Stegosaurs are a major clade of ornithischian dinosaurs, yet because of their fragmentary fossil record, their interrelationships and early evolution are poorly understood. Here, we describe a new stegosaur, Bashanosaurus primitivus, gen. et sp. nov., and some other indeterminate stegosaur materials. We provide new U-Pb detrital zircon ages for horizons bounding the holotypic quarry in the Lower Member of the Shaximiao Formation, Yunyang, Chongqing Municipality, China, which indicate a Middle Jurassic (Bajocian) age. Bashanosaurus represents the earliest record of stegosaurs in Asia and one of the earliest records of this clade in the world. The dorsal vertebrae, scapula, coracoid, femur, and plates of Bashanosaurus primitivus possess several unique characters among Stegosauria, including the elevation of the parapophyses of dorsal vertebrae on stalks at the base of the transverse processes, a flared distal end of the scapula, and a small acromial process. Among armored dinosaurs (thyreophorans), these features are reminiscent of the basally branching taxon Scelidosaurus, indicating that Bashanosaurus possesses a unique mosaic of plesiomorphic thyreophoran and derived stegosaur features. Phylogenetic analysis shows that Bashanosaurus primitivus is the earliest-diverging stegosaur, along with Chungkingosaurus, from the Upper Member of the Shaximiao Formation, consistent with the early age of the taxon.

We describe a new species of the albanerpetontid amphibian Albanerpeton from three localities in the Lower Cretaceous Cloverly Formation of Wyoming, U.S.A. Radiometric dates between ∼111–112 Ma indicate it is slightly younger than A. arthridion from the Antlers Formation. The new species is diagnosed on a pair of fused frontals that possess a unique combination of characters, mixing plesiomorphic features of the internasal process with a more derived overall shape and proportions. Referred material includes premaxillae, maxillae, dentaries, atlantes, ‘axes,’ trunk vertebrae, humeri, and an ilium.

Phylogenetic analyses place the new species near the base of Albanerpeton sensu lato but without fully resolving its position. The inclusion of Shirerpeton and Wesserpeton within this clade opens up the possibility that these genera might be incorporated into Albanerpeton, or that a number of species formerly assigned to Albanerpeton might receive new generic assignments. By including several informal species in our analysis, it becomes clear that character distributions are more homoplastic and that past genus typologies are probably less secure. We assign the new species to Albanerpeton conservatively, pending further phylogenetic study.

The Cloverly Albanerpeton is found in unambiguously aquatic deposits, suggesting that the animal lived near these settings for at least part of its life. This is a common habitat for Mesozoic albanerpetontids, unlike the karst-dominated, often drier, deposits in which Cenozoic species are typically found. Despite the recent discovery of a probable arboreal species, it is likely that albanerpetontids inhabited a range of habitats throughout their evolutionary history.

Small to medium-sized mustelids from the last 18 million years represent a heterogeneous group of carnivorans with a wide-ranging record in the northern hemisphere. They were first referred to the genera Mustela and Martes, but lately ascribed to the latter, and hence considered as the longest-lived genus within Mustelidae. However, a great many of these forms have been based upon fragmentary material and Martes has conformed progressively to a wastebasket nomen for species of uncertain relationships. Here, we describe dentognathic material of a small-sized mustelid from three middle Miocene (MN7 + 8, latest Aragonian) localities of the Iberian Peninsula that constitutes a new genus and species. Aragonictis araid, gen. et sp. nov. represents a distinct taxon if compared with early/middle Miocene forms ascribed to “Martes” spp., especially the similar-sized early Miocene Circamustela? laevidens and the middle Miocene “Martes” caedoti and “Martes” delphinensis. The finding of particular features in A. araid (low p2–3, loss or reduction of the p4 accessory cuspid with its main cuspid centrally located, presence of a sharp, beveled and lingually open m1 talonid, and reduction of M1 lingual platform) indicates affinities with the late Miocene Circamustela in the range of hypercarnivory. Our reassessment of “Martes” indicates possible evidence of cladogenesis for Miocene mustelidae with, at least, two different events being recognized in Europe—the latter during MN7 + 8 to MN9 with presence of Aragonictis and Circamustela. The finding of A. araid further confirms the presence of more densely forested environments than expected in inner Iberia during the latest middle Miocene.

The Quaternary Period is characterized by dramatic global climatic changes. Quaternary fossil deposits, which can offer excellent stratigraphic resolution, provide a unique opportunity to understand how fauna respond to past environmental change. Here, we test if the herpetofauna of McEachern's Deathtrap Cave, a late Pleistocene to Holocene pitfall trap deposit from Victoria, Australia, shows climate-related shifts in taxonomic relative abundance through time. During the last 14,000 years, southeastern Australia experienced pronounced periods of aridity, while temperatures remained relatively stable. We show that the stratigraphic layers of this deposit are characterized by different relative abundances of reptile subfamilies, and that changes in subfamily abundance between layers correlate with known shifts to aridity, based on the percentage of C4 grasses present in the region. We further identify 13 lizard morphotypes from the fossil deposit and compare this diversity with the present-day lizard fauna. Our analyses indicate that gradual changes in community structure, which are typically observed in southeastern Australian vertebrate communities during the Pleistocene–Holocene transition, can partly be explained by changing aridity. These findings represent an important contribution to understanding Quaternary community change in Australia, particularly because evidence of faunal succession of reptile and amphibian communities in Victoria is lacking. Our results further demonstrate the utility of the Australian herpetofaunal fossil record for detecting community responses to past climate change on relatively shallow timescales and at higher levels of taxonomic identification.

Eudromaeosauria is a clade of derived dromaeosaurids that typifies the common perception of ‘raptor’ dinosaurs. The evolutionary history of this clade has been controversial due to conflicting views of taxonomic identity, and because, due to taphonomic bias, several species were diagnosed primarily or solely by the maxilla. The maxilla is therefore crucial in understanding the phylogenetic relationships within the clade. Morphometric characterization has been commonly applied to recognize and distinguish major dromaeosaurid clades. However, morphometrics mainly showed morphological convergence rather than phylogenetic relationships. This approach has made it difficult to get resolution of phylogenetic relationships among eudromaeosaurian taxa, often resulting in large polytomies or inconsistent placement of key species. To test previous character statements, computed tomography was used to analyze the maxillae of Acheroraptor, Atrociraptor, and Deinonychus, and compare them with other eudromaeosaurians from Asia and North America. Morphometric characters were examined, and regressions were used to look for allometric trends in maxillary dimensions and the relationship to topological landmarks within Eudromaeosauria and its outgroups. Characters were improved and implemented to better capture eudromaeosaurian morphological variation and better resolve their phylogenetic relationships. Phylogenetic analysis recovered three well-defined clades within Eudromaeosauria and corroborated occurrence data within the fossil record. Acheroraptor and Atrociraptor were recovered as derived members of Saurornitholestinae. Deinonychus is recovered as a basal eudromaeosaurian, sharing features with dromaeosaurines and saurornitholestines. These results challenge previous biogeographic hypotheses suggesting Asian and North American faunal interchange during the Late Cretaceous and support convergence of traits relating to snout dimensions and proportions.

Archosauromorpha originated in the middle–late Permian and started to diversify in both non-marine and marine ecosystems dominating the world by the Triassic. The evolution of this group is poorly documented because the fossil record is limited. A detailed osteological description of Shringasaurus indicus, a non-archosaurian archosauromorph, from the Middle Triassic Satpura Basin, Central India, is provided here. The collection includes cranial bones, namely the nasal, frontals with and without horns, postfrontal, parietal, maxilla, premaxilla, quadrate, vomer, dentary, and braincase. The collection also comprises postcranial bones such as cervical, dorsal, sacral and caudal vertebrae, and girdle and limb bones. The phylogenetic study incorporates the character states from cranial as well as postcranial elements of Shringasaurus indicus. Furthermore, Malerisaurus robinsonae, another non-archosaurian archosauromorph from India, has been included in the phylogenetic analysis. The analysis reveals that both Shringasaurus indicus and Malerisaurus robinsonae are azendohsaurid allokotosaurs and Shringasaurus indicus is the sister taxon to both the species of Azendohsaurus. The detailed description of Shringasaurus indicus elucidates that the animal had a pair of supraorbital horns, was a large herbivore, and has an incongruous mixture of basal archosauromorph and dinosaurian-like character-states. Hence, the present study helps to fill the gap, to a large extent, in understanding the nature of the morphological diversity of basal archosauromorphs after the Permian–Triassic mass extinction.

Despite an abundance of ornithomimid fossils from the Late Cretaceous of Alberta, Canada, only isolated elements are known from the upper Maastrichtian Scollard Formation. Ornithomimus velox and Struthiomimus sedens are the two taxa recognized from penecontemporaneous formations in the U.S.A., but the incomplete nature of these specimens and the lack of contemporary material from Alberta creates a gap in our understanding of ornithomimid diversity during the late Maastrichtian of North America. Here, I describe the first diagnostic ornithomimid fossils from the upper Maastrichtian Scollard Formation of central Alberta, Canada, providing new information about the taxonomic composition of North American ornithomimids during the late Maastrichtian. The first fossil, an articulated forelimb, exhibits metacarpal ratios and features of the manual unguals that support its referral to the genus Ornithomimus. The second fossil, an associated hind limb, belongs to a large-bodied ornithomimid, and based on characteristics of the pedal unguals is assigned to the genus Struthiomimus. Based on these taxonomic designations, the stratigraphic ranges of both Ornithomimus and Struthiomimus are extended from the upper Campanian Dinosaur Park Formation through to the upper Maastrichtian Scollard Formation of Alberta, which constitutes more than 10 million years of time. These specimens offer new knowledge on the taxonomic composition of ornithomimids in Alberta, but the unusually long stratigraphic range coupled with the difficulty in diagnosing either specimen to species underscores the need for review of North American ornithomimid taxonomy.

A review of the type material of the crocodylomorph ichnotaxon Crocodylopodus meijidei Fuentes Vidarte and Meijide Calvo, 2001 from the Berriasian of Spain is carried out. The review allows a better characterization of this type ichnotaxon and provides interesting new data on the candidate trackmakers and especially on their locomotion. Three different size classes possibly related to different ontogenetic states or sexual dimorphism of the same small- to medium-sized crocodylomorph trackmaker are distinguished. Morphological differences within the sample such as digital impression lengths might be a consequence of differences in allometric growth, assuming similarities with extant crocodylians. Other differences are a consequence of variation in the morphological quality and mode of preservation across the sample. Some trackway features (intermediate-gauge trackways with high pace angulation, absence of tail, belly or drag marks) indicate the trackmakers, presumed neosuchian crocodylomorphs, were walking in a ‘high-walk’ mode with a semi-erect posture at a moderate speed. The trackmaker may have walked with more erect limb posture and with the center of mass located more anteriorly than occurs in extant species, albeit not as erect as quadrupedal animals such as mammals or other extinct archosaurs including trackmakers of other crocodylomorph ichnotaxa (e.g., Batrachopus).

A specimen of Toxodontidae from the upper Pliocene–lower Pleistocene of Uruguay is studied in this paper. The material consists of associated skull and mandibular fragments previously identified as Dinotoxodon paranensis. The full description of the specimen, its comparison with different notoungulates, and a phylogenetic analysis are performed. According to the obtained results, Charruatoxodon uruguayensis, gen. et sp. nov. is recognized as a new taxon with unique features such as nasals compressed laterally, somewhat convex in transversal and longitudinal planes, incisive foramina deep and rounded, and other characteristics shared with several taxa of Toxodontidae. The mandibular expansion, present in the studied material, formerly used as a diagnostic character of D. paranensis (also present in Gyrinodon quassus, Pericotoxodon platignathus, and Hoffstetterius imperator), does not constitute a synapomorphy for these taxa as it appears to have evolved independently in different lineages according to our phylogeny. The new taxon is a medium-sized toxodontid more closely related phylogenetically to Toxodon platensis and D. paranensis than to other toxodontids. The family Toxodontidae constitutes a natural group. The clades within this group do not correspond to the subfamilies classically considered within the family, agreeing with later results. The new late Pliocene–early Pleistocene taxon from the Raigón Formation adds to the endemic fauna from Uruguay.

Anurognathids are a clade of non-pterodactyloid pterosaurs with generally conservative morphology, but specializations as insectivores. They are represented by a disparate collection of adult and juvenile specimens that range in wingspan from ∼0.24–1 m. There have been concerns about the extent to which ontogenetic variation might affect phylogenetic inference, and indeed how aspects of their ontogeny might relate to the distinctive anurognathid adult morphology. Here we perform allometric analysis on 23 key skeletal dimensions in 13 anurognathid specimens. Our results show that all anurognathids share a common growth trajectory in most dimensions, and that ontogeny affects variation in a minority of characters commonly used in phylogenetic analysis. Excluding these ontogeny-related characters, a new taxon, Cascocauda rong gen. et sp. nov., is established. Based on the ontogenetically corrected dataset, our phylogenetic analysis supports Anurognathidae as the sister-group of Breviquartossa and reveals a general trend of tail reduction in the clade. Allometric growth suggests the anurognathid lifestyle remained consistent throughout ontogeny, maintaining a highly maneuverable flight style by near-isometric development in the wing, small prey (i.e., insects), by strong negative allometry in the skull, and an arboreal habit by strong positive allometry in the claws. This specialized lifestyle suggests retention of plesiomorphic juvenile traits into later ontogeny and facilitated morphological stasis by stabilizing selection during over 40 million years of evolution in the group.

We describe two partial skulls of juvenile individuals of Moradisaurus grandis, a moradisaurine captorhinid from the upper Permian Moradi Formation of northern Niger. The juvenile skulls are less than half the length of the largest known skull of M. grandis, and differ in featuring a transversely narrow mandible, only five rows of maxillary teeth, a relatively larger orbit, a relatively taller skull, a cultriform process of the parasphenoid angled upwards at 20–30° from the basal plate, and reduced ossification of the braincase. Most of these features have been considered characteristic of the less derived members of the family (e.g., Protocaptorhinus pricei, Captorhinus laticeps). Data from juvenile Moradisaurus allow us to amend a previous inference that the braincase of the holotype and largest known skull of the moradisaurine Labidosaurikos meachami is characterized by poor ossification: we infer instead that this skull is not skeletally mature and that the braincase would have fully ossified in larger, ontogenetically older individuals of this moradisaurine. An updated cladistic analysis of captorhinids yields Moradisaurus as the sister taxon to Gansurhinus + Rothianiscus, replicating the results of several previous analyses, but improving slightly the robustness of Moradisaurinae and the clade of Labidosaurus + Moradisaurinae with respect to previous work.

A previously unknown evolutionary stage of true lemmings, Lemmini, is recorded in the lower upper Pliocene (early Villanyian, MN16a) of West Siberia. Tobienia fejfari, sp. nov. represents a more advanced evolutionary stage than the previously known European Tobienia kretzoii (late Ruscinian, MN15b), combining rhizodont molar teeth with extreme hypsodonty, crown cement, and occlusal morphology resembling the earliest lemming with rootless molars, Plioctomys, of later Late Pliocene age (MN16b). The new discovery contributes to our knowledge of early stages in the formation of the high latitude mammalian fauna of Eurasia.

A new alvarezsaurid theropod, Dzharaonyx eski, gen. et sp. nov., is documented by a variety of dissociated but well-preserved postcranial bones from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan. It has opisthocoelous posterior dorsal vertebrae lacking infrapostzygapophyseal fossae. The posterior caudal vertebrae are procoelous and have a longitudinal canal within the neural arch. The humerus is intermediate in structure between those of the Argentinian alvarezsaurid Patagonykus and the Mongolian parvicursorine Mononykus in having a small internal tuberosity, similar-sized radial and ulnar condyles, a distally protruding radial condyle, and a greatly reduced entepicondyle. The ulna has a hypertrophied olecranon process, a globular carpal trochlea, and a facet for the aponeurosis tubercle of the radius. On the carpometacarpus, the articular surface of metacarpal III is in line with the distal articular joint of metacarpal II. On manual phalanx II-1, the flexor ridges are similarly developed and the dorsolateral process and the ‘hook-like’ ventrolateral process are absent. The collateral grooves on manual ungual phalanx II-2 are either partially open or completely enclosed to form ventral foramina. The pubis bears a preacetabular tubercle. The pes is arctometatarsalian. Metatarsal II forms a posterolateral flange. Pedal phalanx IV-1 has a protruding proximomedial process, a proximoventral notch, and asymmetrical distal condyles. The flexor tubercles on the pedal ungual phalanges are small. Phylogenetic analysis found Dzharaonyx within Parvicursorinae in a polytomy with other Asiatic taxa. Dzharaonyx is the most plesiomorphic and geologically oldest member of Parvicursorinae known to date.

The thickened frontoparietal in pachycephalosaurid dinosaurs expands dramatically during ontogeny from a flat-headed to a domed state. This expansion results in the formation of zonal tissue characterized largely by differences in vascularity and bony tissue structure that changes through ontogeny. Void space identified in CT scans of the frontoparietal is a suitable proxy for relative vascularity. An increase in relative vascularity occurs with the development of the dome in the pachycephalosaur Stegoceras validum, followed by a significant decrease in late stage ontogeny. We employ a script adapted from an algorithm for human cortical bone imaging to: (1) determine the percent vascularity in any given CT slice; (2) quantify these observed changes in relative vascularity within a complete frontoparietal; and (3) identify ontogenetic changes in vascularity from a cranial growth series of Stegoceras. Morphological landmarks identified in the CT scans facilitate an accurate slice-by-slice comparison of homologous regions of the dome between skulls. This new tool enables: (1) a complete assessment of bone vascularity from CT scans; (2) is applicable to any fossil or modern bone in the vertebrate skeleton; and (3) provides an alternative measure to pixel-by-pixel manual thresholding, a time intensive and subjective process.

Ferrodraco lentoni, an anhanguerid from the Upper Cretaceous Winton Formation of northeast Australia, is the most complete Australian pterosaur described to date, represented by a partial cranium, incomplete cervical series and wing elements. Herein we present a comprehensive osteological description of Ferrodraco, as well as an emended diagnosis for this taxon. In addition, we compare Ferrodraco with other isolated pterosaur remains from Australian Cretaceous deposits. Subtle, yet salient, differences indicate that at least three of these specimens, all derived from the upper Albian Toolebuc Formation, are distinct from Ferrodraco. However, we are uncertain whether these specimens are attributable to Mythunga camara, Aussiedraco molnari, Thapunngaka shawi, or an as yet un-named taxon. Detailed description of the postcranial material of Ferrodraco also provides an opportunity to reassess its phylogenetic position. In one analysis, Ferrodraco and Mythunga are resolved as sister taxa within Tropeognathinae, whereas in another, Ferrodraco, Mythunga, and Tropeognathus form a polytomy within Coloborhynchinae. Either way, these slight differences notwithstanding, a close relationship between Ferrodraco and Mythunga is evident, supporting the interpretation that they form a clade. By contrast, Aussiedraco molnari is resolved as a member of Targaryendraconia, a clade with a cosmopolitan distribution. The presence of several anhanguerian taxa or lineages in the late Early and early Late Cretaceous of northeast Australia is suggestive of even greater diversity in the Australian pterosaur fauna.