RE: Troodon/Orodromeus hypothesis

[Jaime Headden <qi_leong@hotmail.com>]

Jason, all I can say is that the following is intriguing:

"Oddly enough, Montana isn’t the only instance of dinosaur nests found 
fossilized with another type of animal involved. In another case the 
tables may have been turned on the Troodontids. Two partial skulls of 
hatchling troodontids, this time a species called Byronosaurus,
 were found in the nest of an oviraptorosaur  in the Gobi Desert in 
1994. This suggests three possibilities: One, that adult oviraptorids 
were eating hatchling Byronosaurus. Two, that young Byronosaurus left their 
nests and immediately tried to feed on oviraptorid hatchlings or eggs. Or 
three, that adult Byronosaurus were nest parasites on oviraptorids. (Bever, 
G.S. and Norell, M.A. (2009). "The perinate skull of Byronosaurus 
(Troodontidae) with observations on the cranial ontogeny of paravian 
theropods." American Museum Novitates, 3657)"

  We've spent some time talking about various durophages, including ovophages. 
One thing that should be kept in mind here is that to predate an egg, you need 
one primary thing: a way to break the eggshell. Crushing teeth, or slicing 
teeth, or an apparatus that can do so (dropping the egg, using a rock, 
swallowing and slicing within the mouth/throat, etc.). The troodontid 
hatchlings in question lack any of these features, and moreover none of them 
have teeth thicker than the eggshell in question. Their proximity to the eggs 
of a nest filled with oviraptorids implies 2 is improbable if not impossible; 
this leaves 1 and 3. I doubt, based on the jaw anatomy, that troodontids 
destroyed or opened eggs orally, although they could have eaten the neonates 
post-hatching, so I doubt the inverse of 1, but at the same time the evidence 
of nests of troodontids in NA at least implies 3 is not correct (but this is 
based on negative evidence). Nest parasitism is curious, be we've little data 
to indicate that, especially as Bever and Norell indicate that the associated 
eggshells are oviraptorid, of the same type found with the oviraptorid embryo. 
Varricchio et al. document troodontid eggshell, and show it to be extremely 
different from that of oviraptorids, thus confusing the association as 
parasitic (the eggshells associated with the skulls as evidence the neonates 
were hatched in the nest) rather than predatory (the oviraptorids dumping the 
neonates into the nest). I would implicity, as Bever and Norell do 
(tangentially, as this same nest produced the oviraptorid embryo), support 1.

Varricchio, D. J., Horner, J. R. & Jackson, F. D. 2002. Embryos and eggs for 
the Cretaceous theropod dinosaur *Troodon formosus.* _Journal of Vertebrate 
Paleontology_ 22(3):564–576.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Fri, 13 May 2011 02:01:02 -0400
> From: jaseb@amnh.org
> To: dinosaur@usc.edu
> Subject: Troodon/Orodromeus hypothesis
>
> Hi everyone,
>
> I was reading about Paleocene Lithornithids tonight and I came up with a
> new hypothesis about Orodromeus remains in Troodon nests.
>
> Please check it out at my blog (below) and I'd appreciate any feedback,
> further references, and criticism.
>
> In particular, does anyone know what other vertebrate remains are found in
> the nests besides Orodromeus?
>
> http://web.me.com/jasonbrougham/Site/Blog/Entries/2011/5/12_Vertebrate_remains_in_dinosaur_nests.html
>
> Jason Brougham
> Senior Principal Preparator
> Department of Exhibition
> American Museum of Natural History
> 81st Street at Central Park West
> 212 496 3544
> jaseb@amnh.org
>