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Re: Microraptor preyed on birds (official paper in PNAS)
I would also appreciate a PDF, if someone could be so kind.
SWCA Environmental Consultants
On Tue, Nov 22, 2011 at 6:48 AM, Robert Schenck <firstname.lastname@example.org> wrote:
> I don't think its really necessary to consider the paper a flop.
> They're presenting a really interesting case, and a full description
> of the Microraptor specimen can still be published later. The fact
> that its got an arboreal bird in its guts is the really interesting
> thing about this find, so it deserves to be published quickly.
> And its not like this forces anyone to accept that Microraptor was
> arboreal, its a supposition that they're making. Its not like they did
> a cladistic analysis of all maniraptorans, "coded" Microraptor as
> 'arboreal', and then got a new tree topology.
> As far as the devoured bird, IF it was scavenged, then I'd think that
> it going in head first with whole limbs would be unusual, surely
> whatever killed and ate part of it before would've torn apart the
> limbs, or at least the head (unless it just dropped dead out of a tree
> right infront of a Microraptor as it was trundling along on the
> ground). And for that, what kind of animal kills a bird and then eats
> only a tiny bit of it? I've seen my cat kill a bird and when it was
> done, there was a feather or two left, not a head and wings.
> At the same time, it's worth reiterating that just because it ate a
> bird doesn't mean it did so in the trees. I saw a video not too long
> ago of a cow on a farm (i think this was in india) that was eating
> little birds that passed by!
> On Tue, Nov 22, 2011 at 9:28 AM, Mickey Mortimer
> <email@example.com> wrote:
>> Thanks to Tim Williams for a copy of the paper. I can now finally say that
>> nothing in the paper changes my opinion. The only quote which argues the
>> bird was killed instead of scavenged is-
>> "What is preserved of the ingested enantiornithine skeleton is still in
>> articulation with the feet located in the proximal end of the stomach,
>> suggesting that the meal was not scavenged, but captured and swallowed
>> nearly whole and proximal end first, as in most living predatory birds."
>> First, the "skeleton still in articulation" is a partial wing and two feet
>> lying parallel to each other. Sure they're positioned right if we insert
>> the rest of the body between them, but it could also be chance. Yet that
>> doesn't even matter since O'Connor et al. never even bring up the
>> possibility that scavenged prey can be articulated and eaten head first as
>> well. Plenty of birds die while whole, and even more die with two legs and
>> a wing still connected. Nor is there any reason it wouldn't be eaten head
>> first if found dead. But that doesn't even matter either, since we all know
>> living arboreal birds often spend time and are killed on the ground.
>> O'Connor et al.'s only statement defending Microraptor killing it in a tree
>> "The predation of an arboreal enantiornithine suggests Microraptor hunted in
>> an arboreal environment (Fig. 3)."
>> Wow. That's.... completely untrue. Sure it might have killed the bird in a
>> tree, but it might have killed it on the ground, or eaten it after finding
>> it dead on the ground, or dead hanging from a tree branch for all we know.
>> What's especially amusing is that O'Connor et al. note two other cases of
>> fossil diets. One is a mammal skeleton found in another Microraptor, as
>> described by Larsson et al. (2010)-
>> "The morphology of the foot is most similar to Eomaia and Sinodelphys,
>> although this specimen lacks the level of arboreal adaptations seen in those
>> taxa. The foot is relatively long, with a shortened first metatarsal and
>> elongate phalanges possessing a phalangeal ratio of around 1. The preserved
>> unguals are moderately recurved, the phalanges are straight and the ratio of
>> proximal to distal phalanges does not indicate a dedicated arboreal
>> lifestyle but suggests the animal was most likely scansorial."
>> The other is an enantiornithine tibiotarsus found in an ichthyosaur as
>> described by Kear et al. (2003). Maybe it was scavenged, but maybe the
>> ichthyosaur killed it. Sharks kill birds today after all. O'Connor et al.
>> argue the bird's incompleteness indicates scavenging, but the turtles
>> preserved in that ichthyosaur are also incomplete.
>> So here we have a Microraptor that ate a non-arboreal animal, and a
>> definitely non-arboreal animal that ate an enantiornithine. If these two
>> cases don't eliminate the importance of O'Connor et al.'s specimen in regard
>> to Microraptor's arboreality, what would? And yet we get statements like-
>> "This new specimen indicates that M. gui fed on arboreal birds, lending
>> further support to interpretations that M. gui was spending a substantial
>> amount of time in the trees."
>> "Further, because Jehol enantiornithines were distinctly arboreal, in
>> contrast to their cursorial ornithurine counterparts, this fossil suggests
>> that Microraptor hunted in trees thereby supporting inferences that this
>> taxon was also an arborealist, and provides further support for the
>> arboreality of basal dromaeosaurids."
>> My basic issue with this paper isn't that it's wrong, since maybe
>> Microraptor was arboreal and maybe this specimen did kill that bird in a
>> tree. It's that the paper doesn't even try to support the various arguments
>> it takes to get to that point. Where's the data showing scavenged birds are
>> usually disarticulated? Where's the data showing modern predatory birds
>> usually don't swallow carcasses head first? Where's the data showing
>> arboreal birds are usually killed in trees? Nowhere. It's a neat specimen,
>> but to infer anything more than "Microraptor sometimes ate at least
>> partially articulated enantiornithines head first" is story-telling instead
>> of science, at least at the level of O'Connor et al.'s analysis.
>> Taxonomy-wise, O'Connor et al. refer the specimen to M. gui based on "its
>> large size (relative to Microraptor zhaoianus), the proportions of its
>> manual digits, curvature of the pubis, and slight bowing of the tibia",
>> which were all convincingly shown to be problematic by Senter et al.
>> (2004). They also refer the bird to Cathayornithiformes, a group which has
>> never been supported by an analysis or defended by synapomorphies.
>> Finally, I do want to end on a positive note and praise Brian Choo's
>> excellent restoration.
>> Mickey Mortimer
>>> Date: Tue, 22 Nov 2011 17:13:31 +1100
>>> From: firstname.lastname@example.org
>>> To: email@example.com
>>> Subject: Re: Microraptor preyed on birds (official paper in PNAS)
>>> Mickey Mortimer <firstname.lastname@example.org> wrote:
>>> > Well, since it's not open access I can't say anything about the paper
>>> > itself (though I could access it for 2 days for the low low price of
>>> > $10), but the
>>> > Discover article implies the bird wasn't scavenged because it's
>>> > articulated and facing headfirst. This doesn't address the obvious
>>> > argument made
>>> > on the DML that the enantiornithine could have been caught on the ground,
>>> > since that's the case for many modern predators attacking arboreal
>>> > birds. Indeed, I don't see why a predator wouldn't eat a scavenged bird
>>> > the same way it eats a recently killed bird, since the animal still goes
>>> > down
>>> > the throat more smoothly head first. So while I still technically
>>> > reserve final judgement until I read the paper, I stand by my earlier
>>> > statement that it's
>>> > impossible to infer arboreality from one Microraptor eating one arboreal
>>> > bird.
>>> I'm prepared to cut the authors some slack here. Here we have a small
>>> theropod (_Microraptor_) that previous studies have inferred to be at
>>> last partly arboreal. And what turns up in the stomach of one of
>>> these theropods? An arboreal bird.
>>> Yeah, there is no reason to assume that the little bird was
>>> necessarily in a tree when the _Microraptor_ snapped it up. Modern
>>> specialist perching birds often forage on the ground. _Microraptor_
>>> might have pounced on the bird while it was on the ground. Or the
>>> bird might have already been dead when _Microraptor_ gobbled it up.
>>> But the behavior depicted for _Microraptor_ in Fig. 3 is at least
>>> consistent with the skeletal (and integumental) anatomy of this
>>> theropod: the hindlimbs 'walk' up the tree, the hands grip the tree on
>>> either side to provide support, and the jaws catch the prey.
>>> _Microraptor_'s 'wings' could then be deployed to return the animal
>>> to the ground. No perching (or roosting) is required - so
>>> _Microraptor_ doesn't require a perching pes or prehensile manus.
> Robert J. Schenck
> Kingsborough Community College
> Physical Sciences Department
> S332 ph# 718-368-5792
> Follow Me on Twitter: @Schenck
> KCC Class Schedule on Google Calendar: http://tinyurl.com/mqwlcy