Re: Microraptor also ate fish

[Tim Williams <tijawi@gmail.com>]

Mickey Mortimer <mickey_mortimer111@msn.com> 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.


> 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 morphological evidence for
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
little.


> 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?    ;-)


(BTW, these bird-eating rampages by your cats remind me of why I'm not
a cat person.)


> Similarly, I have observed gulls feed on fish carcasses at the beach.


Gulls are well-known for eating carrion, including dead fish washed up
on the beach.


>  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.


> I think calling Confuciusornis terrestrial is taking things too far.
> The pedal claw proportions fall within both terrestrial and arboreal
> ranges, and Chiappe et al. (1999) note "Relative lengths of the
> phalanges in the third pedal digit of Confuciusornis sanctus
> fall within the transition between birds that spend most of their
> time in trees and others that are predominantly terrestrial."
> Sure it couldn't perch as well as some enants or passerines,
> but that hardly makes it terrestrial.


It doesn't make it arboreal either.  _Confuciusornis_'s morphology
(including the pes) is consistent with a biped that spent most of its
time on the ground, but was capable of some perching ability.  It was
about as arboreal as a turkey - maybe a bit less.


> 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.






Cheers

Tim