STL Science Center

STL Science Center

26 October 2012

A New Old Face

©Daniel Benson
The Cretaceous of Alberta 75 million years ago had a number of smaller theropod dinosaurs running around. In 1924 (Gilmore) one of these was named and described under a new genus, Chirostenotes, based on two elongated nearly complete hands, thought to be from a single specimen, discovered in the Judith River Formation of Alberta. Chirostenotes pergracilis was the first, and is to some paleontologists the only, species in this genus. Since 1924 a partial skeleton possessing those hands has been discovered as well, the earliest discovery being described by Currie and Russell in 1988. In 1933 (Parks, based on a foot found in the same area) a new Ornithomimus was named and has, subsequently, been considered as a second species under the name Chirostenotes elegans (it has also been considered as a member of another genus, Elmisaurus, thus leading to the split amongst paleontologists which we will discuss further in the coming week). Gregory Paul (2011) places C. elegans within C. pergracilis and separates another set of remains into an unnamed species of Chirostenotes. Currie and Russell (1988) stated that Chirostenotes was a caenagnathid elmisaurid (see below) while Ostrom thought that Chirostenotes was a synonym of Dromaeosaurus (The Dinosauria, 1990 edition). Regardless of where these other skeletons actually were thought to belong at one time or another, Chirostenotes pergracilis has a specific meaning that is Greek (genus) and Latin (species); the meaning of the name is "narrow hand, gracile throughout." Some animals' names are explanations of what they are in the common name (felis catis is the common house cat and translates to "cat cat" basically), but with dinosaurs we tend to run into these wonderfully descriptive names that are Greek or Latinized that sound, if one can sound them out, nearly impossible to say correctly.

Enough of that aside though; the point of today is to learn about our new dinosaurs. Chirostenotes did indeed have narrow hands. Its hands were elongated, like many Maniraptoriforme dinosaurs, though oviraptorids are not currently considered members of the Maniraptor family (C. pergracilis is placed in the Caenagnathidae which includes Elmisaurus as well and other similar Late Cretaceous oviraptors). As with all oviraptors, Chirostenotes lacked teeth and had a rather large bird-like beak with a healthy looking crest situated on its frontal-nasal ridge which sloped up and over the parietal to come back down in attachment on the squamosal. The remainder of the skeleton is quite typical to oviraptors and small theropods in general. Chirostenotes was mostly like an omnivores, catching small mammals and reptiles with its agility and speed, aided by its large manipulative hands, and eating prey and plant matter alike (possibly eggs as well?) with its toothless beak in a manner possibly similar to the way chickens can eat small insects from time to time.

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