As a single stratigraphic source and site of high-fidelity vertebrate trackways and superbly preserved skeletons, the Lower Permian Tambach Formation, lowermost unit of the Upper Rotliegend, of the Bromacker locality in the middle part of the Thuringian Forest near Gotha, central Germany, provides a unique opportunity of matching late Paleozoic trackways with their trackmakers. Here the track-trackmaker association is firmly established between two species of the ichnogenus Ichniotherium, Ichniotherium cottae and Ichniotherium sphaerodactylum, and the skeletal fossils of the closely related diadectids Diadectes absitus and Orobates pabsti, respectively. These are the first well-documented species-level identifications of the trackmakers of Paleozoic trackways. The Ichniotherium ichnospecies are principally separated by the relative lengths of the digits of the pes imprint and the degree of overstepping of the pes and manus imprints. Both characters are shown to be clearly due to differences in the number and lengths of phalangeal elements and the number of presacral vertebrae of the diadectid species. The unique methods employed here in establishing the track-trackmaker associations provide not only an innovative data source for studying the evolutionary biology, paleo-biogeography, and locomotor behaviour of the trackmakers, but also a valuable methodology for evaluating taxonomic concepts in vertebrate ichnology.

Compagopiscis croucheri and Gogopiscis gradlis (Gardiner and Miles, 1994) were collected in high numbers and in different size classes from the Upper Devonian Gogo Formation, Western Australia. This material has provided the basis for an investigation of ontogentic and phenotypic variation of characters and their phylogenetic implications. We used the Principal Component Analysis to examine if variation between specimens assigned to C. croucheri and G. gracilis could be attributed to random variation. In our analysis we found that only the first two principal components showed any significant ability to discriminate between the specimens assigned to C. croucheri and G. gracilis. The first principal component is a measure of overall size of the specimen, so that variation in this principal component can be explained in terms of maturity and growth within a single species. Not all the anatomical variation observed in this study can be attributed to ontogeny and it is considered that the two-class structure defined by the second principal component is consistent with individual variation. It is, therefore, concluded that Compagopiscis and Gogopiscis represented part of the continuous variation exhibited by the whole population rather than two distinct taxa and therefore Compagopiscis and Gogopiscis are synonomized to a single genus, Compagopiscis containing a single species, Compagopiscis croucheri.

Cretalamna ( = Cretolamna) appendiculata is an extinct lamniform shark primarily known by isolated teeth and traditionally classified into Cretoxyrhinidae. Here, a partial skeleton of C. appendiculata from the Upper Cretaceous Niobrara Chalk of Kansas is described. The reconstructed dentition partially corroborated with some articulated teeth on an upper jaw indicates that the shark had a lamnoid tooth pattern. Adjacent teeth apparently abutted each other without overlap and the dentition likely had a cutting function. The reconstruction presented here differs from previously published reconstructed dentitions of C. appendiculata based on isolated teeth or purely disarticulated tooth sets. The overall dental pattern of C. appendiculata is found to be more similar to the pattern of extant Lamna spp. than to that of a cretoxyrhinid, Cretoxyrhina mantelli, possibly indicating that Cretalamna appendiculata may not belong to Cretoxyrhinidae. The estimated jaw lengths indicate an upper jaw overbite, which concomitantly implies a subterminal mouth in the shark. The jaw morphology indicates the presence of large dorsal and ventral quadratomandibularis muscles. The vertebrae of C. appendiculata are confirmed to be of lamnoid type, reaffirming C. appendiculata to be a lamniform. Cretalamna appendiculata probably had a fusiform body with a caudal fin not as elongate as in modern alopiids. The C. appendiculata individual likely measured at least 2.3 m and possibly as large as 3 m in total length. The extant phylogenetic bracket approach indicates that C. appendiculata possessed a dental bulla in each jaw. Cretalamna appendiculata was probably an ecological generalist.

Sex in non-avian archosaurs has been inferred using a variety of osteological attributes. However, little quantitative data have been presented showing that these phenotypes truly exist. In this study, testing for the presence of pelvic osteological correlates of sex in extant archosaurs was conducted, using skeletons of wild-caught A. mississippiensis as a neontological model. For outgroup comparison, the squamate Iguana iguana is included. A sample of 16 females and 19 males of A. mississippiensis, and 18 females and 10 males of I. iguana were examined. Measurements included pelvic canal area, dorsoventral depth, and mediolateral width of the pelvic canal, mediolateral width between the dorsal edge of each ilium, and ischium orientation. These data were analyzed using analyses of covariance, a t-test, and a recently developed geodesic distance shape analysis. Results indicate that there is sexual dimorphism in the proportions of the pelvic canal in A. mississippiensis, with females typically having deeper pelvic canals than males. This dimorphism might be synapomorphic for Archosauria. No dimorphism was found in I. iguana. The detection of dimorphism in A. mississipiensis required large sample sizes owing to substantial overlap between sexes. Thus, sexing isolated specimens using this metric is tenuous at best. Assuming similar variance in the relative pelvic depth versus width in other non-avian archosaurs, this criterion would also produce imprecise determinations of sex for these taxa.

The fossil record of abelisauroid carnivorous dinosaurs was previously restricted to Cretaceous sediments of Gondwana and probably Europe. The discovery of an incomplete specimen of a new basal abelisauroid, Berberosaurus liassicus, gen. et sp. nov., is reported from the late Early Jurassic of Moroccan High Atlas Mountains. Phylogenetic analysis recovers Ceratosauroidea and Coelophysoidea as sister lineages within Ceratosauria, and Berberosaurus as a basal abelisauroid. Berberosaurus is the oldest known abelisauroid and extends the first appearance datum of this lineage by about 50 million years. The taxon bridges temporal, morphological, and phylogenetic gaps that have hitherto separated Triassic to Early Jurassic coelophysoids from Late Jurassic through Cretaceous ceratosauroids. The discovery of an African abelisauroid in the Early Jurassic confirms at least a Gondwanan distribution of this group long before the Cretaceous.

Basal (cladistically) neoceratopsians are relatively small, gracile members of Ceratopsia (‘horned’ dinosaurs), which also includes larger forms such as Triceratops and Centrosaurus. The Asian basal neoceratopsians share some very important traits not found in any North American group until now, including a fenestrated frill and premaxillary teeth. Likewise, the North American basal taxa have some traits not found in the Asian forms, the most important of which is a very specialized tooth wear pattern. Cerasinops hodgskissi, a new basal neoceratopsian from the Lower Two Medicine River Formation of Montana, exhibits all of the above characters along with others previously found on only one of the two continents. The new species is a sister group to Leptoceratopsidae in a cladistic analysis, and is a link between the taxa on the two continents. Cerasinops also exhibits extremely interesting anatomical and histological features that indicate the possibility of bipedality in this taxon, a locomotor pattern not found previously in basal neoceratopsians (it has been suggested in some, but with little evidence).

An incomplete braincase of a juvenile lambeosaurine hadrosaurid (Dinosauria: Ornithischia) is recognized as the second and smallest cranial specimen of Parasaurolophus from the Belly River Group (Campanian), Alberta, Canada. This specimen provides the first information on the ontogeny of the skull roof and autapomorphic tubular crest in this widely recognized yet poorly known taxon. In addition to the distinctive morphology of the cranial crest, Parasaurolophus is characterized by a suite of skull roof characters associated with crest development that manifest at small size, including verticalization of the nasal frontal joint at the base of the crest. Although the crest is not preserved in the specimen described here, the distinctively thickened and steeply angled frontal platform indicates that the crest and facial profile were significantly different from the equivalent juvenile stages of corythosaurin lambeosaurines (Corythosaurus, Hypacrosaurus, Lambeosaurus), which resemble one another closely. Parasaurolophus therefore appears to deviate from the well-known corythosaurin mode of cranial crest growth early in ontogenetic development.

The Paleocene locality of Punta Peligro (Hansen Member of the Salamanca Formation) in Argentina has yielded not only ‘condylarths’ but also an extraordinary assemblage of therian mammals derived from Laurasian immigrants and non-therian mammals, relicts of the Mesozoic Gondwanan radiation. The materials, a left jaw fragment with the talonid of the second molar and the third molar, and an isolated upper molar, allow the revalidation of Raulvaccia peligrensis considered previously as a junior synonym of Escribania chubutensis. In addition to other characters, Raulvaccia strongly differs from E. chubutensis in its lesser size, the development of the m3 talonid, the presence of a hypocristid, and a postcristid. Originally Raulvaccia and Escribania were considered as Mioclaenidae, Kollpaniinae, together with other ungulates from the Santa Lucía Formation, from the early Paleocene locality of Tiupampa in Bolivia. In contrast to the Tiupampan ‘condylarths,’ Raulvaccia shares derived characters with E. chubutensis, particularly in the upper molars, such as a strong parastyle and the presence of hypocone located close to, but well differentiated from the protocone. These characters support a previous hypothesis which argues for the removal of the Peligran ‘condylarths’ from the more primitive Kollpaniinae, and sustains its relationship to the exclusively South American Didolodontidae. The revalidation of Raulvaccia peligrensis shows that the diversity of placental mammals during the earliest known Paleocene in Patagonia was greater than previously thought, and supports for the early differentiation of the Didolodontidae.

A new species, Trogosus gazini, is represented by eleven upper teeth (i2, P3-M3), eleven lower teeth (i2, i3, c1, and p3–m3), and some fragmentary postcrania of a single individual (USNM 364762), from the Blacks Fork Member of the Bridger Formation, Green River Basin, Wyoming, U.S.A. The new species has unique dental characters with a diminutive parastyle on the P3 and the asymmetrical pattern of the P4 lingual crests (reduced preprotocrista and expanded postprotocrista), in addition to having brachydont molars with dominant shearing wear facets. A phylogenetic analysis based on dental morphology places T. gazini as the sister taxon to either Trogosus latidens or Tillodon fodiens. The result also produces a solution for previously unresolved phylogenetic relationships among Kuanchuanius, Trogosus, and Tillodon. Although the result requires more morphological data to enhance the credibility of relationships among trogosine tillodont species, Trogosus gazini may represents a transitional form to Tillodon fodiens, which is most likely a descendant from a paraphyletic Trogosus with some autapomorphies. On the contrary, Kuanchuanius is allocated as a sister taxon to the Trogosus Tillodon clade.

Of the North American gomphotheres, the status of Tetralophodon, primarily known from the Old World, is among the most controversial. This controversy stems from the incompleteness of the North American specimens. Along with elongation of the M/m3s and a tendency towards double trefoiling on the cheek teeth, Tetralophodon is diagnosed by complete tetralophodonty (i.e., four lophs on D/d 4-M/m2). However, of those progressive North American gomphothere specimens that have plausibly been referred to Tetralophodon only the M/m2s are known to be tetralophodont, with the condition of the M/mls and P/p4s unknown. Thus, it has proven impossible to determine whether these purported Tetralophodon species represent true Tetralophodon immigrants, or one or more parallel radiations from North American Gomphotherium stock. The discovery of an unusual gomphothere in the Clarendonian Kepler Quarry fauna of Nebraska has possible bearing on North American Tetralophodon. This gomphothere resembles North American Tetralophodon in having M/m3 that are both highly elongated and double trefoiled only on the anterior two lophs, and a tetralophodont M/m2. However, more significantly its M/ml and D/d4 are preserved, neither of which is tetralophodont. Thus, the Kepler Quarry gomphothere cannot be referred to Tetralophodon and along with the other North American Tetralophodon species is referred to a new genus, Pediolophodon. The existence of Pediolophodon suggests that during the Clarendonian North American Gomphotherium stock was evolving in parallel with progressive Old World gomphotheres such as Tetralophodon.

According to our previous model for interpreting the fossil record of capybaras the cheek teeth grow in width and length throughout life; flexids (especially h.s.i. and h.t.i.) deepen allometrically resulting in diverse occlusal morphologies during ontogeny; in the more derived species the ‘onset’ of flexid development is pre-displaced, and the relative depth and development rate of the flexids increase. Consequently, we interpreted the different occlusal morphologies found in the fossil record as different ontogenetic stages, leading to a drastic diminution of latest Miocene-Pliocene taxonomic diversity. The analysis of the geologically oldest capybaras, which are from the Arroyo Chasico Formation (Chasicoan SALMA, late Miocene), is added. This study suggests a single species occurs in this formation that cannot be separated at the genus level from Huayquerian species. In the Arroyo Chasicó species, which is older and theoretically more primitive than that of the Huayquerian, the flexids are shallower as predicted. The analysis supports our model of capybara dental ontogeny and evolution and encourages revision of the whole family according to this model.

A new genus of sciurid, Hesperopetes, contains three species: H. thoringtoni (type species), H. jamesi, and H. blacki. H. thoringtoni is from the early Chadronian (late Eocene) White River Formation of central Wyoming and represents the earliest recognized species of sciurid. The other species are from the latest Whitneyan or earliest Arikareean (late Oligocene) Blue Ash local fauna of South Dakota. Hesperopetes is closest in dental morphology to Oligopetes Heissig, which is known only from the early Oligocene of Europe. Hesperopetes may also represent the earliest occurrence of a lineage leading to pteromyine sciurids (“flying” squirrels). It is impossible at this time to construct a phylogeny of North American “flying” squirrels due to their scarcity in the fossil record and their undetermined relationships with Old World taxa.

New dental material of the hyaenid Hyaenictitherium hyaenoides Zdansky, 1924 from the late Miocene Baogeda Ula Formation in central Inner Mongolia is described. An evaluation of the morphological trends and spatial and temporal ranges of the genus Hyaenictitherium follows. The unworn isolated teeth described here represent a nearly complete set of dentition. Furthermore, the Baogeda Ula material is the eastern-most record of this genus, and the only hyaenid record in eastern Asia associated with a layer of basalt capping the fossil producing sediments. Previous studies of the capping basalt and associated small mammal fauna constrain the age of the Baogeda Ula hyaenid at 8–7 Ma. In addition to the Baogeda Ula material, other occurrences of the genus in eastern Asia include Gansu, Shanxi and Shaanxi provinces of northern China. Of the ten species currently thought to belong to the genus, two (H. intuberculatum and H. minimum) appear more primitive than the others. The rest seem to follow a morphological trend of increasing size and robustness of the teeth, as well as reduction of the trigonid of m1. This trend is observed roughly from H. wongi (MN9) to H. namaquensis (MN14). The genus appears to be a cursorial form and first appeared in western Eurasia in MN9. Subsequent range expansion occurred in northern Asia, southern Asia, and in Africa from MN12 on. The observed phylogenetic and morphological gaps between H. namaquensis and H. minimum prevent a clear interpretation of Hyaenictitherium immigration into Africa.