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RE: tiny-armed theropods
*Segnosauria* is not defined as a taxon in a Family-level rank, and thus has
no bearing with relation to *Therizinosauroidea*, the name used in support for
*Therizinosauridae*, etc., which does have priority over *Segnosauridae*.
*Therizinosauroidea* was used to supplant *Segnosauria* as the name of value
for the stem, and has been kept that way based solely on use and the sense of
"whomever defines it first shall have that name be used (even if the definition
It's silly that, until *Therizinosauria* become used more recently,
*Segnosauria* could still be used for the group. But this hasn't been the case
for workers discussing therizinosaur total group, and I think the name will
fall to disfavor unless somehow resurrected.
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: Wed, 12 Oct 2011 16:28:32 +1100
> From: firstname.lastname@example.org
> To: email@example.com
> Subject: Re: tiny-armed theropods
> David Marjanovic <firstname.lastname@example.org> wrote:
> > ...although, in ornithomimo- and segnosaurs alike, the head + neck is still
> > longer than the forelimbs.
> The necks of ornithomimosaurs and therizinosaurs are decidedly long.
> And yeah... I also prefer the name 'segnosaurs' over 'therizinosaurs'.
> ;-) But I guess the latter has priority.
> Jason Brougham <email@example.com> wrote:
> > I see, so you are suggesting that all theropods would benefit from
> > reduction of their pectoral limbs if
> > they could find a way to do without arms in feeding and brooding and
> > whatnot, because it would
> > make them more agile.
> This was the essence of Carrier et al's (2001) paper on rotational
> inertia in theropods (J Exp Biol. 2204: 3917-26). The resulting
> agility while turning might also have driven the evolution of the
> forelimb-folding mechanism in maniraptorans, conferred by the
> semilunate carpal joint. (I don't buy GSP's notion that the
> semilunate carpal evolved as a flight-related/flapping feature.)
> > It's just that dispensing with the arms' uses must have been impossible for
> > many theropods,
> > possibly for a large or even an innumerable set of interacting reasons.
> I've wondered about this. It is likely that bipedality preceded
> predatory behavior in dinosaur evolution. The study of Martinez et
> al. (2011) further indicates that the ancestral body plan for
> dinosaurs included a proportionately long forelimb (~45% hindlimb
> length) and a sharp-clawed manus capable of hyperextension. Theropods
> show a shift to a more raptorial/grasping manus (elongate penultimate
> phalanges of manus, etc). Nevertheless, it appears to me that once
> dinosaurs became bipedal it was a case of: "So, what do we do now with
> these appendages?"