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Re: Microraptor preyed on birds (official paper in PNAS)



PDF rec'd. Thanks!

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



On Tue, Nov 22, 2011 at 7:59 AM, Lee Hall <paleeoguy@gmail.com> wrote:
> 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
>>
>