species determ.

[Jeffrey Martz <martz@holly.ColoState.EDU>]

     The main problem with determining species and genera in fossils has 
to do with the fact since we can't observe living populations, 
determining who can and will interbreed with who is impossible.  
Additionally, without the benefit of soft anatomy, coloration and behavior, 
detrmining how closely related two seperate genera are is even more 
difficult.  Biologists and zoologists generally concentrate on these 
details, rather than on osteology, when classifying species.  Hence, 
relatively little correlation between osteological differences in different 
genra and species of animals, which might be very useful in determining 
species and genera in extinct animals, has been made.  
     The little investigation that has been done into osteological 
differences involved in individual variation and sexual dimorphism, which 
can cause considerable osteologigal variation within a single species 
(I read somewhere that a female lion has physically more in common with a 
female tiger than a male lion) has resulted in considerable combining of 
extinct genera and species in paleontology in recent years.  Examining 
individual variation in modern african ?antelope? led John Ostrom to combine 
the dozen or so Triceratops species under a single species, T.horriblus.  Also 
consider the exploration of sexual dimorphism in theropods, 
including the Coelophysis bauri specimens at Ghost Ranch and Ken 
Carpenter's paper on sexual dimorphism in T.rex (I believe all these 
papers can be found in Dinosaur Systematics: approaches and 
persepctives).        
     However, studying the osteological differences in modern species 
might have limited value in certain cases.  For example there is a genus of 
north amercan bird (don't ask me what type or the genus name) in which all 
the species are essentially identical physically (and presumably 
osteologically).  They are seperated into species based exclusivly on 
thier mating songs.  Since females are 
attracted only to a specific song produced by a male in thier own 
species, this effectively keeps the species reproductivly isolated.  Ken 
Carpenter showed me a chart of a bunch of essentially identical skulls 
belonging to different species of a single lizard genus.  
Again, these species were seperated by biologists based primarily on 
coloration.  Paleontology benefits greatly from any study of osteology of 
modern animals that looks for clues that might help determine species in 
extinct ones.

LN Jeff