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Caenagnathus species

Dinogeorge writes:

><< Chirostenotes elegans (= Caenagnathus sternbergi)
> Elmisaurus elegans >>
>I think these two species are the same, both being renamings of 
>elegans. The oldest available species name for this taxon would be 
>Chirostenotes pergracilis, of which all the described American caenagnathid 
>species are synonyms. Differences are considered to be due to individual 
>variation and sexual dimorphism. (E.g., Caenagnathus collinsi is one sex, 
>C.sternbergi the other.)

Not necessarily.  There's quite a lot of caenagnathid/elmisaurid material 
from North America, most of it from the Judith River Group (and stored at 
the Royal Tyrrell Museum).  Apart from the holotypes of _Caenagnathus 
sternbergi_ and _C. collinsi_, a number of caenagnathid dentaries have been 
found which vary in overall size and in the length and depth of the 
symphysis.  There may be more than one _Caenagnathus_ species represented in 
the Judith River Group.   

_Chirostenotes pergracilis_ and _Ch. elegans_ may be different species, even 
different genera.  _Ch. elegans_ has been referred to _Elmisaurus_ by some 
researchers based upon the form of the tarsometatarsus. 

There's also a new, larger genus of caenagnathid (not yet described) based 
upon cranial material found in the Hell Creek Formation of South Dakota.