Re: Wrong Reconstructions

[Jason Brougham <jaseb@amnh.org>]

Thanks for these observations Jaime, they were most thought - provoking. 

> 
>   It's pretty tricky labeling scansoriopterygids as similar to much of 
> anything, given how divergent their anatomy is and how little we know about 
> simple things like skull anatomy.

Well, the type specimen of Scansoripoteryx (which is apparently synonymous with 
Epidendrosaurus), CAGS02-IG-gausa-1/DM 607, actually has a pretty good lateral 
view of the skull and mandible.


> *Epidexipteryx* differs quite a bit from *Epidendrosaurus*/*Scansoriopteryx*, 
> impairing the use of the skull as an extrapolation, and that's most of what 
> fills in the details of skeletal anatomy that is lacking in the latter 
> specimens. In those specimens/taxa, all that we have of the skull are partial 
> braincases, posterior mandibles, and a bowed-U-shaped mandibular symphysis 
> without any clear indication of teeth, while *Epidexipteryx* has fantastic 
> detail and huge teeth.

True that Epidexipteryx is better preserved, but between the two specimens of 
Epidendrosaurus I think we can tell a lot about head proportions, eye size, 
mandible shape, etc.

> 
>   The real issue is that aside from the "ebff"s, "feathers" in all fossils 
> are non-plumulaceous, lacking apparent barbs, and nothing similar to 
> "feathers" in the conventional (modern) sense.

In CAGS02, there are feather impressions on the ulna that are longer than the 
humerus. Wouldn't that would be most likely to be a poorly preserved pennaceous 
feather, as in NGMC91?

> 
>   --
> 
>   Varricchio's theories on male multi-clutch brooding and unlikelihood of 
> pair-bond feeding "chicks" in "Troodon" nests found in Two Medicine may be 
> accurate, but there are a few caveats:
> 
>   The nests Varricchio is referring to are similar to those of *Citipati 
> osmolskae* in forming concentric rows of stacked eggs set in pairs around a 
> common center; this laying pattern is consistent with a single female laying, 
> rotating, laying, rotating, etc. and not consistent with multiple females 
> laying in a common clutch.

I'm not sure why multiple females couldn't lay egg pairs in concentric circles. 
The minor hens could simply add eggs on the periphery of the dominant females' 
preexisting clutch and follow the same pattern, as they do in tinamous.  Do you 
have any data on that?

> At least some older papers referred nests now considered to belong to 
> *Orodromeus makelai* to "troodontids," showing a less organized, erratic 
> clutch pattern similar to that advocated by Varricchio of "Troodon" in the 
> Two Medicine.

Perhaps, but then these were probably not included in the paper that finds 
paternal care to be the most likely (avian paternal care had dinosaur origin. 
Science 322 pg. 1826, 2008). I believe those included showed paired eggs.
> 
>   So on this point at least, Varricchio would be correct but about the wrong 
> taxon. Implications of *Citipati osmolskae* and "Troodon" nests indicate 
> rather that there were female brooders,

Again, I'm not sure what method you used to determine this. Varricchio et al. 
found that large clutches correlate with paternal care.

> while juvenile fossils found in oviraptorid nests imply prey may have been 
> gathered at the nest, possibly to feed hatchlings. If so, the last two images 
> would be correct on the brooding/feeding arguments.

Now that may be so. But it could also be that the single male brooder (father) 
brought prey to the nest to eat himself. In any case, I don't think Troodontids 
were running around trying to catch enough insects to feed 24 nestlings. 
Insectivorous birds that feed their young usually have, what, three eggs in a 
clutch?

> 
>  --
> 
>   You'll have to forgive the next bit.
> 
>   Owl auditory bullae are large, very large, and extend largely to the 
> external margins of the skull, such that the ear is essentially flush with 
> the skull of the head. In a facial disk, this permits the sound to transfer 
> directly into the funnel without being redirected at an angle before entering 
> the auditory canal. Troodontids (or at least the Dinosaur Park skulls) lack 
> the auditory bullae seen in owls, and the otic region is confined to within 
> the braincase and between the quadrates, rather than extended poteriorly and 
> lateral to them. This makes the case of a troodontid facial disk highly 
> unlikely

I am no expert on auditory anatomy, nor on acoustics, so you should probably 
take this up with Dr. Mateus, who liked my "Tytonoid" reconstructions. What I 
do know is that Troodontids are well known for having parasphenoid bullae, 
and/or parasphenoid pneumatic recesses. The former show up in the more derived 
Troodontids, apparently. That is why I tried to keep the owliness to the more 
derived forms. Though the bullae may not project to the outer margin of the 
skull there seems no a priori reason that pneumatic cavities, with or without 
cartilaginous components, couldn't have. Computer or physical acoustic models 
could definitely be devised to test both hypotheses.

> . I must say, however, that the restoration is fantastic and you should go 
> ahead with it anyways!

Thanks again.

> 
> 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: Tue, 25 Jan 2011 12:17:19 -0500
>> From: jaseb@amnh.org
>> To: dinosaur@usc.edu
>> Subject: Wrong Reconstructions
>> 
>> I have posted three incorrect reconstructions of maniraptorans on my 
>> website. I drew them between 2003 and 2008. I am looking forward to hearing 
>> the thoughts of dml'ers on the subject of reconstruction errors.
>> 
>> http://web.me.com/jasonbrougham/Site/Blog/Entries/2011/1/24_Wrong_Reconstructions.html
>> 
>> 
>> Jason Brougham
>> Senior Principal Preparator
>> American Museum of Natural History
>> jaseb@amnh.org
>> (212) 496 3544
>> 
>> 
>                                         

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544