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Thescelosaurus assiniboiensis, new ornithopod species



From: Ben Creisler
bscreisler@yahoo.com
 
A new paper:
 
CALEB MARSHALL BROWN, CLINT A. BOYD and ANTHONY P. RUSSELL (2011)
A new basal ornithopod dinosaur (Frenchman Formation, Saskatchewan, Canada), 
and implications for late Maastrichtian ornithischian diversity in North 
America.
Zoological Journal of the Linnean Society 163(4): 1157–1198, December 2011
DOI: 10.1111/j.1096-3642.2011.00735.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00735.x/abstract

A small, articulated basal ornithopod skeleton from the Frenchman Formation 
(late Maastrichtian) of Saskatchewan (RSM P 1225.1), previously referred to the 
taxon Thescelosaurus, differs from both recognized species of this taxon 
(Thescelosaurus neglectus and Thescelosaurus garbanii). The differences are 
taxonomically informative and we recognize this specimen as the holotype of a 
new species, Thescelosaurus assiniboiensis sp. nov., diagnosed by the presence 
of two autapomorphies, and displaying plesiomorphic traits more similar to 
those of Parksosaurus, than to those of the other Thescelosaurus species. The 
Frenchman Formation also harbours an intriguing faunal assemblage in which 
Thescelosaurus represents one of the most abundant dinosaur taxa, and preserves 
a relatively high proportion of small (putatively juvenile and subadult) 
specimens of many dinosaur taxa. Further work that increases the faunal sample 
from this formation, and that permits
 quantitative comparisons with contemporary formations, will determine whether 
or not these differences are well supported, and will determine their ultimate 
palaeobiological significance. Identification of a third species of 
Thescelosaurus from the late Maastrichtian of North America suggests that this 
taxon was more diverse than previously recognized, and shows an increase in 
diversity from the Campanian through the late Maastrichtian, contrasting the 
trends seen in most other ornithischian clades.