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Vagaceratops irvinensis

Amazing Story!

Did you ever make a mistake, only to have things turn out really well, maybe even better than you had planned? That's what happened to Canadian Museum of Nature researchers when they opened a plaster field jacket only to discover they had found a new dinosaur, previously unknown to science!

Palaeontologists have debated for years about the legs of ceratopsian (horned) dinosaurs: some think that their front legs were straight, like an elephant's, and some think that their legs bent outwards at the knees, like a turtle's. Former Museum palaeontologist Wann Langston had an idea: why not examine the legs of a dinosaur that had died standing up, to see whether this would resolve the debate? He knew that he had collected such a specimen in 1958, a ceratopsian he thought was likely a Chasmosaurus belli.

Lateral view of the skull of Vagaceratops irvinensis CMNFV41357.
The skull of the holotype of Vagaceratops irvinensis.
Catalogue: CMNFV41357

But field jackets aren't exactly stamped "This End Up". They're lumpy, irregularly shaped things, with no clues as to which end might be the head and which the tail. When Nature's staff opened the field jacket, intending to start at the bottom (to get to the legs first), they found that they had opened the top, and were excavating the frill instead! And lo-and-behold, the frill was different-enough from previously known chasmosaurs to suggest that this one might be a species previously unknown to science!

The skull (including the frill) of this new chasmosaur specimen is about 1.4 m long. At its widest, the frill is 1 m. The animal was probably 3 m long from the tip of its snout to its hip, with its tail adding another 2 m. There is no way to know if the animal was male or female. The dinosaur lived about 72 million years ago.

Lead researcher Rob Holmes doesn't know whether this dinosaur will add anything useful to the front legs debate, but he doesn't seem to mind. The whole Museum team (Rob Holmes, Clayton Kennedy and Kieran Shepherd) is excited to have discovered a new horned dinosaur, right in Nature's collection.

The first task for the research team was to carefully reconstruct the skull; palaeontologists often use the skull to identify a dinosaur. Careful measurements were taken and a phylogenetic analysis was completed. (This analysis constructs a type of family tree in order to compare similarities and differences with known dinosaurs). The result led in October 2001 to the identification of the new species, with its own unique name: Chasmosaurus irvinensis.

Years later, more fossils of the same kind were found in the United States. The information that they offer indicates that Chasmosaurus irvinensis is more distantly related to the other species in the genus Chasmosaurus than originally thought. Consequently, it was reclassified into a new genus, and named Vagaceratops irvinensis. It is the only species in this genus.

In the family tree of phylogenetic relationships, Vagaceratops is found on a later branch than Chasmosaurus; both genera are in the chasmosaurine subfamily (chasmosaurs) of the ceratopsians (horned dinosaurs), but they are not closely related.

Detail of epoccipitals on the Vagaceratops irvinensis frill CMNFV41357.
The distinct curl is obvious in this detail of epoccipitals on the Vagaceratops irvinensis frill.

Illustration of anterior view of Vagaceratops irvinensis skull.
In this illustration of an anterior view of the Vagaceratops irvinensis skull, the "chasms" are clearly visible.

Palaeontologists had described most known horned dinosaurs by the beginning of the First World War, and few species have been discovered until recent years; sometimes it pays to open the wrong end first!


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    A 3D image of the fleshed-out Vagaceratops irvinensis.
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