The histological composition of the galeaspid cephalothoracic skeleton has been much debated: here we attempt to resolve this through the analysis of well-preserved remains of galeaspids from Yunnan Province, and Tarim Basin, Xinjiang Uygur Autonomous Region, China. Our results indicate that the galeaspid dermoskeleton is dominantly composed from an acellular laminar bone in which the mineral is organised into cylindrical crystal bundles that are arranged into three orthogonal sets with associated extrinsic fiber spaces, a unique histology for which the term galeaspedin is coined. This is permeated by a coarse vascular plexus that divides the dermoskeleton into upper and lower zones, and the upper zone into distinct tesserae which, like the bounding vascular network, are polygonal in outline.

The outer surface of the dermoskeleton is ornamented by a series of tubercles centered on tesserae, the latter composed partly from galeaspedin, and partly from a capping layer of microspherulitic, acellular bone, similar to the limiting layer of bone of elasmoid scales. Neither dentine nor enameloid is present, nor do the tissue compositions or their arrangement indicate an odontogenic origin.

The endoskeleton is composed of an outer zone of globular calcified cartilage in contact with the dermoskeleton through a poorly mineralized intermediate zone. The inner zone is finely laminated, resulting from progressive zones of calcification embracing the calcospherites in a direction away from the dermoskeleton. There is no persuasive histological evidence for the presence of appositional perichondral bone. As in osteostracans, the galeaspid endoskeleton is interpreted as an expanded neurocranium. However, the presence of a calcified cartilaginous neurocranium in galeaspids in the absence of a perichondral bone layer indicates that these two histogenic components have distinct evolutionary origins. The presence of perichondral bone is a synapomorphy of osteostracans and jawed vertebrates, while the presence of a mineralized neurocranium unites galeaspids to this clade (possibly also including pituriaspids).

The semionotid Lepidotes piauhyensis Roxo and Löfgren, 1936, is redescribed on the basis of original and new material obtained from the Pastos Bons Formation, ?Upper Jurassic–Lower Cretaceous of the Parnaíba Basin, in northeastern Brazil. The species is a hump-backed semionotid reaching about 480 mm standard length. It exhibits, among other characters: dermal bones of the skull roof and circumorbital series densely ornamented with tubercles, suborbitals disposed in a single row, moderately developed crushing dentition, a bony lamina on the ventral portion of the anterior ceratohyal, a complete dorsal scale row, and smooth ganoid scales of lepisosteoid type. The analysis of well preserved specimens allows the description of anatomical structures previously unknown for the species, particularly of the hyoid arch and suspensorium. Some of these structures are comparable to those of the Jurassic species Lepidotes gloriae Thies, 1989 (Cuba), Lepidotes elvensis (Blainville, 1818) (Europe), and Lepidotes lennieri Sauvage, 1893 (Europe).

A new species of menid fish, †Mene purdyi, is described from northwestern Peru. A Paleocene age (late Thanetian) is estimated for the specimen based on biostratigraphic analysis of planktonic foraminifers recovered from the surrounding matrix. Possible explanations for discrepancies between this result and previous interpretations of an Oligocene age are explored. Stable isotopic analysis of foraminifers associated with the fossil allows for general characterization of the thermal profile of the depositional environment. The small temperature gap between distinct depth-ecological foraminifer assemblages inferred from δ¹⁸O values indicates a low vertical temperature gradient, possibly reflecting a depositional environment dominated by upwelling. Although incomplete, the three-dimensional preservation of this specimen allows for detailed description of much of the skull, the first two vertebrae and the posttemporals. Numerous characters distinguish the new taxon from previously described menids, the most conspicuous being its exceptionally large size. Comments on the relationships of this new taxon to other menid fishes are premature until the osteology of fossil and living forms are better documented. Extinct species are briefly reviewed in order to facilitate future studies of Menidae. An examination of the distribution of fossil menids reveals that the group was once widespread, demonstrating a circum-global pattern during much of the Tertiary, consistent with the historical Tethys.

A fossil turtle skull (ZISP PH 1/17) from the Late Cretaceous (upper Turonian, Bissekty Formation) of Dzharakuduk (Uzbekistan, Asia) was used to score the skull characters for the genus Lindholmemys (a stem testudinoid) in a recent phylogenetic analysis. A description of ZISP PH 1/17 and a new cladistic analysis reveals no characters to support its referral to Lindholmemys elegans or to the stem-testudinoid lineage. ZISP PH 1/17 is very similar to North American Adocus, differing mainly in characters of the upper jaw. Therefore, we hypothesize that ZISP PH 1/17 is the skull of either Shachemys ancestralis or “Adocus” aksary, adocid shell taxa from Dzharakuduk. Pending additional discoveries and description of turtles from Dzharakuduk, we refer ZISP PH 1/17 to Adocidae, gen. et sp. indet.

A nearly complete but badly crushed elasmosaurid plesiosaur skull is described from the Upper Albian Toolebuc Formation of northern Queensland, Australia. The specimen has a long history, being previously referred to the Australian Aptian genus ‘Woolungasaurus’ (considered a nomen dubium), as well as provisionally to Elasmosauridae gen. et sp. nov., and most recently to Tuarangisaurus (Campanian-Maastrichtian, New Zealand and potentially Patagonia). The present assessment alternatively proposes assignment to a new taxon, Eromangasaurus carinognathus, gen. et sp. nov., uniquely characterized by the presence of seven premaxillary teeth (three lateral pairs, one midline), an elongate mandibular symphysis with prominent ventral midline keel, and a combination of osteological features variably developed in other elasmosaurids. Cladistic analysis using 43 discrete cranio-dental and vertebral characters coded for 16 ingroup and one outgroup taxon supports this conclusion, indicating that E. carinognathus is a crown-group elasmosaurid of more derived grade than Occitanosaurus (Lower Jurassic, Toarcian, France). Affinities with other Cretaceous elasmosaurids are poorly resolved. Nevertheless, a close relationship with Tuarangisaurus is not substantiated; instead, E. carinognathus forms a discrete clade with Terminonatator (Campanian, Canada).

The cranial osteology of many prosauropod dinosaurs remains poorly described, hampering broader systematic studies of basal sauropodomorph interrelationships. Here, we present a detailed re-description of the skull of Lufengosaurus huenei Young, 1941a, from the Lower Lufeng Formation (Lower Jurassic) of China. Lufengosaurus can be diagnosed on the basis of four cranial autapomorphies (the presence of bony bosses on the ascending process of the maxilla, the jugal, and the rostrolateral wing of the parietal, and the presence of a ridge on the lateral surface of the maxilla) and distinguished from all other prosauropods by a unique combination of cranial character states. Previous suggestions that Lufengosaurus is congeneric with either Massospondylus or Yunnanosaurus are rejected on the basis of craniodental evidence. Comparison with published character codings for Lufengosaurus reveals numerous discrepancies that are demonstrated to affect the phylogenetic position of the genus and patterns of sauropodomorph interrelationships.

Three taxa of small-bodied ornithischian dinosaurs have been described from the Middle Jurassic (Lower Shaximiao Formation: ?Bajocian) locality of Dashanpu, Sichuan Province, People's Republic of China. The taxonomy of these animals (Yandusaurus multidens, Xiaosaurus dashanpensis, and Agilisaurus louderbacki) has become highly confused, with many conflicting opinions regarding the validity of each species and the possible synonymies that might exist between them and other ornithischian taxa from both China and North America. Following re-examination of the relevant material, we propose that all three of the Dashanpu small ornithischians represent valid taxa, each of which can be diagnosed on the basis of at least one autapomorphy. In addition, these taxa can be distinguished from each other by a large number of cranial, dental, and postcranial character states. We demonstrate that ‘Yandusaurus’ multidens is not congeneric with either Y. hongheensis or any other taxon, and therefore propose the new generic name Hexinlusaurus for the reception of the species 'Y.' multidens. Consideration of the character states present in Hexinlusaurus, Agilisaurus, and Xiaosaurus shows that these taxa are not basal euornithopods ('hypsilophodontids'), as had been suggested by the majority of previous authors, but represent more basal ornithischians. Hexinlusaurus and Agilisaurus can be regarded as Genasauria incertae sedis, whereas Xiaosaurus can only be recognized as Ornithischia incertae sedis on the basis of current data.

Here we redescribe the holotype and only specimen of Segisaurus halli, a small Early Jurassic dinosaur and the only theropod known from the Navajo Sandstone. Our study highlights several important and newly recognized features that clarify the relationships of this taxon. Segisaurus is clearly a primitive theropod, although it does possess a tetanuran-like elongate scapular blade. Nonetheless, it appears to be a coelophysoid, based on the presence of a pubic fenestra, a long and ventrally curved pubis, and some pelvic (and possibly tarsal) fusion. Segisaurus does possess a furcula, as has now been observed in other coelophysoids, thus strengthening the early appearance of this ‘avian’ feature. The absence of an external fundamental system in bone histology sections and the presence of sutural contact lines in the caudal vertebrae, scapulocoracoid, and (possibly) between the pubis and ischium support the inference that this specimen is a subadult, neither a true juvenile nor at full skeletal maturity. A cladistic analysis confirms Segisaurus as a coelophysoid theropod. Poor resolution within Coelophysoidea makes speculation about evolution in this clade difficult, but Segisaurus apparently represents a lineage that had been distinct from Coelophysis and Syntarsus since at least the Carnian.

The osteology of the postcranial skeleton of the holotype of Dubreuillosaurus valesdunensis (Allain, 2002) from the Middle Jurassic Calcaires de Caen Formation (Bathonian) is described here. In addition to previous phylogenetic analyses, characters of the caudal vertebrae show that Dubreuillosaurus, gen. nov., is distinct from Poekilopleuron. Some features of Dubreuillosaurus are unique among Spinosauroidea, including the medioventrally directed femoral head and the convex anterior surface of the distal end of the femur. A re-examination of the observations made by Eudes-Deslongchamps on Poekilopleuron suggests that megalosaurids were piscivorous to a certain extent.

Acrocanthosaurus atokensis, a large carcharodontosaurid theropod, is known from several specimens collected in the 1990s, as well as the two original specimens collected in the 1940s. The holotype, OMNH 10146, contains a well-preserved and complete braincase that was scanned at the High Resolution X-ray Computed Tomography (CT) Facility at The University of Texas at Austin. The resulting images were manipulated using graphics and volume rendering programs to produce a complete digital endocast of the endocranial cavity. The images reveal all of the cranial nerves except for the vestibulocochlear nerve. Also visible are: (1) the pituitary fossa; (2) the fenestra ovalis; (3) the entrance of the internal carotid arteries; (4) all three semicircular canals; and (5) several smaller arteries and veins. This complete endocast allows for: (1) the description of the previously undescribed endocranial cavity of Acrocanthosaurus; (2) determination of skull orientation using the semicircular canals; and (3) comparisons with closely related taxa such as Carcharodontosaurus, Giganotosaurus, Allosaurus, and Sinraptor. The comparisons can consist not only of characters that can be seen in the braincase and endocast, but also of quantitative, volumetric measurements that are available through the volume rendering program used to create the endocast. These comparisons uphold the proposed relationships of Acrocanthosaurus being within the clade Carcharodontosauridae and the sister taxon to Carcharodontosaurus, and allow for new characters to be applied to the data matrices used to determine the relationships.

Tyrannosaurus rex possesses a heterodont dentition composed of three classes (premaxillary, maxillary, and dentary) and several sets. The maxilla contains mesial and distal sets and the dentary contains first dentary tooth (d1), mesial, and distal sets. Teeth were described with four size and two shape variables and several variables describing crown curvature and denticle size. The premaxillary teeth are derived structures with labiolingually oriented long axes, moderate mesial curvature, and mesiolingually and distolingually placed carinae that extend down the lingual faces. The mesial maxillary crowns are large, basally rounded, and moderately curved with mesiodistally oriented long axes. The mesial carinae begin at the apices and curve lingually to about the midcrown point and the distal carinae begin at the apices and extend down the labial sides of the distal faces. The distal maxillary crowns are larger than the premaxillary and smaller than the mesial maxillary and all but the most distal dentary teeth. They have labiolingually oriented long axes and have narrower basal widths than lengths. The carinae roughly define the mesiodistal axes of the crowns. The first dentary tooth is similar to those of the premaxilla. The mesial dentary teeth are similar to the mesial maxillary teeth and the distal dentary teeth are similar to those in the distal maxilla. This examination revealed that several putative systematic characters related to size and shape can be discerned from T. rex teeth, suggesting that useful dental characters may be more common within the Theropoda than has generally been presumed.

New specimens of the unusual theropod Spinosaurus cf. S. aegyptiacus from the Late Cretaceous (early Cenomanian) of Morocco reveal new information about the structure of the snout and the very large adult body size attained by the species. The external naris is retracted farther caudally on the snout than in other spinosaurids and is bordered exclusively by the maxilla and nasal. The fused nasals preserve a longitudinal, fluted crest. The size of the snout suggests that Spinosaurus may well have exceeded the maximum adult body size of other large Cretaceous theropods such as Tyrannosaurus and Giganotosaurus. The new material also supports the monophyly of the Spinosaurinae and the separation of Spinosaurus and Irritator.

Recent field expeditions to Upper Cretaceous deposits within Grand Staircase-Escalante National Monument, southern Utah, have revealed a diverse dinosaurian fauna that includes a previously unknown oviraptorosaur theropod. Represented by a single partial specimen consisting of manal and pedal elements, this new taxon, Hagryphus giganteus, gen. et. sp. nov., is estimated to be 30–40% larger than the coeval oviraptorosaur Chirostenotes. The holotype consists of a nearly complete, articulated left manus, a partial, articulated pedal digit II, and a series of fragmentary pedal phalanges and distal metatarsals. Several autapomorphies are present in the manus, related primarily to proportional differences in metacarpals and phalanges. Previous finds of North American oviraptorosaurs have been restricted to Alberta, Montana, and South Dakota. The discovery of this new specimen from southern Utah greatly expands the known geographic distribution of these theropods, nearly doubling the previously documented range of North American oviraptorosaurs.

Superbly preserved skeletal elements of the new taxon Oromycter dolesorum from the Lower Permian deposits in the Dolese Quarry, near Richards Spur, Oklahoma, record the earliest known evidence of a member of Caseidae. Although found as isolated elements, there is strong circumstantial evidence that the maxillae, premaxillae, lacrimal, and dentary belonged to a single individual. Isolated axial and appendicular elements from this locality are also tentatively attributed to this new form.

Caseasaur autapomorphies of Oromycter include the presence of the premaxillary rostral process, indirect evidence for an external shelf on the nasal, and lateroventrally tilted external maxillary surface. Caseid autapomorphies include the anterodorsally oriented maxillary process, the short, tall lacrimal, typical caseid ornamentation on the lacrimal, procumbent anterior dentition, largest teeth located anteriorly on each bone, and spatulate, lingually curved marginal dentition. However, the available evidence indicates that Oromycter is a sister taxon to all other caseids because it lacks the leafy serrations on the teeth, has a relatively long lacrimal bone, has a larger number of marginal teeth than most other caseids, lacks an external narial shelf on the maxilla while one is poorly developed on the lacrimal. The presence of this early, basal member of the Caseidae at the Dolese Quarry is consistent with the hypothesis that the initial evolutionary history of this group of herbivores occurred away from the typical deltaic, floodplain depositional environments that preserve the majority of the known Permo-Carboniferous terrestrial vertebrate communities.

We describe new material of the insectivoran genus Centetodon and discuss its anatomy and relationships in the context of recently developed hypotheses of mammalian phylogeny. Centetodon shows characters common among insectivoran-grade placental mammals, such as an expanded maxillary contribution to the orbital mosaic and relatively small optic foramina. Additional characters such as an enlarged piriform fenestra and a ventrally convex plane of the alveolar maxilla support its position in a clade with extant Holarctic insectivorans (i.e., erinaceids, Solenodon, soricids, and talpids). Our analysis of a combined genetic-morphological matrix supports the recently proposed hypothesis that Solenodon is the basal-most member of a clade of Holarctic insectivorans, including Centetodon and excluding African tenrecoids. Even though DNA sequences are missing for this and most other extinct taxa, they nevertheless help to identify its phylogenetic relationships by better resolving the clades of extant taxa to which it is related. DNA sequences can also influence the topology of fossils by altering the optimization of morphological characters that are known for extinct taxa. The extent of anatomical convergence in Holarctic and African clades of insectivoran-grade mammals is considerable; nevertheless there are diagnostic features that can help determine the affinities of fossil insectivorans with one of these clades.

During mammalian evolution the simple radial enamel, where prisms follow a straight course from the dentin-enamel junction to the tooth surface, gave rise to the typical arrangement of layers of prisms forming Hunter-Schreger bands (HSB). The formation of HSB is believed to have improved the physical properties of enamel. The pattern of HSB has been used to infer relationships between feeding habits and enamel structure. The evolution of enamel structure in the South American faunas is poorly known. Most studies have relied mainly on fossil teeth of Europe and North America mammals, and the majority of the taxa studied are from the Eocene or younger ages. In the present work the patterns of HSB in the enamel of herbivorous mammals from the Paleocene of the São José de Itaborai basin, Brazil were investigated. Vertical HSB were present in the teeth of large animals (first lower molar width >8 mm), while transverse HSB were present in taxa with first lower molar width ranging from 5.6 to 3 mm. The only exception was Lamegoia conodonta (first molar width = 10.3 mm). However, maybe to compensate for its larger size, in L. conodonta the transverse HSB were highly undulated. Our results indicate that the development of vertical HSB in large lophodont and bunolophodont herbivors may have occurred as a functional adaptation. Vertical HSB wear at a slower rate than transverse HSB, and this adaptation would enhance functional durability of enamel, extending the overall longevity of the teeth and the animal's life span.

The holotype of Sarmatodelphis moldavicus Kirpichnikov, 1954, is an incomplete skull and a cervical vertebra from the Bessarabian Stage (late middle to early late Miocene) of Kishinev, Republic of Moldavia. Sarmatodelphis moldavicus is confirmed as a small distinct species of kentriodontid (Cetacea: Odontoceti: Delphinoidea) in the subfamily Pithanodelphininae Barnes, 1985. The monotypic Sarmatodelphis has close affinities to the contemporaneous Atocetus Muizon, 1988a, but the Moldavian dolphin has less inflated nasals, and the maxillae reach the midline posterior to the nasals. Nasal bone morphology and posterior development of the maxilla separates S. moldavicus from all other named delphinoid genera.

We describe an associated skull and lower jaws of a new species of primitive skunk, Martinogale (subfamily Mephitinae), from the late Miocene Dove Spring Formation (late Clarendonian), Kern County, California. It is also the first occurrence of this genus in the Tertiary of the West Coast of North America. The new species is among the best-preserved primitive fossil skunks and represents one of the earliest members of the New World mephitines. As the smallest skunk so far known, the new Martinogale features some of the most primitive cranial and dental morphologies in mephitines. The new information permits a phylogenetic analysis of basal taxa from North America, which suggests a New World clade for all known fossil and living taxa from North and South America. We place this New World clade in a tribe (Mephitini) of its own. New World mephitines share the following derived characters: presence of a P4 parastyle, m1 hypoconid dominant in talonid, and presence of a lingual cingulum on lower canines. We further postulate that New World skunks are the result of a single immigration event, and the new California skunk is close to the origin of the New World skunks.

Two problems are examined in this paper: (1) the identification of flying squirrels in the fossil record by means of their teeth; and (2) the identification of features of the limbs that indicate that the animals were gliders. Dental features vary widely among flying squirrels and among other squirrels, and a thorough survey demonstrates that most features that have been used to distinguish fossil flying squirrels are also found in some tree squirrels. A review of the descriptions of fossil flying squirrels reveals few convincing arguments that these animals actually belong to the Pteromyini and none to support the hypothesis that they were gliding animals. Recent flying squirrels exhibit a number of distinguishing morphological features in their carpal and tarsal bones and at the proximal and distal ends of their long bones. Some of these morphological structures are obligatory features required for gliding locomotion in squirrels and hence are diagnostic of flying squirrels.

New dental specimens described here from the Barstovian CC South and Flint Creek localities of western Montana are determined to be of two geomyid rodent species, Lignimus transversus and Mojavemys sp. These species were known previously from sparse material and the new samples aid the clarification of their biogeography and evolution. The presence of Lignimus transversus at both localities extends the range of that species to the north. In Mojavemys, a cline of increasing tooth size from south to north is analogous to clines in extant geomyids that correlate with nutritional or climatic gradients. Comparisons of various dental morphologic features of the new material and of the previously described populations of both genera reveal that the examined traits as well as the populations themselves were not genetically linked, and suggest mosaic evolution operated in these species. The differences in dental morphology between the various depositional basins are consistent with the idea of a tectonic influence on mammalian evolution.