[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

I'm all for jeholornithids having neoflightless relatives/descendants.  Maybe 
Yandangornis is such an animal.  But cladistics or no, you have to propose some 
synapomorphies for a relationship and I just don't see anything jeholornithids 
share with Falcarius that's not seen in basal paravians like Rahonavis, 
Archaeopteryx, Anchiornis, Jinfengopteryx, etc..  We know from taxa like 
Achillobator that massive reversals are possible, so I'm not dismissing it out 
of hand, but at least the omnivoropterygid-oviraptorosaur link has some backing 
in anatomy.  Given their skulls, I'd find jeholornithids to be more likely to 
be related to an omnivoropterygid-oviraptorosaur clade than to therizinosaurs.  
Or if not that, features like the short manual phalanx III-2 and good-sized 
pedal ungual II might suggest a relationship with dromaeosaurids.  But 
therizinosaurs?  I just don't see anything.  They're both herbivorous, sure.  
But the only obvious adaptations for that in jeholornithids are in the beak, 
and Falcarius doesn't share them (e.g. heavy jaws, decurved dentary, strong 
symphysis).  The long tails could just as easily be shared with dromaeosaurids, 
or could be primitive based on alvarezsaurids and basal coelurosaurs.  As for 
therizinosauroids' shorter tails, being a heavier, slower and more herbivorous 
animal seems like a good reason to not waste as much resources on a balancing 
organ.  Note therizinosaurids like Nothronychus? graffami have even shorter 
tails than more basal taxa like Alxasaurus or Neimongosaurus, which fits my 
idea, but to fit yours would imply these three genera were all independently 

As for your statement "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", that's rather unfair.  I'm a 
card-carrying cladist and I'm just fine with eudromaeosaurs coming from flying 
microraptorian-like ancestors, derived troodontids coming from flying 
Anchiornis-like ancestors, oviraptorosaurs coming from flying ancestors which 
may be omnivoropterygids, flightless unenlagiines coming from flying 
Rahonavis-like ancestors, Yandangornis coming from flying jeholornithid-like 
ancestors, as well as possibly independently flightless taxa like Mahakala and 
Tianyuraptor.  Whether flight evolved as far back as alvarezsauroids, 
therizinosaurs or ornithomimosaurs I'm successively less confidant of.

Mickey Mortimer

> 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>