The Hell Creek Oviraptorosaur — What Does It Mean For Chirostenotes pergracilis?

Since the 1990′s, a few specimens have been kicking around of a particularly large oviraptorosaur from the Late Cretaceous of North America. Unlike the specimens that form the backbone of the Chirostenotes/Caenagnathus complex, these specimens come from the Maastrichtian, and unlike the similar material recovered from the Horseshoe Canyon Formation and elsewhere, this material comes from the late Maastrichtian. The Hell Creek, to be precise.

Splitting Chirostenotes

Seems audacious of me, eh? Chirostenotes (specifically, Chirostenotes pergracilis) enjoys one of the more interesting synonymy lists among dinosaurs, as it contains (or has contained) no fewer than three generic synonyms and four specific synonyms, but also that it has almost never contained all of these at once, with various authors adding or removing various names depending on newer finds. This has been aided by the difficulty of finding complete or reasonably replete skeletal material of singular individuals of small dinosaurs in the Dinosaur Park Formation of southern Alberta. Instead, partial material abounds. This partial material has led to a rich lesson in synonymy. So … here goes.

Caenagnathidae, comparison of various known skeletal material. Note the exclusion of Caenagnathus collinsi; this is intentional, although I should include it anyways. The three skeletons on the right are considered Chirostenotes (the top is Chirostenotes sp., a non-determinate designation, while the others seem comfortably Chirostenotes pergracilis), the two on the left Elmisaurus rarus.

Better Know a [Dinosaur] – Elmisaurus rarus

This post won’t have much to do with teeth. This will eventually occur, when I focus on toothy things like Suminia (favorite non-mammalian synapsid) or toothless (and known-jawed but edentulous) in which case we come to the oviraptorosaurs, which are odder than you think.

And, plus, I had this image lying around…

Skeletons in silhouette of Elmisaurus rarus. On the left (black silhouette) includes the holotype specimen (ZPAL MgD-I/172, pes) and referred manus+pes material (ZPAL MgD-I/98, partial manus and pes); on the right is the same material expanded to the size of a referred manus+pes (ZPAL MgD-I/20), showing the largest known specimen. Both of these represent only Elmisaurus rarus.