[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Ah ha! That's where therizinosaurs came from



  Sigh. Still trying to find exclusive links between large-bodied terrestrial 
nonavian theropods based on small avialaeans. 

  It's a good thing the "neoflightless" hypothesis wasn't recovered using 
scientific methods, nor is it necessarily testable based on the arguments used 
to support it, because anything that is raised to reject it is ignored (such as 
all the cladistic analyses between 1988 and now that failed -- utterly -- to 
find the relationships Paul inferred in 1988 and 2002). Invoking Maryańska et 
al. (2002) and Osmólska et al. (2004, etc.) analyses but ignoring the 
contradicting Norell et al. (2001) TWG and derivative analyses (e.g., Turner et 
al., 2007) seem to further this issue. 

  Substantively, the analysis of Maryańska et al. (2002) fails in regards to 
the hypothesis placing oviraptorosaurs nearer to birds largely due to excessive 
sampling of oviraptorosaurs and the lack of inclusion of stem-dromaeosaurs like 
*Anchiornis huxleyi,* *Mei long,* *Buitreraptor gonzalezorum,* *Mahakala 
omnogovae* and/or *Shanag ashile*. Moreover, Osmólska (1976) and Maryańska & 
Osmólska (1997) drew heavily on the apparent similarities in oviraptorid crania 
to birds, excluding the much less avian-appearing skulls of caenagnathids, 
caudipterids and protarchaeopterygids; in this, the postcrania also agree on 
the specific, including the arrangement and morphology of the pelvis, 
convergent development of the tarsometatarsus, and the plesiomorphic 
arrangement of the shoulder and the broad but anteroposteriorly short sternum 
with fewer rib facets than in dromaeosaurs. The lack of a pygostyle in 
*Protarchaeopteryx robusta*, a more basal taxon than *Caudipteryx zoui*, and 
its appearance in an array of taxa excluding *Oviraptoridae* does not help 
matters here. Most of these avian features touted by Paul in oviraptorosaurs 
are themselves convergent within *Oviraptorosauria.* 

  It is untenable to assume they are actually consistent when the basal-most 
taxa lack them, or that this generalization of the clade to birds is useful. It 
is at least equally problematic that more avian-like taxa in their basal forms 
appear at the base of the stem leading to *Deinonychosauria*, "Troodontidae" 
and *Dromaeosauridae,* and do not require the invocation of convergence to 
explain their relationship to birds: *Paraves*.

  I'll wait to comment more heavily than I have when some more effective 
analysis is forthcoming placing sapeornithids (or *Omnivoropteryx sinousaorum*) 
at the base of oviraptorosaurs.

Maryańska, T. & Osmólska, H. 1997. The quadrate of oviraptorid dinosaurs. _Acta 
Palaeontologica Polonica_ 42(3):361-371.
Maryańska, T., Osmólska, H. & Wolsan, M. 2002. Avialan status for 
Oviraptorosauria. _Acta Palaeontologica Polonica_ 47(1):97-116.
Norell, M. A., Clark, J. M. & Makovicky, P. M. 2001. Relationships among 
Maniraptora: Problems and prospects. pp.49-67 in Gauthier & Gall (eds.) _New 
Perspectives on the Origin and Early Evolution of Birds: Proceedings of the 
International Symposium in Honor of John H. Ostrom._ Yale University Press (New 
Haven, Connecticut, USA).
Osmólska, H. 1976. New light on the skull anatomy and systematic position of 
*Oviraptor*. _Nature_ 262:683-684.
Osmólska, H., Currie, P. J. & Barsbold R. 2004. Oviraptorosauria. pp.165-183 
in  Weishampel, Dodson & Osmólska (eds.) _The Dinosauria (second edition)._ 
University of California Press (Berkeley, California, USA).
Turner, A. H., Pol, D., Clarke, J. A., Erickson, G. M. & Norell, M. A. 2007. A 
basal dromaeosaurid and size evolution preceding avian flight. _Science_ 
317:1378-1381.

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: Mon, 8 Aug 2011 23:22:17 -0400
> From: GSP1954@aol.com
> To: dinosaur@usc.edu
> Subject: Ah ha! That's where therizinosaurs came from
>
> I was in the Hopkins library gathering material to restore the skeleton of
> Johelornis now that there are enough skulls and skeletons lying around when
> I did the proverbial dope slap as I realized the probable ancestoral source
> for therizinosaurs.
>
> I have long been pointing out that all flightless "theropods" with
> extensive flight adaptations are likely to be secondarily flightless because 
> no one
> has come up with really satisfactory arguments for why and how those flight
> characters evolved outside the context of flight, because early fliers
> should have been spinning off neoflightless descendents that retain flight
> characters, and the situation parallels that of ratites etc.
>
> It now looks pretty good is that as I pointed out back when Ronnie was Prez
> that predaceous Late Jurassic archaeopterygids some of which had fully
> developed wings were the ancestoral type if not group for more derived
> Cretaceous deinonychosaurs some of which had even better flight capabilities, 
> and
> others being secondarily flightless.
>
> At the same time I was pointing out, and Osmolska too, that oviraptorosaurs
> were probably more avian than archaeopterygids and secondarily flightless.
> In the Field Guide I noted that the ancestoral group or type is likely to be
> your herbivorous omnivoropterygids.
>
> What has become most vexing is those pesky therizinosaurs. Some have those
> very long tails. So what basal flying theropods were herbivores with long
> tails? Well duh, jeholornithids. Not that jeholornirds specifically are
> prototherizinosaurs, they lack sufficient teeth for one thing. Now, other
> therizinosaurs have shorter tails. It is unlikely for that to be adaptative 
> among
> evolving land herbivores that should retain long tails to counter balance the
> exapnding belly. It is therefore possible that what we call therizinosaurs
> descended from fliers more than once, with later therizinosaurs spinning off
> shorter tailed fliers.
>
> In this tentative scenario predaceous long tailed deinonychosaurs are the
> least derived, herbivorous long tailed projeholornithids/therizinosaurs more
> derived, and herbivorous short tailed omnivoropterygids/oviraptorosaurs the
> most derived. Deinonychosaurs may be on the avain line or a side branch.
>
> Now it all makes sense, phylonirvana has been achieved and what was
> perplexing now is a lot more logical. Blessed thanks be to the deities that
> probably do not exist. Could be wrong of course, but I suspect that future 
> fossils
> that are the only means of testing the hypothesis will bear out the basic
> idea, although we may never know due to lack of sufficient transitional taxa.
>
> That cladistics does not at least currently support this is not impoprtant
> because of the severely limited fossils on hand. After all, had I been a
> cladist I never would have come up with the neoflightless concept in the first
> place.
>
> What the cladistics would have us believe is that all these predatory,
> omnivorous and herbivorous early fliers were flitting about in the later half 
> of
> the Mesozoic yet for some magical reason were never spinning off
> reflightless forms that show up in the fossil record. Really, that's what the
> cladograms want us to take seriously. But not only that, a bunch of theropods 
> that
> never had flying ancestors for some mysterious reasons happened to evolve not
> only feeding adaptations, heads and bodies eerily like those of the fliers,
> but also flight adaptations even though there is no good explanation why
> that would have happened. And never mind that the nonvolant ancestors of
> therizinosaurs and oviraptorosaurs remain mysterious (probably because they 
> never
> existed. Yes, yes, I know its kind of silly but that's the scenario
> cladistics have been generating so we must bow to the doctrine and think such 
> silly
> things are actually plausible. Or not.
>
> If anyone else came up with the therizinosaurs are neoflightless
> jeholornids please let me know.
>
> And to think that anyone used to think that therizinosaurs were
> transitional to prosauropods-ornithischians! What a nincompoop, what a maroon.
>
> As for the Jeholornis skeletons its way cool, kind of a cross between
> Archaeopteryx and Falcarious (it's much less Archy like than some past
> restorations, arms much more massive). The absence of an accurate restoration 
> may be
> one reason why the possible relationship to therizinosaurs was not picked up
> earlier.
>
> GSPaul</HTML>