STL Science Center

STL Science Center

27 October 2012

Even In Canada I Bet Chirostenotes Is Warmer

An ice chilled day in Kansas folks. I cannot see any ice from my living room but it's clear there is frost on the grass and the temperature was 23 F when I sat down at the computer; that was 2 hours ago, but I have been sifting through a lot of art this morning trying to find some pieces that really highlight what we are looking for this week.

©Jaime A. Headden
I think we should start by looking at what Gilmore and other early paleontologists were looking at when they first unearthed Chirostenotes. The hands in this skeletal illustration are the holotype used by Gilmore to describe a new genus and species; a little goes a long way it appears. The legs are paired by Headden, legs had not been discovered in the earliest finds in pairs like this and it is done "for the sake of elegance" according to the illustrator. In the past I have also shown the holotypes of some genera and species specifically, but I think this may be one of the smallest amounts of data we have had to look at to proclaim a new species so far. That does not mean this has not been done, naming a species, with less material than this before, because it has indeed been done. How do we know that the skull is correct though? Or perhaps the shape of the skull is a new thing?

©Tuomas Koivurinne
The fact is that it is a newer addition to the body in terms of known skeletal material. The hands were discovered initially in 1914, feet in 1932, 1936 gave us lower jaws, the 1960s saw a few other sorted pieces given other names and the discovery of Elmisaurus in Asia, 1988 found Currie and Russell looking at a 1923 stored specimen that tied almost all of the North American specimens back together, and in 1997 Hans Dieter Sues renamed Parks' 1933 specimens as a second species in the Chirostenotes genus. Somewhere in there, during the 1970s I think it was, a skeleton was found that showed some more of the skull shape, mostly lower and forward jaw fragments, and helped to further identify Chirostenotes as an Oviraptorosaur, as if the body pieces found before the skull had not pointed in that general direction to begin with. The overall behaviors and diets of the animal were therefore referred to as being akin to their earlier ancestors and cousins in Asia: omnivorous with an ability to consume leaves and seeds in addition to small prey items like early mammals and lizards of the forest floor.

Courtesy Carnegie Museum of Natural History
via Wikimedia Commons
The most curious bit about any dinosaur restoration comes in the form of filling in the gaps of course. In Chirostenotes that actually has worked a little bit backwards from what we would assume; allow me to explain. Oviraptor is the head honcho of the family, a lot is known about Oviraptor, and as such we would assume that any missing skeletal elements down the line of the family would refer back to Oviraptor ultimately for clarification and reinterpretation. In the skeleton of Chirostenotes we see a lot of inferences made from the skeletal information we have about the particular animal and those made from other members of its family including Oviraptor; however, we have also seen that the discovered bits of skull of Chirostenotes have helped to refine Oviraptor's skull as well. That happens sometimes, but not very often that a more well known species gets tips and pointers from a lesser known species, and that makes Chirostenotes a little bit more interesting in that way. The hands of Chirostenotes have also told us a lot about the evolution of the entire Oviraptorid family as we can compare them to their Asian ancestors and down through the eras to the large gracile hands of Chirostenotes. What this tells us, though, we will try to examine in a later discussion, as those hands are very important and deserve a lot more scrutiny than can be afforded today.

No comments:

Post a Comment