RE: attack on dinosaur--horrific video

[Tim Williams <twilliams_alpha@hotmail.com>]

John Bois wrote:


> Placentals enjoy a great diversity of
> morphologies--probably a greater diversity than is available to, for
> example, marsupials. .... Point
> is, ontogenic imperatives are a limit on morhological diversity in
> marsupials. This is not going to go away for them.

In brief... I don't know how one would go about quantifying "morphological 
diversity", but by whatever yardstick you might use, marsupial diversity is 
pretty darn impressive.  With the exception of volant (bats) and fully 
aquatic/marine (cetaceans, pinnipeds, sirenians), almost every niche occupied 
by a placental has at least an approximate equivalent among the marsupials.  
There's a vast array of marsupial carnivores (thylacoleonids, dasyuroids, 
didelphids, borhyaenoids, etc); marsupial moles (notoryctids); marsupial 
gliders (various phalangeroid taxa); big herbivores (diprotodontids, 
zygomaturids, tapir-like palorchestids, etc); small hopping herbivores (many 
macropods, argyrolagids); small insectivores/omnivores (myrmecobiids, 
microbiotheriids, perameloids, etc); nectar-feeders (tarsipedids); and so on.

True, marsupials seem to have been shouldered aside by the placentals in every 
continent except Australia (where the opposite may be true, based on the 
'condylarth' _Tingamarra_).  But this speaks to the relative success of the two 
clades, and doesn't take anything away from the high level of morphological 
diversity represented by the Marsupialia.  

Cheers

Tim
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