Joffrichthys triangulpterus, sp. nov. is a new species of the family Osteoglossidae, and is described based on two nearly complete, and two partial, articulated specimens from the Sentinel Butte Formation in the Fort Union Group (Paleocene) of central North Dakota, USA. The familial placement is based on three diagnostic characters: uroneurals absent; six hypurals; and a kidney shaped opercle. The generic placement into Joffrichthys is based on two diagnostic characters and eight similar morphologies and meristics shared between the new species and previously described J. symmetropterus: two complete or partial neural spines present on preural 2; one spine or no spines present on ural 1; similar shapes of the maxillary, dentary, preopercle, opercle, and frontal; a similar body silhouette; and a similar vertebral and supraneural count. The specimens are identified as a new species by nine diagnostic characteristics distinguishing it from J. symmetropterus, the most closely related taxon: more posteriorly-placed pelvic fins; a greater dorsal fin ray count (30 total); a triangular dorsal and anal fin; asymmetrically positioned dorsal and anal fins (anterior pterygiophore insertions separated by 8 to 9 vertebrae); the third dorsal and fifth anal pterygiophores being the longest; and two complete spines on preural 2. The North Dakota fish is important because it represents a new species of Joffrichthys and represents the most southern occurrence of the genus to date.

The braincase of Leptopleuron lacertinum Owen, a leptopleuronine procolophonid from the Late Triassic (lower Norian) of Scotland, is described for the first time. Morphologically, the braincase of Leptopleuron is similar to that of the Early Triassic genus Procolophon, and to a number of other procolophonids currently included in the subfamily Procolophoninae Romer, 1956. Several features of the braincase of Leptopleuron are derived within the Procolophonidae, but others are unique to this genus. Apomorphies include a strongly tripartite occipital condyle, a metotic foramen that is not walled by bone anteriorly, an ‘ascending process’ of the basisphenoid that forms a robust flat-ended expansion, and bears ventrally a thin laterally directed lamella, a ‘processus infrastapedialis columellae’ of the stapes that is aligned with the long axis of the footplate, loss of the foramen for nerve IX on the ventral ramus of the opisthotic, and a greatly expanded, vertical basisphenoid rostrum. These features may be autapomorphic for Leptopleuron, or represent synapomorphies of the Leptopleuroninae Ivakhnenko, 1979.

The dentition of Nicrosaurus kapffi, a phytosaur from the Norian of central Europe, consists of three distinct dental sets in the upper jaw, and two in the mandible. Dental sets are defined by: (1) gradual, linear transformations of dental characters within an array that results in characteristic end members; and (2) the position of each array within the jaws. The tip-of-snout set in the upper jaw comprises mainly the large fang-like anteriormost teeth. In the premaxilla set, the teeth grade from a conical, unspecialized form anteriorly to high, D-shaped and bicarinate teeth posteriorly. In the maxilla set the teeth grade from stout, conical, unspecialized forms anteriorly to triangular forms with expanded flanges posteriorly. The tip-of-mandible and the dentary set correspond to the tip-of-snout, and to an elongated maxilla set, respectively, but were studied in less detail. The presence of tripartite and bipartite dentitions (three versus two dental sets in the upper jaw) is suggested as a criterion for defining the degree of heterodonty in phytosaurs. By taking into account positional variation, it is suggested that dental characters can be used to identify the relative position of some isolated teeth and can contribute valuable information to the diagnosis of a phytosaur taxon, although the application of the latter is still limited due to incomplete knowledge. The tooth morphology suggests that the more derived, tripartite phytosaur dentition is differentiated functionally into greatly enlarged anterior teeth probably used to kill smaller prey instantly by stabbing, strong posterior premaxillary teeth to seize and subdue large-sized prey, and trenchant posterior maxillary teeth to effectively dismember larger prey items.

Protosuchus haughtoni from the Lower Jurassic Stormberg series of southern Africa is closely similar to the contemporaneous P. richardsoni from the Moenave Formation of North America. The taxon is based on two well preserved braincases; the rest of the skull is described here, based on an exceptionally well preserved and virtually complete skull.

A new species of the genus Araripesuchus from the Albian–Cenomanian locality of the El Chocón (Neuquén Province, Argentina) is described. The diagnosis of the genus is reviewed and its phylogenetic placement within Crocodylomorpha discussed. Araripesuchus is proposed here as being the sister taxon of Neosuchia, corroborating previous phylogenetic analysis. The new species, Araripesuchus patagonicus, differs from the type species, A. gomesii in the relationships of the prefronto-nasal and lachrymo-nasal sutures, the dermal placement of the postorbital bar on the medial side of the jugal, and the greater extension of the squamosals in the skull dorsum. The African species, “Araripesuchus” wegeneri, does not share the diagnostic traits of the genus, and its reassignment to a new genus needs to be considered. The phylogenetic context of Araripesuchus and “A.” wegeneri permits a reanalysis of the role played by their amphiatlantic distribution in the Aptian-Albian. “Araripesuchus” wegeneri and the South American forms might share a pre-Aptian common ancestor, and have been already differentiated and isolated in the African and South American continents by the time of the Aptian–Albian.

Re-examination of the surviving specimens of Thecodontosaurus antiquus indicates that this plesiomorphic sauropodomorph can be diagnosed on the basis of elongate basipterygoid processes, a relatively short dentary, and a squared posterior process of the ilium. Although much of the original topotype material found in the 1830s in Bristol, England, has now been lost, some 245 specimens remain. These indicate a small, gracile prosauropod, up to 2.5 m in length, distinguished primarily on the absence of derived characters seen in other prosauropods. Although attempts were formerly made to subdivide the Bristol specimens into several dinosaurian, and other, taxa, most appear to pertain to the prosauropod Thecodontosaurus antiquus. The specimens do indicate a clear separation into two morphs, a gracile and a robust form, presumably evidence of sexual dimorphism. A juvenile Thecodontosaurus sp. from South Wales may belong to the same species. A cladistic analysis indicates that Prosauropoda is probably a clade, rather than a series of outgroups to Sauropoda, but support for this conclusion is weak. Echoing other recent cladistic analyses, stronger support is found for the existence of a clade Sauropodomorpha, made up from Prosauropoda Sauropoda, for the clade Sauropoda itself, and for the clade Eusauropoda within Sauropoda.

Sauroposeidon proteles, a new brachiosaurid sauropod, is represented by an articulated series of four mid-cervical vertebrae recovered from the Antlers Formation (Aptian–Albian) of southeastern Oklahoma. Most Early Cretaceous North American sauropod material has been referred to Pleurocoelus, a genus which is largely represented by juvenile material and is not well understood. Regardless of the status and affinities of Pleurocoelus, the new taxon is morphologically and proportionally distinct. Among well-known sauropod taxa, Sauroposeidon is most similar to Brachiosaurus; particularly noteworthy are the neural spines, which are set forward on the centra and are not bifurcate, and the extremely elongate cervical ribs. Sauroposeidon and Brachiosaurus also share a derived pattern of pneumatic vertebral ultrastructure and a mid-cervical transition point, at which neural spine morphology changes from very low (anteriorly) to very high (posteriorly). Autapomorphies of Sauroposeidon include posterior placement of the diapophyses, hypertrophied pneumatic fossae in the lateral faces of the neural spines and centra, and an extraordinary degree of vertebral elongation (e.g., C8 = 1.25 m; 25% longer than Brachiosaurus). Additional sauropod material from the Early Cretaceous Cloverly Formation may be referrable to the new Oklahoma sauropod, which appears to be the last of the giant North American sauropods and represents the culmination of brachiosaurid trends towards lengthening and lightening of the neck.

Ontogenetic changes in the bone histology of Maiasaura peeblesorum are revealed by six relatively distinct but gradational growth stages: early and late nestling, early and late juvenile, sub-adult, and adult. These stages are distinguished not only by relative size but by changes in the histological patterns of bones at each stage. In general, the earliest stages are marked by spongy bone matrix with large vascular canals. Through growth, the cortical bone differentiates into fibro-lamellar tissue that tends to become more regularly layered in the outer cortex. By the sub-adult stage, lines of arrested growth (LAGs) begin to appear regularly. Resorption lines and substantial Haversian substitution in many long bones also begin to appear at this stage, and the external cortex has a lamellar-zonal structure in some bones that indicates imminent cessation of growth.

Judging by the rates of apposition of similar bone tissues in living amniotes, and by the number and placement of LAGs, these patterns suggest that young Maiasaura nestlings grew at very high rates, and at high and moderately high rates during later nestling, juvenile, and sub-adult stages, slowing to low and very low growth rates in adults (7–9 m total length). The nesting period would have lasted one to two months, late juvenile size (3.5 meters) would have been reached in one or two years, and adult size in six to eight years, depending on the basis for extrapolating bone growth rates.

The histological tissues, patterns, and inferred growth rates of the bones of Maiasaura are completely different from those of living non-avian reptiles, generally similar to those of most other dinosaurs and pterosaurs for which data are available, and much like those of extant birds and mammals. No living reptiles (except birds) grow to adult size at these rates, nor do they show these histological patterns. We conclude that Maiasaura did not grow at all like living non-avian reptiles, which cannot be considered informative models for most aspects of dinosaurian growth (or physiology, to the extent that growth rates reflect metabolism). The use of lines of arrested growth (LAGs) to infer dinosaurian physiology has never been tested and is not supported by independent lines of evidence; their use in calculating age is also more complex than previously suggested and should not be based on single bones.

Theropod eggshell is identified for the first time from the Lower Cretaceous of North America. Eggshell microstructure and variability in ornamentation and thickness of this material is comparable to that present in elongatoolithid theropod eggs, known previously only from Asia. This identification is based on re-examination of the holotype of the putative spheroolithid Boletuoolithus carlylensis and description of additional eggshell fragments from the Lower Cretaceous of Utah. This oospecies is characterized by the ornithoid-ratite morphotype (i.e., of theropod parentage) and not, as recently suggested, by the dinosauroid-prolatospherulitic morphotype (i.e., of ornithopod parentage). Additionally, Boletuoolithus carlylensis includes a much broader range of eggshell morphologies than previously described: eggshell thickness ranges from 1.38–3.04 mm, ornamentation is remarkably variable, and sometimes the typical elongatoolithid microstructure is altered by extreme development of both the ornamentation and pore system. The thickness, ornamentation, and elongatoolithid microstructure indicate that the holotype and referred materials assigned to Boletuoolithus carlylensis are indistinguishable from the Asian elongatoolithid Macroelongatoolithus xixiaensis. Accordingly, the oogenus Boletuoolithus is rendered a junior subjective synonym of Macroelongatoolithus. In turn, Macroelongatoolithus xixiaensis is regarded as a junior synonym of Macroelongatoolithus carlylei (new combination and emendation of specific epithet) by virtue of publication priority.

We describe a skeleton from the late early Paleocene (Torrejonian) of the San Juan Basin, New Mexico, which represents the oldest and most primitive known member of the Palaeanodonta. It is here named Escavadodon zygus, gen. et sp. nov., and is assigned to the new family Escavadodontidae. The specimen is one of the most complete skeletons of a small mammal known from the San Juan Basin Paleocene. The skeleton combines fossorial postcranial adaptations closely similar to, but somewhat less specialized than, those of early Eocene palaeanodonts, with teeth reminiscent of those of Leptictidae and to a lesser extent Pantolestidae. It thus appears to be morphologically intermediate between Leptictidae and Palaeanodonta, suggesting that Palaeanodonta evolved from Leptictidae or a leptictid-like mammal, and pushing back the origin of Palaeanodonta to at least early Paleocene time.

Dental remains assigned to nimravid carnivores have been discovered in southern Thailand. These specimens come from the upper Eocene Krabi Basin that has already yielded numerous vertebrate taxa important for the knowledge of mammal evolution. The fossils described here are among the oldest remains belonging to the Nimravidae, and they are attributed to Nimravus cf. intermedius and Hoplophoneus sp. The occurrence of nimravid carnivores in Southeast Asia implies exchanges between Asia and North America during the Late Eocene, and it supports a larger geographical distribution and an origin of the family older than previously known.

Diplacodon progressum Peterson is not referable to the genus Diplacodon Marsh and is assigned the new generic name Pseudodiplacodon. Diplacodon is regarded as a nomen dubium, but may be a senior synonym of Eotitanotherium, a genus that is clearly distinct from Pseudodiplacodon. Only the type species of Pseudodiplacodon is accepted as valid, although there is one large individual belonging to this genus that could potentially represent a second species. Recognition of a second species is regarded as inappropriate, however, in the absence of additional specimens or distinct character differences.

A new genus and species (Antilohyrax pectidens) of gazelle-sized hyracoid from the late Eocene, Jebel Qatrani Formation, Fayum Province, Egypt, exhibits dental, cranial and postcranial specializations unique among hyracoids. The lower incisors are broad, hyper-pectinate teeth similar to those of the extant dermopteran genus Cynocephalus. Upper incisors are apparently absent, and the shape of the premaxilla suggests that the lower incisors occluded against an upper fibrous pad, as in Cynocephalus and ruminants. The cheek teeth are dominated by sharp-edged, crescentic shearing blades, suggesting a folivorous diet. The articulation between the astragalus and navicular is furrowed and condylar in shape, allowing notable midtarsal flexion and extension but limited lateral movement. The tibia and fibula are fused together throughout most of their length. In size and proportions, limb elements resemble those of the extant springbok (Antidorcas marsupialis, Bovidae). Functional inferences derived from these features suggest a cursorial browser, a Paleogene analog to the bovids that do not appear in Africa until the Miocene. The new genus and species adds another adaptive dimension to what was already an extremely diverse record of Tertiary hyracoids, and further underscores that hyracoids were the dominant terrestrial ungulates of the African Paleogene.

A new small to medium-sized hippopotamus, Hexaprotodon lothagamensis is described from the late Miocene of northern Kenya. The material was recovered from Lothagam, a site southwest of Lake Turkana. This narrow-muzzled hippopotamus differs from other Hexaprotodon species in terms of its small size and shallow symphysis. The six incisors are arranged in a straight line across the front of the jaw and the lower canines are almost aligned with the cheek tooth row. H. lothagamensis compares more closely to an Arabian species, Hexaprotodon aff. H. sahabiensis from the late Miocene, than to any other African Hexaprotodon. The phylogeny of the Hippopotamidae is discussed and although the genera names are maintained, the genus Hexaprotodon is paraphyletic. Hexaprotodon lothagamensis appears to be less derived than the extant pygmy hippopotamus, H. (Choeropsis) liberiensis, which was previously considered to be a living fossil.