Re: Questions

["Jaime Headden" <ja_headden@qilong.8m.com>]

Steve Mahon (floridamahon@yahoo.com) wrote:

<Does "it seems" mean unknown or just no?>

  It means that while I am not absolutely certain, the answer is "no." Since I
am hesitant to answer without some form of certaintly, I say "it seems."

<which ones?>

  I don't know off the top of my head. But that's what research is for :) You do
have the resources at hand. And one of the great things about paleo is the long
dusty hours in the stacks reading tedious upon tedious texts that seem to have
nothing at all to do with dinosaurs, but in the end seem to be rewarding in how
you LOOK at them.

<So did all 3 in my list lose or no?>

  Apparently only in troodontids, and then just some. This is a variable
character.

<Does that mean the ischium is 2/3 or less length of pubis?>

  Its around 2/3; to be exact, divide the length of the ischium by the length of
the pubis. Use the same reference points in all taxa, and decide which points
work best to attain similar measurements in which taxa. For instance, the top of
the iliac contact to the distal end is one measurement, or the shallowest rim of
the acetabulum. Just make sure its consistent.

<Some coelurosaurs have short ascending processes of the astragalus>

  Well, therizinosauroids and some birds have very short ascending processes;
which birds hardly matters, since in those birds with clear elements, such as
chickens, this is very short, and you can't really tell in *Passer.*
Alvarezsaurids have short ascending processes, as well.

<so should I change it to greater than 1/5?>

  I would recommend that you figure out the ratios of astragalus height and
tibial length, and see what obvious groups of numbers form; those taxa that seem
to show clear sets of close numbers are likely to be your cut off points between
characters. I say this rather than do the work myself, because I'm lazy right
now, and I think you might benefit from the drudgery :).

<15? soo, could this one be a Maniraptoran character then?>

  These taxa typically have over 15 caudals with transverse processes; the
clincher is that they ARE maniraptorans, because they are closer to birds than
are ornithomimosaurians, therizinosauroids are closer to oviraptorosaurs than
anything else, and in the only other definition of Maniraptora is *Oviraptor* +
birds. So they're maniraptorans however way you slice it. *Caudipteryx* a likely
basal oviraptorosaur, has far fewer than 15 caudals that have transverse
processes. This part of the tree isn't very robust in recent analyses, and only
a few features link *Caudipteryx* to Oviraptorosauria. Most of these are
cranial, such as loss of some teeth, size of the premaxilla, shape of the
dentary and external mandibular fenestra, etc.

<Also, when you say *Erlikosaurus* has a character, does that mean the other
therizinosaurians dont have it, or is it unknown?>

  The feature mentioned was cranial. In fact, only *Erlikosaurus* possesses a
decent skull. The skull of *Alxasaurus* is limited to teeth and a dentary; that
of *Segnosaurus* to the lower jaw; that of *Nothronychus* to teeth and a
posterior braincase; *Beipiaosaurus* has a partial dentary and some fragments of
skull that are largely indistinct where it is not possible to define details
without some ample amount of imagination; and that of *Neimongosaurus* to a
rostral dentary. Nearly the entire skull is known exclusively for
*Erlikosaurus.* Because of this, workers who study the taxa generally do not try
to say that because *Erlikosaurus* has the features, all therizinosauroids do
so.

<Is the nasal anteroventral process absent in any of the Troodontids, birds, or
Therizinosaurians I'm doing in my analysis?>

  In *Byronosaurus,* the process is short but present. In *Sinornithoides*
(Currie and Dong, 2001; CJES 30: 2163-2173) present but not very large, smaller
than in *Byronosaurus* (Makovicky et al, 2003; AMNovitates 3402); and in
*Sinovenator,* (pers. obs. from Xu et al., 2002; Nature 415: 780-784) the region
is broken and incomplete, so is unknown. Cranial material is known for "Troodon"
from the Two Medicine Formation, but this is undescribed. So the issue is not
certain, but they seem to have it. As for therizinosauroids, *Erlikosaurus* has
a very tiny, but distinct process (Clark et al., 1994: AMNovitates 3115). No
taxa _lacks_ the process, and this character is largely useless.

  Cheers,

  Jaime A. Headden

  Little steps are often the hardest to take. We are too used to making leaps in
the face of adversity, that a simple skip is so hard to do.  We should all learn
to walk soft, walk small, see the world around us rather than zoom by it.

  "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)