Monday, 3 December 2012

D is for Daspletosaurus!

Next up in our 'A-Z of Dinosaurs from Alberta' series is the ferocious theropod Daspletosaurus (pronounced 'dass-PLEE-tuh-SAWR-us). Daspletosaurus is a large tyrannosaur found in Alberta and the US, and its name means 'frightful lizard', which I'm pretty sure I don't need to explain. It lived about 77-74 million years ago, close to 10 million years before its more famous relative, T. rex. Although it was likely an apex predator, Daspletosaurus was small for a tyrannosaurid at 2500 kg and 8-9 m long. It's hard to imagine that being considered small! Like other tyrannosaurids, its skull was huge, at about 1 m in length, and it had very short arms with two fingers (although it may have had the longest arms compared to the rest of its body of any tyrannosaur). Unlike other tyrannosaurids, Daspletosaurus has distinct crests around its eyes [1]. 
Currently, just one species is known: Daspletosaurus torosus. However, it is likely that there are more species that are yet to be described including one from Dinosaur Provincial Park here in Alberta [1]. 
Unfortunately, the exact position of Daspletosaurus within the Tyrannosauridae is not clear, especially with these undescribed species. It has been suggested that Daspletosaurus is actually the most closely related dinosaur to Tyrannosaurus (or to the Tyrannosaurus + Tarbosaurus group) [2]. 
Artists impression of Daspletosaurus torosus by Steveoc 86
Daspletosaurus lived alongside another tyrannosaurid, Gorgosaurus. The existence of two large predators, and in fact two tyrannosaurids together is a rare occurrence. In order for both to survive in the same region, they likely had some type of niche partitioning (separation of their ecological positions), either by living in different environments, preying on different animals, being active at different times, or maybe even being separated geographically. Several studies have aimed to answer this, but there is no clear explanation yet. It also lived alongside dinosaurs like Centrosaurus, and likely preyed on large ceratopsians and hadrosaurs. There is even some evidence that Daspletosaurus lived in social groups, or maybe hunted in groups, which is also seen in the tyrannosaurid Albertosaurus
A Daspletosaurus eating a ceratopsian. Image credit to Dmitry Bogdanov
Several daspletosaurs have been found in Alberta, and well known Canadian palaeontologist Philip Currie (currently of the University of Alberta) has worked on this dinosaur before. In fact, during the last field season, the Currie lab was able to remove a very well preserved Daspletosaurus from southern Alberta, which is currently being prepared at the University of Alberta! 

Other 'D' dinosaurs from Alberta

1. Currie, PJ. 2003. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48: 191-226. Download here
2. Carr, TD., Williamson, TE., and Schwimmer, DR. 2005. A new genus and species of tyrannosauroid from the Late Cretaceous (Middle Campanian) Demopolis Formation of Alabama. Journal of Vertebrate Paleontology 25: 119-143.
More information can be found at the Saurian blog on Daspletosaurus

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