Patches of spherulitic calcified cartilage are described inside the paired fins of the osteostracan Escuminaspis laticeps from the Upper Devonian of Miguasha, Canada, thereby confirming Belles-Isles interpretation of these patches as evidence for paired fin endoskeleton. The distribution of these calcified cartilage patches suggests that the osteostracan paired fin endoskeleton was a single cartilaginous plate located in the lateral half of the fin, and was thus not made up of separate radials. This morphology resembles that of the endoskeletal disc of the embryonic and larval pectoral fin of piscine gnathostomes, prior to its decomposition into radials, and may mirror the general condition for the clade that includes osteostracans and gnathostomes.

The middle part of the Fairpoint Member of the Fox Hills Formation in Meade County, South Dakota consists of marine shoreface deposits and contains a chondrichthyan assemblage that includes both pelagic and bottom-feeding forms. The assemblage consists of genera (e.g., Rhombodus, Carcharias, Serratolamna, Ischyrhiza) widely known from Upper Cretaceous rocks of the Western Interior, and from other parts of North America, Europe, Africa, and Asia. This middle Fairpoint assemblage contains many of the same chondrichthyan genera reported by Cicimurri (1998) from the lignitic Stoneville lithofacies of the upper part of the Fairpoint Member. Fairpoint chondrichthyans are probably roughly equivalent in age to the chondrichthyans from the Timber Lake Member of the Fox Hills Formation in North Dakota, and are probably older than the chondrichthyan assemblage from the Breien Member of the Hell Creek Formation. The Breien, Timber Lake, and Fairpoint chondrichthyans are the youngest transitional marine chondrichthyan assemblages yet recovered from Cretaceous rocks of the Western Interior. The Fairpoint Member assemblage consists of chondrichthyan species different from those of the Paleocene Cannonball Formation of North Dakota. This disparity supports Cvancara and Hoganson's (1993) and Hoganson and Murphy's (2002) views that there was a significant turnover among Western Interior chondrichthyans during the interval between the deposition of these units. The cause of this turnover is not yet clear.

Revision of the genus Peltoperleidus leads to recognition of a single persisting deepened scale row as the main diagnostic feature for the newly established genus Altisolepis gen. nov. The counts of deepened scale rows are taken to be very consistent in all species assigned to Peltoperleidus and Altisolepis gen. nov., since they can be perfectly matched with skull bone patterns and counts of lepidotrichia. An initial evaluation shows that presence and array of variably deepened flank scales in fusiform fossil fishes have previously been underestimated in terms of their occurrence and as a putatively phylogenetic signal: the counts of deepened flank scales show some negative correlation with body size in fusiform fishes up to a certain standard length only, and occur predominantly in smallest fishes in the Middle Triassic. No significant correlation exists between scale row counts and standard length with respect to taxonomy; although interrelationships of these actinopterygians are still poorly understood, it appears likely that similar patterns of deepened scale rows may have developed independently during the Early-Middle Triassic.

A new species is described and proposed as a new genus and family belonging to the Order Ichthyodectiformes. The specimens referred to this taxon were collected in limestones of the Middle Member of the Tlayúa Formation of Albian age, near Tepexi de Rodríguez, Puebla, central Mexico. This new species shows a unique combination of primitive and derived characters. Its head and body proportions resemble those of other Cretaceous ichthyodectiforms, but its parietals are unfused and the caudal fin has three epurals and five uroneurals; it is also characterized by an unusually high total vertebral count, which comprises 78–80 centra, and areas of crowded teeth in the dentary and maxilla.

Pintosaurus magnidentis gen. et sp. nov., a latest Permian procolophonoid reptile from the Buena Vista Formation of Uruguay, is described and its relationships are considered. The new taxon is characterized by the absence of a lateral maxillary depression, a premaxilla with a dorsally expanded maxillary process, a maxilla-premaxillary junction almost straight and marked by a shallow, but well-defined step that displaces the premaxillary alveolar margin slightly medially with respect to the maxillary tooth row, and the presence of a large conical, fang-like palatine tooth, which is positioned next to the suture with the vomer. The transitional nature of Pintosaurus is reflected in the retention of several plesiomorphic features that contrast with the presence of synapomorphies that are shared with procolophonids. A phylogenetic analysis suggests a basal position for Pintosaurus within Procolophonoidea, either as the sister taxon of a clade that includes Coletta and procolophonids or as the sister taxon of Coletta itself. The results of our phylogenetic analysis, together with the Permian age of Pintosaurus, are consonant with the hypothesis of a Gondwanan origin of Procolophonoidea.

The new giant turtle species Gopherus donlaloi is described from a partial skeleton with skull collected in the Rancholabrean deposits in northeastern México. The skull resembles the skull of extant turtles G. polyphemus and G. flavomarginatus but the new species shows unique skull and shell features. Shell meristic variation of the new species, G. berlandieri, and G. laticuneus is discussed denoting problems in the assessment of species based on extremely variable shell characters. Lack of diagnostic features in shells of G. edae and G. hexagonatus suggests their status as nomina vana. A cladistic strict consensus tree suggests that Gopherus is a monophyletic group where G. mohavetus falls within the outgroup, questioning its status as a member of Gopherus. Oligocene G. laticuneus is sister to all Gopherus, after which Recent G. berlandieri and G. agassizii branched out paraphyletically. Gopherus sensu stricto is monophyletic but the relationships among its taxa are unknown; these include the Miocene G. brevisternus, G. pansus, and G. vagus, the Plio-Pleistocene G. canyonensis and G. donlaloi, and the Recent G. polyphemus and G. flavomarginatus. A second analysis excluding most incomplete taxa retains the polytomy of G. berlandieri, G. agassizii, and Gopherus sensu stricto, but resolves the relationships within Gopherus sensu stricto. G. brevisternus is sister to the rest of the clade, followed by G. flavomarginatus, after which there is a polytomy formed by G. canyonensis, G. donlaloi and G. polyphemus. Bootstrap and branch-support analyses indicate that the clades within Gopherus sensu stricto are well supported. Reanalysis of biogeographic relationships based on the phylogeny suggests that the origin of Gopherus sensu stricto can be traced to the Miocene on the Central Plains, later extending southward from eastern Arizona to Florida and from northern Texas to Aguascalientes during the Plio-Pleistocene. The extinction of giant gopher turtles in Texas and eastern Mexico associated with the invasion of their distribution area by G. berlandieri is the best hypothesis to explain the recent disjunct distribution of G. polyphemus and G. flavomarginatus.

The ichthyosaur Shonisaurus sikanniensis sp. nov. is described from the Pardonet Formation (Norian, Late Triassic) of northeastern British Columbia. The type specimen is considerably larger than Shonisaurus popularis, with an estimated length of 21 m. It also differs from S. popularis in having a fan-shaped scapula, and relatively longer vertebral centra. Studies of this new species, along with re-examination of S. popularis, suggests that Shonisaurus was not as deep-bodied as previously reconstructed. Teeth are set in sockets, but are known only in a few, small individuals. This implies that teeth were present only in juveniles, and that adults were edentulous. The new species extends the geographical and stratigraphical range of Shonisaurus to the middle Norian of British Columbia.

The Dry Mesa Dinosaur Quarry in western Colorado is characterized by a high diversity of vertebrate fossils, including pterosaur remains. Most of the pterosaur material has been referred to the species Mesadactylus ornithosphyos. Since its original description, additional material of this pterosaur has been uncovered. The new material includes the first described well-preserved basicranium of a Jurassic pterodactyloid pterosaur from North America and several appendicular elements. The cervical vertebra described previously was CT-scanned to reveal a complicated internal pneumatic system that can be compared to the avian system.

Whether the extinct crocodylians given the name Allognathosuchus represent a monophyletic assemblage remains controversial, and some have argued that Wannaganosuchus brachymanus Erickson, 1982 is a form of Allognathosuchus. A revised phylogenetic analysis supports a set of relationships in which the type species of Allognathosuchus (A. polyodon) is closer to Alligator than it is to European “Allognathosuchus” or “Allognathosuchus” from the North American Paleocene, and a close relationship between Allognathosuchus and Wannaganosuchus is not supported. One European fossil assigned to Allognathosuchus, A. woutersi, is similar (and possibly referable) to Diplocynodon. Chrysochampsa mlynarskii can be distinguished from all other Early Tertiary alligatoroids, but its relationships to other members of the clade (and whether it should be placed within Allognathosuchus) are unclear. These results support multiple dispersal events of alligatorines from North America to Eurasia, and suggest that the cranial anatomy thought to distinguish forms such as Allognathosuchus is plesiomorphic at the level of Alligatoridae. The name Allognathosuchus should be applied in a restricted sense to Allognathosuchus polyodon and its closest relatives, with alternative generic names applied to distantly related “Allognathosuchus.”

Here, we provide a comparative survey of the histology of postcranial dermal-armor osteoderms of ankylosaurs, including material of polacanthids (Polacanthus foxii, Gastonia sp.), ankylosaurids (e.g., Saichania chulsanensis, Pinacosaurus grangeri, Ankylosauridae indet.), and nodosaurids (e.g., Struthiosaurus austriacus, Nodosauridae indet.). Samples of osteoderm-bearing outgroups (Scelidosaurus harrisonii, phytosaurs, and crocodiles) as well as literature data on Stegosaurus stenops plates and spikes helped to elucidate histological evolution and character polarity.

The complex histology of ankylosaur osteoderms seems to be of systematic value, as the sectioned osteoderms can be classified into three distinctive groups. All polacanthid osteoderms share a relatively generalized histology with a thickened, uniform cortex completely surrounding trabecular bone. Nodosaurid osteoderms only have an external cortex with the underlying internal spongiosa being much thicker and forming a rather flat base. Ankylosaurids have very thin osteoderms that were greatly strengthened by the incorporation of structural collagen fiber bundles, similar but not identical to Sharpey's fibers, into the thin primary cortex and, uniquely, the secondary bone tissue. Structural fibers are also abundant in nodosaurids but there are significant differences in arrangement and occurrence, being random in ankylosaurids but highly ordered in nodosaurids. In their cortex, the latter have two sets of 3D-orthogonal fibers rotated at 45° to each other. The combination of the greatly strengthened external cortex covering a thick cushion of cancellous bone thus serves to resist local penetration. Ankylosaurid and nodosaurid osteoderms are thus highly optimized towards a resistant yet light-weight armor.

The type material of Genyodectes serus, the first unquestionable non-avian theropod dinosaur to be described from South America, is redescribed in detail and its provenance and systematic position are discussed. Although no detailed information about the provenance of the specimen exists, it is probably derived from the lower part of the Cerro Barcino Formation (Chubut Group; Aptian-Albian) at Cañadón Grande, central Chubut Province, Argentina. Genyodectes is characterized by closely-spaced premaxillary teeth that are arranged in an overlapping en-echelon pattern and extremely transversely compressed maxillary teeth, the longest of which exceed the minimal height of the dentary in apicobasal length. Although systematic information is limited by the fragmentary nature of the material, the combination of fused interdental plates, maxillary and dentary teeth with a pronounced flat or even slightly concave area adjacent to the serrated carinae, premaxillary teeth that are considerably shorter than the maxillary teeth and strongly compressed and very long maxillary teeth indicates neoceratosaurian and, more specifically, ceratosaurid affinities for Genyodectes. Thus, this taxon adds a further lineage of neoceratosaurs to the already diverse South American record of this group.

We describe sauropod material from the Lower Cretaceous (Aptian-Albian) Puesto Quiroga Member of the Lohan Cura Formation, exposed at the Cerro Aguada del León locality (La Picaza area, Neuquén Province, Argentina). The remains consist of disarticulated elements of at least three individuals, and are assigned to an indeterminate species of the rebbachisaurid diplodocoid Limaysaurus gen. nov. Elements from various parts of the skeleton are represented: a tooth, partial dorsal, sacral, and caudal vertebrae, a haemal arch, coracoid, humerus, ilium, pubes, ischium, femora, a tibia fragment, and an incomplete fibula. The Lohan Cura specimens are strongly reminiscent of corresponding elements in the holotype of Limaysaurus tessonei (=“Rebbachisaurus” tessonei, “Rayososaurus” tessonei) from the overlying Upper Cretaceous (lower Cenomanian) Candeleros Formation. We evaluate the phylogenetic relationships of Limaysaurus gen. nov. and other diplodocoids, and provide hypotheses regarding sauropod evolution during the Cretaceous.

Abnormal, multilayered eggshells are frequently reported in fossil specimens. However, previous reports of this pathological condition pertain to taxonomically unidentified fossil eggs or eggshell fragments rather than in situ clutches. A survey of 393 in situ clutches, referable to titanosaur sauropod dinosaurs, from Upper Cretaceous rocks in northwestern Patagonia, Argentina, revealed that six of these clutches contain both normal eggs and abnormal, multilayered eggs within the same clutch. Excavation of one clutch exposed 30 eggs, distributed in three levels, including 27 normal eggs and 3 multilayered eggs. The three abnormal eggs occupied the highest level within the clutch and represent the last eggs laid by the female sauropod. The innermost eggshell layer in multilayered eggs from all six clutches exhibits typical megaloolithid calcite structure. The structure of the overlying, abnormal shell layer(s), however, varies among the clutches and within a single egg. Three types of abnormal eggshell morphology are documented. All previous studies that link abnormal eggshells to dinosaur physiology and the terminal Cretaceous extinction event are incomplete in terms of taphonomy, taxonomic identification, and lack rigorous statistical methods.

We describe fragmentary new postcranial remains of a sauropod from “Continental Intercalaire” rocks of the Tilemsi Valley in northeastern Mali. Addition of this taxon to recently published cladistic analyses indicates that it is nested within Titanosauria and it is among the oldest members of this clade. “Continental Intercalaire” rocks have been poorly understood and, until now, few vertebrate fossils from these rocks have been tied to stratigraphic sections. We present a preliminary description of the dinosaurian locality and tie it to a synthetic stratigraphic section of the Tilemsi Valley. Preliminary analysis of the geology and sedimentology of the locality suggests that the bones fossilized in fluvial deposits of Early Cretaceous (pre-Cenomanian) age.

Two egg types from the Upper Cretaceous Two Medicine Formation of Montana are described and incorporated into a phylogenetic analysis of egg characters. Small (7.5 × 3.5 cm), ellipsoidal eggs with a surface ornamentation consisting of isolated round tubercles represent a new, unnamed ootaxon. The microstructure includes narrow, prismatic shell units with three structural layers. The second egg type, oospecies Prismatoolithus levis, belongs to the theropod Troodon formosus. Although previously described, the presence of a third, external layer had been overlooked. Both eggs display several features typical of avian eggs: narrowly spaced nucleation sites, barrel-shaped mammillae with blocky crystal habit, a squamatic-like texture in the prismatic layer, and a third, structural layer. In addition, the new egg type exhibits a cuticle layer and the eggs of Troodon are asymmetric.

Cladistic analysis of 14 fossil and extant taxa using 15 egg and shell characters favors a phylogeny consistent with more traditional analyses based on osteologic or genetic data and supports a theropod dinosaur origin for birds. No single character unambiguously distinguishes the eggs of avians from those of non-avian theropods, and the new Two Medicine egg type is recognized simply as that of a theropod. Results also indicate that resemblances in egg characters among non-avian and avian theropods are largely homologous and imply a high-level of similarity in reproductive physiology. Egg features are phylogenetically informative; better classifications and greater utility of eggs and eggshell will be gained through their phylogenetic treatment.

A new biarmosuchian therapsid, Lobalopex mordax gen. and sp. nov., from the Permian Teekloof Formation (Tropidostoma Assemblage Zone) of the Victoria West District, South Africa, is described on the basis of a partial skull with lower jaws and the first four cervical vertebrae. The genus is diagnosed by the following autapomorphies: median nasal eminence low and ridge-like; supraorbital boss small and unpachyostosed; posteriorly projecting supratemporal ‘horns’ present but relatively small; ventral surface of transverse flange of pterygoid edentulous and sharply ridged; and laterally-directed knob present lateral to contact between pterygoid and palatine dentigerous bosses. As in some other biarmosuchians, the cervical vertebrae are elongated, being roughly twice as long as they are wide or deep. A cladistic analysis including ten biarmosuchian taxa indicates that Lobalopex is the sister taxon to Burnetiidae and that Lemurosaurus is the most primitive burnetiamorph. These results fail to provide evidence for geographic endemism in these groups of Middle to Late Permian therapsids.

We describe skulls of the Wasatchian perissodactyl Homogalax and the Bridgerian–Uintan perissodactyl Isectolophus from North America for the first time. These skulls provide information on cranial evolution in tapiromorph perissodactyls as well as on primitive character states for Perissodactyla as a whole. They confirm the retention of a primitive rostrum in these taxa, as Radinsky had previously stated without reference to particular specimens. Characters from skull morphology suggest that Homogalax and Isectolophus should not be included in the same family.

We describe a sample of skulls, mandibles and isolated dentitions of Machairodus aphanistus from the Spanish late Vallesian (late Miocene) site of Batallones-1, near Madrid. This is the first time that the cranial morphology of this species has been seen in detail, and shows that late Vallesian M. aphanistus combined a relatively primitive cranial and mandibular morphology with very specialized upper canines, as flattened as in the later, cranially derived species M. giganteus. Cranio-mandibular adaptations for the canine shear-bite are incipient or non-existent, suggesting that the specialized canines of M. aphanistus were used within the context of a biting mechanism more similar to the canine bite of modern felids. Evolution of more extreme machairodont craniodental features in later members of the homotherin lineage converged with smilodontins but occurred independently of the initial development of derived saber-like canines. The high number of specimens, at least 14 individuals represented, reveals considerable variation in size within the population, with indications of sexual dimorphism in the size of the upper canines. Differences in cranial morphology suggest separation at the generic level between M. aphanistus and M. giganteus.

Cranial material from a new genus (Ramphastosula) of Sulidae is described. The material comes from the Early–Lower Pliocene of the Pisco Formation of the central-southern coast of Peru. The skulls are characterized by (1) remarkable convex curvature of the dorsal surface and straight ventral surface of the rostrum, only with a curvature on the third anterior part and the tip of the bill; (2) well developed occipital and temporal regions; (3) broad opisthotic process projecting to the level of postorbital processes; (4) broad temporal fossa, and (5) flat braincase and robust frontal region.