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RE: Microraptor also ate fish
Tim Williams wrote-
I note you didn't even reply to my single Ornithomimus footprint analogy. What
makes the situations different in your eyes?
> > 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.
A spinosaurid with fish ingested like Baryonyx' holotype does not lend support
to the hypothesis it caught live fish. It lends support to the hypothesis it
ate fish, like Microraptor, Scipionyx, Confuciusornis and probably just about
every non-tiny Mesozoic theropod that lived around fish (probably excluding
therizinosauroids and maybe a few other oddball taxa).
I was asking why consistency with predation is notable as opposed to
consistency with scavenging, not why reporting what it ate is notable.
> > 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 prope
> 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.)
None of what you said makes predation of the fish more parsimonious. To be so,
it would have to explain the data better than scavenging, and you admit in the
last paragraph scavenging fish requires no special morphology for a theropod.
So hunting fits its morphology well, and scavenging fits its morphology well.
Again, think of my Ornithomimus footprint analogy- Ornithomimus was well
adapted to running, but this in no way makes it more parsimonious a single
track from it was made while running instead of while standing. All of the
details you can muster for the adaptations of Microraptor or Ornithomimus can't