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Drumheller, Canada

Trace marks on the bones of non-avian dinosaurs may relate to feeding by large carnivores or as a result of combat. Here the cranium and mandible of a specimen of Daspletosaurus are described that show numerous premortem injuries with evidence of healing and these are inferred to relate primarily to intraspecific combat. In addition, postmortem damage to the mandible is indicative of late stage carcass consumption and the taphonomic context suggests that this was scavenging. These postmortembites were delivered by a large bodied tyrannosaurid theropod and may have been a second Daspletosaurus, and thus this would be an additional record of tyrannosaurid cannibalism. Copyright 2015 Hone and Tanke.

Maidment S.C.R.,Natural History Museum in London | Maidment S.C.R.,Imperial College London | Henderson D.M.,Royal Tyrrell Museum | Barrett P.M.,Natural History Museum in London
Naturwissenschaften | Year: 2014

The exceptionally rare transition to quadrupedalism from bipedal ancestors occurred on three independent occasions in ornithischian dinosaurs. The possible driving forces behind these transitions remain elusive, but several hypotheses—including the development of dermal armour and the expansion of head size and cranial ornamentation—have been proposed to account for this major shift in stance. We modelled the position of the centre of mass (CoM) in several exemplar ornithischian taxa and demonstrate that the anterior shifts in CoM position associated with the development of an enlarged skull ornamented with horns and frills for display/defence may have been one of the drivers promoting ceratopsian quadrupedality. A posterior shift in CoM position coincident with the development of extensive dermal armour in thyreophorans demonstrates this cannot have been a primary causative mechanism for quadrupedality in this clade. Quadrupedalism developed in response to different selective pressures in each ornithischian lineage, indicating different evolutionary pathways to convergent quadrupedal morphology. © 2014, Springer-Verlag Berlin Heidelberg.

Eberle J.J.,University of Colorado at Boulder | Eberth D.A.,Royal Tyrrell Museum
Canadian Journal of Earth Sciences | Year: 2015

We describe early Eocene (Wasatchian) occurrences of the isectolophid Homogalax, tapiroids Heptodon posticus, Heptodon cf. H. posticus, and Heptodon sp., as well as early middle Eocene (Bridgerian) fossils of the brontothere Palaeosyops from localities in the Margaret Formation of the Eureka Sound Group on Ellesmere Island, Nunavut, Arctic Canada. Their occurrence on Ellesmere Island considerably extends the geographic range of these taxa, previously known from mid-latitude localities in British Columbia (only Heptodon), the Western Interior of the United States, and Asia (Homogalax, Heptodon, and Palaeosyops). We also place the fossil localities near Bay Fiord on central Ellesmere Island into a refined lithostratigraphic framework based upon data from three measured stratigraphic sections. Our stratigraphic data confirm the presence of two, stratigraphically distinct fossil assemblages — a late Wasatchian-aged lower assemblage and a Bridgerian-aged upper assemblage that were previously hypothesized by others based on faunal differences—that are separated by a 478mthick stratigraphic gap that appears to lack fossil vertebrates. From a paleoenvironmental perspective, occurrence of the tapiroid Heptodon in the Eocene Arctic corroborates an hypothesis put forward by others that tapiroids are proxies for densely forested habitats, although they were adapted to a range of temperatures including near (or at) freezing temperatures of Eocene Arctic winters. Further, Arctic occurrences of tapiroids and brontotheres imply that these typical mid-latitude ungulate mammals were adapted to Arctic environments, thereby increasing the probability of Trans-Beringian dispersal during early and middle Eocene time. © 2015, NRC Research Press. All rights reserved.

Brinkman D.B.,Royal Tyrrell Museum | Densmore M.J.,Harvard University | Joyce W.G.,University of Tubingen | Joyce W.G.,Yale University
Bulletin of the Peabody Museum of Natural History | Year: 2010

Two partial "macrobaenid" shells are described from a single Late Paleocene (Clarkforkian 1) quarry at Burns Mine near Washoe, Carbon County, Montana, USA, and are referred to "Clemmys" backmani, a taxon typified in the Paleocene Ravenscrag Formation of Saskatchewan, Canada. Though tentative, morphological, temporal and spatial arguments highlight similarities between "Clemmys" backmani and the Campanian taxon Judithemys sukhanovi, and we therefore suggest the new combination Judithemys backmani. Judithemys sukhanovi and Judithemys backmani both originate from the eastern margins of the western landmass Laramidia and exhibit a pronounced ridge along the visceral side of the first costal and C-shaped bridge peripherals into which the flat thoracic ribs insert superficially, characters that must be interpreted as symplesiomorphies. By contrast, the coeval taxon Osteopygis emarginatus originates from the eastern shores of the eastern landmass Appalachia, lacks the visceral ridge of the first costal, and possesses massive, triangular peripherals into which the peglike thoracic ribs insert deeply. © 2010 Peabody Museum of Natural History.

Longrich N.R.,Yale University | Sankey J.,California State University, Stanislaus | Tanke D.,Royal Tyrrell Museum
Cretaceous Research | Year: 2010

Recent work in the Campanian Aguja Formation of Big Bend, Texas, has resulted in the recovery of two frontoparietal domes from a new genus of pachycephalosaur. Texacephale langstoni gen. et sp. nov. is diagnosed by a tall, arched nasal boss, flange-like processes articulating the dome with the peripheral elements, and a low pedicel separating the cerebral fossa from the skull roof. The skull dome is composed largely of the fused frontals and parietals, with limited participation of the peripheral elements, and the supratemporal fenestrae remain open. Phylogenetic analysis indicates that Texacephale langstoni is a basal member of the Pachycephalosauria. The discovery of Texacephale supports previous suggestions that the dinosaur fauna of Texas was distinct from that of contemporary assemblages to the north. The phylogenetic analysis presented here indicates that the Asian pachycephalosaurs form a monophyletic group, deeply nested within the Pachycephalosauridae, and that the basal members of the group are all North American. This finding indicates that pachycephalosaurids originated in North America, rather than Asia, as previously believed. The high diversity of North American pachycephalosaurs and the late appearance of pachycephalosaurs in Asia are consistent with this hypothesis. The biology of Texacephale and other Pachycephalosauridae are also discussed. The morphology of the dome in Texacephale and other pachycephalosaurs supports the hypothesis that pachycephalosaurids engaged in intraspecific combat, while the occurrence of Texacephale and other pachycephalosaurs in nearshore deposits argues that the pachycephalosaurs were not restricted to inland habitats. © 2010 Elsevier Ltd.

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