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RE: Troodon/Orodromeus hypothesis



Jason Brougham wrote:

  <Well, if you are suggesting that, since some Troodontids were not nest 
parasites, that Byronosaurus was most likely not a nest parasite, I agree that 
that is supported, but the evidence is by no means decisive. We must 
acknowledge that an archosaur family, such as the Cuculidae, can contain both 
parasitic and nest - building members. I believe that some ducks are even 
opportunistic nest parasites, so that the same species will rear their young if 
they have to, but will dump them in other nests if they can.>

  While hypothetically possible, and thus not discountable (without having such 
a fundamental system as a nest with eggs for every known species and 
"variation" of troodontid), it is also not supportable (for the same reasons). 
My argument is based on this specific case.

  <Do you have a reference on that? In the Bever, Norell paper I can only find 
a mention that two small pieces of eggshell adhere to the right rostral region, 
but no mention of the nature or origin of the eggshell. But in Norell et al., 
1994, they do mention that the outer, convex, surface of the eggshell contacts 
the rostrum, implying that the egg did not enclose the skull when it was 
deposited.>

  "The perinate skulls (IGM 100/972 and IGM 100/974; figs. 1–4) were found in a 
weathered nest of at least six eggs in the Late Cretaceous Xanadu sublocality 
of Ukhaa Tolgod, Djadoktha Formation, Mongolia (Loope et al., 1998; Norell et 
al., 1994; Dingus et al., 2008; fig. 5). [...] Because embryonic remains of an 
oviraptorid theropod were found inside one of the eggs (Norell et al., 1994) 
and other occurrences of adult oviraptorids associated with eggs of this 
eggshell type are documented (Osborn, 1924; Currie et al., 1993; Norell et al., 
1995; Dong and Currie, 1996), the nest is inferred to be that of an oviraptorid 
dinosaur."

Bever, G. B. & Norell, M. A. The perinate skull of *Byronosaurus* 
(Troodontidae) with observations on the cranial ontogeny of paravian theropods. 
_American Museum Novitates_ 3657:1-51.
Norell, M. A., Clark, J. M., Dashzeveg D., Barsbold R., Chiappe, L. M., 
Davidson, A. R., McKenna, M. C., Altangerel P. & Novacek, M. J. 1994. A 
theropod dinosaur embryo and the affinities of the Flaming Cliffs dinosaur 
eggs. _Science_ 266:779–782.

  By inference, rather. Norell et al., 1994, clarify and validate the eggshell 
morphology is elongatoolithid. Eggshells from troodontids are prismatoolithid, 
and involve a large range of surficial, fundamental, and porous differences. 

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 10:50:29 -0400
> Subject: RE: Troodon/Orodromeus hypothesis
> From: jaseb@amnh.org
> To: qi_leong@hotmail.com
> CC: jaseb@amnh.org; dinosaur@usc.edu
>
>
> >   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;
>
> Norell et al., (Science, vol. 266, no 5186, Nov 4, 1994, pg. 779) wrote
> "the possibility that the dromaeosaurids (-sic, later found to be
> troodontids)... were predators on the the oviraptorid eggs or
> hatchlings,... cannot be discounted". Of course I agree that the hatchling
> Troodontids were unlikely to break the eggs. But that's not to say they
> didn't mistakenly try. I think I've seen films of juvenile foxes gnawing
> on eggs but failing to break them. Moreover, the troodontids could have
> been attracted to the eggs in order to snatch the chorioallantoic
> membranes upon hatching. So I think that your use of the word "impossible"
> was overstated.
>
> 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,
>
> Well, if you are suggesting that, since some Troodontids were not nest
> parasites, that Byronosaurus was most likely not a nest parasite, I agree
> that that is supported, but the evidence is by no means decisive. We must
> acknowledge that an archosaur family, such as the Cuculidae, can contain
> both parasitic and nest - building members. I believe that some ducks are
> even opportunistic nest parasites, so that the same species will rear
> their young if they have to, but will dump them in other nests if they
> can.
>
>
> > especially as Bever and Norell indicate that the associated eggshells are
> > oviraptorid, of the same type found with the oviraptorid embryo.
>
> Do you have a reference on that? In the Bever, Norell paper I can only
> find a mention that two small pieces of eggshell adhere to the right
> rostral region, but no mention of the nature or origin of the eggshell.
> But in Norell et al., 1994, they do mention that the outer, convex,
> surface of the eggshell contacts the rostrum, implying that the egg did
> not enclose the skull when it was deposited.
>
> > 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.
>
> Overall I'd say that's perfectly plausible, but I do urge consideration of
> the complexity of the situation.
>
>
> >
> > 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
> >>
> >
>
>
> 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
>