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RE: Microraptor also ate fish
Tim Williams wrote-
> > Consistency does not equal corroboration when there
> > is an alternative the evidence is equally consistent with.
> So we have a _Microraptor_ with an arboreal bird in its belly. Well
> maybe the bird was caught on the ground. We also have a _Microraptor_
> with a fish in its belly. Well maybe the fish was already dead...
> Or maybe we have a versatile, opportunistic hunter that targets live
> prey wherever and whenever it can: in trees, in shallow water, as well
> as on land.
> I'm aware that you're saying "The fossil described can't tell us
> whether _Microraptor_ preyed or scavenged the fish it ate."
> Nevertheless, the discovery of a fish inside a _Microraptor_ is
> consistent with what was previously inferred about this theropod based
> on morphology: that it was a versatile hunter.
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?
This whole situation is like if we found a single ornithomimid footprint, then
published a paper saying how this probably indicates it ran. And I reply we'd
expect the same print if it were just standing (ignore that in reality there
would be details of depth and such that could distinguish the situations).
Then you say, but having a footprint is consistent with running, and look at
how Ornithomimus has elongated lower limbs and a large cnemial process that
suggest it was a good runner. Of course we already inferred Ornithomimus ran
and stood. So why would you continue to emphasize the running possibility?
> > You would have to demonstrate hunting is more parsimonious in
> > both cases, and that hunting arboreal birds in trees is more
> > parsimonious than doing so on the ground in the first case.
> The jaws, teeth and feet were adapted for catching and processing
> small prey. Plus, _Microraptor_ has morp
> scansoriality. I'm matching morphological adaptations with dietary
> evidence here. I believe O'Connor &c and Xing &c were doing the same
> - even if they might have overstated their respective arguments a
That doesn't make it more parsimonious. Most every predator that has jaws,
teeth, etc. adapted to catch and process prey scavenges as well. Again, you're
just noting consistency with one possibility while not caring about equal
consistency with the other.
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" 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.
> > My cats have caught their share of arboreal birds (mostly juncos,
> > robins and starlings) in my life, and every time I've seen it,
> > the bird's been on the ground.
> Is this simply because *you* happen to be on the ground? ;-)
I'm not arguing arboreal birds are most often captured on the ground by cats
(though that might be true), just that it happens often enough that terrestrial
predators engaging in that behavior shouldn't be viewed as unparsimonious.
> > Exactly what behavior do you have in mind that makes
> > scavenging unparsimonious, as the whole Tyrannosaurus
> > predator vs. scavenger debate basically established any
> > (non-vulture) terrestrial tetrapod predator both hunts and
> > scavenges?
> True. But these predators have adaptations for hunting live prey.
> Not just scavenging.
And they no doubt hunted. But the fish and bird skeletons in their stomachs
don't tell us any more abo
> > We'd need some study of Aves hallux length equated to
> > lifestyle as we have for claw curvature to tell. Some
> > modern birds with even tinier halluces can perch fine, like
> > wood ducks-http://www.nejohnston.org/Birds/feet/WoodDuck_1.jpg
> > Confuciusornis really seems intermediate.
> I agree that confucisuornithids are intermediate in terms of the
> evolution of the perching pes. But I disagree that wood ducks are
> appropriate analogs. The legs of a wood ducks are very short, and the
> claws are specialized for gripping branches. They are a far cry from
> the legs and pedal claws of _Confuciusornis_, neither of which are
> adapted for arboreality.
Not that the Confuciusornis / wood duck thing has anything to do with Xing et
al., since they don't make the Sinocalliopteryx point you did, but... are wood
ducks' legs actually notably shorter than Confuciusornis', or do they just look
that way due to feathers making the body seem bigger and only the
tarsometatarsi being exposed? Also, Confuciusornis pedal unguals are much
larger and more curved than the wood duck's, so I don't see why you think the
latter are better adapted for perching.