|The holotype of Saurolophus osborni (AMNH 5220). Panel mount photographed by Barnum Brown in 1913. Image from Wikimedia Commons.|
In order to compare the skin impressions on the two Saurolophus species, Bell had to first establish a terminology that could be used to describe the various types of scales present. That terminology is, briefly, as follows: there are 'basement scales' which serve as a backdrop to 'feature-scales', the larger more distinct scales. 'Interstitial-tissues' lie between the scales, and allow the skin its flexibility. There are 'midline feature-scales' that run down the backs of the animals, and 'polygonal scales' which are, as you may have guessed, polygonal in nature and can be either 'basement' or 'feature'. On the other hand, 'pebbly scales' (also known as 'pebbles') are the smallest type of scales, and always form the 'basement'. There are asymmetrical 'shell scales', circular ' shield scales', and 'irregular scales' with no clear geometric proportions. Bell looked at skin impressions containing these types of integument from the skull and mandible, the forlimbs and hindlimbs, the tail, and the main body of the animals. And based on the location of these scales on the body, their anatomical direction (in relation to the axial midline of the animal), and the scale shape and pattern, he was able to establish a scale morphology that can actually be used to show taxonomic differences between these two very closely related dinosaur species. Did I mention how cool this is?
|Figure 12. Regions of skin impressions (light grey) currently known from (A) S. osborni and (B) S. angustirostris. Image from Bell, 2012.|
|Figure 13. Soft tissue reconstructions of Saurolophus based on skin impressions from (A) S. osborni and (B) S. angustirostris. Illustration by L. Xing and Y. Liu, from Bell, 2012.|
Cool. Cool, cool, cool. There is nothing else to say. This is great research, and can be applied to other skin impressions, both from other hadrosaurs, and possible dinosaurs at large. I cant' wait to see what new studies come out of this one.
Bell, P. R. 2012. Standardied Terminology and Potential Taxonomic Utility for Hadrosaurid Skin Impressions: A Case Study for Saurolophus from Canada and Mongolia. PLoS ONE 7(2): e31295. doi:10.1371/journal.pone.0031295