The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)

Ceratopsids (“horned dinosaurs”) are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)

Ceratopsids (“horned dinosaurs”) are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)

Ceratopsids (“horned dinosaurs”) are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

A large onychodontiform (Osteichthyes: Sarcopterygii) apex predator from the Eifelian-aged Dundee Formation of Ontario, Canada

The Devonian marine strata of southwestern Ontario, Canada, have been well documented geologically, but their vertebrate fossils are poorly studied. Here we report a new onychodontiform (Osteichthyes, Sarcopterygii) Onychodus eriensis n. sp. from the Dundee Formation (Eifelian–Givetian boundary, 390–387 Ma) of southwestern Ontario represented by two well-preserved onychodontiform lower jaws. The most complete specimen consists of a large (28 cm), well-preserved right jaw with most of the dentition present. The dentary has 50 teeth, not including the parasymphysial tusk whorl, which is poorly preserved but consists of at least three tusks. The anteriormost teeth of the dentary are also not complete, but the second dentary tooth is notably procurved. The posterior teeth are conical and approximately equal in size for much of the length of the tooth row. Onychodus eriensis n. sp. differs from the closely related contemporary species Onychodus sigmoides and all other onychodonts in that it has a strong dorsal curvature of the anterior dentary ramus and marked anterior expansion of the dentary. An expanded phylogenetic analysis of Devonian onychodontiforms suggests that O. eriensis is closely related to Onychodus jandamarrai. The new material indicates that Onychodontiformes is more diverse than previously recognized, and that further analysis of vertebrate remains from southwestern Ontario will lead to additional insights into the diversity of Devonian sarcopterygians.

The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Late Cretaceous, Mississippi, USA)

Ceratopsids (“horned dinosaurs”) are known from numerous specimens in western North America and Asia, a distribution reflecting the inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

The dentary ofAustralovenator wintonensis(Theropoda, Megaraptoridae); implications for megaraptorid dentition

Megaraptorid theropods were an enigmatic group of medium-sized predatory dinosaurs, infamous for the hypertrophied claw on the first manual digit. Megaraptorid dentition is largely restricted to isolated teeth found in association with skeletal parts; however, thein situmaxillary dentition ofMegaraptorwas recently described. A newly discovered right dentary pertaining to theAustralovenatorholotype preservesin situdentition, permitting unambiguous characterisation of the dentary tooth morphology. The new jaw is virtually complete, with an overall elongate, shallow profile, and fifteen visiblein situteeth at varying stages of eruption.In situteeth confirmAustralovenatorexhibited modest pseudoheterodonty, recurved lateral teeth with a serrate distal carina and reduced mesial carina, similar to other megaraptorids.Australovenatoralso combines of figure-of-eight basal cross-section with a lanceolate shape due to the presence of labial and lingual depressions and the lingual twist of the distal carina. Computed tomography and three-dimensional imagery provided superior characterisation of the dentary morphology and enabled an accurate reconstruction to a pre-fossilised state. The newly established dental morphology also afforded re-evaluation of isolated theropod teeth discovered at theAustralovenatorholotype locality and from several additional Winton Formation localities. The isolated Winton teeth are qualitatively and quantitatively similar to thein situdentary teeth ofAustralovenator, but are also morphometrically similar to Abelisauridae, Allosauridae, Coelophysoidea, Megalosauridae and basal Tyrannosauroidea. Qualitative characters, however, clearly distinguish the teeth ofAustralovenatorand the isolated Winton teeth from all other theropods. Evidence from teeth suggests megaraptorids were the dominant predators in the Winton Formation, which contrasts with other penecontemporaneous Gondwanan ecosystems.

The skull and appendicular skeleton of Gryposaurus latidens, a saurolophine hadrosaurid (Dinosauria: Ornithopoda) from the early Campanian (Cretaceous) of Montana, USA

The osteology of the holotype and referred specimens of the saurolophine hadrosaurid, Gryposaurus latidens , from the lower Two Medicine Formation of Montana (USA), is described in detail. With an estimated early Campanian (Late Cretaceous) age, this dinosaur is one of the oldest known hadrosaurids. Gryposaurus latidens shows several autapomorphies, including dentary tooth crowns, with an apicobasal length/mesiodistal width ratio of 1.7–2.2, a single median carina, and large marginal denticles in sections of the dental battery; deep and oval depression on the posteroventral premaxillary surface; and, in the context of Hadrosauridae, a shallow lacrimal process of the rostral process of the jugal. Furthermore, G. latidens differs from G. notabilis and G. monumentensis in having a broadly arcuate anterolateral oral margin of the premaxilla, a posterior margin of the narial fenestra that is wider than the dorsoventral depth of the proximal region of the narial bar, with a nasal crest that rises above the level of the frontals (in adults) and is located above the posterior margin of the narial fenestra, and wide and shallow posteroventral margin of the rostral process of the jugal, among other characters. This study confirmed a previous hypothesis supporting G. latidens as the sister taxon to a clade composed of the other species of Gryposaurus .

Ancistrus falconensis n. sp. and A. gymnorhynchus Kner (Siluriformes: Loricariidae) from central Venezuelan Caribbean coastal streams

A new species, Ancistrus falconensis, is described from the Hueque and Ricoa Rivers, small, isolated Caribbean drainages of northwest Falcón state, (Western Caribbean Zoogeographic Province) Venezuela and compared with A. gymnorhynchus Kner 1854 which occurs in adjacent drainages to the south. Adults of Ancistrus falconensis usually have small light spots on the abdomen in preserved specimens whereas A. gymnorhynchus almost always has the abdomen uniformly gray). They are further distinguished by the following ratios in specimens greater than 60 mm SL: mouth width/pectoral spine length (0.661–0.915 vs. 0.480–0.669, (two specimens of 88 overlap), dentary tooth cup length/ pectoral spine length (0.207–0.264 vs. 0.143–0.198), and premaxillary tooth cup length/pectoral spine length (0.146– 0.215 vs. 0.215–0.318). Falcón state is arid in the area of the type locality of A. falconensis, and water resources face increasing demands for urban, agricultural and industrial uses. Deforestation, river channelization and water diversion heavily impact most coastal streams, causing accelerating habitat loss and degradation. Thus, this new species must be considered vulnerable to extinction.

A new ankylosaur (Dinosauria: Ankylosauria) from the Lower Cretaceous Cloverly Formation of central Montana

A cranium and other associated skeletal elements representing a new ankylosaurid dinosaur, Tatankacephalus cooneyorum gen. et sp. nov. possess several diagnostic features that indicate that this new taxon differs from the only other known ankylosaur from the Cloverly Formation, Sauropelta edwardsorum . These features include a frontoparietal dome, an enlarged nuchal ridge that obscures the occipital region, a circular orbit, ventral curvature in the posterolaterally directed paroccipital processes, a posteroventrally directed foramen magnum, and a number of features on the braincase. The phylogenetic analysis positions Tatankacephalus with Ankylosauridae based on its sharing of several characters with other members of this clade, including an enlarged nuchal segment that obscures the occiput in dorsal view, a ventrally curving lateral profile of the cranium anterior to the orbit, pyramidal postorbital boss, laterally projecting pyramidal quadratojugal boss, the presence of a postocular shelf, the presence of paranasal sinuses, and the lack of a cingulum on a maxillary (or dentary) tooth. It is considered a basal member of Ankylosauridae because it retains premaxillary teeth and a visible lateral temporal fenestra, in contrast to the absence of premaxillary teeth and an obscured lateral temporal fenestra in younger members of this clade.