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Re: Microraptor preyed on birds (official paper in PNAS)
PDF rec'd. Thanks!
SWCA Environmental Consultants
On Tue, Nov 22, 2011 at 7:59 AM, Lee Hall <firstname.lastname@example.org> wrote:
> I would also appreciate a PDF, if someone could be so kind.
> Lee Hall
> SWCA Environmental Consultants
> On Tue, Nov 22, 2011 at 6:48 AM, Robert Schenck <email@example.com> 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
>> <firstname.lastname@example.org> 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
>>> "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: email@example.com
>>>> To: firstname.lastname@example.org
>>>> Subject: Re: Microraptor preyed on birds (official paper in PNAS)
>>>> Mickey Mortimer <email@example.com> 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