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RE: Microraptor also ate fish



First, thanks to Xing for making this freely available.

But just as with the previous paper claiming the Microraptor which ate bird 
parts was probably arboreally catching birds, this paper's conclusions are 
questionable.  The ironically accurate sentence in the paper is-

"In the latter report, O’Connor et al. (2011) interpreted this evidence of 
presumed predation on flight-capable prey as proof that M. gui was an adept 
hunter in an arboreal environment. The gut contents of QM V1002 now provide 
equal evidence that M. gui was an adept hunter of aquatic prey."

Equally possible but also equally likely to be due to scavenging in both cases, 
yes.  To Xing's credit, he goes on to state-

"As is always the case with dietary inferences based on preserved gut contents, 
scavenging (as opposed to active predation) cannot  be  ruled  out—although,  
in  the  case  of  QM  V1002,  the relatively short spoilage time of fish 
carrion provides circumstantial evidence against a scavenging interpretation— 
and caution is always warranted in the extrapolation of behavioral and 
microhabitat specializations from single instances of gut content preservation."

Then he points out Sinocalliopteryx also ate birds and was near certainly not 
arboreal.  All of this would seem to nullify much of the impact of the paper.  
If the point was to show O'Connor et al.'s conclusion was unsupported, that 
would be fine, but it then goes to argue an equally unsupported point.  
Further, since the abstract leaves out the caveats, it makes the fish hunting 
hypothesis seem more strongly supported than it is.

Take the short spoilage time as the one piece of non-anatomical evidence given. 
 Is it really shorter than tetrapods?  I had a cabezon carcass sitting behind 
my shed that took much longer to rot than any comparably sized opossum.  It 
ended up just drying with the bones articulated and skin stetched over it.  I 
would think if anything, the constant influx of salt and/or maggot-drowning 
water would lead to a longer shelf life for carcasses washed ashore.
ch is much easier to search than most habitats due to everything being in a... 
well... line and the lack of vegetation.  Thus carcasses on the shore could be 
more likely to be eaten by terrestrial predators than those in other 
environments.

I hate to use the term misleading, but the abstract states "Several 
morphological adaptations of Microraptor are identified as consistent with a 
partially piscivorous diet, including dentition with reduced serrations and 
forward projecting teeth on the anterior of the dentary."  Is this really right 
to say when the paper identifies only these two characters as indicating 
piscivory?  "Two (which does not mean several) adaptations are identified, 
including these two"?

Serrationless anterior teeth are standard for maniraptoriforms, with serrations 
re-evolving in derived troodontids and eudromaeosaurs.  Procumbant anterior 
dentary teeth are found in Epidexipteryx, Archaeopteryx, Jinfengopteryx, 
Byronosaurus, Dromaeosaurus, Sinornithosaurus, Anchiornis, Protarchaeopteryx, 
etc..  It's harder to find basal chuniaoaens (ovis+paravians) without them than 
with them.  But would anybody suggest the myriad of basal chuniaoaens in their 
various habitats were notably adapted to catching fish?  Zanno and Makovicky 
(2010) used both traits to argue for herbivory.

Perhaps I'm just being grumpy about this new spate of 'stomach remains indicate 
behavior' papers for theropods (recall the 'Velociraptor scavenged pterosaurs' 
paper too).  I think Dal Sasso and Maganuco (2011) had it right when they said 
finding two kinds of fish were eaten by Scipionyx (which has serrationless but 
non-procumbant anterior dentary teeth) could only tell them exactly that.  It 
made up one part of one paragraph in their paper.

Mickey Mortimer





----------------------------------------
> Date: Fri, 19 Apr 2013 18:54:49 -0700
> From: bcreisler@gmail.com
> To: dinosaur@usc.edu
> Subject: Microraptor also ate fish
>
> From: Ben Creisler
> bcreisler@gmail.com
>
> A new online paper:
>
> Lida Xing, W. Scott Persons IV, P
hang,
> Tetsuto Miyashita, Fengping Wang & Philip J. Currie (2013)
> Piscivory in the feathered dinosaur Microraptor.
> Evolution (advance online publication)
> DOI: 10.1111/evo.12119
> http://onlinelibrary.wiley.com/doi/10.1111/evo.12119/abstract
>
>
> The largest specimen of the four-winged dromaeosaurid dinosaur
> Microraptor gui includes preserved gut contents. Previous reports of
> gut contents and considerations of functional morphology have
> indicated that Microraptor hunted in an arboreal environment. The new
> specimen demonstrates that this was not strictly the case, and offers
> unique insights into the ecology of nonavian dinosaurs early in the
> evolution of flight. The preserved gut contents are composed of
> teleost fish remains. Several morphological adaptations of Microraptor
> are identified as consistent with a partially piscivorous diet,
> including dentition with reduced serrations and forward projecting
> teeth on the anterior of the dentary. The feeding habits of
> Microraptor can now be understood better than that of any other
> carnivorous nonavian dinosaur, and Microraptor appears to have been an
> opportunistic and generalist feeder, able to exploit the most common
> prey in both the arboreal and aquatic microhabitats of the Early
> Cretaceous Jehol ecosystem.