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Re: Microraptor also ate fish

Mickey Mortimer <mickey_mortimer111@msn.com> wrote:

> But why is that notable?  It's equally consistent with what was previously 
> inferred about
> Microraptor based on it being a carnivorous land tetrapod: that it scavenged 
> meat when it found
> some.  So why should we make a big deal of the hunting consistency but not 
> the scavenging
> consistency?

Good question.  Because the morphology of a predator can lead to
hypotheses regarding the kind of prey targeted by the predator.  For
example, based on craniodental traits, spinosaurids are predicted to
be piscivorous.  So when a spinosaurid is discovered with a fish
inside it, this lends support to that hypothesis.  I know the support
is not compelling (after all, pterosaur and small ornithopod remains
have also been preserved as spinosaurid gut contents).  And there is
an element of circular reasoning to this, for sure.  But given the
limited evidence available from the fossil record, I think finding gut
contents for *any* dinosaur fossil is a notable discovery.

> That doesn't make it more parsimonious.  Most every predator that has jaws, 
> teeth, etc.
> adapted to catch and process prey scavenges as well.

Securing and processing prey require specific adaptations.  All
predatory theropods were not the same; they show variations in
morphology that are often related to the kinds of prey that were
targeted.  Cursorial hindlimbs might indicate a propensity to chase
down fast prey; powerful and reinforced jaws might indicate that the
jaws were used to seize large prey; procumbent anterior teeth could
indicate the jaws were used to grasp slippery prey; short, strong
forelimbs could be used help secure large prey; and so on.

The morphology of _Microraptor_ indicates a theropod that targeted a
wide variety of small prey. IMHO, the reason it had scansorial
abilities was so it could climb trees to procure small arboreal prey;
and the reason it had "wings" was so it could return to the ground
afterward.  So when an arboreal bird turns up in the gut contents of
_Microraptor_, this finding is consistent with this hypothesis.  Not
concrete proof, I admit.  But unless we happen to find a _Microraptor_
preserved clinging to a tree branch with a bird in its mouth, it's the
best evidence we have.

However, testing for opportunistic scavenging ability based on
morphology is a lot harder.  After all, the thing being eaten is
already dead - no adaptations for pursuing, catching and securing the
prey are required.  So it's difficult to test for opportunistic
scavenging based solely on the morphology of the predator.  (Obligate
scavengers might be different... but that's another story.)

> Both O'Connor et al. and Xing et al. overstated their cases very much- "this 
> fossil suggests
> that Microraptor hunted in trees thereby supporting inferences that this 
> taxon was also an
> arborealist"

I concur that _Microraptor_ was not an arborealist.  Occasionally
venturing into trees, probably.  Spending most of its time in trees,

> and "The feeding habits of Microraptor can now be understood better than that 
> of any other
> carnivorous nonavian dinosaur, and Microraptor appears to have been an 
> opportunistic and
> generalist feeder, able to exploit the most common prey in both the arboreal 
> and aquatic
> microhabitats of the Early Cretaceous Jehol ecosystem."  The most data we can 
> actually tell
> is "Microraptor sometimes ate birds and fish."  But maybe that doesn't sound 
> as flashy.

I agree it doesn't sound as flashy.  :-)  But the fact that a
predatory theropod sometimes ate birds and fish makes me wonder if it
had adaptations consistent with catching birds and fish.