For the first time, systematic treatment of the ultrasculpture on the exoskeleton of Palaeozoic Agnatha (Thelodonti, Heterostraci, and Osteostraci) is given, supplemented with a discussion of the main published sources on Gnathostomata, such as Acanthodii, Chondrichthyes, and Osteichthyes. Seven main types of ultrasculpture have been determined: (1) fine longitudinal striation; (2) transverse lamellae; (3) short V-shaped slits and branching grooves; (4) polygons separated by walls; (5) polygons separated by intercellular grooves; (6) micronodules; and (7) microtubercles. Five of these types occur on the scales of thelodonts. No ultrasculpture has been found on sandiviiform and loganelliiform thelodonts, anaspids, some Ordovician taxa, and placoderms. A smooth surface might be the most primitive condition for the scale surface. Fine longitudinal striation, transverse lamellae, and polygons separated by walls are the features connected with enameloid tissue. Polygons separated by intercellular grooves may characterize both enameloid and enamel. Microtubercles (as has been shown earlier) characterize true enamel. All ultrasculpture types with certain different features occur in more than one higher taxonomic group. Among Thelodonti these types mirror the classification of the subclass into four higher-rank taxonomic groups. Relationships between thelodonts and chondrichthyans based on ultrasculpture characteristics are much more complicated than previously discussed. Four types of ultrasculpture, found among thelodonts, occur also on the scales of chondrichthyans and/or putative chondrichthyans. Different ultrasculpture types might also point to the polyphyletic nature of the Thelodonti.

The claim that the Carboniferous chondrichthyan genus Cladodus Agassiz, 1843, is a nomen vanum is critically examined. The teeth of C. mirabilis, the type species of the genus, are re-examined from Agassiz's syntypes and other material. It is concluded that C. mirabilis offers a suite of characters adequate for definition of the genus Cladodus. Comparison of the teeth of Cladodus with those of other Carboniferous shark genera confirms its status as a valid taxon. From this revision it is concluded that C. marginatus, C. vanhornei, C. bellifer, and C. elegans should all be included within Cladodus, while C. striatus Agassiz is placed in the new genus Saivodus. Both Cladodus and Saivodus are considered to belong in the Ctenacanthiformes.

The Lumbrera Formation is the uppermost unit of the Santa Bárbara Subgroup of the Salta Group, exposed in northwestern Argentina. It consists of fine clastic sediments of characteristic brick red color with an intercalation of green mudstone levels, which are called Faja Verde. The specimen described here was collected from the middle part of the Faja Verde II at the Alemania locality in sediments dated as Eocene. The material comprises a specimen, preserved as part and counterpart, which is assigned to a new genus and species: Proterocara argentina, gen. et sp. nov. The phylogenetic analysis to establish its position within Cichlidae was based on a matrix with 51 taxa and 91 characters. The most parsimonious tree shows P. argentina as sister group of the clade formed by the subfamilies Cichlasomatinae and Geophaginae based on three characters: articulating process of premaxilla moderately distinct, first hemal arch on last abdominal vertebra, and 13–14 pectoral-fin rays. Two autapomorphies are recognized for P. argentina: ascending arm of premaxilla as long as dentigerous arm, and dorsal lateral line on caudal fin between caudal rays D2 and D3. Extant members of the family Cichlidae live mostly in lentic freshwater bodies, corroborating the lacustrine paleoenvironment assigned to this formation.

Remains from the Upper Devonian (Famennian) of Belgium attributed to an early ‘amphibian’ during the nineteenth century are reviewed. This putative tetrapod material is identified here as a rhynchodipterid lungfish, possibly Soederberghia, a genus previously known from the Upper Devonian of East Greenland, Pennsylvania, and Australia. Newly discovered material from Belgium is also attributed to this large, cosmopolitan lungfish genus. Remains attributed to ?Jarvikia, another long-snouted dipnoan from East Greenland, have also been recovered from Famennian strata in Belgium. These occurrences provide additional evidence for paleobiogeographical links between Greenland and the central southern coast of the Euramerican continent during the Late Devonian.

More data are provided on the recently described temnospondyl Iberospondylus schultzei from the Upper Carboniferous (Stephanian C) of the Spanish Puertollano Basin. It represents the only known occurrence of a Paleozoic stegocephalian in a Spanish basin. This taxon appears to be more closely related to eryopoids and dissorophoids than to edopoids, as shown by four synapomorphies. However, decay index and bootstrap analyses show that the presented phylogeny, like other recently published phylogenies of temnospondyls, is not robust. Recently published phylogenetic data do not resolve the position of Dendrerpeton in temnospondyl phylogeny. Iberospondylus appears to have lived in the coastal marine environment in which it was preserved. The Spanish material supports the suggestion that the temnospondyls were sometimes coastal, near-marine animals. The widely held idea that many temnospondyls possessed a tympanum is poorly documented; the stapes of this group is always more massive than that of similarly-sized extant tetrapods that possess a tympanum. Other arguments presented to support the presence of a tympanum in temnospondyls appear to be invalid. Therefore, the widely held thesis that a tympanum was present in temnospondyls is questioned.

A new paracryptodiran turtle, Arundelemys dardeni, gen. et sp. nov., is described on the basis of an isolated, nearly complete skull from the Early Cretaceous Arundel Clay facies of Maryland, USA. The basicranial region exhibits the paracryptodiran condition of a single foramen for the canalis caroticus internus located midway along the basisphenoid. As revealed by CT scans, the basicranial region of Arundelemys is unusual in that the right and left canales carotici interni merge just before reaching the sella turcica and the canalis caroticus lateralis is very small or absent. A phylogenetic analysis places Arundelemys dardeni as the basal-most member of the Paracryptodira. Within the Paracryptodira, Arundelemys dardeni is most similar to Compsemys victa in general proportions.

A new aetosaur, Tecovasuchus chatterjeei gen. et sp. nov., from the Upper Triassic (middle or upper Carnian) Tecovas Formation of Texas is described, based primarily on osteoderms from several individuals. The diagnosis is based on a unique suite of osteoderm characters: very wide dorsal paramedian osteoderms; a low, keel-shaped dorsal boss on the dorsal paramedians that does not reach the posterior margin of the osteoderm; a strut on the ventral surface of the dorsal paramedians; ornamentation on the dorsal paramedians with both deep pits and fainter radiating grooves; a unique strongly thickened and beveled posterior edge on the dorsal paramedians; a prominent raised anterior bar on both the dorsal paramedian and lateral osteoderms; lateral osteoderms with dorsoventrally flattened, posteriorly excavated horns, reduced, tongue-like dorsal flanges, and larger, plate-like ventrolateral flanges. The low number of diagnostic criteria for identifying aetosaur osteoderms results in mandatory splitting at the generic level. Some specimens of Tecovasuchus have been misidentified previously as Paratypothorax, suggesting that shoehorning osteoderms into previously recognized taxa may conceal greater taxonomic diversity among aetosaurs than has generally been appreciated. Specimens with multiple osteoderms assignable to a single individual are important in naming and characterizing new aetosaur taxa, and at least one complete osteoderm is usually necessary when assigning specimens to pre-existing taxa.

The binocular fields of view of seven theropod dinosaurs are mapped using sculpted life reconstructions of their heads and techniques adopted from ophthalmic field perimetry. The tall, narrow snout and laterally facing eyes of the allosauroids Allosaurus and Carcharodontosaurus restricted binocular vision to a region only approximately 20° wide, comparable to that of modern crocodiles. In contrast, the coelurosaurs Daspletosaurus, Tyrannosaurus, Nanotyrannus, Velociraptor, and Troodon had cranial designs that afforded binocular fields between 45–60° in width, similar to those of modern raptorial birds. Binocular field width and predatory style (ambush versus pursuit) is examined for extant taxa, along with a discussion of cranial adaptations that enhance binocular vision. The progressive increase in frontal vision in the tyrannosaurids culminates in broader binocular overlap than that of a modern hawk. The visual acuity and the limiting far point for stereopsis is estimated for Tyrannosaurus based on reptilian and avian models.

The basal therapsid clade Burnetiamorpha is currently known from six genera of Middle-to-Late Permian age. Bullacephalus, Burnetia, Lemurosaurus, and Lobalopex are from the Beaufort Group of South Africa, whereas Niuksenitia and Proburnetia are from Russian deposits. Here we describe a new taxon from the Upper Permian Teekloof Formation of South Africa that is remarkably similar to Proburnetia. Paraburnetia sneeubergensis, gen. and sp. nov., is diagnosed by the following autapomorphies: supratemporal ‘horn’ oriented vertically with bulbous terminal end, supra-orbital boss with well-defined apical crest, and palatine-pterygoid boss elongate. Paraburnetia and Proburnetia share features indicating a sister-taxon relationship, including the presence of a well-developed median nasal crest and tall supraorbital bosses. Along with the close morphological similarity and phylogenetic relationships of several dicynodont taxa from Russia and South Africa, the discovery of Paraburnetia indicates that long-distance, north-south interchange was commonplace during the Late Permian and that burnetiamorphs likely had a Pangean distribution.

The Italian fossil baleen whale Aulocetus sammarinensis Capellini, 1901, represents a new genus, Titanocetus. The holotype skull of Titanocetus sammarinensis has a long ascending process of the maxilla, a wide and flat rostrum, a triangular interorbital region of the frontal, an anteriorly extended apex of the zygomatic process of the squamosal, and an anteriorly rounded, concave supraoccipital. Features primitive for mysticetes include strong bulging of the squamosal and parietal into the temporal fossa, a lambdoidal crest posterior to the occipital condyles, and a marked intertemporal constriction involving the parietals. Archaeocete-like features are the round anterior process of the supraoccipital and nasals that are transversely constricted anteriorly. These and other features suggest that Titanocetus sammarinensis represents an early-diverging baleen-bearing mysticete probably related to Cetotherium-like taxa.

Recent fossil discoveries of early cetaceans and sirenians document the functional transitions that occurred as each group adapted to a completely aquatic existence, but the timing and path of their ecological transition remain uncertain. We analyzed the stable-isotope composition of tooth enamel from several early members of each group to reconstruct the dietary, foraging, and habitat preferences of basal taxa. Carbon isotope (δ¹³C) values provided evidence of foraging within freshwater, terrestrial, and marine environments, including seagrass beds, whereas oxygen isotope (δ¹⁸O) variation was used as a measure of commitment to aquatic habitats. Enamel samples were collected from four regions (south Asia, north and west Africa, and southern Europe) spanning the late early Eocene (ca. 53.5 Ma) to the late Eocene (ca. 36 Ma). Sirenian and cetacean taxa included species that were likely capable of some terrestrial locomotion, and more specialized forms that were morphologically fully aquatic. Cetacean δ¹³C and δ¹⁸O values indicate that some early members of this group (some pakicetids) inhabited freshwater environments, but later members (e.g., remingtonocetids, protocetids, and basilosaurids) moved quickly into estuarine and marine environments. Low δ¹⁸O variation confirms that all of these early forms were primarily aquatic, but δ¹³C and δ¹⁸O values for early sirenians indicate an early transition to a marine seagrass diet without any evidence of an intermediate connection to freshwater habitats.

The arvicoline rodent Microtus is represented in the Irvington fauna by 72 specimens. The majority of these are isolated molars. Lower first molars are diagnostic and clearly identifiable as Microtus specimens with five closed triangles. No other arvicolines are present in the fauna. Morphological variation in the sample is present, but not extensive. Morphological features permitting species-level identification are lacking, and no species assignation can be supported with the available data. Changing perspectives on Pleistocene biochronology and reinterpretation of several purported early records of Microtus indicate that the Irvington specimens of Microtus with five closed triangles are among the oldest recorded in North America. Chronological control is limited to paleomagnetic data that reveal that the Irvington fauna dates to somewhere between 0.78 Ma and somewhat older than 1.21 Ma. The uncertainty cannot be reduced based on current understanding of the taxonomic affinity and known temporal extent of other mammals from Irvington.

The northernmost records of early Eocene brontotheres, fossils of cf. Eotitanops and Brontotheriidae gen. et sp. indet., are described here from late Wasatchian-aged strata of upper parts of the Eureka Sound Group on central Ellesmere Island (∼79°N). Although the fossils were initially tentatively identified on faunal lists as Lambdotherium, their larger size and dental morphology ally them more closely to mid-latitude Eotitanops and Palaeosyops. The Ellesmere Island specimens are dentally most similar to mid-latitude Eotitanops, but can be distinguished from the latter by derived characters on their premolars that are shared with the younger (i.e., Bridgerian) Palaeosyops. The presence of brontotheres in early Eocene strata on Ellesmere Island implies that the group's evolution was well underway early in its history at northern high latitudes, and is consistent with either an Asian or North American origin and trans-Beringian dispersal. While cf. Eotitanops from Ellesmere Island appears dentally too advanced to be ancestral to mid-latitude co-eval Eotitanops, it may be a suitable ancestor to Palaeosyops. The presence of cf. Eotitanops on Ellesmere Island may reflect a high-latitude lineage that subsequently dispersed to mid-latitudes during early middle Eocene (Bridgerian) time.

A new species of hegetotheriid notoungulate, Hemihegetotherium trilobus, is described from the middle Miocene (Laventan SALMA) Quebrada Honda Fauna of southern Bolivia. It differs from all previously described hegetotheriines in possessing a distinctly trilobed m3, a character state previously recorded only in pachyrukhine hegetotheriids. It further differs from other species of Hemihegetotherium in having a proportionately larger p2 and in overall size (being smaller than H. achataleptum and larger than H. torresi). A phylogenetic analysis of hegetotheriid genera coded for 26 characters supports referral of this species to Hemihegetotherium, but does not support the monophyly of Hegetotheriinae; the monophyly of Pachyrukhinae (including Prosotherium and Propachyrucos) is strongly supported. The resulting tree suggests that the lack of tibiofibular fusion in Oligocene pachyrukhines is a secondarily derived trait, but additional postcranial data are needed to provide a stronger test of this hypothesis.

Hemihegetotherium trilobus is the most abundant ungulate at Quebrada Honda and is the only species of hegetotheriid present. This contrasts with most other South American paleofaunas in which pachyrukhines are more common than hegetotheriines (e.g., Arroyo Chasicó) and/or other small notoungulates are more common than hegetotheriids (e.g., Chucal, Nazareno). Although the absence of pachyrukhines at Quebrada Honda may be due to a lack of suitable habitat, it is also possible that pachyrukhines had not dispersed north to southern Bolivia by the middle Miocene. Further investigations of Quebrada Honda may help discriminate between these two alternatives and should also help clarify the biogeographic histories of other Miocene taxa.

Discoveries of three species of Eocene sirenians in District Kachchh, State of Gujarat, India, are reported. A species of the protosirenid Protosiren is represented by cranial and postcranial material, and the halitheriine dugongid Eosiren is represented by a poorly preserved mandible. Neither of these can be identified at the specific level. A new species of haltheriine dugongids is described: Eotheroides babiae, n. sp. The species is based on a lower jaw with teeth. Another new fossil sirenian is reported from the Oligocene (Chattian) Maniyara Fort Formation. The new species, Bharatisiren indica, n. sp., is based on a well-preserved skull, mandibles, and several postcranial specimens. Bharatisiren is a basal dugongine dugongid, close to previously described Bharatisiren kachchhensis and possibly near the origin of the modern genus Dugong.

Fossil crania from the late middle or early late Miocene (ca. 12–10 Ma) Ichibangawa Formation, Hokkaido, northern Japan, are described as a new genus and species of the archaic odobenid, Pseudotaria muramotoi, gen. et sp. nov. Pseudotaria muramotoi is characterized by having a dorsoventrally thick, posterolaterally expanded pterygoid strut, bony tentorium appressed to the petrosal (odobenid synapomorphies), double-rooted M1, reduced pseudosylvian fossa, and transversely arched palate (basal odobenid synapomorphies), and by retention of double-rooted premolars, except the P1. A phylogenetic analysis reveals that P. muramotoi possesses basal odobenid synapomorphies but lacks synapomorphies of the later diverging odobenids, and therefore, the taxon is nested in the paraphyletic stem group within the Odobenidae. The analysis also indicates that P. muramotoi might be viewed as a metataxon that shows the least modified condition in the transformation series to the later diverging odobenids.

A postcranial skeleton of the viverravid carnivoran, Viverravus acutus from the early Eocene of Wyoming, is described and compared to contemporary carnivorans (the viverravid Didymictis, and the miacids Miacis and Vulpavus), and to extant taxa belonging to the families Mustelidae, Procyonidae, Canidae, Viverridae, and Herpestidae. Based on humeral and femoral midshaft diameters, body mass for this animal is estimated to have been about 250 g, less than all but a few living species of Carnivora. Shoulder and hip morphology indicate a considerable range of motion and the structure of the humeroulnar joint suggests habitually flexed postures, characteristics typical of extant carnivorans that are excellent climbers. These similarities are also shared with miacids, supporting the hypothesis that basal members of the order Carnivora were well adapted for exploiting arboreal habitats. An astragalus tentatively attributed to the middle Eocene species Viverravus gracilis, however, is similar to that of Didymictis and suggests a greater emphasis on terrestrial locomotion than is found in miacids.

A medium-sized, counterclockwise spiral-horned antelope from the late Miocene (Turolian) locality of Perivolaki, Greece, is described and compared with several late Neogene and Quaternary taxa from Eurasia. The new form can be distinguished in several cranial and horn-core features and is the basis of a new genus and species: Pheraios chryssomallos. Pheraios is characterized by a flat cranial roof smoothly angled on the face, wide nasals, raised frontals, relatively long face, wide and low occipital facing posteriorly, low-crowned teeth, large premolars, and weakly twisted, very openly spiraled, and strongly laterally divergent horn-cores. Cladistic analysis based on 46 cranial features supports the close relationship of Pheraios to the African tragelaphins. Interpretation of the characters in comparison with fossil and extant Tragelaphini leads us to recognize Pheraios as a late Miocene tragelaphin stem taxon, necessitating a discussion of the origin and biogeography of this predominantly African group. We suggest that the common ancestry of Pheraios and of African tragelaphins occurred before 8 Ma, outside Africa.

The first North American mammals of definite Santonian age are described from the John Henry Member of the Straight Cliffs Formation of the Grand Staircase-Escalante National Monument of southern Utah. The fauna includes the oldest documented record of the multituberculates Mesodma (Mesodma sp., cf. M. minor and Mesodma sp.), the Cimolomyidae (?Cimolomys sp.), the tribotheres Potamotelses sp., Picopsis sp., and the marsupial Varalphadon sp. Also present in the fauna is the multituberculate Cimolodon foxi (formerly only known from the Judithian), other cimolodontids (Cimolodon spp., ?Cimolodon sp.), Cedaromys sp., cf. C. hutchisoni, Cedaromys sp., the symmetrodont Spalacotheridium sp., and the marsupials Alphadon sp., cf. A. halleyi, and a stagodontid(?). The fauna has close affinities with the fauna of the Milk River Formation of Alberta, Canada, and may indicate that the Milk River fauna is of latest Santonian age rather than early Campanian.

A partial skull from the early Eocene London Clay of the Isle of Sheppey, England, is referable to the gavialoid clade Eosuchus, otherwise known from the late Paleocene of continental Europe and North America. It differs slightly from Paleocene forms, but there is insufficient material on which to base a new species. This extends the range of Eosuchus beyond the Paleocene and represents the first unambiguous occurrence of a gavialoid in the early Eocene.

We examined the feeding strategy of the extinct hypsodont antilocaprid Stockoceros onusrosagris through an analysis of tooth mesowear and microwear and compared it to available data on the extant pronghorn Antilocapra americana. The mesowear pattern of both pronghorns is very similar. Molar teeth display relatively sharp apical cusps with slightly rounded extreme tips characteristic of a relatively low-abrasion diet. While S. onusrosagris displays a slightly more abrasive mesowear pattern than A. americana, the difference is not statistically significant. Microwear analysis, however, firmly places S. onusrosagris with extant mixed feeders, while A. americana has microwear typical of extant browsers. Our observations suggest that S. onusrosagris incorporated more grass in its diet than the modern pronghorn and browsed and grazed on a regional or seasonal basis. The fact that the mesowear pattern in S. onusrosagris shows relatively little abrasion may suggest that grasses taken may have been C3 grasses. Results of this study may shed light on the extreme hypsodonty seen in the modern pronghorn despite the fact that it consumes relatively soft food items.