Interatheriinae is one of the most derived subfamilies of South American notoungulates. Several interatheriines have been described since the 19th century, but most of them have not been revised, or been formally reexamined, for more than a century. Most interatheriine taxa were erected based on materials collected from Argentinean Patagonia, particularly from the Santa Cruz Formation (early–middle Miocene), Santa Cruz Province. Within the framework of an exhaustive unpublished systematic revision of Interatheriinae (early Oligocene–late Miocene), we studied the holotype of Santacrucian Icochilus undulatus, leading to the recognition of a new monospecific genus, Neoicochilus gen. nov., and the new combination N. undulatus. In addition, we formalize the taxonomic revision of Cochilius, proposing the following: Paracochilius is the junior synonym of Cochilius; Cochilius consists of C. volvens, C. fumensis, and C. brevirostrus; Paracochilius chubutensis and Protypotherium minor are junior synonyms of Cochilius brevirostrus; Cochilius pendens is the junior synonym of Cochilius columnifer; and the holotype of Cochilius columnifer exhibits the diagnostic features of Protypotherium, so we propose the new combination Protypotherium columnifer, pending publication of our thorough taxonomic revision of Protypotherium. Our taxonomic scheme is supported by a cladistic analysis, which places Neoicochilus undulatus in a derived position within Interatheriinae, as the sister taxon of the monophyletic genus Cochilius, and the clade Neoicochilus plus Cochilius positioned as the sister taxon of Interatherium. Our phylogenetic results support the monophyly of Miocene interatheriines.

Evolutionary relationships of the endemic South American ungulates (SANUs), both to each other and to other major placental clades, have been robustly debated for more than a century. Morphological evidence has not provided unambiguous resolution of these controversies, although recent paleoproteomic and paleogenomic analyses have supplied unequivocal evidence that at least Litopterna and Notoungulata are most closely related to each other and then to crown Perissodactyla. A recent study based on morphological characters has gone much further, claiming that litopterns and South American condylarths are stem to, or even nested within, Perissodactyla, but are not otherwise related to any North American clades of archaic ungulates. This study also concluded that the alleged shared presence of perissodactyls in Paleogene South America and India, along with several other biological groups, is evidence of a fluid biotic interchange early in the Cenozoic. Our assessment of this study revealed various conceptual and methodological errors, including misinterpretation of homologies, scoring errors, and failure to include relevant taxa such as Notoungulata. Our corrected phylogenetic analysis, performed with essentially the same taxon/character sampling and searching options, recovered all litopterns and their relatives in a single monophyletic clade, separate from the one representing Perissodactyla s.s. Both clades are clearly derived from Laurasian ungulate ancestors. In addition to the absence of true perissodactyls in Paleogene South America, most of the biological groups postulated as shared by both continents are not found in Paleogene strata of India. In sum, there is no meaningful evidence supporting the alleged multiclade, multiterrain biotic interchange.

The fossil record of Early Cretaceous birds in South America has been restricted to members of Enantiornithes from the Crato Formation (Aptian) of Brazil. Here we describe a new genus and species of bird discovered at Pedra Branca Mine, Nova Olinda County, Ceará State, Brazil, which adds to the avian fossil record from the Crato Formation. The specimen is represented by an isolated foot that is exposed in plantar view. A plantarly displaced metatarsal III with a well-developed hypotarsus supports its referral to Ornithuromorpha, representing the oldest member of the clade reported for Gondwana. Its unique foot conformation indicates that it may belong to an unknown ornithuromorph clade with some cursory similarities to extant flightless ratites. The presence of Early Cretaceous ornithuromorphs in Brazil indicates that the clade was widespread in Gondwana during the Mesozoic.

We describe several mammal taxa from the poorly known late Eocene locality of Bang Mark, Krabi Basin in southern Thailand. Most of them were unknown in that locality that now includes 19 distinct taxa. The new material corresponds to dental remains that can be attributed to a carnivoran, a dichobunid, ruminants, anthracotheres and perissodactyls. These remains provide information on the affinities of several genera that were uncertain so far. Archaeotragulus might be more closely related to Siamotragulus from the Miocene of Southeast Asia, Pakistan and East Africa, and the tragulid status of Krabitherium is supported by the morphology of its p4. We also describe the smallest known anthracothere, Geniokeryx nanus, sp. nov., and a new species of eomoropid chalicothere, Eomoropus meridiorientalis, sp. nov., that represents the first record of that family in the Krabi fauna. This work also supports the contemporaneity of Bang Mark with Wai Lek and Bang Pu Dam.

The fossil record for pangolins is sparse. Current biogeographic data suggest this clade originated in Europe, though pangolins seem to have disappeared from the European paleontological record during the middle Miocene, when they were hypothesized to have been pushed toward more tropical and sub-tropical equatorial environments due to global cooling trends. Here we report on a nearly complete humerus of a pangolin from the early Pleistocene (∼2.2–1.9 Ma) site of Grăunceanu, Romania. This fossil revises this previous understanding of pangolin evolution and biogeography and represents both the youngest fossil pangolin from Europe and the only fossil from Pleistocene Europe. The new species described here, Smutsia olteniensis, sp. nov., shares several synapomorphic traits with other Smutsia species, which are currently found only in Africa. However, relative to extant Smutsia, it has several unique traits that set it apart, including a longer and narrower entepicondyle, an enlarged supinator crest, and an enlarged greater tubercle. Together this unique suite of features justifies the description of a new species. This specimen definitively demonstrates that pangolins were present in Europe during the Pleistocene. Further, Smutsia has previously been thought to be an African taxon, with the oldest specimen from South Africa at ∼5 Ma and living species found across Africa. This specimen now demonstrates that Smutsia previously had a far larger biogeographic range. Finally, Grăunceanu has been reconstructed to have consisted of relatively open grasslands and woodlands, which is an unusual habitat for most pangolins.

The Eocene was a key interval for the diversification of squamates worldwide. However, little is known about their early evolution in Africa due to the scarcity of Paleogene fossil squamates from that continent. One of the most important Eocene vertebrate assemblages in Africa is known from the Fayum Depression of Egypt, but only a few lizards and snakes have been reported from these deposits. Here we report the first Paleogene record of the clade Amphisbaenia in Egypt, from the lowest upper Eocene Birket Qarun Locality 2 (BQ-2). It corresponds to a mid-trunk vertebra characterized by a depressed centrum with a flattened base, hemispherical synapophyses, and absence of a neural spine. Additional material from BQ-2 includes seven vertebrae attributed to colubroidean snakes. One trunk vertebra resembles those of early Eocene Procerophis from India while the remaining colubroidean vertebrae are referred to Renenutet enmerwer. Caudal vertebrae of Renenutet are described here for the first time. Similarities in the caudal vertebral morphology between BQ-2 Renenutet and Thaumastophis missiaeni from the lower Eocene of India reinforce the hypothesis of a close affinity between them. The presence of cf. Procerophis and Renenutet in Egypt adds to the evidence for terrestrial faunal exchange between Asia and northern Africa during the early/middle Eocene along the southern margin of the Tethyan Sea.

Hudiesaurus sinojapanorum is a Late Jurassic sauropod from northwestern China that was erected on the basis of a cervicodorsal vertebra, four teeth, and a nearly complete forelimb. However, re-evaluation of this material, and comparisons with other taxa, indicate that there are few grounds for regarding these specimens as congeneric. Consequently, although we retain the vertebra as the holotype specimen of Hudiesaurus, the forelimb is assigned to a new taxon—Rhomaleopakhus turpanensis, gen. et sp. nov. The teeth previously referred to Hudiesaurus are poorly preserved but resemble those of several other ‘core Mamenchisaurus-like taxa’ (CMTs) from East Asia, such as Mamenchisaurus sinocanadorum. Phylogenetic analyses confirm that Hudiesaurus is a CMT and the sister taxon of Xinjiangtitan. Despite some uniquely shared features, their large size, and close geographic provenance, Hudiesaurus and Xinjiangtitan are retained as distinct genera based on their stratigraphic separation and numerous anatomical differences. Rhomaleopakhus is also shown to be a CMT in all analyses, being most closely related to Chuanjiesaurus and Analong. We link the convergent evolution of robust antebrachia and an enlarged olecranon in CMTs, titanosaurs, and some ornithischians (e.g., ceratopsids) to a more flexed orientation of the forearm, an enhanced role for the forelimb in locomotion, and an anterior shift in the whole-body center of mass. CMTs and titanosaurs potentially converged on a feeding strategy in which the ability to increase browse height via bipedal rearing was sacrificed in return for more efficient locomotion that improved travel between patchily distributed food sources.

Semionotiformes is a diverse extinct group in Neopterygii. It is well represented in the Mesozoic, occurring in marine and continental strata worldwide. However, some diagnostic characters of Semionotiformes and, in particular, of Semionotidae, have been under debate, due to the description of new taxa or revision of previously known ones. In this paper, we provide a detailed description of the first unequivocal record of Semionotidae from Gondwana, i.e., Lophionotus parnaibensis, sp. nov. from the Pastos Bons Formation, Upper Jurassic, in the Parnaíba Basin, northeastern Brazil. It was included in the genus Lophionotus mainly due to the presence of smooth cranial bones, triangular lateral expansion of antorbital portion of frontal, and ratio length/width of frontals lower than three times. It was recovered as a new species due to a unique combination of characters. This discovery represents the most recent occurrence of the genus, which was previously recorded only in the U.S.A. up to the Early Jurassic.

Variation in postcanine teeth is relevant to answering questions about both taxonomy and diet. In such contexts, understanding the patterns and the amounts of variation present in a single species is fundamentally important. Here we use dental topographic analysis (DTA) to study variation in functional aspects of the lower second molar (n = 51) and lower fourth premolar (n = 41) in a large, stratigraphically controlled sample of the early Eocene stem primate Microsyops latidens, which permits study of fine scale variation through time in a single species, during a period of notable climatic change. To contextualize variation in M. latidens, we used DTA to study extant euarchontan taxa, representing three orders and seven families (n = 96). Previous study of M. latidens suggested that it was highly variable in size and lower molar morphology, potentially giving rise to later species of microsyopids. However, comparison with extant taxa suggests that the dental form of M. latidens shows low levels of intraspecific variation. The dental topography of M. latidens also does not reflect the previously postulated taxonomic split. Our results suggest instead that M. latidens likely did not undergo change in dental topography consistent with a shift in either dietary adaptive niche or ecospace. Taken together, our results suggest low levels of variation in dental form and potentially diet of M. latidens, indicating that this taxon likely remained within a single adaptive zone.

The Cuban bare-legged owl (Margarobyas lawrencii) is a poorly studied bird of uncertain affinities within Strigidae (true owls). Molecular data indicate that M. lawrencii may be one of the earliest diverging lineages of crown group Strigidae, but the evolutionary history of this taxon remains obscure. Here we describe a fossil species of Margarobyas from the Upper Pleistocene of Western Cuba and for the first time address the comparative osteology of this genus. The osteological survey confirms the remarkable morphological distinctiveness of the modern Margarobyas lawrencii. Margarobyas displays a derived similarity to Ninox owls (hawk-owls, subfamily Ieraglaucinae) in the morphology of the quadratum, but in the overall morphology of the skeleton it is also similar to members of the subfamily Striginae and species of Megascops (screech owls) in particular. The mixture of characters of both Striginae and Ieraglaucinae implies an early (no later than Oligocene) divergence of Margarobyas, thus supporting a long evolutionary history of these owls compared with other endemic owl species of the West Indies. The antiquity of Margarobyas makes it, along with Todidae (todies), one of the most archaic components of the modern West Indian avifauna.

The upper Fremouw Formation (Middle Triassic) of Antarctica preserves a diverse record of temnospondyls, with three species currently recognized. To date, all of the described material belongs to a single clade, Capitosauria. Our reanalysis suggests that cursory historical reports suggesting the presence of a benthosuchid (Trematosauria) are in error. Here we report substantial amounts of hemimandibular material of large-bodied temnospondyls from the upper Fremouw Formation. All seven specimens, including the historic material attributed to Trematosauria, exhibit features indicative of capitosaurian affinities. These specimens represent a notable expansion in the physical and conceptual body of temnospondyl material known from the Fremouw Formation, although they cannot be definitively associated with any of the three previously named Antarctic species in the absence of skeletal overlap. In addition, all of the specimens come from large-bodied individuals (i.e., skull lengths exceeding 70 cm), which likely reflects a taphonomic filter created by the high-energy channel lag deposition of the fossiliferous horizon of the upper Fremouw Formation. We also report the first occurrence of a non-capitosaur, an interclavicle belonging to a plagiosaurid. This represents only the third occurrence of Plagiosauridae in southern Pangea during the Triassic, in contrast to a much richer record of this clade in northern parts of the supercontinent and a rich record of the closely related brachyopids in the southern hemisphere. Together with the continued absence of trematosaurs in Antarctica, the plagiosaurid record hints at nuances in the distribution of cosmopolitan clades patterns that are tied to presently unrecognized ecological and physiological differentiators.

Trilophosauridae are an extinct group of archosauromorphs from the Upper Triassic of western North America and Nova Scotia. Possible trilophosaurids Tricuspisaurus thomasi and Variodens inopinatus have also been reported from Upper Triassic fissure fills in the southwest of the United Kingdom, based on their multi-cuspid dentitions. Here, we provide an updated description of V. inopinatus and add to the description of T. thomasi, including re-examining CT scans of its holotype dentary. We confirm that the apparent gap on the dentary of T. thomasi is pathological, with the dentine of the teeth on either side of the gap asymmetrically thick, and that heavy vascularization of the anterior part of the dentary confirms it likely had a keratinous rhamphotheca. Our cladistic analyses, to which we add nine new characters, confirm that T. thomasi and V. inopinatus are closely related taxa and the youngest known trilophosaurids. Further, we support a previous suggestion that the relatively small size of these two European trilophosaurids results from insular dwarfism.

Tyrannosaurid theropods topped the terrestrial food chain in North America and Asia during the latest Cretaceous. Most tyrannosaurids, exemplified by Tyrannosaurus rex, had deep snouts, thick teeth, and large jaw muscles that could generate high bite forces. They coexisted in Asia with a morphologically divergent group of long-snouted relatives, called alioramins. Qianzhousaurus sinensis, from the Maastrichtian of Ganzhou, China, is the largest alioramin yet discovered, but has only been briefly described. Here we present a detailed osteological description of the holotype cranium and mandible of Qianzhousaurus. We identify several new autapomorphic features of the genus, and new synapomorphies that unite alioramins (Qianzhousaurus, Alioramus altai, Alioramus remotus) as a clade, including a laterally projecting rugosity on the jugal. We clarify that the elongate skull of alioramins involves lengthening of the anterior palate but not the premaxilla, and is reflected by lengthening of the posterior bones of the lower jaw, even though the posterior cranium (orbit and lateral temporal fenestra) are proportionally similar to deep-skulled tyrannosaurids. We show that much of the variation among the alioramin species is consistent with growth trends in other tyrannosaurids, and that A. altai, A. remotus, and Qianzhousaurus represent different ontogenetic stages of progressive maturity, across which the signature nasal rugosites of alioramins became less prominent. We predict that the holotype skull of Qianzhousaurus represents the adult level of maturity for alioramins, and propose that the skull morphology of Qianzhousaurus indicates a much weaker bite than deep-skulled tyrannosaurids, suggestive of differences in prey choice and feeding style.

Five specimens of the late Permian cynodont Cynosaurus suppostus, inferred to represent an ontogenetic growth series, were imaged using X-ray microtomography in order to determine the pattern of tooth replacement for the species. Due to the small sample size, and damage to the rostrum in several specimens, replacement patterns of the incisors could not be accurately determined. Evidence supporting the presence of two maxillary canine loci in a juvenile Cynosaurus is presented. Replacement of the mandibular canines ceased at a basal skull length of ∼88 mm, whereas replacement of the maxillary canines ceased at a basal skull length of ∼90 mm. The final canine generation to erupt in both the maxillae and mandible had open-rooted apices. An alternating pattern of replacement is described for the maxillary and mandibular postcanine series. Postcanine replacement generations in the maxilla are seemingly separated by two tooth loci, whereas in the mandible replacement activity occurs at alternating loci. Cessation of replacement in the first maxillary postcanine locus (PC1) is synchronized with the eruption of the replacement tooth in the third locus (PC3). This cessation of replacement at PC1 results in a distal migration of the entire maxillary postcanine series. This pattern provides possible evidence for a finite number of replacement generations occurring at the active PC1. There appear to have been two replacement cycles per postcanine locus in Cynosaurus, which is a lower number of total replacements per postcanine locus than previously estimated for the Early Triassic basal cynodont Thrinaxodon liorhinus.

The fossil record of abelisaurid theropods in South America is mostly limited to Brazil and Argentina. In Argentina, abelisaurids are generally known from Patagonia, where their record is relatively abundant and includes well-known and complete specimens. However, for North-western Argentina, abelisaurids are represented by incomplete and isolated bones and teeth that remain largely unpublished. The aim of this contribution is to report a nearly complete abelisaurid braincase from the Late Cretaceous Los Blanquitos Formation (Campanian), Amblayo Valley, Salta province, Argentina. The specimen shows plesiomorphic features for abelisaurids, including a thin skull roof, absence of skull projections like horns or bulges, and low and narrow parietal eminence that lie at the same level as the sagittal crest. Furthermore, the specimen possesses some autapomorphies that support its status as a new taxon and its small size allows it to be assigned as one of the smallest abelisaurids recorded up to date. The finding of this specimen constitutes the first unequivocal occurrence of an abelisaurid in Northwestern Argentina and brings new evidence concerning the geographic distribution of the clade during Late Cretaceous times in South America.

Whereas sauropod dinosaurs from the Jurassic and Cretaceous Periods were the largest land animals that ever lived, some of their early relatives evolved relatively large bodies during the Triassic Period. The evolutionary pathways followed by the earliest sauropodomorphs towards the acquisition of massive bodies are poorly understood. However, new finds from South America and Africa are reshaping our knowledge of this issue. Here, we describe a new early and relatively large sauropodomorph represented by a partial postcranial skeleton excavated from Carnian-aged beds (Upper Triassic) of southern Brazil. The new specimen is recovered as a sauropodomorph more closely related to bagualosaurians than saturnaliids or other early-diverging forms in two phylogenetic analyses. The new specimen is generically indeterminate but provides important evidence of an early increase in body size in Sauropodomorpha, being significantly larger than that of coeval or older forms (except Bagualosaurus agudoensis). Furthermore, the specimen is about 3.2 times heavier than Buriolestes schultzi, the earliest-branching sauropodomorph. The slender hind limbs and typical cursorial proportions present in the earliest sauropodomorphs are mostly maintained in the new specimen despite its larger body size.

Triassic strata of the Economy Member of the Wolfville Formation (Newark Supergroup) exposed along the shorelines in Colchester County, Nova Scotia, have yielded an assemblage of continental tetrapods that is clearly different from other Triassic tetrapod communities in eastern North America, including the Late Triassic (Carnian) one from the overlying Evangeline Member of the Wolfville Formation. Although dissociated and fragmentary, the skeletal elements document the presence of a lonchorhynchine trematosaurid and at least two taxa of capitosauroid temnospondyls, procolophonid parareptiles, several taxa of archosauromorph reptiles, and a kannemeyeriiform dicynodont synapsid. Particularly noteworthy is the first definite record of the long-necked archosauromorph Tanystropheus from eastern North America. The strata of the Economy Member were deposited in a semiarid setting but the presence of various temnospondyls indicates the existence of perennial bodies of water. The age of this unit has long been regarded as Middle Triassic (Anisian to Ladinian) based on the tetrapod record, and the present study supports this assessment. The tetrapod assemblage most closely resembles those from the upper Moenkopi Formation of the American Southwest and the upper Middle to Upper Buntsandstein of Germany. The Economy Member is the oldest known Triassic tetrapod-bearing stratigraphic unit as well as the first occurrence of Middle Triassic continental tetrapods in eastern North America.