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Re: Parts & Non-Recreation (was: Ceratonykus)



Jaime Headden <qi_leong@hotmail.com> wrote:

>  Virtually all myrmecophagous carnivores use non-dental processing to deal 
> with termites and ants, which would necessarily seem to invoke the 
> "vestigialization" argument for them with regards to their
> teeth ... yet despite this, they have teeth and a lot of them. Like 
> troodontids, this dentition is arrayed into a blade-like jaw margin.


I took "myrmecophagous carnivores" to mean "myrmecophagous Carnivora".
 If the latter, I know only of two: the aardwolf (_Proteles
cristatus_) and the sloth bear (_Ursus ursinus)_.  However, I don't
think the sloth bear really qualifies as myrmecophagous; it's more of
an omnivore.  In any case, among ursids its termite-eating habits
appear to be extremely recently acquired.


Among extant mammals, there is a sliding scale as to how the jaws and
teeth have been specialized for myrmecophagy.  Echidnas, anteaters
(vermilinguans), and pangolins have all lost their teeth, and the
mandibles are fairly shallow and delicate.  Others retain teeth
(numbat, aardvark, aardwolf, some armadillos), but tend to have small
homodont teeth housed in a long and tubular skull.  Of the latter,
some have reduced the number of teeth, others show a slight increase.
The aardwolf retains large canines.  Elephant-shrews have large
canines, and hypsodont cheek teeth.


There really are no hard-and-fast rules regarding the craniodental
adaptations of myrmecophagous mammals - either than there being a
trend to simplify the dentition (sometimes culminating in outright
loss), and narrowing and lengthening of the rostrum.  In that context,
I'm prepared to go along with alvarezsaur jaws and teeth being adapted
for omnivory or insectivory, with termites making up a component of
the diet.  But I would not call any alvarezsaur a "dinosaur anteater".




Cheers

Tim