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RE: UCMP 143274 (RE: Leptorhynchos)



I am actually working on these questions currently. Unfortunately, the current 
status of my research is preliminary, though suggestive, and would require more 
detailed examination of the specimen in question than has been done to go 
further. Given that only three real papers have been produced that concern the 
specimen *(Stidham's, Mayr's response, and Hope's analysis of fossil parrots), 
but their presentation of details has been either pro-bird or pro-caenagnathid, 
detailed examination of these positions only regarding the former. That's where 
I come in, but the data is ambiguous in general at the moment.

This year sees an opportunity to attend SVP in Los Angeles, and if I can 
attend, will allow me to take a trip up to Berkeley and examine the specimen 
(curators willing). should this happen, more can be done, and thus more can be 
said.

My intial hypothesis -- and note that this is preliminary -- is that the 
specimen is particularly unique; should it be a bird, it is probably not a 
parrot, but should it be a nonavian dinosaur (barring identification as a 
turtle or whatever) it is likely to be a caenagnathid. Problematically, the 
size of the specimen lends an ontogoenetic spin on the identity of the 
specimen, as Eike notes; but as only TWO specimens have been described of 
caenagnathid-ish jaws (those of *Caenagnathasia martinsoni*), and the relative 
amount of fusion between them does not come with distinct size differences, it 
may be difficult to say anything as yet about relative ontogenetic state. There 
is no indication of "woven bone" surface texture, but this may not mean 
anything.

The basic assumption, that this specimen represents a near-adult animal, is 
tantalizing, and if so, would further support taxic uniqueness for the 
specimen, regardless of whether it was a bird or caenagnathid. There is also 
the option the specimen may be crocodilian (an identity only invoked because of 
*Macelognathus vagans*/*Hallopus victor*), testudinean, or even a teleostean or 
chondrichthyan! (I should note those last two are
very unlikely.)

As of right now, I have no grounds or reason to change what I wrote in "A 
Cretaceous Parrot" for my blog -- 
http://qilong.wordpress.com/2011/03/02/a-cretaceous-parrot/ -- which was itself 
rather tantalized by the idea of caenagnathid identity. UCMP 143274 does 
represent something unique to the Lance Formation, and probably the 
Maastrichtian; but the implications (parrot or not) require further study.

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, 26 Apr 2013 10:20:37 +0100
> From: koreke77@yahoo.de
> To: dinosaur@usc.edu
> Subject: UCMP 143274 (RE: Leptorhynchos)
>
>
>
> --- Jaime Headden <qi_leong@hotmail.com> schrieb am Do, 25.4.2013:
>
> > Von: Jaime Headden <qi_leong@hotmail.com>
> > Betreff: RE: Leptorhynchos, new caenagnathid theropod from Late Cretaceous 
> > of North America
> > An: "Dinosaur Mailing List" <dinosaur@usc.edu>
> > Datum: Donnerstag, 25. April, 2013 19:04 Uhr
> > In my post below, I argued that ICZN
> > Art. 70.1 allowed automatic type fixation. I am incorrect on
> > this score, as explained in the comments here: 
> > http://qilong.wordpress.com/2013/04/25/an-oviraptorosaur-worth-the-name/
> > .
>
>
> Seeing the material of "L." gaddisi brought me back to 
> http://qilong.wordpress.com/2011/03/02/a-cretaceous-parrot/ ... anything the 
> new study (or other recent studies) adds on this case? Any indications in the 
> presently-known caenagnathid hypodigm whether the 
> presence/absence/structure/shape/pattern of surface ornamentation may be 
> ontogenetic?
> Or in the absence of material evidence (the hypodigm of very young 
> caenagnathids is, IIRC, still m
 ontogenetic dietary shifts in caenagnathids? Evidence in favor of a dietary 
shift is not proof of change in surface ornamentation, but it can argue in 
favor of it, even strongly so (in cases of extreme shifts that demand gross 
ontogenetic changes in morphology).
> (IF the beak of caenagnathids was an adaptation to shear through strongly 
> sclerotized plant tissue, a dietary shift is perhaps more likely than not, as 
> such food would doubtfully be nutritious enough to sustain a theropod growing 
> to moderate or largish size. Juveniles would probably have fed on 
> easier-digested, softer plant tissues... or have been extremely slow-growing, 
> but that makes the lack of caenagnathid growth series in the hypodigm 
> puzzling. And if juvies ate softer food, the null hypothesis would be their 
> jaws had a less structured surface than those of adults.)
>
>
>
> FWIW the latest phylogenetic studies on stem Psittaciformes, eg 
> http://www.bioone.org/doi/abs/10.1080/02724634.2012.641704, virtually rule 
> out a psittaciform identity of UCMP 143274
> ot jaw was a late Paleogene or early Neogene apomorphy postdating crown 
> psittaciform TMT apomorphies - and ecologically building on these, 
> nut-gripper foot opening a niche for evolution of nut-cracker beak -, as far 
> as anyone can tell ATM.
>
> The general shape, particularly the outer curvature of UCMP 143274 is 
> remarkably *un-*parrot-like in fact; if this was avian, the entire mandible 
> would have been closer to that of Aequornithes in shape (ie narrow and 
> elongated)... in Psittaciformes with rounded mandibular tips, the length of 
> the symphysis is subequal to (at most) barely superequal to its width. On the 
> other hand, in UCMP 143274 it is almost twice as long as wide and the rami 
> ran almost parallel at least in the the distal part; if they were not 
> exceptionally short, a parrot-like bill shape (short and blunt) in UCMP 
> 143274 can be rejected by these two features combined already: it is simply 
> too narrow for its length.
>
>
>
> TL;DR:
> What did the mandibular symphysis of a *hatchling* or "fledg
 2081* 
(http://qilong.wordpress.com/2012/01/22/the-hell-creek-oviraptorosaur-should-or-shouldnt-it-be-chirostenotes-pergracilis/)
 look like? In gross morphology and size at least, UCMP 143274 would be the 
closest match there is in the fossil record, if I'm not mistaken.
>
>
> * Or maybe the smaller coeval and sympatric caenagnathid, if that was not 
> just a subadult of the same taxon as FMNH PR 2081.
>
>
>
> (FWIW, the standards of evidence and sweepingness of conclusions in Stidham 
> (1998) are simply scary 15 years in hindsight... stuff you only see in 
> high-priced high-impact low-quality-of-peer-review journals:
>
> "The discovery of this parrot [sic] in the Lance Formation indicates that the 
> lineage leading to the parrot crown group was present by the end of the 
> Cretaceous. If this parrot were a lory [sic], as suggested by its morphology 
> [sic], ..."
>
> Eerily recalls of studies 25 years older, when K-Pg boundary avians were 
> still routinely assigned to crown "families".
> Stidham may be excused a bit for the second gaffe, because the
> ption at that time still was that "Loriidae" was basal or almost basal among 
> crown Psittaciformes. They are not; on the contrary, the origin of lorikeets 
> cannot be realistically pushed back much further than mid-Neogene.
> So in the light of present-day phylogenetic knowledge and fossil record, the 
> argument of Stidham (1998) for a psittaciform identity of UCMP 143274 is 
> entirely demolished; it is a rather funny (or sordid; you decide) case of 
> verification bias. To draw any conclusions from a comparison of UCMP 143274 
> with lories is as meaningless as to argue an unusually rounded mammalian 
> calvaria from the Danian were "proof" for crown Hominidae in the late 
> Cretaceous.)
>
>
> Thus, at the present time I can only conclude that a thorough comparison of 
> UCMP 143274 with any and all caenagnathid material pertinent to its identity, 
> and inferring what can be inferred from the rest re: ontogeny, diet, and 
> Maastrichtian caenagnathid diversity in North America, would be more 
> warranted than e
>
>
> Regards,
>
> Eike