Skeletal bone enlargement (hyperossification) was thought to only occur in endochondral and dermal bones (e.g., endoskeletons of marine tetrapods and dermal bones of certain jawless vertebrates, placoderms, and teleost fishes). However, in some arthrodiran placoderms (basal jawed vertebrates), i.e., Millerosteus minor, Compagopiscis croucheri, Eastmanosteus calliaspis, several types of bone enlargement also occur within the endoskeleton, affecting the vertebral column. Significantly, placoderm endoskeletal bone is thought to be thin-walled, ossifying only in the fibrous layer surrounding a cartilage precursor (historically called perichondral bone), rather than endochondrally/dermally. Hyperossification differs among these three species, revealing a range of internal and external bone morphologies undescribed for the placoderm endoskeleton. Thus, neural arches of M. minor are swollen in external appearance, in cross-section showing considerable deposition of layered, compact bone. In contrast, the arches of E. calliaspis are unswollen externally, with the neural spine cortex composed of the thin perichondral bone expected for placoderms. Histologically, though, the arch comprises numerous layers of perichondral bone. In C. croucheri, as in E. calliaspis, the spine and arch are unswollen externally, but the perichondral bone is thickened and compact, more similar to the condition in M. minor. Vertebral hyperossification in these taxa differs considerably in the degree and mode of cortical tissue thickening, via addition of tissue to the bone's external (periosteal) and/or internal (endosteal) surfaces. Hyperossifcation in these arthrodires demonstrates that increases in endoskeletal bone mass are not restricted to crown-group gnathostomes (Chondrichthyes + Actinopterygii), representing a first step in the evolution of this process, involving modifications to cortical bone layers.

A chimaeroid mandibular dental plate from the nearshore upper Oligocene Sooke Formation west of Victoria, Vancouver Island, British Columbia, is described here as a new genus of chimaerid fish (Holocephali, Chimaeridae), Canadodus suntoki, gen. et sp. nov. The new genus differs from mandibular plates of both Recent and Cenozoic Chimaeridae (Chimaera, Hydrolagus) in having a more robust plate with a massive symphyseal tritor filled by laminated whitlockin, the presence of a large compound median tritor and a small inner tritor, as well as the absence of solid whitlockin in the dental structure. The chimaerid individual is estimated to have measured nearly 1 m in total body length. This is a first record of a Paleogene chimaeroid fish in both British Columbia and Canada and only the second record from the Oligocene of the northern Pacific. In addition, the species Chimaera gosseletiWinkler, 1880, is transferred to the genus Harriotta, resulting in the new combination Harriotta gosseleti (Winkler, 1880).

The Sangkarewang Formation of the Ombilin Basin in Sumatra, Indonesia, has been known for its fossil fishes for over 150 years, and a monograph on the fishes from freshwater deposits of the basin was published over 80 years ago. Most of the material previously reported was placed in living genera; however, based on reexamination of some previously collected material and newly collected material, none of the taxa from these deposits are considered to be congeneric with any modern fishes. New collections, from paper shales representing deeper water in the paleolake than that previously sampled, are composed predominantly of cyprinoid fishes. Two previously unreported cyprinoid taxa are here named as new: Sangkarewangia sumatranus, gen. et sp. nov., and Hadromos sandersae, gen. et sp. nov. The previously described Puntius bussyi is removed to Pauciuncus, gen. nov., yielding Pauciuncus bussyi, comb. nov. All of the cyprinoids from the formation, those reported here as new as well as those previously reported, are assessed for their possible subfamily affinities. Most belong to Barbinae, with Labeoninae, Smiliogastrinae, and Rasborinae tentatively represented. The age of the Sangkarewang Formation has been controversial; it has been variously attributed to Cretaceous, Paleocene, Eocene, and Miocene. Although the fish fauna does not definitively date the formation, recent studies support an early to mid-Eocene age, and the ichthyofauna does not contradict this.

An isolated pterygoid tooth plate of a lungfish from the Lower Devonian (Lochkovian–Pragian) of Vietnam is described. The material is negatively preserved and lacks associated jawbones to assign a reliable taxonomic status and phylogenetic position. The tooth plate is composed of five main tooth rows radially arranged, separated by several interrow denticles and flanked medially and laterally by smaller accessory rows and by a denticulated posterolateral field. The general structure of the tooth plate displays predominantly primitive traits similar to those known in the contemporaneous Diabolepis from China. However, as opposed to Diabolepis, the tooth plate possesses fewer and more organized rows of teeth, a condition typical of more derived dipnoans. Comparisons with other primitive forms indicate that the arrangement of teeth into distinct rows with a lack of interrow denticles is typical of juvenile specimens of Diabolepis, which may imply that the presence of discrete tooth rows in more derived lungfish taxa is a product of paedomorphosis. Given its puzzling mix of primitive and derived features, this new pterygoid tooth plate can be tentatively assigned to a previously known lungfish prearticular from northern Vietnam, although with caution. Pending the finding of more complete remains, the condition shown by this new form might indicate that the establishment of the modern lungfish tooth plate organization occurred no later than the Pragian.

We describe new material of the tristichopterids cf. Langlieria socqueti and cf. Eusthenodon wangsjoi and other unassignable tetrapodomorph remains from the upper Famennian locality of Strud, Belgium. Because of recent improvements in our tristichopterid knowledge, a new phylogenetic analysis is presented in addition to a paleobiogeographic analysis using the Bayesian binary Markov chain Monte Carlo (MCMC) statistical method. The origin of the whole tristichopterid clade is reconstructed with a very likely western European origin. Much of the early tristichopterid history took place in Euramerica. During the Late Devonian, tristichopterids most probably spread from Euramerica into Gondwana. The highly nested tristichopterid clade formed by Cabonnichthys burnsi, Mandageria fairfaxi, E. wangsjoi, Edenopteron keithcrooki, and Hyneria lindae most likely differentiated in Australia. Then dispersal events occurred from Australia to Euramerica with Hyneria lindae (to eastern North America) and E. wangsjoi (to Greenland/western Europe). The latter dispersal events, during the Famennian, are in agreement with the Great Devonian Interchange, which predicts dispersal events between Gondwana and Euramerica at this time.

The strata of the American Southwest, particularly the Chinle Formation and the Dockum Group, are critical to our understanding of faunal diversity and evolution in the Late Triassic. In recent decades, these strata have informed the evolution of close dinosaur relatives, which remain poorly sampled and enigmatic in their geographic distribution. Here, we describe and discuss a new non-dinosaurian dinosauromorph assemblage from the Los Esteros Member of the Santa Rosa Formation at the base of the Dockum Group in east-central New Mexico. This assemblage includes hindlimb fragments assignable to Silesauridae and Lagerpetidae. Much of the lagerpetid material, assignable to Dromomeron, is of unusually large size. Based on a dataset of complete lagerpetid femora, we estimate a total femoral length of 221.9 mm for one partial femur, making it the largest reported individual. We also provide biochronological support that at least a portion of the Los Esteros Member corresponds to the Otischalkian land vertebrate faunachron through the identification of non-Mystriosuchinae phytosaurs. Subsequently, we question the presence of a bifurcated lateral ridge on the squamosal of all phytosaurs currently assigned to Parasuchus. This is the first Otischalkian fauna identified from New Mexico, and it reveals lagerpetids achieved large body size earlier than previously recognized. Our identifications expand the geographic and temporal range of non-dinosaurian dinosauromorphs in the American Southwest. The material presented here, in conjunction with an increasing number of Dromomeron specimens, demonstrates that non-dinosauriform dinosauromorphs could match or exceed the body size of many coeval dinosaurs.

This study presents the first plesiosaurs recovered from the Jurassic of the Atacama Desert that are informative at the genus level. One specimen is represented by an articulated axial section that shows distinctive features, such as cervical vertebrae with oval articular facets and gracile neural pedicles. The second specimen preserves similar vertebrae, teeth, propodials, and pectoral elements. Their anatomical characteristics allow us to refer them to Muraenosaurus, a genus of cryptoclidid plesiosaur previously reported in Callovian rocks of Europe and Argentina. A third specimen is represented by a fragmentary jaw, which coincides precisely in size and anatomical features with that of Vinialesaurus caroli, another cryptoclidid plesiosaur exclusively known from the Oxfordian of Cuba. The material studied represents the first record of Muraenosaurus in the Oxfordian of the Profeta-La Ternera Basin in northern Chile, adding to previous regional occurrences of the genus and to the record of Cryptoclidus, both also known from the Callovian of Argentina. On the other hand, the specimen referred to Vinialesaurus is the first appearance of this genus in the Southern Hemisphere. These new records give strong support to the exchange of marine vertebrates between the northern Tethys and the southern Pacific through the Caribbean Seaway during the Middle and Late Jurassic.

Skeletal remains of a small reptile with a distinctive dentition from the Lower Keuper (Erfurt Formation; Middle Triassic, Ladinian) of the Schumann quarry near Eschenau, in the municipality of Vellberg in Baden-Württemberg, Germany, represent a new taxon of non-archosaurian archosauriforms, Polymorphodon adorfi. It is diagnosed by various craniodental autapomorphies, including mesial and distal carinae of labiolingually flattened maxillary and dentary tooth crowns with large, somewhat hook-shaped denticles aligned at distinct angle to apicobasal axis of tooth crown; premaxilla with long, leaf-shaped posterodorsal process that is slightly longer than body of element; presence of prominent lateral fossa on premaxilla anteroventral to external narial fenestra; premaxilla with five gently recurved, conical teeth; medial surface of maxilla with distinct ledge above the interdental plates; and maxilla and dentary with distinctly heterodont dentition. Phylogenetic analysis recovered Polymorphodon adorfi in a position crownward of Erythrosuchus africanus but in an unresolved polytomy with derived non-archosaurian archosauriforms such as Proterochampsidae and Euparkeria capensis and with Archosauria. The maxillary and dentary teeth of Polymorphodon adorfi differ from those of other non-archosaurian archosauriforms and indicate a different, possibly omnivorous diet, suggesting that these reptiles were more diverse in terms of feeding habits than previously assumed.

Deinosuchus is a lineage of giant (≥10 m) Late Cretaceous crocodylians from North America. These were the largest semiaquatic predators in their environments and are known to have fed on large vertebrates, including contemporaneous terrestrial vertebrates such as dinosaurs. Fossils have been found in units of Campanian age from northern Mexico to Montana in the west and Mississippi to New Jersey in the east. Three species have been named, and recent consensus suggests that they represent a single, widely ranging species. The authors studied newly collected material from western Texas and increased sampling from throughout North America to review species-level systematics of Deinosuchus and help refine its phylogenetic placement among crocodylians. Deinosuchus from eastern and western North America can be consistently differentiated and represent different species. A phylogenetic study is conducted including new character states. This work reinforces the identity of the ‘terror crocodile’ as an alligatoroid. Reference to the holotypes indicates that the generic name holder, Deinosuchus hatcheri, is extremely incomplete. As a result, the three known species of Deinosuchus cannot be differentiated. To ensure nomenclatural stability, the type species for Deinosuchus should be transferred to Deinosuchus riograndensis, a species known from multiple mostly complete individuals. Additionally, Deinosuchus rugosus is based on a holotype that is not diagnostic, and a new species, Deinosuchus schwimmeri, is named to encompass some specimens formerly assigned to D. rugosus.

Crocodylian fossils are well documented from Upper Cretaceous and lower to middle Paleogene deposits in the mid-high latitudes of the Western Interior, whereas the only extant North American taxon, Alligator mississippiensis, is restricted to the lower-latitude wetlands of the southeastern United States. The departure of crocodylians from the Western Interior has been inferred to represent a major shift from more equable, warmer, wetter climates in the Paleogene to more seasonal, cooler, drier climates in the Neogene. The timing of further geographic range shifts during the Neogene, including the local extinction (extirpation) of crocodylians from the Great Plains, is poorly constrained. We document the Neogene crocodylian fossil record of the Central Great Plains (CGP) in order to constrain the timing of mid-continental crocodylian extinctions against a backdrop of climatic and environmental changes. The Neogene CGP crocodylian fossil record consists of mostly incomplete specimens, likely referable to the extant genus Alligator, and appears to document multiple latitudinal range shifts that are spatiotemporally consistent with regional climatic and environmental changes inferred from independent proxy evidence. The last appearance datum (LAD) for crocodylians in the CGP is ∼6 Ma, which suggests that climatic and environmental conditions in the region were unfavorable to crocodylians after this time. In general, Neogene crocodylian fossils throughout the Great Plains are not abundant. Barring taphonomic biases or sampling issues, this could imply low population densities, and/or that the fossil-bearing areas in this region were close to the northernmost limits of crocodylian (cf. Alligator) distributions during the Neogene.

Carcharodontosaurian allosauroids were temporally restricted to the Cretaceous, being known from all land masses with the exception of Antarctica. In addition to Veterupristisaurus from Tanzania, exceptions to this distribution have been reported recently, consisting on fragmentary materials from Upper Jurassic strata of China, Germany, and Portugal. Here, we propose a new Late Jurassic carcharodontosaurian taxon, Lusovenator santosi, gen. et sp. nov. based on the reevaluation of previously described specimens from the Lusitanian Basin, Portugal. The performed phylogenetic analysis recovered Lusovenator santosi as an early branching carcharodontosaurian allosauroid diagnosed by an exclusive combination of characters, including three autapomorphic features: (1) large recesses in neural arch of anterior dorsal vertebrae; (2) well-developed and continuous longitudinal laminae extending from the tip of the prezygapophyses to the distal end of the postzygapophyses in mid-caudal vertebrae; and (3) supraacetabular crest of ilium forming a prominent ventrolaterally projecting shelf. Lusovenator santosi is the oldest carcharodontosaurian allosauroid yet discovered from Laurasia and supports unequivocally the hypothesis of a pre-Cretaceous scenario for the radiation of the clade. The identification of this taxon highlights the high diversity of medium- to large-bodied theropods in the later part of the Late Jurassic of the Iberian Peninsula. Carcharodontosauria is not yet known in correlative levels of the North American Morrison Formation, and the existence of contacts after the late Tithonian between these landmasses could explain the distribution of this clade and other dinosaur groups present in the Iberian Jurassic and in the North American Lower Cretaceous.

Microraptorine dromaeosaurids are characterized by a lateral pubic tubercle or process on the midshaft of the pubis. Initially proposed as a tubercle for muscle attachment, this structure has since received little attention beyond identifying its presence or absence in theropods. Examination of this tubercle reveals inconsistencies in texture and topology with attachment sites for pelvic musculature. However, its unevaluated homology precludes meaningful utilization in comparative or paleobiological studies. Here, the homology, form, and function of the lateral pubic tubercle are explored in the context of the extant phylogenetic bracket. This framework, combined with dissection of extant relatives and direct observation of osteological correlates in extant and extinct archosaurs, permits assessment of various tissues that are potentially associated with the microraptorine lateral pubic tubercles. Consideration of pelvic soft tissues reveals that these tubercles are most parsimoniously interpreted as an osteological correlate for pubogastralial ligaments, which anchor the most posterior row of gastralia to the hip in extant crocodylians. Homologous structures that are correlates for pubogastralial ligaments vary widely in morphology across archosaurs. A series of alterations occurred in paravian theropods while undergoing pubic retroversion and ventilatory changes. The relationship between the lateral pubic tubercles and the pubic apron also imposed functional consequences on surrounding tissues, most notably locomotory musculature arising from the pubic apron. This elucidates why the lateral pubic tubercle is only expressed in Microraptorinae.

Recently, Repelinosaurus robustus from Laos was proposed as the basal-most member of Kannemeyeriiformes and regarded as Early Triassic in age. A new dicynodont specimen from the Sunjiagou Formation of Shanxi, China, is described and named as Taoheodon baizhijuni, gen. et sp. nov. It is characterized by autapomorphies such as a shallow fossa on a triangular region at the proximal side of the postorbital bar, a basisphenoid contribution to the basisphenoid-basioccipital tubera that slopes anterodorsally at a shallow angle, and the absence of a pterygoid keel. It is further differentiated from other dicynodontoids by the combination of characters such as a narrow median pterygoid plate, a pterygoid that does not contact the maxilla, an occipital condyle that is wide and arc-like in posterior view, and without a circular central depression or fossa, and the lateral dentary shelf that is thin but with distinct dorsal and ventral surfaces. A phylogenetic analysis recovers T. baizhijuni as sister taxon of the Laotian Counillonia superoculis plus Repelinosaurus robustus, a ‘core-Dicynodon’ clade that includes species from Africa, Russia, China, and Laos. Based on the current phylogenetic and geological evidence, the Laotian dicynodonts should be late Permian rather than Early Triassic in age. The migration route of the Laotian clade should have passed through the east margin of the South China Block.

The earliest complete glyptodonts (Glyptodontidae, Cingulata) found belong to the Propalaehoplophorinae from Santa Cruz Formation (late early Miocene, Burdigalian) in Patagonia, Argentina. Although several skulls and mandibles have been described from this formation, and assigned to five genera (Propalaehoplophorus Ameghino, Cochlops Ameghino, Asterostemma Ameghino, Eucinepeltus Ameghino, and Metopotoxus Ameghino), the fossil record and knowledge of juvenile specimens of glyptodonts are still poor. Here, we provide a detailed morphological description of a mandible of a juvenile propalaehoplophorinae glyptodont from the Santa Cruz Formation, using micro-computed tomography and scanning electron microscopy images. We compare the juvenile mandible with adult specimens and discuss the taxonomic assignment, the juvenile and adult mandibular and dental characters, and dental eruption and tooth wear.

During the last decade, field work carried out in the lower Eocene deposits of the Àger Basin (southern Pyrenean basins, northeast Spain) has allowed the publication of new early primate material, including the first identification of plesiadapiform remains in Spain (Arcius ilerdensis from Masia de l'Hereuet) and the description of two new species of adapiforms: Agerinia smithorum from Casa Retjo-1 and Agerinia marandati from Masia de l'Hereuet. However, the fossil material recovered is still scarce and fragmentary. For this reason, during the last few years prospecting has been carried out in order to find new localities with primate remains. This paper describes the results of these campaigns, reporting four new lower Eocene primate localities, in which some previously unknown elements have been recovered. More specifically, the locality of Cabana del Llúcio-1 has yielded the first I1, I2, and P1 for the genus Agerinia and the first M1 of the species A. smithorum. Moreover, a fragment of calcaneus from this site provides further information about the morphology of this bone in A. smithorum. The material from Cabana del Llúcio-1 displays some intermediate traits between A. smithorum from Casa Retjo-1 and A. marandati from Masia de l'Hereuet. These transitional features are consistent with the stratigraphic position of Cabana del Llúcio and support the previously proposed anagenetic lineage Agerinia smithorum–A. marandati–A. roselli.

The later part of the Oligocene (Arikareean North American Land Mammal Age) was a time of major faunal change in North America. It is during this time period that archaic mammalian faunas dominated by extinct families started giving way to more modern faunas, including families still extant today. Studies of this faunal transition have so far focused on the Great Plains and the Columbia Plateau. I present here the first quantitative analysis for the northern Rocky Mountains, combining four new radioisotopic dates and almost 1,000 specimens from a series of vertebrate microfossil assemblages through the Cabbage Patch beds of Montana. I demonstrate that the rise of modern mammalian communities was already under way in the Rocky Mountains 30 million years ago, at the base of the beds. However, the major faunal turnover event took place ca. 28 million years ago, at the transition from the lower to the middle units of the Cabbage Patch beds, and led to the disappearance of many archaic mammal taxa that dominated the start of the Arikareean. This event was synchronous across the Great Plains, the Rocky Mountains, and the Columbia Plateau and was driven by the diversification of descendants of immigrants from Eurasia that had reached North America through Beringia. Holdovers from archaic mammalian faunas persist into the upper unit of the beds later than in the Great Plains, but not the Columbia Plateau. Future biogeographic analyses will be necessary to assess the role of topography and environmental change in the rise of modern mammalian communities.

Two well-preserved delphinid crania have been recovered from the Haraichi Formation, Annaka Group, Gunma Prefecture, Japan (earliest late Miocene, Tortonian; 11.29–11.25 Ma). The specimens represent a new genus and species of delphinid, Norisdelphis annakaensis. The new species is characterized by transversely narrow and anteroposteriorly elongated external bony nares, and a wider proximal extremity of the left premaxilla. Phylogenetic analysis suggests that Norisdelphis is the most basal member of the Delphinidae. The previous oldest known described delphinid, Eodelphinus kabatensis, is from the upper Miocene (ca. 9 Ma), and other reliably dated and described fossil delphinids are no older than Pliocene; thus, N. annakaensis is the oldest convincingly dated and well-diagnosed fossil delphinid species yet described. Norisdelphis annakaensis expands the geological range of the family Delphinidae.

Over the past decade, we recorded exact locations of in situ fossils and measured calcareous nodules in paleosols of the Oligocene and lower Miocene (Whitneyan–Arikareean) John Day Formation of Oregon. These data enable precise biostratigraphy within an astronomical time scale of Milankovitch obliquity cycles and also provide mean annual precipitation and vegetation for each species. Fossils in paleosols of the John Day Formation alternated between semiarid shrubland and subhumid woodland communities every 41 ka. Land snails ‘Polygyra’ expansa and Monadenia dubiosa were found in semiarid paleosols, but Vespericola dalli and Monadenia marginicola were found in subhumid paleosols. Cicada burrows (Naktodemasis bowni) were found in semiarid paleosols, whereas dung beetle balls (Pallichnus dakotensis) and earthworm castings (Edaphichnium lumbricatum) were found in subhumid paleosols. Among hypertragulids, Hypertragulus hesperius was found in semiarid paleosols and Nanotragulus planiceps in subhumid paleosols. Among glires, the aplodontiid Haplomys liolophus, geomyids Pleurolicus sulcifrons and several species of Entoptychus, castorid Palaeocastor peninsulatus, and leporid Archaeolagus ennisianus were found in semiarid paleosols. Large ungulates were found primarily in subhumid paleosols, including the agriochoere Agriochoerus antiquus, oreodonts Eporeodon occidentalis and Promerycochoerus superbus, equid Miohippus annectens, and rhinos Diceratherium annectens and Diceratherium armatum. The inferred niches of fossil mammals are consistent with interpretations based on their morphology; taxa with adaptations for life in open, arid habitats, such as high-crowned teeth and semifossorial or cursorial limb structure, were mainly in semiarid paleosols, but taxa with arboreal adaptations were only found in subhumid paleosols.