Sunday 14 May 2017

Zuul crurivastator: A new and exceptionally well preserved Ankylosaur from the Late Cretaceous Judith River Formation of northern Montana.

The Ankylosaurids were large armoured Dinosaurs from the Cretaceous of Europe, Asia and North America. Their bodies were encased in heavy armour forming an effective shell and they had large bony clubs on the ends of their tails. They are believed to have been entirely herbivorous, and had beak-like mouths, occasionally with residual teeth. Despite the extensive armour of the Ankylosaurids, which gives them excellent preservational potential, complete skeletons of these Dinosaurs are rare, hampering our understanding of the group.

In a paper published in the journal Royal Society Open Science on 10 May 2017, Victoria Arbour and David Evans of the Department of Palaeobiology at the Royal Ontario Museum and the Department of Ecology and Evolutionary Biology at the University of Toronto, describe a new and exceptionally well preserved Ankylosaurid Dinosaur from the Late Cretaceous Judith River Formation of Hill County in Montana.

The Judith River Formation was laid down between 75 and 80 million years ago on what was then a coastal plain on the Bear Paw Sea coast of the island of Laramida, and is now northern Montana. It is roughly equivalent in age to the Oldman and Dinosaur Park formations of southern Alberta and the Two Medicine Formation of Montana. These strata have been excavated for Dinosaur remains since the early nineteenth century, though the majority of material produced from the Judith River Formation has been fragmentary in nature.

The new Dinosaur is named Zuul crurivastator, where 'Zuul' refers to 'Zuul the Gatekeeper' a monster in the 1984 film Ghostbusters, and 'crurivastator' means 'destroyer of shins' in Latin, in reference to the large tail-club of the specimen. The species is described from a single specimen located during the excavation of a Tyraosaurus specimen by a commercial fossil extraction company and later acquired by the Royal Ontario Museum. The specimen comprises two blocks recovered from the overturned above the Tyranosaurus specimen (i.e. material that was removed because it was above that specimen), one containing the head and torso and the other the tail.. The specimen had been exposed prior to discovery and was partially eroded away, nevertheless it appears to be fairly complete (it has not yet been completely extracted from the rock matrix) with an almost complete skull and some soft tissue preservation.

Well-preserved skull and jaws of Zuul crurivastator showing quality of preservation. Arbour & Evans (2017).

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