Two embryonic skeletons preserved inside thin-shelled eggs of a partially preserved clutch from the Upper Elliot Formation (Lower Jurassic) of South Africa have been attributed to the sauropodomorph dinosaur Massospondylus carinatus. A virtually complete skeleton is exposed in right lateral view, with the slightly telescoped skull and several cervical vertebrae extending beyond the eggshell. A second, partial skeleton has a skull preserved in dorsal view. The embryos have proportionately very large skulls, with the broad skull table formed by wide parietals and frontals. The wide posterolateral wing of the frontal separates the postorbital from contact with the parietal. The embryos have short rather than elongated cervical vertebrae, with tall rather than low neural arches. The large forelimbs are only slightly shorter than the hind limbs, which suggests an obligatory quadrupedal posture for the hatchlings. This pattern may represent an ontogenetic constraint related to the large size of the head and horizontally oriented neck. Similarities between the embryonic and post-hatchling specimens include the slenderness of the lower jaw and slight ventral curvature of the symphyseal portion of the dentary, the large supraorbital process of the prefrontal, and the tall antorbital and infratemporal fenestrae. There are 10 cervical, 14 dorsal, and three sacral vertebrae. The large distal claw-bearing phalanx of manual digit 1 is longer than any other phalangeal element of either manus or pes. The embryos of Massospondylus carinatus represent the oldest dinosaurian embryos known to date.

The late Devonian—Carboniferous (D–C) shark Thrinacodus has been known only from highly distinctive teeth since its first description from North America in 1875. The poor quality of illustrations of the type material meant that the thrinacodont tooth form remained unrecognized until the early 1980s when similar teeth were found in D–C boundary beds in Australia. Since then, Thrinacodus taxa have been found globally with a Paleotethyan distribution. Discovery of articulated specimens in the Serpukhovian of Montana could have helped to clarify their phylogenetic relationships and paleobiology of Thrinacodus, but their first formal description has caused taxonomic confusion rather than resolving problems of the thrinacodont taxonomy. A new genus, Thrinacoselache Grogan and Lund, 2008, was mistakenly erected, the introduction of which is rectified here and supported by taxonomic arguments. A new interpretation of the phylogeny of Thrinacodus is proposed.

A new, well-preserved specimen of Palaeobates polaris from the Smithian ‘fish horizon’ of Spitsbergen (Svalbard archipelago, Arctic Norway) is presented. The find is more complete than the type material of P. polaris and contains amongst others the left mandibular branch with associated dentition and labial cartilage as well as elements of the hyoid arch and a portion of the anterior dorsal fin. P. polaris shares with the other species of the genus Palaeobates the same tooth histology (orthodont teeth with pulp cavity), but the ornamentation of the teeth is different. Several studies have shown that it is problematic to deduce phylogenetic relationships among hybodontiform sharks by means of tooth histology. Moreover, orthodont teeth with a pulp cavity are probably plesiomorphic for hybodontiforms. Based on the new find of P. polaris, three other characters are proposed to be apomorphic for Palaeobates in general: (1) the lower margin of the dental groove of Meckel's cartilage runs nearer to the ventral than to the dorsal border of the mandible in P. polaris but medially to these margins of the lower jaw in the crown group hybodontoid Acrodus; (2) the number of tooth files and arrangement of the teeth of P. polaris are well-distinguishable from those of Acrodus and Asteracanthus; and (3) the dorsal fin spines of P. polaris, and also of P. angustissimus, tend to be more slender compared to those of Hybodus and Acrodus. Nonetheless, more material is needed to ascertain if these traits are useful to separate Palaeobates from other hybodontiforms.

Ilia of anurans (frogs) and urodeles (salamanders) are commonly recovered from microvertebrate fossil localities. Ilia in these clades are distinctive when complete and articulated with the rest of the pelvic girdle, but when preserved as isolated and broken fossils they may appear superficially similar. Reliable identification of urodele ilia is further hampered by limited information about the basic structure and contacts of the bone and its variation within the clade. Here we demonstrate that the ilium is more variable among urodeles than previously realized and provide the first detailed inventory of features that are potentially useful for differentiating ilia of anurans and urodeles. Many of these features relate to differences between the two clades in the orientation of the ilium and its contacts with other bones and with soft tissues. Based on the results of our survey, we re-interpret the holotype and two referred ilia of Nezpercius dodsoni (Late Cretaceous; Montana, U.S.A.) as being from an indeterminate urodele, not an anuran as originally described. Additional examples of Late Cretaceous urodele ilia are documented to highlight some of the variation seen in fossil urodele ilia and to aid in the proper identification of such specimens.

Dermal ossifications are widespread in Permian and Triassic tetrapods, but only members of the Chroniosuchia possess a series of dorsal osteoderms with a complex plate-to-plate articulation mechanism in addition to a contact between each osteoderm and its associated vertebral spine. The stratigraphically youngest chroniosuchid, Madygenerpeton pustulatus, from the Triassic of Kyrgyzstan provides new insight on the function of the chroniosuchian osteoderm system. Osteoderms of M. pustulatus are broad, peaked-roof-shaped to arched, with enlarged posterodorsal and anteroventral articulation facets bearing unique sets of concentric rail-like ridges and furrows. Supplementing the multiple-overlap chroniosuchiantype articulation, the interlocking ridges and furrows confined the relative motion of two neighboring osteoderms to a rotation in slightly oblique and curved contact planes. Given the significant lateral narrowing of the dorsal ornamented non-overlap area, the horizontal component of the plate-to-plate rotation angles could reach up to 7.5°, enabling more extensive lateral flexion of the trunk than in other chroniosuchids. Considering functional analogs, the chroniosuchian osteoderm system probably stabilized the vertebral column against shearing, torsion, tension, and compression loads and thus facilitated terrestrial locomotion at the expense of trunk flexibility. With its particular morphology, the carapace of M. pustulatus, however, was more suitable for locomotion styles featuring lateral body undulation than the carapaces of Permian chroniosuchids. We interpret this speciality as a secondary adaptation to an aquatic habitat.

Chupacabrachelys complexus, n. gen. n. sp., is an unusual bothremydid pleurodire of the tribe Taphrosphyini found in the Campanian Aguja Formation in the Big Bend region of West Texas. The type example is one of the most complete bothremydid specimens known. Its skull and lower jaw are very narrow, triangular, and dorsoventrally compressed, with the coronoid process posterior to midlength of the jaw. The orbits are elongate anteroposteiorly with narrow extensions along the maxilla-prefrontal sutures, and rugose maxillary projections at the anterolateral corners of orbits. Its reduced temporal emargination, weak posteroventral flange on the squamosal, weak lateral extension of the squamosal along the quadrate suture, and posteroventral knob on opisthotic suggest affinity with Taphrosphyini. The shell has six neurals and a nuchal with sharp midline embayment, and is nearly identical to those of Chedighaii and Bothremys. Chupacabrachelys provides additional evidence for the dramatic evolutionary radiation of bothremydid turtles in tropical paralic environments during Late Cretaceous time.

Australian Cretaceous ichthyosaur material is amongst the most complete in the world. This study describes postcranial remains referred to the upper Albian species Platypterygius australis, including the first record of pelvic and hind limb elements for this taxon. A combination of phylogenetically significant traits such as lack of fusion between the atlas-axis complex and third cervical centrum, the presence of three distal facets on both the humerus/femur for accommodation of the anterior zeugopodial elements plus the radius/tibia and ulna/fibula, concave preaxial accessory facet surfaces on both the humerus and the femur, and complete fusion of the ischiopubis with closure of the obturator foramen, are considered diagnostic for the species and (in conjunction with other previously identified cranial/postcranial features) may serve to distinguish P. australis from the other paleogeographically disparate Platypterygius spp.

Cryptocleidoid plesiosaurs from the Upper Jurassic are well known from the Oxford Clay (Callovian) of the United Kingdom. The plesiosaurs of the nearly coeval Sundance Formation (Oxfordian) of North America are poorly known, but are thought to include two cryptocleidoid taxa: Pantosaurus striatus and Tatenectes laramiensis. Here we present two specimens recently recovered from the Bighorn Basin of Wyoming. The first specimen comprises three articulated adult cervical vertebrae and fragments of a fourth. This specimen preserves a posteriorly directed cervical neural spine, a character diagnostic of Pantosaurus striatus. It also resembles Pantosaurus in the morphology of its cervical rib articulations. The second specimen is a partial articulated skeleton comprising a complete pelvic girdle, dorsal, sacral, and caudal vertebrae, and numerous ribs and gastralia. This specimen displays a number of unique characters, including posteriorly directed dorsal, sacral, and caudal neural spines, highly autapomorphic illia, and a pathologically asymmetric pelvic girdle. Despite the lack of overlapping material, it is tentatively referred to Pantosaurus on the basis of posteriorly directed neural spines. These specimens represent the first significant adult material provisionally referable to Pantosaurus striatus, as well as the first posterior axial column and pelvic girdle.

A new pterodactyloid pterosaur is identified from the Early Cretaceous Doushan Formaiton of Laiyang, Shandong Province, China, based on a fragmentary humerus. The humerus exhibits several diagnostic characters: deltopectoral crest is elongate and un-warped, its base is slightly displaced relative to the humeral shaft axis, and the crest is swollen terminally and ventrally displaced; humeral shaft is straight and thin-walled with a ‘D’-shaped cross-section. Based on these features, the specimen is referable to the superfamily Azhdarchoidea as Azhdarchidae indet. As the oldest known azhdarchid fossil, the specimen represents a significant stratigraphic range extension for the family. Other non-azhdarchid azhdarchoids such as tapejarids and chaoyangopterids are common in the Jiufotang Formation of western Liaoning, which possibly is equivalent to the Doushan Formation of Laiyang with an age of about 120 Ma. Consequently, the possible coexistence of these azhdarchoids lineages documents that the azhdarchids split from the main azhdarchoid clade occurred no later than the Early Cretaceous.

Pterosaur fossils from Australia are rare. All the specimens that have been described previously are Cretaceous in age, with the majority deriving from the Aptian—Albian shallow marine succession within the Eromanga Basin of western Queensland. The Queensland specimens have tentatively been referred to the pterodactyloid clades Pteranodontidae, Ornithocheiridae, and Archaeopterodactyloidea (cf. Ctenochasmatoidea), each in varying taxonomic guises. Due to their fragmentary nature, more specific referrals of these specimens have not been possible. As such, the overall composition and more precise relationships of Australia's Cretaceous pterosaur fauna have remained enigmatic. Since 1987, a number of new pterosaur specimens have been found in the shallow marine late Albian rocks of the Eromanga Basin of western Queensland. Four of these specimens are described herein: a partial mandible, a metacarpal IV, a wing phalanx, and a humerus. The mandible is assigned to Ornithocheiridae, gen. et sp. indet., whereas the metacarpal and wing phalanx are assigned Ornithocheiridae cf. Anhanguera. The morphology of the humerus suggests that it may belong to a ctenochasmatoid lophocratian. Based on these findings, we hypothesize that Australia's Early Cretaceous pterosaur fauna comprises a mix of taxa already known to occur in Europe and South America in addition to a slightly younger ctenochasmatoid. However, the older specimens may alternatively represent new taxa that combine cranial characteristics of an Ornithocheirus-like taxon or a closely related form, with an Anhanguera-like postcranium. A more precise characterization of Australia's Cretaceous pterosaur fauna cannot be resolved until more complete specimens are found.

The neural spines of the sauropod presacral vertebrae contain a series of osseous laminae of unquestionable phylogenetic significance. However, the lack of articulated presacral series has impeded identification of these structures in many taxa. Titanosaur sauropods present a pattern of neural laminae that is somewhat different from other groups, especially to diplodocids. Understanding these differences is important in order to score adequately characters related to vertebral anatomy, in phylogenetic analyses of the Sauropoda. Particularly, many titanosaurs present two spinodiapophyseal laminae in the posterior dorsal vertebrae. Additionally, these taxa show the apparent disappearing of the postzygodiapophyseal lamina in those vertebrae. Other titanosaurs have a single posterior dorsal spinodiapophyseal lamina, but this probably corresponds to one (probably the anterior) of the two spinodiapophyseal laminae of the posterior dorsals of the other titanosaurs.

We describe a new coelurosaurian theropod, Zuolong salleei, gen. et sp. nov., from exposures of the upper part of the Shishugou Formation at the Wucaiwan locality, Xinjiang Autonomous Region, People's Republic of China. Zuolong has a large, inclined quadrate foramen that extends onto the medial surface of the quadratojugal, an unusually large fovea capitis on the femoral head, and an apomorphically large distal condyle of metatarsal III with a medially projecting flange on the extensor surface. Radiometric dating of the Shishugou Formation constrains the age of the specimen to the beginning of the Late Jurassic (Oxfordian). A cladistic analysis of Zuolong salleei in a broadly sampled theropod data matrix recovers it as a basal coelurosaur. These data make Zuolong one of the oldest coelurosaur fossils yet known that preserves both cranial and postcranial bones.

The cheek teeth of Ectoganus and Stylinodon, the most derived genera of Taeniodonta following recent phylogenies, show various morphological and microstructural characteristics that are unusual for herbivores of their size. Their continuously growing premolars and molars have blunt occlusal surfaces without shearing facets and enamel is restricted to the lingual and buccal sides of the teeth. The anterior and posterior walls of the teeth are covered with a thick layer of cementum to which the periodontal ligament is attached. The enamel band is relatively thin. The schmelzmuster is one-layered and features weakly developed Hunter-Schreger bands that are only recognizable in longitudinal section. In cross-section, the enamel prisms show a ‘keyhole pattern’ with an incomplete prism sheath. There is no interprismatic matrix. The microstructure of the dentine has the regular mammalian pattern and shows no special similarity to that of xenarthrans. Taeniodonts seem to have used their hypsodont cheek teeth almost exclusively for squeezing and some crushing of food and only to a minor degree for grinding. Weakly developed Hunter-Schreger bands indicate only light loading during mastication.

Since 2006, new field studies at the late Oligocene site of Quebrada Fiera (Mendoza, Argentina) have increased the previous faunal record from these levels that are presently considered as the base of the Agua de la Piedra Formation. Former faunal lists included Pyrotherium and Proborhyaena gigantea, representatives of the Deseadan Age. Among new materials, a complete skull and two associated metatarsals, two maxillary fragments with left I1-M2 and right I1-P3, and five isolated upper teeth represent the Family Notohippidae. Even though some characters are not comparable between the skull and maxillaries, shared features lead us to consider them as a unique and new taxon, Mendozahippus fierensis, gen. et sp. nov., and the isolated molars as cf. M. fierensis. As in previous phylogenies, our analysis indicates the Family Notohippidae is a paraphyletic group. The inclusion of Plexotemnus, Pampahippus, and Puelia within Notohippidae is not supported, but without them, the group is still paraphyletic. Leontiniids appear as basal taxa to the remaining notohippids and toxodontids. Mendozahippus presents one autapomorphy (lingually projected protocone of M3) and four homoplastic characters. It occupies a basal position with respect to other notohippids plus toxodontids. Mendozahippus increases the diversity and geographic distribution of Notohippidae during the late Oligocene. This and other taxa add some distinctiveness to this Deseadan fauna compared to other better-known assemblages from Patagonia or Salla (Bolivia), whereas other groups maintain clear affinities. The intermediate latitudinal position of Mendoza might explain these faunal characteristics.

The first skull associated with postcranial elements of Macraucheniidae (Litopterna) from the Sarmiento Formation in Cabeza Blanca (Chubut, Argentina) are described herein. The material consists of a nearly complete skull, nearly complete right humerus, left metacarpal IV, and three phalanges (proximal, intermediate, and distal of the same digit) of the same individual. It is compared with the Santacrucian genus Theosodon Ameghino, the Colhuehuapian Cramauchenia Ameghino, and the Deseadan species Coniopternium andinum and C. primitivum Soria and Hoffstetter. The comparative study leads us to recognize this specimen as Cramauchenia normalis. The presence of this species in Cabeza Blanca increases its biochronological distribution to Deseadan South American Land Mammal Age (SALMA) (late Oligocene).

Artiodactyls show a step-wise morphological transition from groups with a primitive and pentadactyl limb configuration to groups with more derived and didactyl limb configurations. An analysis of proportions of the forelimb segments indicates that artiodactyls can be separated based on digit number along a morphometrical axis indicating relatively longer segments of manus (carpus, metacarpus, and phalanges). The three digit configurations in artiodactyls (pentadactyl, tetradactyl, didactyl) are identified and the relevant bony characteristics of each configuration are described. Among tetradactyl groups, there are two grades of anatomy in the manus. In the more derived tetradactyl groups (tayassuids, tragulids, and early camelids), the proximal volar metacarpal process becomes flatter and joints of the digit become more ginglymal in comparison with the less derived tetradactyl groups (ticholeptine and merychyine oreodonts, leptomerycid traguloids, primitive cainotheres, oromerycids, and protoceratids). The foot posture of members of the pentadactyl groups is interpreted as digitigrade. The evolution of unguligrady took place between the morphological condition of the primitive type of tetradactyl manus and the derived type of tetradactyl manus. This transition to unguligrady occurred at least three times and was facilitated each time by the formation of ginglymal joints of the digit and the transition to interosseus ligaments from muscular precursors.

Direct radiocarbon dating and stable isotope and biometric analyses are evidence that the holotype of Equus laurentius Hay, 1913 comprises the skull and jaw of two different horses that are less than 500 years old. The size and morphology of the specimens fall within the range of like elements of modern Equus caballus Linnaeus, 1758. The mandibular cheek teeth exhibit bit wear, demonstrating that the mandible is that of a domestic animal. The taxonomy of the purportedly late Pleistocene species is therefore resolved, and Equus laurentius Hay is a junior synonym of Equus caballus Linnaeus. Equus laurentius and its holotype are neither taxonomically nor phylogenetically pertinent to studies of North American Pleistocene Equus.

Cavioidea sensu stricto groups three traditionally recognized families that are characterized by hypsodont, double-heart-shaped cheek teeth and moderate hystricognathy: Eocardiidae, Caviidae, and Hydrochoeridae. Eocardiidae was erected to include a diverse assemblage of extinct and plesiomorphic taxa, whereas Caviidae and Hydrochoeridae (the crown group of Cavioidea) include the lineages with extant representatives (cuyes, maras, and capybaras). A new genus and species of Cavioidea sensu stricto, Guiomys unica, is described here from the middle Miocene of west central Patagonia (Argentina). The new taxon is known from mandibular and maxillary fragments with molars, and isolated cheek teeth. A phylogenetic analysis of Cavioidea sensu stricto shows G. unica as the sister taxon of the clade formed by the crown group of Cavioidea sensu stricto (‘medialis series’). The new species displays characters states intermediate between eocardiids and the ‘medialis series.’ The most outstanding character of Guiomys unica is the autapomorphic position of the notch for the insertion of the masseter medialis pars infraorbitalis muscle, isolated from both the masseteric and horizontal crests. This notch is located at the anterior end of the masseteric crest in eocardiids and represents the plesiomorphic state for Cavioidea sensu stricto. In caviids and hydrochoerids, the notch is located at the anterior end of the horizontal crest, the derived state for this character. G. unica allows reinterpretation of the homologies of the mandibular crests in basal cavioids and clarifies the evolutionary origins of crown-group cavioids (Caviidae Hydrochoeridae).

Dipodid rodent fossils from Gashunyinadege at ∼17 Ma, one of the oldest Neogene localities in central Nei Mongol, China, include six genera (Heterosminthus, Plesiosminthus, Litodonomys, Sinodonomys, gen. nov., Omoiosicista, gen. nov., and Sicista) and nine species, including four new species (P. vegrandis, sp. nov., L. minimus, sp. nov., S. simplex, sp. nov., and O. fui, sp. nov.). The high diversity and abundance of dipodid rodents in Gashunyinadege indicate the evolution of basal dipodids was centered in Nei Mongol. Omoiosicista is described on the basis of eight isolated teeth and characterized by possessing one autapomorphy. This new taxon shares seven synapomorphies with Sicista, suggesting Sicista is the closest relative.