New specimens and the reassessment of many silesaurids have recently shed light on the origin and early evolution of dinosaurs and their close relatives. Yet, the group is relatively poorly represented in South America, an area that likely played an important role in dinosaurian origins. Since the discovery of Sacisaurus agudoensis from the Norian Caturrita Formation, only the fragmentary Gamatavus antiquus and Amanasaurus nesbitti have been reported from the Triassic of south Brazil. Here we describe disarticulated silesaurid remains from Waldsanga, one of the most important tetrapod-bearing localities of the Santa Maria Formation, which represent the second Carnian occurrence of the group in Brazil. The postcranial elements exhibit a combination of dinosauromorph symplesiomorphies and silesaurid diagnostic traits, showing that a conservative anatomy is pervasive among early dinosauromorphs. We also conducted a set of exploratory analyses to infer the phylogenetic relations of the new occurrence and the robustness of some of the most recent phylogenetic hypotheses in face of the increasing diversity of Silesauridae. This revealed a rather uncertain evolutionary scenario not only for Silesauridae, but for early dinosauromorphs in general.

A new clevosaurid rhynchocephalian is described from the Upper Triassic Tiki Formation of the Rewa Gondwana Basin of India. The material is based on several partial craniomandibular elements containing acrodont and fully ankylosed tooth implantations and on the basis of multiple diagnostic features is assigned to a new taxon, Clevosaurus nicholasi. Phylogenetic analysis nests the Tiki rhynchocephalian within the clade Clevosauridae, where it is recovered as an early-diverging taxon basal to the other clevosaurs except for a clade comprising C. convallis + Sigmala sigmala. The autapomorphic characters of Clevosaurus nicholasi include a very robust dentary with an obliquely angled narrow lip of the secondary bone at the symphysis, anteriorly bifurcated Meckelian canal, a sub-dental shelf on the dentary, acrodont marginal anterior teeth, and absence of or smooth lateral and medial wear facets on the marginal dentary and maxillary teeth, respectively. The Late Triassic rhynchocephalian record of the Gondwana is relatively sparse in comparison with that of the Laurasian regions, and the new clevosaur represents the first Late Triassic record from India. Based on the paleobiogeographic distribution, a possible Gondwanan origin for Clevosauridae is hypothesized.

The posterior portion of a sturgeon skull preserved in a nodule was recovered from the latest Campanian sediments of the Horseshoe Canyon Formation in the city of Edmonton, Alberta, Canada. It is described here as a new genus and species of Acipenseriformes. The skull represents an individual of at least 2 meters in total length. This species is of particular interest because different bones of the skull show a surface ornamentation with different patterns; the clavicle has large pits, the dermal skull bones have smaller pits and radiating ridges, and the subopercle shows fine radiating ridges. The new taxon, here named †Boreiosturion labyrinthicus, can be confidently included in the extant family Acipenseridae but a phylogenetic analysis does not further resolve relationships. This fossil is the first documentation of sturgeon in the latest Campanian of North America, and bridges the gap between the mid-Campanian assemblage of Dinosaur Park and the late Maastrichtian material from the Hell Creek Formation.

Fossil ‘ovibovin’ bovids are described from the Upper Miocene of Çorakyerler (north-central Anatolia). Two taxa have been recognized: the predominant Criotherium argalioides, known by several craniodental remains, and the less common Hezhengia? cf. inundata, documented by a few dentitions. A review of C. argalioides records from Samos and Kemiklitepe D and a thorough comparison with the Çorakyerler sample provides new data on the morphological and metric variability of this taxon, as well as its chronological and geographic range. Hezhengia? cf. inundata from Çorakyerler reveals important similarities with the Garkin (Turkey) taxon, which, in contrast to previous studies, we find more similar to the Chinese Hezhengia than to the Chinese Plesiaddax as originally suggested. The same is true for “Plesiaddax” simplex from Kayadibi (Turkey), which is referred to as Hezhengia? simplex. The co-occurrence of two ‘ovibovin’ bovids of similar size in the same assemblage was previously suspected but never before documented.

Endocranial cavities preserve a record of neural anatomy often used for hypotheses of behavior in extinct organisms. Two reconstructions of cranial endocasts of Allosaurus fragilis and A. jimmadseni from computed tomography data expand understanding of theropod endocranial anatomy including endocranial volume, inner ear shape, and trigeminal ganglion size. Endocranial and trigeminal ganglion volumes are compared with a sample of birds, crocodylians, and non-avian theropod dinosaurs. Allosaurus is found to have a relatively small trigeminal foramen for its body size when compared with foramina of birds and crocodylians. The inner ear is fragmentary but similar in shape to semicircular canals of other large-bodied theropod dinosaurs. These findings suggest Allosaurus had generalist neural structures relative to other non-avian theropod dinosaurs. Like other large-bodied theropod dinosaurs, Allosaurus likely had a large dural venous sinus, potentially important for brain cooling. Allosaurus did not have a derived sense of facial somatosensation akin to that found in crocodylians or some birds. Additional data like these, collected from other tetanuran dinosaurs, will help clarify the evolution of neurosensory systems in the lineage.

Pliocene South American mammals prior to the Great American Biotic Interchange comprise the evolutionary pinnacle of a long-lasting process of continental isolation, in which large-scale orogeny and climate change were instrumental. These processes resulted in unique assemblages of extinct groups with peculiar anatomies. However, interpretation of the functional roles that these organisms would have played in the ecosystem is challenging because well-preserved fossils of this time interval in South America are scarce. Here, we describe a new Early Pliocene assemblage of native herbivorous megamammals documented by skeletons in anatomical connection from the Peruvian Andean plateau (city of Yauri in Espinar, Cusco Department). Fossil-bearing deposits pertain to Member C of the El Descanso Formation dated at 4.75 ± 0.5 Ma, when the plateau attained near-modern elevations and a Puna-type plant ecosystem. The mammal assemblage is dominated by xenarthrans, including three ground sloths (cf. Megatheriops rectidens, Simomylodon uccasamamensis, and Proscelidodon sp.) and Andinoglyptodon mollohuancai gen. et sp. nov., the first Pliocene glyptodontine known by a well-preserved cranium and dermal armor. Notoungulates are represented by the toxodontid Posnanskytherium viscachanense. Both selective and bulk feeders are identified, suggesting the existence of diverse plant resources in the Pliocene Puna ecosystem. These native mammals constituted the typical Pliocene herbivorous guild of the central Andean plateau and provide an opportunity to investigate the structure of mammalian communities just before the arrival of Holarctic immigrants.

Los mamíferos sudamericanos del Plioceno previos al Gran Intercambio Biótico Americano constituyen el pináculo evolutivo de un proceso prolongado de aislamiento continental, en el que la orogenia a gran escala y el cambio climático fueron fundamentales. Estos procesos resultaron en ensambles únicos de grupos extintos con anatomías inusuales. Sin embargo, la interpretación de los roles funcionales que estos organismos habrían jugado en el ecosistema es un reto porque fósiles bien preservados de este intervalo temporal en Sudamérica son escasos. Aquí, describimos un nuevo ensamble de megamamíferos herbívoros nativos del Plioceno temprano documentado por esqueletos en conexión anatómica del altiplano Andino peruano (ciudad de Yauri en Espinar, departamento de Cusco). Los depósitos con fósiles pertenecen al Miembro C de la Formación El Descanso datados en 4.75 ± 0.5 Ma, cuando el altiplano alcanzó elevaciones casi iguales a las modernas y un ecosistema de plantas de tipo Puna. El ensamble de mamíferos está dominado por xenartros, incluídos tres perezosos terrestres (cf. Megatheriops rectidens, Simomylodon uccasamamensis y Proscelidodon sp.) y Andinoglyptodon mollohuancai gen. et sp. nov., el primer gliptodonte del Plioceno conocido por elementos craneales y la armadura dérmica bien conservados. Los notungulados están representados por el toxodóntido Posnanskytherium viscachanense. Se identificaron tanto alimentadores selectivos como masivos, lo que sugiere la existencia de diversos recursos vegetales en el ecosistema de la Puna del Plioceno. Estos mamíferos nativos constituyeron el gremio de herbívoros típico del Plioceno del altiplano andino central y proveen una oportunidad para investigar la estructura de las comunidades de mamíferos justo antes de la llegada de los inmigrantes holárticos.

Rattus (sensu stricto) is one of the groups of rodents and is most closely related to human activities. The diversity of extant Rattus species is the highest among rodents, but fossil species are rare, mainly found in Asia during the Late Pliocene to Early Pleistocene. Here, we described a Late Pliocene new species of Rattus based on material from the upper Yangyi Formation in Baoshan county, Yunnan Province, China. The primitive morphological characteristics of fewer molar roots, t12 preserved on M1–2, t9 preserved on M3, and buccal stylids well developed on lower molars indicate that the new Rattus is by far the most primitive form in the Rattus genus. In dental morphology of Rattus, the molars have an evolutionary trend of gradually increasing the number of roots and fusing cusps into an arched ridge, reduction to disappearance of the t7 and t12 on upper molars, and reduction to disappearance of the mesiocentral cusp on m1, the anterior buccal stylid on m1–3 and hypoconid on m3. Discovery of the new Rattus from Baoshan confirms that Rattus probably originated in southern Asia before the Late Pliocene, and also provides new fossil evidence to calibrate the molecular clock of the divergence of Rattus from other murines. In addition, we also reported five associated small mammals: Neotetracus sp. nov., Anourosorex qianensis, Soricidae gen. et sp. indet., Ia io, and Kowalskia sp. Most of them inhabit warm and humid tropical or subtropical montane forests or shrubland environments. The composition of this mammalian assemblage indicates that the paleoelevation and paleoclimate of Baoshan area in the Pliocene are very similar to those of the present.

To date, 25 species of non-mammalian cynodonts have been histologically sampled, but few record a definitive and well-developed external fundamental system (EFS) indicative of skeletal maturity. Here, I report an EFS in the femoral histology of Scalenodon angustifrons and discuss the factors that could explain why skeletally mature tissue is rarely documented in cynodont osteohistology. My sample includes two equivalently sized individuals that document marked histological variation, as only one shows evidence of slowing growth rate and an EFS. Variation in the bone histology between femora of the same size suggests that attainment of skeletal maturity does not follow a discrete developmental pattern for S. angustifrons, a pattern that is also seen in the bone histology of other traversodontids and some non-gomphodontian cynodonts. From these results, a flexible growth strategy is inferred for S. angustifrons. To contextualize the validity of this pattern among other cynodont species, I summarize the sampling coverage of cynodonts that have been thin-sectioned and report limited coverage across size classes/ inferred development stages. This is often a result of sampling one isolated element that is not standardized to one skeletal element, which contributes to a poorly constrained comparative sample (in terms of size coverage, spatial and temporal resolution, and taxonomic coverage). Despite this, many cynodont species show shifts towards slow growth, but very few instances of unequivocal evidence of skeletal maturity. This result underscores the need for standardized iterative histological sampling to assess longevity, life history, and developmental patterns of non-mammalian cynodonts more accurately.

Amebelodon and Konobelodon are two members of a group of proboscideans called shovel-tusked gomphotheres. The phylogenetic relationship between them is uncertain, with some authors considering them to be closely related taxa while others consider them only distantly related. This uncertainty stems from confusing issues related to morphology, biochronology, and biogeography. Contributing to this confusion, Amebelodon consists of two distinct morphotypes that do not obviously resemble each other. One, typified by A. floridanus, possesses a conservative dentition and lower tusks, while the other, represented solely by A. fricki, possesses an advanced dentition and lower tusks that closely resemble those found in Konobelodon. In a traditional evolutionary scenario involving these taxa, conservative Amebelodon appeared in North America during the latest Miocene and gave rise to advanced Amebelodon. Advanced Amebelodon in turn gave rise to Konobelodon, with Konobelodon then dispersing into Eurasia. However, new discoveries of Konobelodon in the Late Miocene of Europe and Asia render this hypothesis implausible, and suggest rather that Amebelodon first appeared in Asia during the Late Miocene, where it gave rise to Konobelodon. These findings in turn suggest that A. fricki in North America represents an immigrant from Eurasia. If this new hypothesis is correct, then the status of the conservative species such as A. floridanus within Amebelodon becomes problematic, with the implication that Amebelodon is polyphyletic. On this basis as well as extensive morphological differences, one of these conservative species, Amebelodon floridanus, is here referred to a new genus, Stenobelodon.

The genus name of the Cretaceous protostegid turtle Microstega Hooks, 1998 (type species Microstega copei Wieland, 1909) is preoccupied by Microstega Meyrick, 1890 (type species Microstega pandalis Hübner, 1825), a modern lepidopteran. The new name Kansastega McDavid & Hooks nom. nov. is proposed to replace the junior homonym, with the new combination Kansastega copei (Wieland, 1909).

A new typothoracine aetosaur is described based on multiple isolated and articulated left paramedian and lateral osteoderms recovered from the Upper Triassic lower Dharmaram Formation of India. The partial carapace of the new taxon is reconstructed as strongly discoidal based on the curvature of the paramedian osteoderms with the widest one positioned dorsal to the mid-dorsal trunk vertebra. Asymmetric lateral osteoderms with acute flexion are considered as precaudals with the angle of flexion decreasing posteriorly. Phylogenetic analysis recovered the new taxon as deeply nested within the clades Typothoracinae and Paratypothoracini, and a sister taxon to Kocurypelta silvestris. The autapomorphic characters involving paramedian osteoderms dorsal to the trunk vertebrae include dorsal surface ornamented by large, irregular pits surrounding the dorsal eminence and radiating ridges in other areas, straight anterior margin of the anteromedial corner of the anterior bar in dorsal view, and raised or ridged and ornamented posteromedial corner. The current study highlights the significance of the new aetosaur, and the age of the lower Dharamaram Formation is modified here as mid-Norian to Rhaetian based on global correlation with other coeval horizons. The recovery of this taxon marks the first record of Paratypothoracini from high paleolatitudes of the Gondwanan region. The study corroborates the earlier findings of a strong Laurasian faunal influx in India during the Late Triassic suggesting possible land bridges and/or conducive environmental conditions for faunal dispersal.

Lepidochelys is a genus of extant marine turtles that includes the critically endangered Kemp's Ridley turtle. The evolutionary history of this genus is poorly understood due to the lack of an undisputed fossil record for the group. Here we describe a partially preserved carapace from the Upper Miocene Chagres Formation of Panama, which represents the oldest fossil record of Lepidochelys. The specimen has rectangular, anteroposteriorly short pleural scutes, a characteristic shared with members of Lepidochelys. It is potentially closely related to L. olivacea because it shares a similar number of pleurals, but its precise taxonomic status remains uncertain. We discuss the ecological role that a marine turtle played in the paleoecosystem of the Chagres Formation. The new specimen exhibits exceptional preservation of bone sutures, sulci, sculpturing, and bone microstructure, including remains of blood vessels, collagen fibers, and osteocytes. This is the first time that a histochemical stain (DAPI) indicates preservation of a compound consistent with DNA in a fossil vertebrate outside Dinosauria. These data demonstrate the potential for DNA to persist in specimens that are both millions of years old and are from lower latitudes, which challenges traditional paradigms of biomolecular preservation.

Extant rhinoceroses are represented only by five species and are characterized by the presence of a nasal horn. In the past, they were much more diverse, with one of the best-known groups being the aceratheriines, i.e., hornless rhinoceroses. Chilotheres are a group of hornless rhinos that inhabited Eurasia during the Late Miocene. Their westernmost geographic range reached Eastern Europe, where overall eight species have been erected. Four of these were described based on material from the Upper Miocene of Samos Island (Greece), two of which are not considered valid anymore. Unfortunately, the type skulls of all four species are lost and there are several issues concerning their taxonomy. Therefore, we herein designate two skulls housed in historical collections from Samos as neotypes for the first two species, Chilotherium schlosseri (Weber, 1905) and Eochilotherium samium (Weber, 1905), and provide detailed comparisons for the separation of the species from each other and from any other chilotheres. Our results prove that the two species are valid and justify their separation on a generic level. Chilotherium schlosseri seems to be more closely affiliated with the other European Chilotherium species, whereas E. samium is more similar to the Chinese ‘Chilotherium’ wimani and ‘Chilotherium’ primigenium, based on their more plesiomorphic characters.

Fossils referable to the gorgonopsian Gorgonops sp. and to the dicynodont Endothiodon sp. are described from the Permian Madumabisa Mudstone Formation of the Mid-Zambezi Basin of southern Zambia. Specimens of the former taxon conform to recent diagnoses of the genus (e.g., five postcanine teeth, transverse flange of the pterygoid backswept, postorbital bar rugose and moderately expanded), but differ slightly from South African material in some respects (e.g., reduced dentition on the transverse flange of the pterygoid). Fossils of the latter are less complete, but show diagnostic features such as a dentary with numerous teeth, a ventral boss, and a shallow posterior dentary sulcus, oval palatine pads, and a narrow intertemporal region of the skull, although a species-level identification is not currently possible. Although the relevant fossils were never described, a vertebrate fossil assemblage including Endothiodon was previously reported from the Madumabisa Mudstone Formation in northern Zimbabwe (i.e., K5d), suggesting that this biozone was relatively broadly distributed across the Mid-Zambezi Basin. The Mid-Zambezi Basin of southern Zambia was previously demonstrated to host Guadalupian Tapinocephalus Assemblage Zone-equivalent strata, with rhinesuchids, burnetiamorphs, tapinocephalids, and dicynodonts recognized. The recognition of Lopingian Endothiodon Assemblage Zone-age rocks expands the stratigraphic range of vertebrate-bearing horizons in southern Zambia.