Cretaceous marine hind-limbed snakes are considered to be key fossils for understanding the origin and evolution of snakes. In view of the rarity of such fossils, performing new analyses on described specimens using emerging, cuttingedge techniques should bring important new insights on these forms. We investigated the three-dimensional morphology and inner architecture of the pelvic girdle and hind-limb bones of the type specimen of Eupodophis descouensi Rage and Escuillié, 2000, one of the three taxa for which at least one hind-limb is known, using synchrotron-radiation computed laminography (SRCL), a recently developed non-destructive technique that overcomes some of the limitations of synchrotron microtomography for flat, laterally extended objects. This experiment allowed a virtual exhumation of the second, hidden leg of the specimen. The morphology and proportions of the regressed pelvic and hind-limb bones of Eupodophis resemble those of the hind-limbed snakes Pachyrhachis and Haasiophis. As in Haasiophis, four tarsals are observed in each limb, but there are no traces of metatarsals or phalanges. Moreover, despite the presence of osteosclerosis and pachyostosis in the vertebrae and the ribs of Eupodophis, the inner structure of its limb bones is devoid of these osseous specializations and displays a microanatomical organization similar to that of extant terrestrial lizards. This suggests that limb regression in Eupodophis was not due to a qualitative alteration of growth but, more likely, to a local decrease in growth rate or shortening of growth duration.

All previous records of the lamniform shark, Archaeolamna kopingensis, are based on isolated teeth. Here we describe a partial skeleton from the Sharon Springs Formation of the Pierre Shale Group of western Kansas, U.S.A. The specimen includes portions of the upper and lower jaws with articulated teeth. The dentition consists of two files of upper and lower anterior teeth that, together with a single file of intrabullar intermediate teeth, are housed in a dental bulla, as well as multiple files of lateral teeth, along with at least two files of lower symphysial teeth and a single file of upper symphysial teeth. The intrabullar intermediate tooth is slightly shorter than the other anterior teeth and has a median cusp with distinctive distal curvature. The dental sequence of A. kopingensis is unique among both extinct and extant lamniforms. Associated with the jaws are fragments of the neurocranium and multiple vertebral centra. A sagittal section through a centrum shows that this shark deposited 18 annual marker bands after its birth and adult size was attained by the 10th band. The robust but penetrating tooth morphology and large jaw circumference suggest that A. kopingensis likely fed upon large prey items.

The first Mochokus (Siluriformes, Mochokidae) remains of the fossil record are described, including a new species based on a sub-complete neurocranium discovered in the Late Miocene deposits of Toros-Menalla, Chad, Central Africa, dated to 7.0 Ma. Mochokus gigas, sp. nov., is the first fossil species described for the family Mochokidae, which is the largest family of African catfishes. The description is based on the comparison with the two living species of the genus, M. niloticus and M. brevis. Mochokus gigas, sp. nov., is a very large species presenting original features, notably on the pectoral spines and on the anterior part of the neurocranium. One of the apomorphies characterizing the modern genus Mochokus is found on the fossil: the root of the mesocoracoid arch is located on the posterior side of the vertical lamina of the coracoid and lacks any dorsally directed prominence. Several other Mochokus fossil remains, including nuchal plates, cleithra, and dorsal spines, are described and attributed to Mochokus, sp. indet., or Mochokus sp. Finally, and on the basis of preliminary observations of the fossil fish assemblages from different sites of Toros-Menalla, the lack of Mochokus fossil remains is discussed.

The Amphibamidae are undergoing intensive investigation at present, with many new species recently described to better understand their interrelationships and role in the origin of extant amphibians. A new genus and species of amphibamid, Rubeostratilia texensis, represented by a skull from the Early Permian of Texas, shows many similarities with a recent described species from Richards Spur, Oklahoma, Pasawioops mayi. The skull is elongate and oval, with enlarged external naris and orbits, typical of the other amphibamids within the Micropholis-Tersomius cluster. The skull exhibits the laterally exposed palatine (LEP) and the dorsal quadrate process typical of the Dissorophoidea. Unlike Pasawioops, the new species preserves only a few additional characters relevant to amphibamid relationships: the pterygoid contacts only the ectopterygoid, the postfrontal's shape is falciform, and the alary processes do not extend further posteriorly than one-half of the length of the external naris. We included Rubeostratilia in a recently published amphibamid matrix, to which we added four characters, and conducted two separate phylogenetic analyses, differing in the coding of three characters in the genus Plemmyradytes. The results demonstrate the importance of precision in coding for each character, because these minor changes lead to two different topologies. A brief morphometric analysis of amphibamid cranial anatomy was conducted to better understand the nature of the different morphotypes among which the new species clusters. The results of both morphometric and phylogenetic analysis add support to the emerging consensus that amphibamids cluster into two distinct clades.

Eocene caldera-lake deposits from Río Pichileufú have yielded anuran remains in association with a taxonomically diverse flora. The floral evidence suggests that these anurans lived under climatic conditions similar to those of extant subtropical rainforests. One of the anurans is a helmeted neobatrachian, which is represented by articulated remains and represents a new species that can be assigned to the extant genus Calyptocephalella on the basis of both cranial and postcranial traits. Calyptocephalella pichileufensis, gen. et sp. nov., indicates that, despite the relatively conservative skeletal anatomy of the genus, Calyptocephalella has not always been associated with the temperate austral forests that it inhabits today. The new species also provides evidence of a biotic link with Australia, which has been proposed on the basis of other faunal and floral records, as well as on the paleogeographic history of Patagonia during the mid-Cretaceous—Eocene interval. We also discuss the significance of neobatrachian cranial features that might reflect hyperossification.

A new pleurosternid turtle from the Upper Jurassic of the Central West of Portugal is described. Pleurosternids are abundant in the European and American Upper Jurassic and Lower Cretaceous fossil record. Despite this, at present, there is no reference to any genus of pleurosternids before the upper Tithonian in Europe. Selenemys lusitanica, gen. et sp. nov., represented by several specimens from the upper Kimmeridgian of the Lusitanian Basin (Portugal), constitutes the most ancient generic attribution to a pleurosternid turtle in Europe. A cladistic analysis shows that Selenemys is more closely related to the European Lower Cretaceous pleurosternids than to the Jurassic North American representatives of this group. This is interpreted as a vicariant biogeographical distribution of the group on both sides of the North Atlantic during the Uppermost Jurassic, in contrast to that observed in other groups of reptiles.

Wumengosaurus delicatomandibularis Jiang et al., 2008, is restudied on the basis of three new specimens. Many elements of the skeleton that were either briefly or not described at all in the original study are detailed. With the additional information derived from the new specimens, we have revised the diagnosis of W. delicatomandibularis. A phylogenetic analysis further demonstrates that the Pachypleurosauria is not a monophyletic group and questions that W. delicatomandibularis is closely related to the Pachypleurosauria. W. delicatomandibularis might represent the basal-most member of a monophyletic clade that includes the Nothosauroidea and those taxa assigned to the ‘Pachypleurosauria.’ The five known specimens show morphological variation in W. delicatomandibularis, as in Keichousaurus and in pachypleurosaurs such as Neusticosaurus and Serpianosaurus.

The cranial roof ornamentation and the degree of neurocentral closure in the holotype of the pachy cephalosaurian dinosaur Homalocephale calathocercos is described in detail for the first time in order to assess its ontogenetic status and taxonomic validity. The parietosquamosal ornamentation consists of five primary nodes along the posterior margin of the skull roof on each side of the midline. The medial-most node is prominently enlarged relative to the others in the series and is bisected by the parietal-squamosal suture. Beneath the primary node row, a second enlarged node occurs immediately medial to lateroventral corner node on each side of the parietosquamosal bar. The degree of suture closure in the vertebral column suggests that the holotype specimen of H. calathocercos is immature, rather than adult. The presence of cranial doming at maturity is therefore unknown in H. calathocercos, and hypotheses that it represents a primitive flat-headed stage in pachycephalosaur evolution or is pedomorphic in the development of its skull roof cannot be supported or refuted at this time. Despite the probable immaturity of the holotype, H. calathocercos has a unique pattern of parietosquamosal ornamentation that is distinct from all other pachycephalosaurs, including Prenocephale prenes from the same host formation. Morphological differences in the cranial ornamentation, jaws, and dentition between the similarly sized holotype skulls of H. calathocercos and P. prenes provide weak support for recent suggestions that H. calathocercos is conspecific with the latter taxon. This study tentatively reaffirms the presence of two pachycephalosaur species in the Nemegt Formation

Titanosauriform sauropods were one of the most widely distributed groups of dinosaurs during the Cretaceous. In contrast to most derived forms from the Upper Cretaceous, the most basal taxa of the group are poorly known. Thus, studies on these forms are of special interest for understanding the origin and early evolution of Titanosauria. Chubutisaurus insignis del Corro, 1975, is known from postcranial remains found in the Bayo Overo Member of the Cerro Barcino Formation (Chubut Group), which is commonly regarded as Aptian—Cenomanian in age. Phylogenetic analyses that include Chubutisaurus recovered this taxon as the sister group to Titanosauria. Nevertheless, most published studies have not included this taxon, probably due to its brief description and fragmentary remains. Fieldwork conducted in the quarry where the holotype was found yielded new materials that are regarded as part of the same specimen. These new materials, together with additional undescribed, and briefly described elements, originally collected by G. del Corro, are described here. The new information allows the recognition of a more extensive diagnosis of this taxon. The phylogenetic analysis presented here resolves Chubutisaurus as the most basal somphospondylian.

Sixteen isolated theropod teeth were discovered in two areas in the upper Middle-lower Upper Jurassic Shishugou Formation of the Xinjiang Uyghur Autonomous Region, northwest China. This sample can be divided on the basis of qualitative features and simple quantitative metrics into seven tooth morphotypes, each of which probably represents a distinct taxon. Three of the morphotypes may be attributable to theropods already known from the Shishugou Formation, namely the alvarezsauroid Haplocheirus and the basal tetanurans Monolophosaurus and Sinraptor. The other four morphotypes, however, appear to represent new taxa, taking the known theropod diversity of the Shishugou Formation from six species to at least ten. One of the new taxa is probably a dromaeosaurid. Another appears to represent a troodontid or a relative of the potentially troodontid-like Paronychodon, itself so far known only from isolated teeth. Of the remaining two taxa, one appears to be a basal tetanuran or tyrannosauroid, whereas the other either belongs to one of these same groups or represents a ceratosaur. The probable deinonychosaurian teeth in our sample are among the oldest fossils known for this clade, and highlight the diversity of coelurosaurs in the Shishugou Formation.

Modern archosaurs have extensive pneumatic diverticula originating from paranasal and tympanic sinuses. This complex anatomy is present in many fossil archosaurs, but few descriptions of the complete cranial pneumatic system exist. The cranial pneumatic morphology of birds and non-avian theropods are the best studied, but complete description of this anatomy for an ornithomimid was lacking. We describe the cranial pneumaticity of a well-preserved ornithomimid theropod dinosaur, Ornithomimus edmontonicus (RTMP 95.110.1), from computed tomography (CT) scan data and computer-aided reconstruction with quantitative measurements. New details for ornithomimids include an internal promaxillary recess, an internal palatine recess, pneumatic communications between the supraoccipital recess and posterior tympanic recess, and a complex basioccipital recess that connects to the anterior tympanic recess and median pharyngeal system. The pneumatic morphology of the quadrate is similar to modern birds, which have a complete siphoneal duct. We interpret the jugal diverticulum of non-avian theropods to be homologous or at least morphologically related to the avian suborbital diverticulum. Cranial pneumatic morphologies present in Ornithomimus and tyrannosaurids include an extensive internal palatine recesses and a pneumatic articular that is likely derived from a separate siphoneal diverticulum similar to modern birds. Recent phylogenetic hypotheses of theropods imply two equally most parsimonious solutions: that these shared morphologies are either independently derived in each taxon or diagnose Coelurosauria.

A partial postcranial skeleton of a small alvarezsaurid from the Late Cretaceous of the Mongolian eastern Gobi Desert locality of Khugenetslavkant represents the first reported articulated theropod material from that locality. The specimen is recognized as the holotype of a new taxon herein named Albinykus baatar, gen. et sp. nov. Phylogenetic analysis places Albinykus within Alvarezsauridae as the sister taxon of Shuvuuia, another Late Cretaceous Mongolian taxon from the slightly younger Djadokhta Formation. The complete coossification of the proximal tarsals with the tibia, and of the distal tarsals and proximal metatarsals, present in Albinykus are previously unknown in Alvarezsauridae. Extensive fusion is consistent with histological data from the tibia indicating that the individual was a subadult. These results are striking given that Albinykus is among the smallest known non-avian dinosaurs with a body mass no greater than 1 kg and ranks among the smallest known alvarezsaurids. Alvarezsauridae shows a decreasing size trend throughout its evolutionary history, a rarity among dinosaurian clades. Within maniraptoran dinosaurs, such a trend has thus far only been recognized within Avialae and at the origin of Paraves with respect to other coelurosaurs. The holotype was recovered articulated in a ‘seated’ position, with hind limbs aligned and the feet tucked under the body. This body posture, which is present in Aves, has been previously noted in other maniraptoran clades (i.e., Oviraptoridae Troodontidae) and is now recognized in Alvarezsauridae.

A new enantiornithine bird, Bohaiornis guoi, gen. et sp. nov., is described in this paper. The holotype, presumably a sub-adult, is a complete, fully articulated skeleton from the Lower Cretaceous Yixian Formation of western Liaoning, northeastern China. Bohaiornis exhibits some similarity in morphology to Eoenantiornis, but Bohaiornis is much larger than Eoenantiornis and differs from all previously known enantiornithine birds including Eoenantiornis in having the following features: caudal end of the articular pointed caudoventrally, sacral centra strongly compressed transversely, and clavicular ramus straight with a laterally expanded omal end. The almost perfectly preserved skeleton of this new specimen not only reveals many morphological features previously unknown in basal birds, but also clarifies many fine details of previously known features.

Cimolestids are a minor component of early Paleocene (Puercan) faunas of western North America. Here we report on cimolestids from the early Paleocene (middle and late Puercan; Pu2–3) of the Nacimiento Formation, San Juan Basin, New Mexico. New specimens of Puercolestes simpsoni include portions of the deciduous and lower dentition not previously known. We conclude that “Genus B” of Van Valen is probably conspecific with this taxon. Two new genera and species, Chacopterygus minutus and Betonnia tsosia, are from the Pu2 and Pu2–Pu3, respectively. One additional unnamed taxon is based on isolated teeth from Pu2–3 localities. A phylogenetic analysis indicates that Puercolestes simpsoni is sister to Cimolestes. Chacopterygus minutus, Betonnia tsosia, and the unnamed cimolestid form a polytomy that is sister to Procerberus. This resulting clade is sister to Batodon Maelestes. The results of this analysis suggest that P. simpsoni is descended from Cretaceous taxa of western North America. The origins of other early Paleocene cimolestids from either Asia or North America is equivocal. The species diversity of Cimolestidae in the Puercan of New Mexico and other Puercan localities of western North America is similar to that of latest Cretaceous (Lancian) faunas of the northern Rocky Mountain Region.

Specimens that give new information on the tooth eruption sequence in European Hyaenodon are described. These specimens show a marked difference from the tooth eruption sequence established for North American Hyaenodon. The eruption of p4 after p3 and m3 and the earlier eruption of the permanent canine in European specimens versus the eruption of p4 before p3 and m3 and the eruption of the permanent canine as the last tooth in North American specimens indicate divergent evolutionary pathways for New and Old World lineages. In conjunction with other skeletal differences, described in the literature, our findings support the need for a reanalysis of the taxonomy of Hyaenodon.

The first cranial and upper dental remains of a proterotheriid referred to Neolicaphrium cf. N. recens Frenguelli, 1921, are described from the late Pleistocene of northern Uruguay (Sopas Formation). An isolated molariform from the Pleistocene of northeastern Pampean Argentina is considered as Neolicaphrium sp. It is the last surviving Pleistocene Proterotheriidae. An expanded diagnosis of this genus-based until now only on mandibular characters-is provided. The following combination of characters distinguish it from other genera of proterotheriids for which characters of the skull have been described: dorsal surface of skull almost parallel to the occlusal surface of the cheek teeth series; relatively large orbits and diastema; very large caniniform upper incisors; upper premolars and molars relatively low crowned; P2 nearly quadrangular; molariforms (at least P4 and M1–3) with anterolingual cingulae; anteroposteriorly short upper molar series; M1–3 with metaconule reduced to a small transverse crest connecting the hypocone to the metacone; hypocone reduced (or nearly absent), particularly in M3; M3 located below the orbit. A principal component analysis places it near the smallest species of proterotheriids, which were separated very well along the second component, usually related to shape.

Diplacodon gigan is a new species of uintan brontothere recognized from an exquisitely preserved skull from the Wiggins Formation, Hot Springs County, Wyoming. Close affinity to Protitanotherium emarginatum has been suggested based on similarities of canine size and horn shape. However, evidence suggests that canine size and horn morphology were sexually dimorphic among brontotheres, and differences in these traits between single specimens or very small samples of specimens are suspect. Analysis of coefficients of variation of canines and other craniodental variables in brontotheres demonstrates a marked increase in the intraspecific variability of canines among horned brontotheres and closely related hornless species. The evolution of sexual dimorphism in the Brontotheriidae follows a pattern repeated in the evolutionary histories of other ungulates, including ruminants and rhinoceroses, where the evolution of sexually dimorphic canines or canine-like incisors commonly precedes the evolution of horns or horn-like cranial appendages. A phylogenetic analysis, which incorporates new character data on horn size, horn shape, canine size, and canine dimorphism, places D. gigan as the sister of D. elatus, and is the basis for the referral of this new species to Diplacodon. Phylogenetic analysis demonstrates that similarities between P. emarginatum and D. gigan, particularly with respect to canine and horn morphology, are plesiomorphic traits shared with basal horned brontotheres, such as Protitan. The shared nasal bone morphology of D. elatus and D. gigan, where the lateral margins of the nasal bone are angled markedly dorsalward, is a synapomorphy of the genus Diplacodon and is not observed in other brontotheres.

Late Oligocene and early Miocene, nearly flat-lying and dominantly volcaniclastic, continental strata in the lower part of the Chalk Canyon Formation are exposed in central Arizona along the southwestern margin of the Transition Zone and the adjacent northeastern margin of the Basin and Range Province. The strata have yielded both of the two known oreodont records reported from Arizona. These occurrences represent the Cave Creek and Black Canyon Local Faunas. Both records are assigned tentatively to the early late Arikareean (Ar3), small-bodied oreodontid species Merychyus calaminthus, based primarily on their occlusal and basicranial anatomies and on the comparatively small sizes of the individuals they represent. Both fossil sites are in discontinuous exposures separated by about 28 km (17 mi). Overlying olivine-rich basaltic lava flows still in the lower part of the formation in the Cave Creek area are as old as 23.3 ± 2.7 Ma in age, based on whole-rock Potassium-Argon radiometric age determinations. On the other hand, a pumice-rich air-fall tuff bed at the base of the formation is only 20.98 ± 0.06 and 21.03 ± 0.06 Ma old, based on ⁴⁰Argon/³⁹ Argon (Ar/Ar) analysis. A blue ash layer in the Black Canyon City area and at the approximate level of the oreodont site is 23.7 ± 0.9 Ma old, based on the ²³⁸Uranium²⁰⁶Lead analysis of zircon crystals. The oreodont records and nearly all available radiometric data suggest that the fossilbearing strata in the lower part of the Chalk Canyon Formation are correlatives of the Harrison Formation in the northwestern Nebraska Panhandle. The Agate Ash in the Harrison Formation is 23.23 ± 0.13 Ma in age on the basis of Ar/Ar analysis.