Monday, 6 May 2013

X is for Xenoceratops

Today we introduce the final Albertan dinosaur from our Albertan dinosaurian alphabet with 'X is for Xenoceratops'. This dinosaur is the only one from Alberta that starts with 'X', and was named only last year. 

In 1958, a well-known American palaeontologist named Wann Langston Jr. discovered a partial skull of a ceratopsian in the Foremost Formation (near the town of Foremost) of southern Alberta. These remains were then returned to the Canadian Museum of Nature in Ottawa, and were left undescribed. 50 years later, some palaeontologists became aware of these bones, and wondered about the animal that they belong to. Upon further examination, they concluded that it was a new animal, and named it Xenoceratops foremostensis [1]. The name Xenoceratops means 'foreign/alien horned face', referring to the fact that it is the only known ceratopsian from the Foremost Formation. It lived during the Late Cretaceous, about 78 million years ago, making it the oldest known ceratopsian found in Canada so far. 
Reconstruction of the frill of Xenoceratops foremostensis (centre) from Ryan et al. [1]
Xenoceratops was a centrosaurine ceratopsian, a group of dinosaurs that get their name from another Albertan ceratopsian, Centrosaurus. In the above image, Xenoceratops is surrounded by other centrosaurines including Centrosaurus (B), Styracosaurus (C) and Pachyrhinosaurus (F). As you can see, it has a very different frill from the others: the midline of the frill bore two thick bony knobs,  two pointed spikes (pointing to the rear and top of the animal in life), several small bumps, and a larger bony projection in the most anterior (forward) position. 

Through analysis of the bones, they determined that Xenoceratops was the most primitive centrosaurine found thus far. Unfortunately, the fragmentary nature of the remains makes it difficult to know for sure where it would have sat in the ceratopsian family. An unprepared skull found in the same region in 2010 does have portions of the face including elongated orbital horns, and has been referred to Xenoceratops. It also may have had  low, ridge-like nasal ornamentation, like those seen in Albertaceratops and Medusaceratops

This find was especially exciting for palaeontologists as it was only the second dinosaur fossil found in the Foremost Formation from more than just teeth. Very few outcrops of this formation are present, making it difficult to excavate and less likely to find fossils than the younger Oldman and Dinosaur Park Formations also of southern Alberta. Unsurprisingly, the species found in this formation are from known groups of dinosaurs from this area, but they are consistently more basal in their respective groups. 

Xenoceratops is yet another ceratopsian from Alberta, and is unfortunately the last dinosaur that we will talk about from Alberta, since no 'Y' or 'Z' dinos exist from our province. Stay tuned for next week, with a theropod from China!

1. Ryan, M.J., et al. 2012. A new ceratopsid from the Foremost Formation (middle Campanian) of Alberta. Canadian Journal of Earth Sciences 49: 1251-1262.

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