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RE: Wrong Reconstructions
Jason Brougham wrote:
<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.>
Yes, it has a good view of a skull that is crushed, and splayed, such that
the dorsal roof of the skull is visible in almost undistorted fashion (being
identical in form to that exposed for *Epidendrosaurus ningchengensis* in
ventral view) alongside the lateral circumorbital and suspensorial portions of
the skull; no material is apparent anterior/rostral to the lachrymal. In the
mandible, the posterior dentary is virtually absent, providing us only with a
slender, U-shaped apparatus of paired dentaries in *Epidendrosaurus
ningchengensis*, which [apparently] had many small, similarly-sized alveoli
arranged around most of its length. The mandible, in fact, resembles that of
anurognathids (and someone on the DML suggested at one point it was associated).
This leaves us with a scansoriopterygid skull that is missing the rostral
half, including any indication of precisely how long it really is. Way back
when, I speculated on the skull in lateral view of both of these specimens:
And just for kicks, *Epidexipteryx hui*:
There's probably less variation in the rostrum than I seem to imply above
with the first two lacking features that can tell us what this region of the
skull looked like; if the mandible of *Epidendrosaurus ningchengensis* is
correctly associated, it implies a form quite dissimilar to *Epidexipteryx hui*
-- although the postcrania are very similar otherwise.
<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?>
Possible. So far, however, the specimens have not been redescribed since
their publication, requiring us to wait for the chance to examine them in a
fashion far superior (so far) than Zhang et al. or Czerckas & Yuan. Most of
this would likely wait for a good analytical revision, especially with new
material from the sites for which we know these specimens come from (not the
case for *Scansoriopteryx heilmanni*).
Barbs are present in NGMC 91, as indicated by the consistency of the vane,
rather than random brachiating tufts cobbled together; this would be the case
for CAGS02-IG-gausa-1 as well, but there is no real particular reason why this
should imply the feathers are implicative of flight capability, which you'd
think needs barbules, and those are not apparent as yet. Ratite feathers, a
common analogy on this level, lack barbules (but are degenerate from a form
which preserves them, as in tinamous) and preserve a pennaceous structure. All
that is required of these feathers to "look feathery," is to possess a long
rachis and have barbs. Flight feathers, on the other hand, almost certainly
appaar to require barbules to contain the vane into a plane while force is
applied to the surface, and we simply have no evidence for this in either NGMC
91 or CAGS02-IG-gausa-1 [yet].
Jaime A. Headden
The Bite Stuff (site v2)
"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
> Date: Fri, 28 Jan 2011 17:45:41 -0500
> From: firstname.lastname@example.org
> To: email@example.com
> CC: firstname.lastname@example.org
> Subject: Re: Wrong Reconstructions
> 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: email@example.com
> >> To: firstname.lastname@example.org
> >> 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
> >> email@example.com
> >> (212) 496 3544
> Jason Brougham
> Senior Principal Preparator
> American Museum of Natural History
> (212) 496 3544