Monday, 25 February 2013

N is for Nichollssaura

This week for the Albertan dinosaurian alphabet, we bring you 'N is for Nichollssaura'. The first thing to point out, is that Nichollssaura is not a dinosaur, but a marine reptile called a plesiosaur. I was struggling to find a dinosaur genus that started with the letter 'N' from Alberta (there are none that I could find), and a Twitter follower (thanks Dan!) suggested Nichollssaura. Although not a dinosaur, it is a very well preserved fossil found in Alberta. 

Although Alberta is better known for dinosaur and terrestrial fossils, there are actually a large number of marine fossils found as it was once covered by a large body of water called the Western Interior Seaway. It stretched from the Arctic Ocean to the north, all the way down through the Northwest Territories, Alberta, and western US, down to the Gulf of Mexico. It existed during much of the Cretaceous, and is the reason why Alberta is full of marine fossils. Large marine reptiles like plesiosaurs, pliosaurs, and mosasaurs were common fauna during this time, and can be found often in marine deposits in Alberta from this time. The dinosaurs in Alberta are of ages younger than the seaway, in the very Late Cretaceous. 
Image showing the extent of the Western Interior Seaway (from the USGS)
Now this is where our feature animal Nichollssaura comes in. Nichollssaura had a typical plesiosaurian shape, with a long neck and small head, that lived approximately 110 million years ago. The only known fossil was found in a Syncrude Mine near Fort McMurray, when a large electric shovel knocked off part of the skeleton in 1994. Fortunately, the worker recognised that there was a fossil, stopped digging, and notified the correct people who were able to excavate the fossil. It was first named 'Nichollsia' in honour of Elizabeth "Betsy" Nicholls, former curator of marine reptiles at the Royal Alberta Museum of Palaeontology [1]. However, 'Nichollsia' was preoccupied by a crustacean, and so was renamed Nichollssaura [2]. The single specimen is nearly complete, and was a juvenile or young adult, as seen from the lack of fusion in the vertebrae. It was 2.6 m long and had four flipper-like limbs used for propelling it through the water. The discovery of Nichollssaura filled a 40 million year gap in plesiosaur diversity in the Early Cretaceous. Before this find, there was a huge gap with no plesiosaurs, and this helped us to better understand plesiosaur evolution. This nearly complete, extremely well preserved fossil has revealed a wealth of morphological information on plesiosaurs of this age. 
Artists impression of Nichollssaura by ArthurWeasley
Next week, we'll move on to 'O' with a fairly well-known theropod dinosaur. 

1. Druckenmiller, P.S., and Russell, A.P. 2008. Skeletal anatomy of an exceptionally complete specimen of a new genus of plesiosaur from the Early Cretaceous (Early Albian) of northeastern Alberta, Canada. Palaeontographica Abteilung A 283: 1-33.
2. Druckenmiller, P.S., and Russell, A.P. 2009. The new plesiosaurian genus Nichollssaura from Alberta, Canada: replacement name for the preoccupied genus Nichollsia. Journal of Vertebrate Paleontology 29: 276.

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