Richardoestesia is an enigmatic theropod dinosaur originally described on the basis of a pair of dentaries (holotype of R. gilmoreiCurrie et al., 1990) and isolated distinctive teeth, which are abundant in the Upper Cretaceous of North America. Richardoestesia asiatica (Nesov, 1995) is represented by numerous isolated teeth from the Upper Cretaceous Khodzhakul, Bissekty, and Aitym formations of Uzbekistan. Richardoestesia asiatica shows the typical features of the genus, including small mesial and distal denticles (on average 28.4 and 34.5 denticles per 5 mm, respectively), rectangular or knob-like denticles, and an apically convex distal margin of the tooth crown. The sample of R. asiatica has a large proportion of straight teeth (morphotype A) and includes several types of recurved teeth related to their position in the jaws (morphotypes B–E). This species differs from R. gilmorei in the presence of straight teeth and fully serrated mesial carinae. Richardoestesia asiatica cannot be distinguished from R. isoscelesSankey, 2001, which we consider a nomen dubium due, in part, to the imperfect nature of its holotype. Discriminant function analysis (DFA) of dental measurements found no distinction between the samples from Khodzhakul and Bissekty formations. In DFA including North American samples, the morphospace of R. asiatica completely overlaps that of the sample from the Lance Formation (Maastrichtian) of Wyoming and only partly overlaps with that of the sample from the Milk River Formation (Santonian) of Alberta.

The Eocene–Oligocene transition was a period of high faunal and floral turnover, often correlated with climatic deterioration. Crocodyliforms are climate sensitive, and they have been often used for reconstruction of paleoclimates. The description of crocodylian material from the Bartonian of Aaiun-Tarfaya Basin (Morocco) allows the recognition of at least two longirostrine crocodylians, including a gavialoid. This identification is important, because the migration of gavialoids to South America probably occurred during the late Eocene. Close relationships between late Eocene–early Oligocene Eogavialis africanum from Egypt, Argochampsa krebsi from the Paleocene of Morocco, and the South American gavialoid clade suggests that Morocco could have had a particular place in the gavialoid dispersal route to South America. The resemblance between Moroccan material described herein and E. africanum is thus important in this context. Analysis of the distribution of longirostrine crocodylians in the Peri-Tethys area through the Eocene–Oligocene shows a strong difference in the evolution of the distribution between longirostrine crocodylians and Diplocynodon. Whereas the freshwater Diplocynodon has a continuous distribution in western Europe, the mainly marine longirostrine crocodylians have a northern maximal expansion that moves southward during the middle Eocene, being restricted to North Africa during late Eocene–early Oligocene. European freshwater Asiatosuchus-like taxa also disappear during the late Eocene. Climatic deterioration, helped by sea level oscillations, may have strongly impacted the diversity and latitudinal distribution of the crocodylians, but we highlight a possible differential tolerance in range of climatic conditions between crocodylians. This could help to refine the use of crocodylians as paleoclimatic proxies.

As one of the three major groups of gomphotheres, the Miocene Choerolophodontidae were long considered to have been distributed in Europe, Africa, and South Asia, with a few localities in East Asia, whereas choerolophodontids never extended into North America during the Miocene. In this paper, we report new Choerolophodon fossil materials from the early and middle Miocene of China, which suggest morphological similarities to the enigmatic North American Gnathabelodon thorpei. The new fossils were recovered from the lower Miocene of Linxia (C. guangheensis) and the middle Miocene of Junggar (Choerolophodon sp.) basins, suggesting the persistence of this genus in East Asia during the early–middle Miocene. The cheek tooth morphology of the new specimens resembles that of early–middle Miocene Choerolophodon from elsewhere (i.e., C. palaeindicus, C. kisumuensis, and C. chioticus), in addition to striking affinities with Gnathabelodon thorpei. The upper tusk and mandibular characters of G. thorpei, which include upwardly bent maxillary tusks without enamel bands, and elongated and trough-like mandibular symphysis without mandibular tusks, also support its relationship with the choerolophodontids. The occurrence of a possible member of Choerolophodontidae in the late Miocene of North America (i.e., G. thorpei) reveals intercontinental dispersals of choerolophodontids from East Asia across Beringia possibly between 16.0 and 11.0 Ma, at roughly the same time as other proboscideans, e.g., Mammutidae, Amebelodontidae, and Gomphotheriidae. Together, these new materials significantly revise previously established models of the geographic distribution, taxonomic diversity, and ecological adaptations of Choerolophodontidae within China and elsewhere across the Holarctic.

New vertebrate remains are reported from the Late Devonian (?Frasnian) Cuche Formation of northeastern Colombia, including a new taxon of antiarch placoderm (Colombialepis villarroeli, gen. et sp. nov., previously reported as Asterolepis) and a new taxon of arthrodiran placoderm (Colombiaspis rinconensis, gen. et sp. nov.). We also report evidence of a stegotrachelid actinopterygian, a diplacanthid acanthodian (cf. Florestacanthus morenoi), a second antiarch placoderm (Bothriolepis sp.), a putative megalichthyid, and a putative tristichopterid. The absence of typical Euramerican markers, e.g., Asterolepis and Strepsodus, in this assemblage suggests that faunal interchange between Euramerica and Gondwana was less pronounced during the Frasnian–Famennian than previously thought (i.e., the Great Devonian Interchange hypothesis). Three arthropod taxa, including two families of spinicaudatan branchiopods and the eurypterid Pterygotus cf. bolivianus, are found to be associated with the reported vertebrate fauna. Pterygotus cf. bolivianus represents the first eurypterid described from Colombia and the youngest known pterygotid eurypterid, highlighting that pterygotids, which were competitors for large predatory fishes, did not go extinct during the major vertebrate radiation in the Early and Middle Devonian.

The Middle Jurassic docodont Borealestes serendipitus was the first Mesozoic mammal found in Scotland over 40 years ago. Its affinities and morphology have remained poorly understood. Although multiple dentary fragments and isolated teeth have been recovered from Scotland and England, they have not yet been described in sufficient detail. We report new, more complete specimens collected during recent field work on Skye, Scotland, combined with previously collected material. This includes upper and lower dentition and an almost complete right dentary. We present an updated description and diagnosis of the genus Borealestes, based on high-resolution micro-computed tomography (micro-CT) and synchrotron scans. We identify seven key features that distinguish Borealestes from other docodonts, including a pronounced a–c crest, absence of the a–g crest on cusp a, an anterior fovea at the buccolingual midpoint of the upper molar, and the convergence of the Meckel's groove with the ventral margin of the mandible. We also present a revised diagnosis for the second species, B. mussettae. Our phylogenetic analysis supports a clade formed by Borealestes, Haldanodon, Docofossor, and Docodon. Ontogenetic variation in the mandibular morphology of Borealestes is similar to that seen in Docodon and Haldanodon, with the delayed emergence of the ultimate lower molar, the shift of the last molar to the front of the coronoid process, and a posterior shift of the Meckel's sulcus in successively older individuals. This supports a distinctive growth pattern in the clade including Borealestes and Docodon, one that may be present in Docodonta as a whole.

Glyptosaurinae is an extinct group of anguid lizards commonly found in the Cretaceous and Paleogene fossil record of North America and Eurasia. Glyptosaurines are well documented up until the middle Oligocene, but the temporal extent of the group was never constrained precisely. Here, I document the youngest known record of glyptosaurine lizards. I describe 10 fossils of the glyptosaurine Peltosaurus granulosus from the Monroe Creek and upper Sharps formations of Sharps Corner, South Dakota. The youngest known occurrence of Peltosaurus and Glyptosaurinae is between 27.4 and 26.4 Ma, based on a correlation of the magnetozone of the Monroe Creek Formation with chron C9n. Those dates are in the age range of a hypothesized middle–late Oligocene warming event. I review relevant morphological characteristics previously described for Peltosaurus and provide images of the holotypes of Peltosaurus abbotti and Peltosaurus granulosus, as well as two relatively complete specimens of Peltosaurus granulosus. I also establish an apomorphy of Peltosaurus on the frontal bone. Additionally, I correct an error in the literature pertaining to the original description of Peltosaurus.

Within the Twin Mountains Formation, the Proctor Lake dinosaur locality in central Texas is distinct from other Early Cretaceous localities by having an abundance of vertebrate fossils representing a low-diversity assemblage. However, it has yielded two small-bodied crocodyliforms, Wannchampsus kirpachi and Tarsomordeo winkleri, gen. et sp. nov. This new species is represented by a single partial skeleton with a complete dentary, trough-shaped mandibular symphysis, amphicoelous vertebrae, nearly square dorsal osteoderms, and gracile, elongated limbs. In addition, limb morphology indicates a parasagittal posture, an attribute for a terrestrial lifestyle that could have allowed T. winkleri to fill an ecological niche as an active predator of nesting dinosaurs and other small prey. A phylogenetic analysis places this new taxon within Eusuchia as a member of Paralligatoridae and the sister taxon to Paralligator major and Rugosuchus nonganensis, providing further evidence for the presence of this clade in North America. This new Proctor Lake crocodyliform expands the taxonomic diversity of the Early Cretaceous units of central Texas and provides additional insight into the paleoecology of the Proctor Lake dinosaur nesting site.

Fossil sloths from Hispaniola are predominantly represented by records from Haiti. Recent exploration of underwater caves in the Dominican Republic has produced many new sloth specimens, including specimens from two sites that represent the easternmost record for the genus Neocnus. Upper Pleistocene specimens from the localities of Padre Nuestro and Oleg's Bat House are considered to be N. cf. dousman, based on size and comparison with other Neocnus specimens; they differ strongly from those of Acratocnus and Parocnus. Padre Nuestro produced a right radius and a right femur. The Oleg's Bat House specimen is a partial skeleton comprising four vertebrae, first ribs with fused sternebrae, a complete pelvis, a scaphoid, and a phalanx. The Oleg's Bat House specimen also demonstrates a developmental pathology, with the preservation of a cervical rib in association with a vertebra that morphologically is more akin to a thoracic than a cervical vertebra. The pelvis exhibits a number of morphological characteristics that distinguish it from the other island sloths: flattening of the sacral crests and the shape and orientation of the iliac blades. The distal radius and scaphoid morphology indicate a greater range of wrist motion in Neocnus versus that of Parocnus and likely made this sloth more arboreally capable than the more terrestrial Parocnus.

A new fossil species of miniature lightfish, †Vinciguerria orientalis, sp. nov., is described from the middle Miocene beds of the Duho Formation, South Korea. This is the second extinct species of this genus described from skeletal remains. The new Neogene species is very similar to recent congeners in its general appearance, morphometrics, and body proportions. It is characterized by a combination of the following features: 37–40 vertebrae, 13–16 dorsal fin rays, 13–17 anal fin rays, 13–16 photophores in the ventral series from the pectoral fin base to the pelvic (ventral) fin base, 14 or 15 photophores in the ventral series from the anal fin base to caudal fin base of the ventral series, ca. 26 gill rakers, and a caudal body part length of more than 30% of standard length. The main difference separating †Vinciguerria orientalis from all other representatives of the genus is the lack of fusion between hypurals 1 and 2 and hypurals 3 and 4 and the separation of the urostylar centrum from hypural elements. This caudal skeleton structure appears to be a transition link between the Paleogene and Neogene–Recent species of this evolutionary lineage.

Environmental and climatic conditions of the South American temperate grasslands (Pampas) during the Last Glacial Period have typically been regarded as mostly arid and cold, whereas humid and mild conditions such as those prevailing today may have been established only recently. This hypothesis has been built mostly upon fossil mammals that come from coastal areas and date from the end phase of this period and thus provide both temporally and geographically biased data. Other fossil vertebrates, including anurans, have been overlooked when addressing these conditions in spite of being potentially very informative due to their ecological requirements. Here, we analyze an anuran assemblage from the Last Glacial Period of the inland Pampas. In addition to the description of new records, we discuss the taphonomic settings and the correlation of the fossil-bearing beds with levels referred to the interstadial Marine Isotope Stage (MIS) 3 from other Pampean localities. Based on this evidence, together with what is known for extant anurans, we discuss the environmental and climatic conditions of the Pampas during the Last Glacial Period. The presence of Rhinella arenarum and, particularly, Ceratophrys ornata in the fossil assemblage and their persistence in the Pampas throughout the Quaternary suggest that the range of environmental changes in the region during the Last Glacial Period might have been more limited than has traditionally been acknowledged. In this regard, this study highlights the value of anuran fossil assemblages when addressing environmental and climatic conditions during the Quaternary.

Zupaysaurus rougieri is an early neotheropod from the middle Norian Los Colorados Formation of northwestern Argentina represented by an almost complete skull and several postcranial bones. Most of its braincase morphology has remained obscured by other skull bones and sediment. Additional mechanical preparation and X-ray computed tomography on the single known specimen of Zupaysaurus has allowed a detailed description of the braincase, the cranial endocast, and the inner ear of this Triassic dinosaur. Basal theropod braincases are poorly sampled and there is little information on this region, and even poorer knowledge on the brain and inner ear anatomy of Triassic forms. The virtual reconstruction of the braincase of Zupaysaurus shows anteroventrally oriented, finger-like basipterygoid processes, an elongate and horizontally projected cultriform process, and well-developed preotic pendant, basisphenoid recess, and subsellar recess. The endocranial morphology is partially reconstructed, showing an anteroposteriorly short but dorsoventrally tall cranial endocast, with well-marked demarcations between the forebrain, midbrain, and hindbrain. The inner ear preserves the three semicircular canals, but not the lagena. The posterior semicircular canal is proportionally large when compared with that of other theropods. The new information presented here on Zupaysaurus rougieri contributes to the knowledge of the neuroanatomy of basal theropods and sheds light on the evolutionary patterns of the braincase morphology in nonavian Theropoda.

We describe a virtually complete proboscidean cranium and other remains from the late Miocene of Skoura near Ouarzazate, Morocco, assigning them to a derived species of Tetralophodon. African finds of this genus are scarce and are of additional interest due to their potential importance for elephantid phylogeny. The Skoura material adds significantly to the African record of non-anancine tetralophodonts and to the Neogene proboscidean record of northwestern Africa.

A functional analysis of a well-preserved snout of the early-diverging mammaliaform Morganucodon watsoni, with matching upper and lower dentitions, and of the holotype of Megazostrodon rudnerae, showed that both taxa had a primarily orthal occlusal path. In Morganucodon, the direction was individually variable and either strictly orthal or slightly distally or mesially inclined. An analysis with the Occlusal Fingerprint Analyser (OFA) software confirmed an earlier hypothesis that the main cusp A of the upper molars occluded between cusps b and a of the lower antagonists. According to the OFA analysis, there was more extensive contact between cusp a and the preceding anterior upper molar than previously assumed, showing some similarities to the two-on-one pattern described for Megazostrodon. According to our analyses, the molars of Morganucodon and Megazostrodon had an adaptation to piercing, as well as shear-cutting. ‘Shearing flanks,’ which were the focus of previous studies, seem to be a result of attrition, rather than functional areas in themselves. The posterior upper molars in Morganucodon were rotated along their longitudinal axis and lingually inclined within the tooth row, resulting in a triangle between M1 and M2 into which the large m2 can occlude. Together, this suggests a predetermined tooth placement and that contrary to previous hypothesis Morganucodon did not rely on extensive wear in order to form a precise occlusion.

A collection of fish bones was recovered from upper Pleistocene (Gamblian) deposits near the confluence of the Kagera and Rurubu rivers in Tanzania, west of Lake Victoria. The Rurubu/Kagera bones include two families: the Clariidae (Clarias gariepinus, Clarias sp.) and Cichlidae (tribes Oreochromini, Haplochromini; Oreochromis sp.). Geological, paleontological, and molecular data presented here provide new insights into Pleistocene eastern African biogeography and into the evolution and past affiliations of the Rurubu/Kagera and Lake Victoria fish taxa. The data indicate that the Rurubu/Kagera taxa were descended from Miocene-aged populations in the Congo and/or Nile rivers. Data also suggest that the Rurubu/Kagera haplochromines may have been part of a shared Kagera River/Lake Victoria basin haplochromine clade, whose later members radiated into hundreds of species in Lake Victoria over the past approximately 15,000 years.

Brazilichthys macrognathus is the only named actinopterygian from the Permian (Cisuralian) Pedra de Fogo Formation of northeastern Brazil, in which it is represented by a single three-dimensionally preserved, but incompletely described, skull of unclear systematic placement. We used X-ray micro-computed tomography (µCT) to redescribe its anatomy, in particular parts of the internal skeleton, and assess its phylogenetic affinities. We correct errors in the original description, including the number of infraorbital bones and the misidentification of the dermosphenotic as sclerotic ossifications. These reinterpretations of external anatomy are accompanied by new data on internal structure, including the palate, the parasphenoid, and the branchial and hyoid arches. A maximum parsimony analysis of anatomical data resolves Brazilichthys as a stem actinopterygian, crownward of all Devonian species. This placement is supported by the absence of a dermosphenotic posterior ramus and the presence of opercular process of the hyomandibula. A similar placement is suggested by a Bayesian analysis of the same data set, although relationships throughout the tree are less resolved. Our results reject previous interpretations of Brazilichthys as a relative of Birgeriidae, a Triassic group traditionally placed within the actinopterygian crown. Although Acrolepis is too poorly known to be included in our analysis, we also reject relationship between that taxon and Brazilichthys, because their only shared similarities appear to be broadly distributed among early actinopterygians.

We report a third archosaur from the Late Triassic cavity-fill sediments of Pant-y-ffynnon Quarry in South Wales, in addition to the basal crocodylomorph Terrestrisuchus and the basal sauropodomorph dinosaur Pantydraco. The new taxon, Aenigmaspina pantyffynnonensis, previously referred to informally as ‘Edgar,’ was recovered in 1952 and is preserved as a tight cluster of vertebrae, ribs, and a scapula in a single block, as well as numerous associated, but now isolated, elements, including skull bones, vertebrae, further putative elements of the forelimb, and a partial pelvis. We present a digital model based on computed tomography (CT) scans of the main associated blocks, which shows exquisite detail of an associated series of 12 cervical and anterior dorsal vertebrae, with ribs and a scapula. The well-developed spine tables and eight matching osteoderms confirm that this is a crurotarsan archosaur, but it lacks apomorphies of all major crurotarsan clades. Phylogenetic analysis gives equivocal results, showing weak relationships with Proterochampsidae and Ornithosuchidae; the new taxon might lie close to Erpetosuchidae, based on the ‘Y'-shaped spine tables.

A new taxon of monodontid cetacean, Casatia thermophila, gen. et sp. nov., is here described on the basis of a partial skull from lower Pliocene (5.1–4.5 Ma) marginal-marine deposits of Tuscany (central Italy). This new taxon belongs to Monodontidae based on the presence of a medial exposure of the maxillae anterior and lateral to the external bony nares; it mainly differs from all other named monodontids by the presence of a median depression of the premaxillae anterior to the premaxillary sac fossae and by a medial margin of the premaxillary-maxillary suture that does not parallel the anterolateral profile of the external bony nares. Our phylogenetic analysis, the first including all taxa of Monodontidae, recovers Casatia as a crown monodontid, more closely related to Delphinapterus than to Monodon and sister group of an unnamed taxon from the North Sea. The holotype of Casatia represents the first and only fossil monodontid from the Mediterranean Basin. Taking its place beside abundant fossils of strongly thermophilic marine vertebrates, such as the bull shark Carcharhinus leucas, the tiger shark Galeocerdo cuvier, and the extinct sirenian Metaxytherium subapenninum, Casatia thermophila represents the strongest evidence supporting the hypothesis that monodontids once thrived in low-latitude, warm-water habitats. On the basis of our phylogenetic reconstruction, early relatives of the extant monodontids might have adapted independently to the high-latitude, cold-water environments they currently master. The definitive disappearance of the Neogene thermophilic monodontids could be attributed to the cooling episode that accompanied the onset of long-term Northern Hemisphere glaciation around 3 Ma.

Chindesaurus bryansmalli is an early dinosaur of uncertain affinities from the Late Triassic Chinle Formation at Petrified Forest National Park, Arizona. Since its first description in 1995, the taxon has been considered a plateosaurid, a noneusaurischian saurischian, a herrerasaurid, and/or a non-neotheropod member of Theropoda. Chindesaurus bryansmalli is usually scored for about 25% of the characters in a given phylogenetic analysis, and many characters have been scored secondhand from misidentified elements. Here, we provide a redescription of the holotype specimen of C. bryansmalli, correct misidentifications, introduce previously unknown elements, and discuss novel morphological character observations. Chindesaurus bryansmalli is supported as the sister taxon to the non-neotheropod theropod Tawa hallae from the Chinle Formation at Ghost Ranch, New Mexico. The same two most parsimonious trees, with increasing node support, result from iteratively removing the three most incomplete taxa in the employed data set, suggesting that the relationships of stem-averostran theropods are not highly affected by the inclusion of fragmentary specimens. The Chindesaurus + Tawa clade recovered here may represent a potentially diverse group of early theropods prior to the end-Triassic mass extinction.

Azhdarchid pterosaurs have been known since 1972 from upper Campanian deposits of Alberta, Canada. Originally represented by only very fragmentary remains tentatively assigned to the genus Quetzalcoatlus, additional material uncovered over the years has revealed that the taxonomic identity of the Alberta pterosaur material is at odds with this in the light of the growing understanding of azhdarchid diversity. Here, we describe previously undocumented pterosaur remains from Alberta and reassess previously studied material. The specimens collected from the Dinosaur Park Formation can be assigned to a new genus and species Cryodrakon boreas, gen. et sp. nov. The largest elements referable to this taxon suggest that this genus reached sizes comparable to those of other giant azhdarchids.

Stegosiren macei, a new genus and species of halitheriine dugongid from the mid-Oligocene of South Carolina, U.S.A. (Ashley and Chandler Bridge formations, late Rupelian–late Chattian), represents a stage of halitheriine evolution more derived than that of the Old World early Oligocene Eosiren imenti and Halitherium schinzii, but slightly less derived than the West Atlantic late Oligocene Metaxytherium albifontanum. It is more comparable in stage of evolution to its early Oligocene contemporaries Caribosiren turneri and Priscosiren atlantica and may be a sister taxon of these two. It is distinguished autapomorphically from all other sirenians by a notably broadened frontal roof and a thickened anterior tip of the frontal, which formed a butt joint with the premaxilla. Analogous (independently evolved) joints in several other sirenians (principally dugongines) are correlated with enlarged upper tusks thought to be used for excavating seagrass rhizomes. This suggests that large tusks also may have been present (although not preserved) in Stegosiren, which is only the second halitheriine in which such a feature has been observed. Stegosiren macei brings to at least seven the number of potentially sympatric sirenian species lineages known from the West Atlantic-Caribbean Oligocene (six or more from South Carolina alone). This extraordinary sirenian diversity, unmatched elsewhere in the world, poses problems for ecomorphology and feeding-niche partitioning.