Monday, 1 April 2013

S is for Saurolophus

For this week's Albertan dinosaurian alphabet post, we took to social media to find out what people wanted to hear about. The question was simple: would you prefer to learn about a hadrosaur (duck-bill) or a carnivorous theropod? Much to my surprise, the responses were remarkably one-sided, with only 2 people voting for a theropod, and everyone else going for the hadrosaur. So, the public has spoken, and this week we give you 'S is for Saurolophus'. 

Saurolophus was a large hadrosaur that lived during the Late Cretaceous (approximately 69 million years ago) in both western North America and Mongolia. It's name means 'lizard-crest' in reference to the small crest found on the back of it's skull. The first fossil was found by Barnum Brown in 1911 along the Red Deer River, and constitutes a nearly complete skeleton now on display at the American Museum of Natural History. This is the type specimen for the species Saurolophus osborni, and was nearly 10 m long and weighed 1900 kg. Currently, one other valid species exists, S. angustirostris, and represents the larger Mongolian specimens at as many as 12 m long. The crest of Saurolophus was long and blade-like, and is found in younger specimens as well as adults. Although the crest was largely solid, it did have some hollow chambers, and several different functions have been proposed including respiration, sexual selection, muscle attachment, and visual signalling. 
Photograph of the original Saurolophus osborni skeleton found by Brown along the Red Deer River
Saurolophus lived alongside many well known dinosaurs from the Horseshoe Canyon Formation of Alberta such as the armoured dinosaurs Euoplocephalus and Edmontonia, other hadrosaurs like Edmontosaurus and Hypacrosaurus, and the tyrannosaurs Albertosaurus and Daspletosaurus. In Asia, it lived with some less well-known animals like the armoured Tarchia, troodontid Saurornithoides and the tyrannosaur Tarbosaurus, a close relative to T. rex. Like other hadrosaurs, it was able to walk on 2 (bipedal) or 4 (quadrupedal) legs, and was a herbivore that used its massive battery of teeth to chew and grind tough plant material. 

In recent years, much of the work on Saurolophus has been done by Phil Bell, former University of Alberta student who is now the palaeontologist at the future Philip J. Currie Dinosaur Museum near Grande Prairie. Some of you may remember his talk at Jurassic Forest last season on skin and scale patterns in hadrosaurs. In his study, he proposed that S. osborni and S. angustirostris could be differentiated by their scale patterns, as significant fossilised skin has been found for both species [1]. He described the Mongolian species (S. angustirostris) as having a row of distinctive square scales that ran along the back and tail, while the Albertan S. osborni lacked this row and had only smooth scales. Furthermore, the Mongolian species had vertical rows of scales on the tail, which likely corresponded to a striped pattern in life, while Albertan ones had a radial scale pattern which may have represented a mottled/spotted colouration. This is quite interesting since dinosaur skin is so rarely fossilised, and even more rarely in this much detail or large amounts, making it difficult to distinguish patterns. This was the first time skin had been used as a possible method to distinguish different species. 
Possible colouration patterns in A. S. osborni and B. S. angustirostris. Image copyright Lida Xing and Y. Liu (Bell [1])
And that's it for Saurolophus! I hope everyone that voted for the hadrosaur is happy, and those of you that didn't have learned something interesting about this dinosaur. Next week we're on to the letter 'T' and we'll talk about a well known carnivore (but no, it's not T. rex!)

Other 'S' dinosaurs from Alberta

1. Bell, P.R. 2012. Standardized terminology and potential taxonomic utility for hadrosaurid skin impressions: a case study for Saurolophus from Canada and Mongolia. PLoS ONE 7: e31295 - Freely accessible here doi:10.1371/journal.pone.0031295

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