The articulated acanthodian Gyracanthides murrayi Woodward from the Lower Carboniferous of Mansfield, Victoria, Australia, is redescribed from original and newly aquired material. It includes the only known head region from a member of the Gyracanthidae. A new reconstruction and interpretation of the pectoral area are proposed, incorporating the elements from the original description as well as a new bone interpreted as a procoracoid attached to a prepectoral spine. The posterior free pectoral spine described by Woodward is reinterpreted as a scapulocoracoid. A subsequent reconstruction of the pectoral girdle which synonymised the anterior and posterior prepectoral spines is rejected. A clear difference in size and shape of the pectoral and pelvic fin spines is established. The morphology of the tubercular ornament of the paired fin spines is used to distinguish species of Gyracanthides. Gyracanthides murrayi had a covering of dermal polyodontodia with spinose crowns and a concave base with a central vascular canal opening.

The systematic position of the Gyracanthidae remains unclear, with the family retained within the Climatiiformes only on the basis of the broad-based, fin spines with nodose ornament.

We describe a new species of coelacanth, Miguashaia grossi sp. nov., recognized from isolated cranial, shoulder girdle bones and scales from the Upper Givetian Gauja and Lode Formations of two Latvian localities. This coelacanth, together with comparisons with other Devonian coelacanths, allows a more precise description of the plesiomorphic condition of the lower jaw, shoulder girdle, and palate. These plesiomorphic conditions are as follows. The dentary is shallow throughout, the articular-retroarticular is deep posteriorly where it is developed as two processes—one for the symplectic articulation and the other demarcating the posteroventral angle of the jaw. In the shoulder girdle plesiomorphic attributes include the large triangular clavicle, a cleithrum which is directed anterodorsally and possibly a large and polygonal extracleithrum. In the palate the pterygoid shows a dorsal process of unknown function mid-way along the dorsal margin and this is also a plesiomorphic feature of coelacanths.

Two nearly complete, articulated, mature specimens of the amphibian Seymouria are described from the Lower Permian Tambach Formation, lowermost unit of the Upper Rotliegend, of the Bromacker locality in the midregion of the Thuringian Forest near Gotha, central Germany. They are assigned to S. sanjuanensis, known elsewhere only from the Lower Permian deposits of Wolfcampian age in the southwestern United States. This confirms an earlier referral of two immature specimens from the same locality to this species. The new specimens are unusual in being highly ossified and allow for the first time a complete description of the carpus and tarsus of Seymouria.

The Bromacker Seymouria specimens are part of an assemblage that is unique among Lower Permian localities in Europe in its taxonomic composition and its depositional environment. The Bromacker vertebrate assemblage includes many taxa found elsewhere only in the Lower Permian of the United States. All are adapted to a highly terrestrial existence, and the herbivore Diadectes and a closely related diadectid yet to be described are the most abundant forms, accounting for over half the articulated specimens encountered. Carnivorous, pelycosaurian-grade synapsid reptiles are exceedingly rare.

Fossils at the Bromacker quarry were preserved near the center of a small, internally drained, Early Permian basin, the Tambach Basin. The vertebrates of this extraordinarily rich quarry are commonly excellently preserved, often complete and articulated, and occur almost exclusively in sheet-flood deposits that were almost certainly responsible for their death and burial with little or no transport; only minor attritional processes are evident. Relationships of the paleoenvironments and the biology of the vertebrates of the Bromacker locality based on the stratigraphy, paleontology, sedimentology, and basinal context of the Tambach Formation indicate that the Bromacker assemblage may represent the earliest known and best documented Early Permian example of a truly terrestrial “uplands” ecosystem. It apparently evolved and maintained itself independent of contemporary, water-based food chains that included aquatic and semi-aquatic forms.

A specimen of a juvenile individual of Dinochelys from the Dry Mesa Quarry, Morrison Formation, provides the first record of the skull and neck in this genus. Dinochelys is interpreted as related to Glyptops on the basis of a similar development of sculpture on the vertebral scutes of juvenile individuals, and a similar development of a beak on the premaxilla and dentary. Desmemys, a turtle from the Early Cretaceous of Europe is interpreted as closely related to Dinochelys on the basis of similarities in the proportions of the scutes of the carapace and similar development of fenestration on the carapace and plastron. The relationship between Desmemys and Dinochelys further emphasizes the connections between the turtle assemblages of North America and Europe during the Jurassic and Early Cretaceous.

Based primarily on two previously undescribed skulls, this paper presents a detailed description of the skull and mandible of the latest Triassic procolophonid reptile Hypsognathus fenneri Gilmore, 1928. One of the new skulls, belonging to a presumed juvenile, clearly establishes for the first time the sutural pattern, which differs significantly from that in Procolophon and more basal procolophonid taxa. A number of shared derived features in the structure of the skull and mandible indicate that Hypsognathus is closely related to Leptopleuron from the Upper Triassic Lossiemouth Sandstone Formation of Scotland. Hypsognathus had a wide geographic and stratigraphic distribution in eastern North America during the latest Triassic (Norian-Rhaetian).

A new platynotan lizard, Primaderma nessovi, gen. et sp. nov., from the Mussentuchit Local Fauna, Cedar Mountain Formation (Albian–Cenomanian) of Utah is unique in having a premaxillary process of the maxilla that forms a vertical flange and fine serrations on anterior and posterior edges of the maxillary teeth. Primaderma is the oldest-known terrestrial platynotan and phylogenetic analysis indicates that it is a member of Monstersauria, a clade of helodermatid-like platynotans. The teeth of Primaderma show several derived platynotan characteristics, but do not possess venom grooves. The distribution of this trait in fossil taxa is reassessed. Although a North American origin of helodermatid-like platynotans is likely, it is possible that Primaderma represents another example of an Asian influence on the North American Cretaceous fauna. As with similar taxa, Primaderma was likely highly predaceous, presumably taking vertebrate prey and it appears that helodermatid-like lizards have changed very little since the Albian–Cenomanian.

The type specimen of the enigmatic marine reptile Omphalosaurus is reexamined to test its postulated affinity with the Ichthyopterygia. Some of the specimens that have been assigned to the genus cannot be linked to the type specimen, and the rest fails to establish any of the basal ichthyopterygian synapomorphies in the genus. The similarities between the genus and some ichthyopterygians are either symplesiomorphies or common convergences; none of them are unique to the two. The genus also possesses characters that do not exist in any ichthyopterygians, such as a splenial jaw symphysis. Although the affinity of Omphalosaurus is inconclusive at this point, there is insufficient reason to prefer ichthyopterygians as its sister group among others.

A new skull of Saurosuchus galilei is described from a specimen collected at the base of the Upper Triassic Ischigualasto Formation in San Juan Province, Argentina. The skull of this taxon is described in detail and compared to those of other suchians. The poor ossification of the articular end of the quadrate, disarticulation of the braincase from the dermatocranium, and poor development of the suture between exoccipital and basioccipital in the skull of Saurosuchus indicate that the specimen was a juvenile. Possible cranial autapomorphies of Saurosuchus include: a thick, sculptured skull roof; reduced postfrontal; slender ventral projection of the lacrimal; lateral process of the posterolateral frontal; development of a crista on the dorsal supraoccipital; development of large lateral processes of the laterosphenoid; basal tuber wider than occipital condyle; and elongate anterior process of the coronoid.

Absence of an ossified calcaneum has been suggested as a synapomorphy of Diplodocidae and used to construct sauropod phylogenetic hypotheses. Restudy of sauropod material at the Carnegie Museum of Natural History revealed a diplodocid pes with an unknown ossified pedal element. The relatively complete pes, CM 30767, has been identified as Diplodocus. Comparisons with known sauropod calcanea, carpals, and phalanges, indicate that this element is a calcaneum. The presence of an ossified calcaneum in a diplodocid has important functional and systematic implications. Ossified calcanea may have helped to stabilize the pes during locomotion and assisted in the proper alignment and insertion of lateral plantar musculature. The unusual morphology and unreliable preservation of the sauropod calcaneum suggest that its presence or absence should not be used as a character state, nor should the absence of the calcaneum be used as a synapomorphy of Diplodocidae.

We report the well preserved skeleton of a small theropod dinosaur, Nqwebasaurus thwazi, gen. et sp. nov., from the Lower Cretaceous Kirkwood Formation of South Africa. Nqwebasaurus has an elongate three-digit manus with a partially opposable first digit, a long and slender pes with a highly reduced metatarsal IV, and preserves gastroliths (stomach stones) in its abdominal region. As a basal coelurosaurian, Nqwebasaurus pushes back the Gondwanan record of this derived group of tetanuran theropods approximately 50 million years. This confirms that coelurosaurians were present on the Gondwana supercontinent well before its main phase of fragmentation and supports the hypothesis that this clade could have achieved a global distribution early in their evolution. Nqwebasaurus is one of the most complete and best preserved Cretaceous theropods described thus far from Africa.

We here describe a near-complete dentition, partial rostrum, and associated lumbar vertebrae of the multituberculate mammal Cimexomys judithae, discovered on a dinosaur nest horizon at Egg Mountain, in Montana's Campanian Two Medicine Formation. This specimen confirms associations of isolated teeth made by previous authors and provides a wealth of phylogenetically useful information. A phylogenetic analysis including this specimen indicates that Cimexomys is diagnosed on the basis of primitive and widely distributed character states, is probably not monophyletic, and that C. judithae is more derived than other species of Cimexomys. Species of Cimexomys are too primitive to be included in the suborders Taeniolabidoidea or Ptilodontoidea, and are thus useful as outgroups in future analyses, but they must be scored separately to insure monophyly.

Leptotragulus, from the upper middle Eocene of North America, is the most plesiomorphic member of the Protoceratidae, an enigmatic group of selenodont artiodactyls. Until now Leptotragulus was known primarily from teeth, limb bones and a few skull fragments. A previously undescribed series of crania shows that Leptotragulus exhibits the typical protoceratid skull morphology, with a broad, flattened forehead, pronounced lambdoid crests enclosing a deep complexus fossa, and broad occipital condyles with a pronounced anteroventral margin. It is suggested that these features, which are suited to forms of agonistic, intraspecific behaviour such as head-butting, may indicate that the evolution of such behaviour occurred comparatively early in the history of the protoceratids. Study of the anatomy of the otic region in Leptotragulus suggests that there are a number of similarities in periotic morphology between leptotragulines and plesiomorphic ruminants such as hypertragulids and leptomerycids, which may indicate a sister group relationship between the Protoceratidae and the Ruminantia.

The perissodactyl family Brontotheriidae is represented by large numbers of specimens from latest early and middle Eocene sediments of the Western Interior of North America. Species level taxonomy of brontotheres has been confusing, and the relationships of the earliest occurring species to those that occur later have not been well documented or understood. Evidence based on new specimens from the earliest Bridgerian from the Green River Basin, in particular from South Pass and Opal, coupled with a reanalysis of previously existing specimens has led to the following conclusions concerning the alpha taxonomy of Bridgerian North American brontotheres. Four genera (Eotitanops, Palaeosyops, Mesatirhinus, and Telmatherium) are recognized. Eotitanops is represented by two species, E. borealis and E. minimus, and Palaeosyops by five species, P. paludosus, P. fontinalis, P. laevidens, P. robustus, and P. laticeps.

A re-examination of the temporal distribution of brontotheres requires that the biochronologic framework of the latest early to earliest middle Eocene be modified. The earliest Bridgerian can be defined by the first appearance of Eotitanops borealis in the Wind River Basin and Wapiti Valley, both in Wyoming and at Huerfano Park, Colorado. This interval has been termed the Eotitanops borealis Assemblage Zone and is equivalent to the early Gardnerbuttean, Bridgerian Biochronologic Zone Br0. The first appearances of Palaeosyops fontinalis and Eotitanops minimus mark the onset of the second biochronologic interval of the Bridgerian, Br1, here referred to informally as the ”Palaeosyops fontinalis Assemblage Zone.” This interval includes the late Gardnerbuttean (Br1a) and Bridger A (Br1b). Biochronologic Zones Br0 and Br1 are now included in the latest early Eocene while Br2 coincides with the beginning of the middle Eocene.

Seven local faunas (Little Muddy I–VII) of early to middle Eocene age are described from the Little Muddy Creek area in the southwestern Green River Basin. These assemblages were collected from approximately 400 m of interfingering alluvial and lacustrine deposits in the Wasatch, Green River and Bridger formations. This is the first time the Wasatchian-Bridgerian boundary has been delineated within the southwestern Green River Basin. A continuous stratigraphic section from the late Wasatchian (Wa7) through the late Bridgerian (Br3) is now known in the southern Green River Basin.The Lostcabinian (Wa7) in the southwestern Green River Basin is recognized by the occurrence of Lambdotherium and the presence of Meniscotherium and Notharctus nunienus. The temporal range of Anemorhysis wortmani is extended upward to include the Lostcabinian of the southwestern Green River Basin. The late Gardnerbuttean (Bridgerian Biostratigraphic Zone Br1a) is recognized in the southwestern Green River Basin by the first appearances of Palaeosyops fontinalis and Hyrachyus. “Bridger A” (Bridgerian Biostratigraphic Zone Br1b) is recognized in the southwestern Green River Basin by the first appearances of Orohippus pumilus, Omomys carteri, Leptotomus parvus, and Washakius insignis. Other important records include the earliest occurrences of Tetrapassalus sp. and Parasauromalus. The presence of a new genus and species of crocodylian and a new genus and species of helaletid perissodactyl are documented.

A new, relatively complete and well-preserved mandible and dentition of the mesonychian Ankalagon saurognathus from the early Paleocene (Torrejonian) of the San Juan Basin, New Mexico, provides evidence of sexual dimorphism in dentary depth and canine size in Mesonychidae. The new specimen has a particularly well-preserved postcanine dentition, and m1 and m2 differ little in morphology or size from those in the holotype. The p3–p4 and m3 in the new specimen are smaller in length and width than in the holotype, but the size differences fall within the intraspecific range of variation exhibited in extant carnivorans. The holotype differs from the new specimen in having a canine that is approximately 1.5 times greater in length and width, as well as a dentary that is substantially deeper and larger. It has been suggested that two other mesonychians, Hapalodectes and Dissacus, also exhibit sexual dimorphism but evidence for this remains equivocal. We discuss the phylogenetic and behavioral implications of this character.