Estimating body mass and locomotor habits of fossil rodents is challenging for taxa without available postcranial material. Although equations exist to estimate body mass from dental dimensions based on extant rodents, the applicability of such equations is doubtful given that modern rodents have evolved highly specialized teeth, whereas fossil taxa often exhibit a much less derived condition. For the present study, 11 cranial variables from a sample of 203 extant rodents of known body mass representing a range of taxonomic groups were assessed using reduced major axis (RMA) regression. The results show a strong correlation between body mass and each of the 11 cranial variables. The best estimators for body mass are skull length and cheek-tooth area, whereas the least reliable measures are palate length, and foramen magnum, as well as braincase and occipital condyle dimensions. We estimated body mass for specimens of five fossil Ischyromyidae rodents for which body mass had never been estimated (Paramys copei, P. delicatus, Reithroparamys delicatissimus, Rapamys atramontis, and Ischyromys typus). Principal components and canonical variates analyses based on 10 cranial dimensions for 103 members of Sciuromorpha demonstrate that a relationship exists between locomotor habits and cranial variables in this suborder. In these analyses, early ischyromyids are all placed in the terrestrial group with Aplodontia, Marmota, Cynomys, and Spermophilus. This contradicts previous hypotheses regarding early rodent locomotion, which suggested that they were arboreal or more generalized in their habits.

During the last decade, abundant ichthyopterygian material has been found from the Triassic of South China as well as the Upper Jurassic and Lower Cretaceous of Europe and South America, significantly expanding our knowledge of ichthyopterygian diversity through the Mesozoic. Previous phylogenetic hypotheses of the group no longer account for these extensive additions, necessitating a new phylogenetic framework for the entire Ichthyopterygia to enable evolutionary studies of the group. We present here a comprehensive phylogenetic hypothesis for Ichthyopterygia based on cladistic analysis of 163 characters coded for 59 ingroup and five outgroup taxa. The monophyly of Ichthyopterygia is strongly supported by a Bremer index value of 7. Five major groups of Ichthyopterygia during the Triassic, viz., Grippioidea, Cymbospondylidae, Mixosauridae, Shastasauridae, and Toretocnemidae, are well supported by Bremer index values between 3 and 5. Major clades that evolved in the Triassic, including Merriamosauria, Euichthyosauria, and Parvipelvia, are also robustly supported, whereas most post-Triassic clades are very weakly supported with a Bremer index value of 1, with a few exceptions, such as Thunnosauria and Ophthalmosauridae. The traditional Shastasauridae is expanded to comprise six genera but excludes Callawayia, which is more closely related to Parvipelvia than to Shastasauridae. ‘C.’ wolonggangensis is a shastasaurid but does not form a monophyletic clade with Callawayia neoscapularis or Guizhouichthyosaurus tangae as previously asserted. The new phylogenetic hypothesis is generally consistent with the stratigraphic occurrences of each taxon especially for the Triassic taxa.

Yinlong downsi, from the Upper Jurassic Shishugou Formation, Xinjiang, northwestern China, is the oldest known ceratopsian dinosaur. Here we provide a detailed description of the skull and mandible based on the holotype, three partial skulls, and disarticulated materials from several other specimens. Yinlong can be diagnosed by six autapomorphies: a distinct fossa along the midline of the frontals; a slit-like carotid canal bordered by laminae; premaxillary teeth with a vertical wear facet and a basal shelf; a deep sulcus on the ventral surface of the quadratojugal; large oval nodules concentrated on the lateral surface of the jugal; and a squamosal with an expanded dorsal surface and a long, constricted quadrate process. A detailed comparison with other basal ceratopsians suggests that Yinlong downsi may belong within Chaoyangsauridae. Yinlong also shares many derived characters both with Psittacosaurus and neoceratopsians, suggesting that character evolution in early ceratopsians is complex. Additionally, a caniniform premaxillary tooth is present in one small specimen (IVPP V18636), which may suggest sexual dimorphism or individual variation.

The Eocene was a time of high ophidian diversity across much of the world, dominated by booid-grade snakes. A series of extinction events during and at the end of the Eocene resulted in a depauperate fauna of mainly small snakes in Europe and North America, and the disappearance of several lineages. Due to a poor Eocene fossil record, it is not yet known whether similar extinction events occurred in Afro-Arabia, but later fossils suggest that African snake faunas evolved differently from those in Europe. Here we report the first well-known Eocene snake fauna from Africa, derived from the Priabonian-aged locality BQ-2 in the Fayum region of northern Egypt. The fauna is diverse, consisting of seven species, including the previously known madtsoiid Gigantophis garstini and the palaeophiid Pterosphenus schweinfurthi. Additional species include two booids, a tropidophiid, a probable russellophiid, and a new colubroid, Renenutet enmerwer, gen. et sp. nov. The fauna in many respects presents a typical Eocene character, dominated by booid species and Pterosphenus, and including a madtsoiid. However, it is atypical in the relative importance of the colubroid R. enmerwer, consisting of ∼15% of the total number of specimens. Also unexpected is the tropidophiid, today restricted to the neotropics; however, it provides a possible connection between the extant range and European fossils referred to Tropidophiidae. The description of this fauna provides initial context for further study of the evolution of snakes in Africa, particularly with respect to changes through the Eocene and beginning of the Oligocene.

A new species of Sparassodonta (Mammalia, Metatheria), Lycopsis padillai, sp. nov., is described on the basis of a partial left maxilla with M1–M4 and fragments of lacrimal and jugal. The material comes from the early to early middle Miocene Castilletes Formation, La Guajira Peninsula, Colombia. This specimen represents the northernmost record of a fossil metatherian in South America and integrates a highly diverse vertebrate association, recently discovered in the north of Colombia. The La Guajira specimen is referred to the genus Lycopsis, as supported by the results of our phylogenetic analysis. This analysis also demonstrates that species of Lycopsis (L. torresi, L. longirostrus, L. viverensis, and L. padillai) constitute a monophyletic group and are placed as the basal taxon of Borhyaenoidea. Lycopsis padillai is a large-sized sparassodont with a body mass of about 22 kg. The presence of Lycopsis from La Guajira extends the geographical distribution of the genus to the entire South America, representing the sparassodont with the widest latitudinal distribution.

The ilium has been considered a ‘key’ element in anuran paleontology, but its terminology is inconsistent across the literature. Therefore, we here review the terminology used so far to describe anuran ilia and provide an annotated glossary of main ilial features. We also survey ilial morphology and comment on variation exhibited by each ilial feature among major anuran lineages. We do so with special consideration for myological correlates, provide muscle maps for a few species, and aim to clarify hypotheses of primary homology. We consider previous work that compartmentalizes part of the described variation into cladistic characters, with the intention of providing a starting point for using ilial features in future research on osteology-based phylogenetics of anurans. Finally, we remark on some aspects regarding the dorsal prominenceprotuberance complex.

A new genus, Taraschelon, is proposed here for the largest tortoise known in the European Paleogene record. Its type and only known species, ‘Testudo’ gigas, was described in the first half of the 19th century. It comes from the French locality of Bournoncle-Saint-Pierre, in Auvergne (Haute-Loire). Extremely limited and partially incorrect information about this species has hitherto been available. Detailed study confirms the validity of this species and for the first time allows for a diagnosis. Taraschelon is the first genus of tortoise identified in the European Oligocene record, and one of the few genera known from the Paleogene of this continent. Comparison of Taraschelon with other primitive European forms shows an important diversity of Testudinidae in the Paleogene of this continent.

Cryptodont dicynodonts are some of the most abundant therapsid taxa in the upper Permian fossil record. Despite extensive taxonomic study of these families, the species diversity of geikiid cryptodonts remains problematic, particularly for the set of edentulous taxa in the genera Pelanomodon, Propelanomodon, and Geikia. Here, all known specimens of tuskless geikiid dicynodonts from the upper Permian Karoo Basin of South Africa are reevaluated. The genus Pelanomodon is redescribed based on a series of skulls representing a range of sizes. All tuskless geikiids from the Karoo Basin are considered to represent a single species (Pelanomodon moschops) that exhibited cranial dimorphism as adults. The nominal species Pe. moschops and Pe. rubidgei differ only in degree of facial boss development and are most parsimoniously interpreted as sexual dimorphs. Propelanomodon is considered to represent the juvenile morphotype of Pelanomodon moschops, as indicated by the geographic and stratigraphic overlap of the two taxa, the lack of any small skulls of the Pelanomodon morphotype in well-sampled localities, and the presence of specimens of intermediate size and morphology. ‘Propelanomodon’ specimens are distinctive among juvenile dicynodonts in having a significantly narrower intertemporal region than adults. Analysis of intertemporal width relative to total skull size in Pelanomodon and the abundant cryptodont taxa Aulacephalodon, Oudenodon, and Tropidostoma suggests that Pelanomodon had a unique growth trajectory. Based on available stratigraphic data, Pelanomodon was restricted to the uppermost Permian Daptocephalus Assemblage Zone of the South African Beaufort Group and was a victim of the end-Permian mass extinction.

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The braincase anatomy of pterosaurs is poorly known because this region of the skull is rarely preserved, particularly in basal pterodactyloid pterosaurs (Archaeopterodactyloidea). We present new information on the braincase morphology of the Early Cretaceous Argentinean ctenochasmatid Pterodaustro guinazui. Morphological information collected from several specimens permits the description of many features of this area of the skull for the first time. The braincase of Pterodaustro is characterized by a skull roof with subtriangular, elongated frontals and rounded, posteroventrally oriented parietals; low nuchal crest; ossified ethmoidal elements; ossified interorbital septum; short and fan-shaped paroccipital processes with undulating lateral and medial surfaces; occipital condyle formed mainly by the exoccipitals; forkshaped basioccipital; long, anteroventrally directed basisphenoid body with keeled ventral surface and short basipterygoid processes; well-developed rostral tympanic recess; rod-like columella; and separate foramina for cranial nerves XII and IX-XI within a common subdivided recess. We were able to identify foramina for cranial nerves II, V, VI, and VII; vascular foramina, such as the caudal middle cerebral vein, the dorsal head vein, and the internal carotid artery; and the columellar recess. This research reveals many features of the braincase of Pterodaustro—some of which are considered potential autapomorphies—for the first time. It also provides new insights into the neurocranial anatomy of pterosaurs, and in turn, contributes to the understanding of the evolution of the braincase in Pterosauria.

A nearly complete skeleton of Polycotylus latipinnis (SDSM 23020) from the upper Niobrara Formation (early Campanian) of South Dakota (U.S.A) greatly improves information for this formerly poorly known taxon. Specimens SDSM 23020 and YPM 1125 (paratype P. latipinnis) exhibit numerous postcranial characters that distinguish Polycotylus, in particular presacral vertebral count, nature of chevron facets, unique ilia, and highly derived paddles including five epipodial ossifications and increased hyperphalangy. Greater vertebral and phalangeal counts of Polycotylus are accompanied by exceptional foreshortening; thus, the relative body and limb proportions are likely similar to less derived polycotylids, with fewer, more elongate vertebrae and phalanges. The complete skull, derived among polycotylids, has short temporal fenestrae, elongate frontals, exceptionally slender parasphenoid with prominent cultriform process, and exceptionally long extensions of the angulars and splenials within the mandibular symphysis. Cladistic analysis indicates that Polycotylus nests firmly within derived Polycotylidae as a potential sister taxon to Dolichorhynchops osborni and Trinacromerum, despite a ‘primitive’ presacral vertebral count. Future improvements in available data, in particular better information regarding basal polycotylids, and refinement of character selection to nullify homoplasy could significantly alter the tree structure to show distinct subgroups within Polycotylidae. North American polycotylids with elongate temporal fenestrae, elongate podials, and relatively long vertebrae are confined to occurrences of late Cenomanian and earliest Turonian age, whereas polycotylids distinctly foreshortened in these respects are restricted to post-Turonian occurrences. Ilium morphology is highly variable among polycotylids and, in addition to taxonomic utility, may be in part attributable to sexual dimorphism.

A new species of the genus Armigatus is described from the Cenomanian/early Turonian Akrabou Formation of Morocco. Similar to other ellimmichthyiforms, Armigatus oligodentatus, sp. nov., has parietals in contact with each other along the midline, has a beryciform foramen in the anterior ceratohyal, and lacks the recessus lateralis. The new species is placed in the genus Armigatus based on the incomplete predorsal series of heart-shaped scutes with rounded and smooth posterior border. However, this new species differs from the other known members of the genus in the lack of teeth on the parasphenoid and endopterygoid bones. This is the first report of a species of Armigatus from southeastern Morocco; previously, the genus was known only from the Late Cretaceous deposits of the eastern part of the Tethys. Therefore, Armigatus oligodentatus sp. nov. extends the distribution of the genus across the Tethys Sea and provides valuable information about the evolutionary history and paleoecology of the Ellimmichthyiformes.

Seggeurius is the basal-most hyracoid known to date, and one of the earliest known fossil afrotherians. This taxon has a dramatic importance in mammalian phylogeny, but until now it was known from dental remains only. Here we describe previously unpublished material of Seggeurius, including some mandibular and maxillary fragments, and a braincase. This study is the first to thoroughly describe and discuss the morphology of the ear region and osseous inner ear of a Paleogene hyracoid. It allows a reappraisal of some important characters that are often used in cladistic analyses of Paenungulata. In particular, it seems that in stem hyracoids the orbit is located caudally, the eustachian sac is absent or reduced, the course of the internal carotid artery is intrabullar and medial, and a deep epitympanic sinus, a basisphenoid contribution to the bulla, and the stapedial artery are present. The cochlear canal is rather flattened, and the secondary common crus was rapidly lost. A cladistic analysis of stem placental mammals highlights three derived traits shared by Seggeurius and stem sirenians (the tuber-shaped postglenoid process, the squared and massive mastoid apophysis of the petrosal, and the presence of a swelling on the septum metacochleare) and supports molecular analysis that hypothesizes a Hyracoidea-Sirenia sister-group relationship. This study demonstrates how useful the petrosal and labyrinthine characters of fossils can be for mammalian phylogenetic inference.

Dromaeosaurids were rare components of most Late Cretaceous terrestrial ecosystems and are poorly known from high palaeolatitudes. New dromaeosaurid material, including a frontal and associated postcranial elements, is described from a dense monodominant ceratopsid bonebed on Pipestone Creek, near the city of Grande Prairie (Unit 3, Wapiti Formation, upper Campanian), central-western Alberta, Canada. This stratigraphic interval is significant because it records a period of terrestrial deposition at a time when much of the western interior of Canada and the United States was inundated by the Bearpaw Sea. A phylogenetic analysis recovers Boreonykus certekorum, gen. et sp. nov., as a derived eudromaeosaur, possibly within Velociraptorinae. The identification of a new dromaeosaurid from the Wapiti Formation simultaneously helps fill an important gap in the record of late Campanian dromaeosaurids, bolsters support for a partly endemic fauna within the Wapiti Formation, and potentially adds to the North American record of a predominantly Asian Velociraptorinae.

The theropod genus and species Ornithomimus velox was erected based on a partial hind limb recovered from the late Maastrichtian Denver Formation. A partial manus, which likely belonged to the same individual, was also recovered and described in the same paper. Ornithomimus edmontonicus is the only other valid species currently recognized in the genus. The validity of Ornithomimus velox has been questioned due to its fragmentary nature and because the diagnostic features identified when the species was erected are now considered characteristic for the family. The pes and manus of Ornithomimus velox were never fully prepared. In the original description, reconstructed metatarsals were figured, but manual phalanges, although preserved, were not described. Here we describe and reevaluate Ornithomimus velox based upon a new preparation of the specimen. Metacarpal proportions are diagnostic for the genus, with metacarpal I longer than metacarpal II, which in turn is longer than metacarpal III. The pes and manus of Ornithomimus velox are smaller than in the type specimen of Ornithomimus edmontonicus. Ornithomimus velox can be distinguished from Ornithomimus edmontonicus based on the robusticity of the pes. Material previously referred to Ornithomimus velox from the Kaiparowits Formation of Utah is older and morphologically distinct and does not represent the same species. The morphological disparity and temporal separation observed in specimens referred to Ornithomimus edmontonicus suggest that it may represent a species complex. The redescription and diagnosis of Ornithomimus velox provides a new framework to investigate ornithomimid systematics.

A new species of Toxodontia (Mammalia, Notoungulata), Pampahippus secundus sp. nov., is described based on remains recovered from outcrops of the Lumbrera Formation exposed in Salta Province, northwest Argentina. The material studied consists of mandibular, maxillary, and premaxillary fragments with complete and incomplete teeth representing at least three individuals. It differs from the type species P. arenalesi by its smaller size and the presence of several dental features: I2 smaller than the I1 and I3, paraconule absent on the P3, upper molars wider than long and subquadrangular, with a single crista projecting from the ectoloph, strong mesiolingual cingulum surrounding the protocone on the M1, conspicuous metacone fold on the ectoloph of M1 and M2, and absence of labial cingulids on lower molars. In order to determine the phylogenetic position of P. secundus as well as different Paleogene notoungulates of northwestern Argentina, we performed a cladistic analysis. This analysis supports the paraphyly of Notohippidae proposed by previous authors and validates the monophyly of the genus Pampahippus, which ranks as a relatively basal taxon within Toxodontia. This contribution illustrates the significant and yet poorly known diversity of Paleogene toxodontians from northwestern Argentina and the importance of their study in the reconstruction of the evolutionary history of Notoungulata.

A new genus and species of Rhinocerotidae, Persiatherium rodleri, gen. et sp. nov., a new acerathere rhinocerotid from the early upper Miocene (ca. 9 Ma) locality of Kopran, Maragheh (northwestern Iran), is described. The new taxon can be clearly distinguished from the three species previously reported at Maragheh: Iranotherium morgani, Ceratotherium neumayri, and Chilotherium persiae. Moreover, P. rodleri can be distinguished from the latest middle and late Miocene elasmotheres, teleoceratins, and rhinoceroses recorded in Eurasia and Africa. The new taxon displays morphological characters close to Aceratheriini. However, the presence of plesiomorphic characters on the teeth (presence of P1, continuous lingual cingula on the premolars, labial cingula on the premolars, lingual cingula on the molars, weak protocone constriction on the molars, absence of crista and antecrochet on the molars), of peculiar morphological characters (e.g., lingual side of the protoloph and metaloph directed disto-lingually on P2 with the presence of a lingual groove on the hypocone), as well as some derived characters (e.g., short metaloph on the molars), enable its distinction from other Aceratheriini. A cladistic analysis shows that P. rodleri is the sister taxon to ‘Aceratherium huadeensis'. Though the latter displays more derived features than P. rodleri, their phylogenetic relationships allow inclusion of both species in the same new genus.

We provide a detailed description of a well-preserved enantiornithine specimen (GSGM-05-CM-004) from the Lower Cretaceous (Aptian) Xiagou Formation of northwestern Gansu Province, China, for which we erect the new taxon Feitianius paradisi, gen. et sp. nov. This specimen has a distinctive pelvic morphology and can be further distinguished from all other Mesozoic birds by a unique caudal plumage formed by multiple rectricial morphotypes. This newly documented tail morphology reveals a previously unrecognized level of complexity in the plumage of basal birds. This complex tail-feather morphology has a parallel in extant sexually dimorphic birds in which the males have the most altered tails; thus, we identify this specimen as male. Ornamental tail morphologies, such as the novel tail plumage described here, dominate Enantiornithes. This reinforces hypotheses that sexual selection was a major driving force in the evolution of basal bird plumage.

The terrestrial Neogene Basin of Denizli, located in southwestern Turkey, yields rodent faunas from nine localities dated between MN6 and MNQ18–19. Arabosminthus gansus, which is known in China and Mongolia, is recorded for the first time in Turkey at the Yenicekent localities (MN8–9), an older stratigraphical level than it is usually known from. Another species from the same localities, Microdyromys complicatus, is described for the first time in Anatolia in a younger locality than usual known in Western Europe. Myomimus dehmi, Myocricetodon eskihisarensis, Dryomys tosyaensis, and Dryomys sp. are the other species described in the present study. A new species of fossil Mus (Mammalia, Rodentia), Mus denizliensis, sp. nov. (MNQ18–19), has been found at the G€okpınar locality. This is the oldest fossil species of this genus known from Turkey or continental Europe.

We describe a new record of the dyrosaurid crocodyliform genus Hyposaurus, from the ?Campanian— Maastrichtian Shendi Formation of Sudan, based on a partial mandibular symphysis, two posterior portions of the upper jaw, and a fused frontal bone, all belonging to a single individual. The material can be assigned to Hyposaurus on the basis of the elliptical shape of the mandibular symphysis (wider than high) and the overall flat shape of the mandible. At the same time, the fossil material differs from other species of Hyposaurus in having (1) an enlarged eighth alveolus of the dentary relative to the other alveoli; (2) a reduced interalveolar space between the ninth and tenth alveoli; and (3) a prominent ridge and groove sculpturing on the dorsal side of the mandible along the symphyseal region. However, due to the fragmentary nature of the material, we refrain from drawing any higher-resolution taxonomic conclusions. The occurrence of Hyposaurus within the Shendi Formation represents the first record of this genus from the Late Cretaceous of Africa and potentially extends its temporal range to the Campanian. Whereas this occurrence in the Late Cretaceous of Sudan supports previous hypotheses of an African origin for Hyposaurus, more complete material is needed for evaluating these hypotheses in a phylogenetic framework.We also wish to stress that the genus Hyposaurus requires detailed revision.