb. An apomorphic combination of features of the genus Pelophylax can also be recognized, such as the more open sacral diapophysis, and less elongated and more robust femora than usually observed in the genus Rana. Finally, some discrete characteristics permit establishing a close relationship with P. pueyoi, such as the large size of the fossil, the wide proportion of the skull, and the somewhat trapezoidal distal contour of the V4 transverse processes. The carpus of P. pueyoi is described here for the first time, suggesting a similar condition of the adult carpal morphology found in most Neobatrachian species. Presence or absence of a praepollex in P. pueyoi still cannot be resolved.

A new extinct sclerorhynchoid sawfish, Ptychotrygon ameghinorum sp. nov., is presented here based on abundant isolated teeth and some dermal denticles, which were recovered from the Mata Amarilla Formation, belonging to the lower Upper Cretaceous of the Santa Cruz Province in the Austral Basin of Patagonia, Argentina. This new species is the first Ptychotrygon occurrence in the southern hemisphere, which so far only has been reported from northern hemisphere deposits (Europe, North Africa, and North America). The presence of P. ameghinorum sp. nov. in these southern high-latitude deposits of Patagonia, Argentina, extends the geographic range of Ptychotrygon considerably southwards. This distribution pattern in the “middle” Cretaceous seems to correlate with the South Atlantic opening at the end of the Albian. The presence of lateral cephalic dermal denticles and the simultaneous absence of rostral denticles in the abundant fossil material support the view that Ptychotrygon did not develop such rostral structures. A reinvestigation of all known species assigned to Ptychotrygon reveals that P. ellae is a junior synonym of P. boothi, P. benningensis belongs to Texatrygon, P. rugosum belongs to Asflapristis, and P. clementsi represents an unidentifiable species (Ptychotrygon? sp.). The stratigraphic distribution demonstrates that Ptychotrygon might have originated in the Albian in south-western Europe and subsequently dispersed to obtain its widest distribution during the Cenomanian. In the Coniacian, a steep diversity decline is recognizable with a subsequent distribution shift from Europe to North America.

Isolated teeth belonging to the genus Ptychodus Agassiz, 1834 (Chondrichthyes; Elasmobranchii) from the Upper Cretaceous of the Ryazan and Moscow Oblast regions (European Russia) are described and discussed in detail herein. The taxonomic composition of the Ptychodus assemblage from the Ryazan region is very diverse including the first records of the cuspidate species P. altior and P. anonymus, which thus is largely consistent with those from other contemporaneous European localities. Ptychodus ubiquitously inhabited epicontinental seas of Europe during most of the Cretaceous with the most diverse assemblages coming from southern England, northern Italy, Belgium, and European Russia. Additionally, the material documented here from the Cenomanian of Varavinsky ravine area (Moscow Oblast) represents the northernmost occurrence of Ptychodus hitherto reported from Europe. It is evident that the Late Cretaceous shallow seas of the Russian platform represented a crucial pathway for the dispersal of Ptychodus from the European peri-Tethys to the eastern margins of the Neo-Tethyan Ocean. The Albian–Campanian records of Ptychodus from Europe indicate that its dominance in the peri-Tethys persisted for most of its evolutionary history. A local temperature drop across most of the European shallow seas probably contributed to the narrowing of its geographic range in the peri-Tethyan seas towards the end of the Mesozoic Era. The fossil remains of Ptychodus documented herein are accordingly of utmost importance for better understanding the taxonomic composition of Russian fossil ichthyofaunas and also inform about the dispersal of Ptychodus towards western and eastern peri-Tethyan seas during the Late Cretaceous.

Neotragocerus represents the earliest recognized occurrence of the Bovidae in North America but is rare and poorly understood, known principally by scattered horn cores assigned to two species. Recently, the largest sample of Neotragocerus was discovered in the Fort Rock Formation of south-central Oregon where Eurasian immigrants co-occur. Horn cores, cranial fragments, dental material, and postcranial elements were found at five closely related sites and provide significant morphological data of this enigmatic ungulate. The specimens occurred in a ferruginous-stained basalt gravel that represents a paleochannel. Associated faunal elements indicate deposition during the Hemphillian NALMA, and ⁴⁰Ar/³⁹Ar dates from interbedded tephras, ranging from 6.11 + 0.08 to 5.74 + 0.01 Ma correspond with the Hemphillian assignment. Neotragocerus was a medium-sized bovid with relatively short horn cores, normally with dorsoventral ridges, ovate cross-section at the base, very short pedicles and a brachyselenodont dentition. Morphologies suggest assignment of Neotragocerus to the “Boselaphini,” the least derived tribe of living bovids or at least derivation from a “boselaphine” synapomorphic complex. The Hemphillian genus does not appear to be closely related to later occurring North American bovids, and a close Eurasian relative is not obvious. Based on the range of variation displayed by the Oregon specimens, Neotragocerus improvisus is retained, and Neotragocerus lindgreni is considered a nomen dubium.