Search Results (9)

The end of the Cretaceous saw the Western Interior Seaway divide North America into two land masses, Laramidia in the west and Appalachia in the east. Laramidian dinosaurs inhabited a narrow strip of land extending from Mexico to Alaska. Within this geographically restricted area, dinosaurs evolved high diversity and endemism, with distinct species in the north and south. Here, we report a new tyrannosaurid from the Late Campanian-aged Cerro del Pueblo Formation of Coahuila, Mexico, which is part of a tribe of tyrannosaurs originating in southern Laramidia. Phylogenetic analysis recovers the new tyrannosaur as part of a clade including Labocania anomala from the La Bocana Roja Formation of Baja California Norte, Bistahieversor sealeyi from the Kirtland Formation of New Mexico, Teratophoneus curriei from the Kaiparowits Formation in Utah, and Dynamoterror dynastes from the Menefee Formation of New Mexico. Distinct frontal morphology and the younger age (~72.5–73 Ma versus >75.8 Ma for L. anomala) support recognition of the new tyrannosaur as a distinct species of Labocania, Labocania aguillonae. The Labocania clade dominated southern Laramidia at a time when the north was dominated by daspletosaurins and albertosaurines. The high endemism seen in tyrannosaurids is remarkable, given that modern apex predators have large geographic ranges and hints that the diversity of carnivorous dinosaurs has been underestimated. Full article

The Late Cretaceous of Western North America (Laramidia) supported a diverse dinosaur fauna, with duckbilled dinosaurs (Hadrosauridae) being among the most speciose and abundant members of this assemblage. Historically, collecting and preservational biases have meant that dinosaurs from Mexico and the American Southwest are poorly known compared to those of the northern Great Plains. However, evidence increasingly suggests that distinct species and clades inhabited southern Laramidia. Here, a new kritosaurin hadrosaurid, represented by the anterior part of a skull, is reported from the late Campanian of the Cerro del Pueblo Formation, ~72.5 Ma, in Coahuila, Mexico. The Cerro del Pueblo Formation kritosaur was originally considered to represent the same species as a saurolophine from the Olmos Formation of Sabinas, but the Sabinas hadrosaur is now considered a distinct taxon. More recently, the Cerro del Pueblo Formation kritosaur has been referred to Kritosaurus navajovius. We show it represents a new species related to Gryposaurus. The new species is distinguished by its large size, the shape of the premaxillary nasal process, the strongly downturned dentary, and massive denticles on the premaxilla’s palatal surface, supporting recognition of a new taxon, Coahuilasaurus lipani. The dinosaur assemblage of the Cerro del Pueblo Formation shows higher diversity than the contemporaneous fauna of the Horseshoe Canyon Formation in Alberta. Furthermore, Kritosaurini, Lambeosaurini, and Parasaurolophini all persist into the latest Campanian in southern Laramidia after disappearing from northern Laramidia. These patterns suggest declining herbivore diversity seen at high latitudes may be a local, rather than global phenomenon, perhaps driven by cooling at high latitudes in the Late Campanian and Maastrichtian. Full article

An articulated group of skeletal elements comprising a sacrum, both ilia and a first caudal vertebra, plus an isolated tooth found in immediate proximity to the bones, from the lower Cenomanian Chalk at Saint-Jouin-Bruneval (Seine-Maritime, Normandy, France) is described and attributed to a new genus and species of abelisaurid theropod, Caletodraco cottardi, on the basis of several characters of the sacrum and pelvis. The peculiar shape of the transverse process of the first caudal vertebra shows that Caletodraco cottardi differs from majungasaurine abelisaurids previously described from Europe, such as Arcovenator escotae, and belongs to the Furileusauria, a group of derived abelisaurids hitherto recognized only from South America. The presence of a furileusaurian abelisaurid in the Cenomanian of Normandy suggests that the biogeographical history of the Abelisauridae in Europe was more complex than hitherto admitted. Several previously described European abelisaurids, such as the Albian Genusaurus sisteronis, may in fact belong to the Furileusauria. Full article

Tyrannosaurs are among the most intensively studied and best-known dinosaurs. Despite this, their relationships and systematics are highly controversial. An ongoing debate concerns the validity of Nanotyrannus lancensis, interpreted either as a distinct genus of small-bodied tyrannosaur or a juvenile of Tyrannosaurus rex. We examine multiple lines of evidence and show that the evidence strongly supports recognition of Nanotyrannus as a distinct species for the following reasons: 1. High diversity of tyrannosaurs and predatory dinosaurs supports the idea that multiple tyrannosaurids inhabited the late Maastrichtian of Laramidia; 2. Nanotyrannus lacks characters supporting referral to Tyrannosaurus or Tyrannosaurinae but differs from T. rex in >150 morphological characters, while intermediate forms combining the features of Nanotyrannus and T. rex are unknown; 3. Histology shows specimens of Nanotyrannus showing (i) skeletal fusions, (ii) mature skull bone textures, (iii) slow growth rates relative to T. rex, (iv) decelerating growth in their final years of life, and (v) growth curves predicting adult masses of ~1500 kg or less, showing these animals are subadults and young adults, not juvenile Tyrannosaurus; 4. growth series of other tyrannosaurids, including Tarbosaurus and Gorgosaurus, do not show morphological changes proposed for a Nanotyrannus–Tyrannosaurus growth series, and deriving Tyrannosaurus from Nanotyrannus requires several changes inconsistent with known patterns of dinosaur development; 5. Juvenile T. rex exist, showing diagnostic features of Tyrannosaurus; 6. Phylogenetic analysis suggests that Nanotyrannus may lie outside Tyrannosauridae. Tyrannosaur diversity before the K-Pg extinction is higher than previously appreciated. The challenges inherent in diagnosing species based on fossils mean paleontologists may be systematically underestimating the diversity of ancient ecosystems. Full article

Turiasauria is a clade of basal sauropod dinosaurs hitherto only known from the Middle Jurassic (Bathonian) to the Lower Cretaceous (Valanginian). A new find of a shed tooth crown from the Lower Jurassic (Pliensbachian), Halse Formation of Bornholm, Denmark, is spoon-like, asymmetrical, and heart-shaped, which identifies the tooth as turiasaurian, pushing the origin of the Turiasauria some 17 My back into the Lower Jurassic. This suggests a North Pangean/Laurasian origin of the turiasaurian clade, which then, during the Middle to Late Jurassic, dispersed through Europe, India, and Africa, with their latest representatives found in the Early Cretaceous of England and North America. Furthermore, this is the first record of a sauropod from the Pliensbachian in Europe. Full article

The first discovery of a dinosaur bone from the Kingdom of Cambodia is reported in this paper. It consists of a sauropod fibula from a sandstone layer on Koh Paur island, in Koh Kong province, in south-western Cambodia. The dinosaur-bearing bed belongs to the non-marine Grès Supérieurs series and is apparently of Early Cretaceous age. On the basis of various characters, notably the development of the anteromedial crest, the dinosaur fibula from Koh Paur is referred to a euhelopodid titanosauriform. This first dinosaur discovery in Cambodia suggests that the thick non-marine formations which cover vast areas in the south-western part of the country are potentially an important source of continental Mesozoic vertebrates. Full article

The Lo Hueco fossil site (Cuenca, Spain) is one of the most relevant localities for the study of Late Cretaceous continental vertebrate faunas from Europe. The fossil record of theropod dinosaurs from this locality is represented by scarce isolated postcranial materials that were preliminarily attributed to abelisaurids and to a possible giant bird, in addition to a large assemblage of isolated teeth that were related to different maniraptoran clades. Here, we describe an isolated partial left tibia articulated with the proximal tarsals and discuss their taxonomic affinities. A review of the European fossil record of Late Cretaceous theropods was performed to analyze possible changes in the faunistical composition during this period. The specimen from Lo Hueco exhibits some characters that have been interpreted as apomorphies for maniraptoran coelurosaurs and a combination of features compatible with deinonychosaurians. Within this clade, the specimen is more favorably comparable with velociraptorine dromaeosaurids and is tentatively interpreted as a member of this group. This specimen is one of the few non-dental specimens of dromaeosaurids described thus far from the Upper Cretaceous of the Iberian Peninsula and contributes to a better understanding of the composition and evolutionary history of the European theropod fauna during the last stages of the Mesozoic. Full article

The eastern Iberian Peninsula is one of the places with most stegosaur fossils in all of Europe. In the present study, we describe new remains from six different fossil sites from the Upper Jurassic of the Villar del Arzobispo Formation (Kimmeridgian–Tithonian). The remains comprise: a left humerus from CT-61 (El Castellar, Teruel), a dermal spine from Puntal de la Magdalena (Alpuente, Valencia), two caudal neural arches and five caudal vertebrae from Cañada París (Alpuente, Valencia), two caudal centra from Alpuente (Valencia) and four caudal vertebrae from Barrihonda-El Humero (Riodeva, Teruel). The left humerus (CT-61-1) and dermal spine (MPA D-110) are referred to Stegosauria indet. The caudal vertebrae from Alpuente (Cañada París specimen, MPA-653 and MPA D-1086) are referred to cf. Dacentrurus sp. Finally, the caudal vertebrae from Riodeva (Barrihonda-El Humero specimen) are referred to Dacentrurus armatus and assigned to a previously known caudal series from this site. The presence of abundant localities with stegosaurian remains reaffirms the important role of stegosaur dinosaurs in Late Jurassic coastal ecosystems. Full article

Iguanodon bernissartensis is the most frequently and widely cited styracosternan ornithopod in Western Europe during the Early Cretaceous, although some of these assignments likely need to be revised to establish the true distribution of the taxon. Here, we describe a new specimen of I. bernissartensis from the upper Barremian of the Iberian Peninsula. Based on the unique combination of shared characters, the new specimen from the Arcillas de Morella Formation at Morella locality (Castellón, Spain) can be confidently referred to Iguanodon bernissartensis. These characters include parallel-sided anterior and posterior margins of the dorsal and the caudal neural spines as well as the presence of a ventral keel in the posterior dorsal centra and a broad ventral sulcus in the midline of the central surface of the most posterior sacral vertebrae. This new evidence of Iguanodon bernissartensis reinforces the knowledge about styracosternan ornithopods as the most frequently recorded dinosaur group in the Arcillas de Morella Formation. Full article