Tuesday 16 December 2014

A Ceratopsian Dinosaur from the Early Cretaceous of Montana.

Ceratopsian Dinosaurs are thought to have originated in Asia in the Early Cretaceous, spreading to Europe and North America, and becoming the most important and diverse group of herbivorous Dinosaurs in North America by the end of the Period. Unfortunately, while the group are well known from Latest Cretaceous fossils in North America, for much of the period they are only known from isolated teeth and bone fragments. It is not certain when they first reached North America, nor whether they got their via northeast Asia and Alaska or via Europe.

In a paper published in the journal PLoS One on 10 December 2014, Andrew Farke of the Raymond M. Alf Museum of Paleontology and the Sam Noble Oklahoma Museum of Natural History, Desmond Maxwell of the Department of Biological Sciences at the University of the Pacific and the Sam Noble Oklahoma Museum of Natural History, Richard Cifellialso of the Sam Noble Oklahoma Museum of Natural History and Mathew Wedel of the College of Podiatric Medicine at the Western University of Health Sciences and of the Sam Noble Oklahoma Museum of Natural History describe a new species of Ceratopsid Dinosaur from the Early Cretaceous Cloverly Formation of Carbon County in southern Montana.

The new species is named Aquilops americanus, where ‘Aquilops’ means ‘Eagle-face’, a reference to the Dinosaur’s hoked beak, and ‘americanus’ means ‘American’. The specimen comprises a partial skull 84.2 mm in length, with an accompanying left lower jaw in three fragments. The skull is slightly compressed mediolaterally and dorsoventrally, leading to some deformation, particularly at the rear, and the right side is better preserved than the left.

Cranium of Aquilops americanus. (A) Right lateral and (B) left lateral views. Farke et al. (2014).

Aquilops americanusis about 60% of the size of specimens of the early Ceratopsians Liaoceratops yanzigouensis and Archaeoceratops oshimai, both of which are presumed to be adults, and pf a similar size to a presumed juvenile specimen of Liaoceratops yanzigouensis. Developmentally it shows a mixture of features associated with juvenile and adult Ceratpsians, and Farke et al. suggest that the specimen is a subadult (i.e. an animal that had almost reached adult size).

Cranial reconstruction of Aquilops americanus in (A) right lateral and (B) dorsal views. Farke et al. (2014).

Aquilops americanus is the earliest described Ceratopsian from North America, dating from about 104–109 million years ago. This suggests that Ceratopsians had reached the continent much earlier than previously supposed; however as we currently understand the phylogeny of Ceratpsian Dinosaurs it occupies a position very close to the base of the group’s family tree, with the more derived Ceratopsians of Late Cretaceous North America emerging from a group of Dinosaurs that were apparently still in Asia much later the period, suggesting that Aquilops americanus is the result of an earlier, separate invasion of the continent, and has little bearing on the origins of these later animals.

Hypothesis of phylogeny and biogeography for Neoceratopsia. Some terminal taxa have been combined for space considerations, and the range bars for each taxon indicate uncertainty rather than known geological ranges. Continent icons indicate the ancestral areas reconstructed by DEC modeling. Silhouettes depict representative members of major clades and grades. Farke et al. (2014).

Life restoration of Aquilops americanus. Brian Engh in Farke et al. (2014).

See also…

Ceratopsid Dinosaurs were a speciose group of large, herbivorous Dinosaurs from the Late Cretaceous of...

Ceratopsid Dinosaurs were a speciose group of large, herbivorous Dinosaurs from the Late Cretaceous of Asia and North America. They were large, quadruped Dinosaurs with distinctive neck-frills and horns, and...

Ceratopsid dinosaurs changed considerably during growth, which caused early palaeontologists to name different growth stages of the same animal as different species, or even genera. The Maastrichtian (Latest Cretaceous, 70.6-65.5 million years ago) Ceratopsids of North America were at one point divided into 22 species...

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