An unusual fork-tailed coelacanth from the Lower Triassic Sulphur Mountain Formation of British Columbia, Canada, marks the first considerable departure in actinistian body form since the Mississippian Period. Rebellatrix divaricerca, gen. et sp. nov., is unique among coelacanths in its possession of a bifurcated caudal fin, reduced segmentation of fin rays, and fusion of caudal fin elements. Parsimony analysis of a character-taxon matrix of 109 characters and 29 taxa recovered R. divaricerca as sister taxon to Latimerioidei. The family Rebellatricidae is erected to include only R. divaricerca. This novel body shape of the new coelacanth raises questions about the idea that coelacanths were morphologically static following the Mississippian. Rebellatrix divaricerca also emphasizes the morphological diversity of coelacanths during the Early Triassic, a time when species diversity of coelacanths was also highest. The slender, fork-tailed body form suggests fast swimming and an active lifestyle, unique among known fossil and extant coelacanths.

We describe a new semionotiform genus, which was recognized while studying Macrosemimimus fegerti, gen. et sp. nov., from the Late Jurassic Solnhofen Archipelago, Germany. Macrosemimimus (Lepidotes) lennieri from the early Kimmeridgian of Cap de la Hève, France, including Lepidotes toombsi from the Lower Kimmeridge Clay in Cambridgeshire, England, as a junior synonym, also belong to the new genus. Though different species, the presence of the same fish genus in different biodiversity zones suggests that semionotiforms might have been less sensible to the ecological and physical factors that caused the endemisms recognized in the invertebrate faunas. Macrosemimimus is mainly distinguished by the peculiar shape of the antorbital portion of the frontal bones, a single pair of extrascapular bones that do not reach the dorsal midline, anteriorly open circumborbital ring, only two suborbital bones, edentulous maxilla, a large quadratojugal involved in the jaw articulation, four postcleithra, and the pectoral fins placed very low and joining ventrally. The two included species differ in the ornamentation of the skull bones, the morphology of the scales, the relative size and position of the extrascapular bones, the dorsal extension of the preoperculum, and the kind of dentition. Although the phylogenetic relationships of Macrosemimimus are not yet established, the particular shape of the antorbital portion of the frontals and the patterns of the extrascapular and suborbital bones indicate possible systematic affinity with the macrosemiids, “Lepidotes” gloriae from the Oxfordian of Cuba, and “Lepidotes” microrhis and “Lepidotes” tanyrhis from the Barremian of Las Hoyas, Spain.

Mawsonia, the largest actinistian, was a non-marine form common in continental and estuarine deposits of the Tithonian—Cenomanian of western Gondwana. The genus has been recently reviewed, and only two species are recognized as valid: M. gigas and M. tegamensis. Herein we describe new material that can be referred to this genus, including two basisphenoids, a coronoid, a pterygoid, a metapterygoid, one operculum, and two posparietals. The Uruguayan record represents the southernmost occurrence of Mawsonia and the Mawsoniidae in the world, and strengthens the Late Jurassic—Early Cretaceous age proposed for the unit.

The second member of the Trematosaurinae (Temnospondyli, Stereospondyli) from Australia is described as Microposaurus averyi, n. sp., from the Anisian Rouse Hill Siltstone (Ashfield Shale, Wianamatta Group, Sydney Basin). This is the first occurrence of the genus from outside South Africa. M. averyi and the South African M. casei share an anterior emargination of the nostril that accommodated the dentary fangs (a condition unique among temnospondyls), but the emargination is much larger in the Australian taxon. The Anisian stereospondyls from the Sydney Basin occur in sediments younger than the early Anisian and may fill a worldwide gap in terrestrial tetrapod faunas from that time.

Paracryptodira is composed of North American Baenidae and an undefined group of North American and European turtles known from the Middle Jurassic to the mid-Paleocene. Traditional members of Pleurosternidae are included in this group. Whereas the North American record extends into the mid-Paleocene, it was proposed that European nonbaenid paracryptodirans disappeared during the Early Cretaceous. However, an analysis of turtle remains from the upper Paleocene of Western Europe revealed the presence of a new paracryptodire, herein named Berruchelus russelli. This taxon is distinguished as the only post-Neocomian European representative of Paracryptodira, and thus increases the European temporal distribution of non-baenid paracryptodirans. Cladistic analyses identify B. russelli as closely related to the Late Cretaceous—middle Paleocene North American Compsemys victa. It is proposed that, after the disappearance of the European Mesozoic paracryptodiran taxa, Europe was recolonized by a paracryptodiran lineage originating from North America, which resulted in B. russelli.

A new elasmosaurid plesiosaur, Albertonectes vanderveldei, gen. et sp. nov., is described on the basis of an almost complete postcranial skeleton from the upper Campanian, Bearpaw Formation in Alberta, Canada. The new taxon is distinguished by a unique set of characters—76 cervicals, lateral longitudinal ridge on posterior-most cervicals, relatively wide clavicular arch, tapered ventral projection at the median symphysis of coracoids, pointed anterolateral projection of pubis, fused posterior-most caudal vertebrae, and a relatively slender humerus. Ninety-seven chert gastroliths were also recovered with the specimen, and their mean diameters range from <1 to 13.5 cm. Shape analysis indicates that most of the gastroliths were ingested in the vicinity of a beach environment. Evidence that the carcass was scavenged by sharks includes a tooth-marked coracoid, two shed Squalicorax sp. teeth, and small, localized disruptions to the skeleton. Preliminary phylogenetic analysis confirms the inclusion of Albertonectes in a clade comprised of ‘middle’ to Late Cretaceous, long-necked elasmosaurid plesiosaurs. The number of cervical vertebrae associated with different elasmosaur genera does not show any correlation with phylogeny. Both neck and total body length of Albertonectes are the longest among known elasmosaurs, and highlight the morphological extremes attained by this group of plesiosaurs.

A new phytosaur taxon from Petrified Forest National Park, Arizona, is here described based on cranial material from a single individual. This specimen previously was included in an extensive phylogenetic analysis, and it was found to possess a combination of character states that differs from all known phytosaur taxa in addition to two autapomorphies within the braincase and an autapomorphy of the mandible. The new taxon adds to the taxonomic diversity recognized from the Sonsela Member of the Chinle Formation. The continued increase in phytosaur diversity emphasizes the need to more accurately characterize and identify taxa within a phylogenetic systematic context in order to produce a more refined signal for biostratigraphic correlations, biochronologic inferences, and faunal dynamics during the Late Triassic.

We describe a new crocodile, Crocodylus thorbjarnarsoni, sp. nov., on the basis of skulls and jaws from Pliocene and Pleistocene deposits in the Lake Turkana Basin of Kenya. The new species has a comparatively broad, deep snout and resembles an extinct horned crocodile from the Quaternary of Olduvai Gorge (C. anthropophagus), but the squamosal ‘horns’ are not as well developed. The skull table has a strongly trapezoidal outline different from those of the living Nile crocodile (C. niloticus) and crocodiles from late Miocene deposits in the Turkana Basin. The largest specimens are from animals up to 7.5 m in total length. It would have been the largest predator in its environment, and the early humans found in the same deposits were presumably part of its prey base. A phylogenetic analysis, including the new species and an improved sample of extinct crocodyline diversity, suggests a more complex phylogenetic and biogeographic history for the clade in Africa and the eastern Indian Ocean region than previously supposed. The analysis limits the known geographic and stratigraphic range of Rimasuchus lloydi, previously thought to occur throughout Africa from the early Miocene through the Pleistocene of northern Africa. Crocodylus niloticus is not known with certainty from units older than the Quaternary, and most late Miocene fossils from the Turkana Basin previously referred to C. niloticus can instead be referred to C. checchiai. The current first appearance datum for Crocodylus in Africa is approximately 7 Ma.

For the first time an association of adult and juvenile rebbachisaurid sauropods is described. The material comes from the Early Cretaceous locality of Agrio del Medio (Neuquén, Argentina). The three specimens apparently formed a single group, and their death seems to have been almost simultaneous. The two juvenile specimens are represented by axial and appendicular bones. They show a close relationship with Zapalasaurus bonapartei, which comes from a different sector of the same basin, but which is approximately the same age. The discovery at Agrio del Medio suggests that rebbachisaurid sauropods displayed gregarious behavior. The paleoenvironments in which rebbachisaurids are normally recorded implies a greater tolerance toward extremely arid environments than that shown by macronarian sauropods.

Argyrosaurus superbus is one of the earliest-named Argentinean dinosaurs. The holotype comprises a complete forelimb, probably from the upper member of the Bajo Barreal Formation (Late Cretaceous), Chubut Province. Numerous remains have been referred to Argyrosaurus from Argentina and Uruguay; however, the type specimen has not been adequately diagnosed and referrals have predominantly been based upon their large size. Here we redescribe Argyrosaurus, demonstrating it to be a valid titanosaur genus based on five autapomorphies, as well as an unique character combination. The exact placement of Argyrosaurus within Titanosauria is uncertain, although the probable presence of carpal bones, otherwise unknown in titanosaurs, may indicate a basal position. None of the referred remains can be attributed to Argyrosaurus, and most should be regarded as indeterminate titanosauriforms. The exception to this is a partial skeleton from the lower member of the Bajo Barreal Formation (early Late Cretaceous), Chubut Province, comprising dorsal and caudal vertebrae, as well as numerous appendicular elements. This specimen is distinct from Argyrosaurus and can also be differentiated from other sauropods based on an unusual character combination (including plesiomorphic tarsus), plus one autapomorphy. Elaltitan lilloi, gen. et sp. nov., displays numerous titanosaur characters and shares several features with derived taxa such as Neuquensaurus, Opisthocoelicaudia, Rapetosaurus, Saltasaurus, and Trigonosaurus. Elaltitan can be referred to Lithostrotia; however, its precise position within this clade must await future phylogenetic analysis. The revision and description of the titanosaurs Argyrosaurus and Elaltitan provides new information on this diverse but still poorly understood clade.

Recent studies have blurred the distinctness of two major avian groups: the Enantiornithes, a major radiation of early birds in the Cretaceous, and the Ornithuromorpha, the clade including extant birds. Here we describe a new enantiornithine bird from the Lower Cretaceous Jiufotang Formation of western Liaoning, China, Xiangornis shenmi, gen. et sp. nov., which further reduces the morphological gap between the two groups. Xiangornis shenmi has several enantiornithine features, including a furcula with a significantly elongated hypocleidium, a coracoid with a convex lateral margin, and a minor metacarpal that extends further distally than the major metacarpal. However, it also possesses some derived ornithurine features, such as a short alular metacarpal (about one-sixth as long as the major metacarpal) that is completely fused to the major metacarpal, a large extensor process on the alular metacarpal, proximal and distal fusion between the minor and major metacarpals, and an intermetacarpal space positioned significantly distal to the alular metacarpal. This new find indicates that a carpometacarpal morphology similar to that seen in modern birds probably evolved independently in enantiornithines and appeared earlier than in Ornithuromorpha, and demonstrates that character evolution in early birds was more complex than previously believed.

Early hystricognathous rodents from Africa are primarily documented by two basal and extinct groups, the paraphyletic “Phiomyidae” and the Gaudeamuridae, which were particularly well diversified through the late Eocene and the early Oligocene. However, in the absence of a comprehensive late Oligocene fossil record, the evolutionary history of African hystricognathous rodents during the end of the Paleogene is unclear. Continuing field efforts in the Lokichar Basin of Kenya (western Turkana Basin) have led to the discovery of dental remains of a ‘phiomyid’ from the Lokone site LOK 13. The dental pattern of this rodent is unusual among ‘phiomyids,’ which led us to propose here a new taxon: Turkanamys hexalophus, gen. et sp. nov. Turkanamys shares a similar dental bauplan with early Afro-Asian hystricognaths (early ‘phiomyids’ and ‘baluchimyines’), and as such appears evolutionarily conservative with respect to some Oligocene and all the Miocene hystricognaths. Conversely, Turkanamys is also highly autapomorphic in developing a hexalophodont pattern on upper molars. The discovery of this peculiar rodent highlights the persistence of this ancestral ‘phiomorph’ group at the end of the Paleogene. Given the great familial diversity of hystricognaths in the early Miocene of East Africa, the virtual absence of their stem representatives in the late Oligocene record of the same province suggests either important taphonomic/sampling biases or a real absence of these families in this province at that time. This would suggest that hystricognathous rodents diversified elsewhere and colonized East Africa by the late Oligocene—early Miocene transition.

Several new fossil remains of Felidae from the late Miocene (Turolian age, MN 13, local zone M2) locality of Las Casiones (near the village of Villalge Baja, Teruel, Spain) are studied in the present paper. This felid community includes the machairodontines Amphimachairodus giganteus, Paramachaerodus orientalis, and Metailurus major, and the felines Pristifelis attica and a small, undetermined species, previously unknown in the late Miocene. With this high diversity of felids, the environment of Las Casiones was probably relatively vegetated, with shrubs and trees that allowed smaller felid species to avoid dangerous encounters with the larger ones.

Shape variation in the vertebrate skull is often studied by considering this bony structure as a single discrete unit, but it can also be interpreted exploring covariation among functionally and developmentally distinct regions, or modules. In this paper, we explore the evolution of skull shape in extant and fossil carnivoran cats by looking at covariation between two distinct modules: the rostrum (splanchnocranium) and braincase (neurocranium). Previous work suggests that the evolution of extreme skull shapes in sabertoothed cats may occur along developmental axes similar to the allometric trajectory observed for extant conical-toothed cats. Here, we reassess this hypothesis by using geometric morphometric data to test for covariation between rostral and braincase modules in sabertoothed and conical-toothed cats. Using partial least squares analysis, we detect a correlated pattern of evolution between rostrum and braincase shape in both forms. However, when we compare within-module integration between conical and sabertoothed cats, we find significant differences in vector trajectories for the rostrum but not the braincase. Both skull modules of conical-toothed cats are more influenced by allometry. For sabertoothed taxa, relative canine height drives shape in the rostrum, but both size and canine length affect braincase shape. We suggest that sabertoothed skull morphology is the result of genetic and developmental processes that were affected by the growth rate of the upper canines. The striking convergence between independent sabertooth radiations indicates that elongation of the canines influenced interspecific skull shape variation in different lineages but in a similar way.

Metaxytherium subapenninum was a halitheriine dugongid distributed along the northwestern coasts of the Mediterranean Basin during the early and late Pliocene. It represents the latest sirenian species of the Mediterranean Basin, the latest Metaxytherium species in the world, and also the latest species belonging to the paraphyletic subfamily Halitheriinae. We review M. subapenninum in the light of new discoveries, including its stratigraphic and geographic distribution, osteology, paleoecology, and relationships. M. subapenninum represents a more derived stage of evolution in comparison with the earlier Metaxytherium species. It is characterized in particular by an increase in body size, an increase in tusk size, and a dorsal broadening of the nasal process of the premaxilla. Its variation in tusk size does not appear to represent sexual dimorphism as in the modern Dugong, but instead progressive intraspecific evolution of larger tusks as a feeding adaptation convergent on that of derived dugongines. It was a relict species limited to the Mediterranean Basin, and responded to long-term climatic cooling by an increase in body size and by an increase in tusk size and rostral reinforcement in order to obtain a more nutritious diet richer in rhizomes.

In the early 20th century, human skeletal remains were excavated from the Vero Beach site in southeastern Florida in direct stratigraphic association with extinct late Pleistocene mammals, including giant ground sloths, armadillos, carnivores, camels, tapirs, and horses. Despite the demonstrable stratigraphic context, prominent scientists during the early 20th century, such as the anthropologist Aleš Hrdlička, dismissed these human remains from the Vero Beach site as younger, intrusive burials. Although several other important late Pleistocene/early Holocene sites have been found elsewhere in North America with human and extinct faunal association, the Vero Beach site remains significant because of the quality of preservation of the human skeletal remains, and its geographic location in the southeast. More recent attempts to provide age control at Vero, e.g., using direct ¹⁴C dating of associated fossil bones, have so far been unsuccessful, including in this study, almost certainly resulting from diagenesis. Here we establish the relative ages of the fossils from Vero Beach by comparing the relative uptake of REEs (rare earth elements) during fossilization. The human and late Pleistocene mammal specimens found in situ from the same stratigraphie levels (stratum 2 and the base of stratum 3) at Vero Beach have similarly high REE concentrations and patterns; the concentrations are significantly greater than those from a control group of modern mammals from the same area. We therefore interpret these data to indicate that the humans are contemporaneous with late Pleistocene mammals from the Vero Beach site in Florida.