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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.
Thanks,
Lee


Lee Hall
Paleontologist
SWCA Environmental Consultants
http://sites.google.com/site/leehallpaleo/Home
paleeoguy@gmail.com



On Tue, Nov 22, 2011 at 6:48 AM, Robert Schenck <schenck.rob@gmail.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
> <mickey_mortimer111@msn.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 
>> is-
>>
>> "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."
>>
>> and
>>
>> "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: tijawi@gmail.com
>>> To: dinosaur@usc.edu
>>> Subject: Re: Microraptor preyed on birds (official paper in PNAS)
>>>
>>> Mickey Mortimer <mickey_mortimer111@msn.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.
>>>
>>>
>>>
>>>
>>>
>>>
>>> Cheers
>>>
>>> Tim
>>
>>
>
>
>
> --
> 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
>