Re: Revising Hou et al, 96 (very very long)

["Fam Jansma" <fam.jansma@worldonline.nl>]

Mickey Mortimer wrote:

>Perhaps, but it's complicated.  First I should note that the "propubic >
>mesopubic > opisthopubic" trichotomy is probably oversimplified.  We should
>look for actual angles between the pubis and ilium, the direction the base
>points and other such things.  But assuming we utilize the simple method
for
>the moment, look at the distribution-

If we happen to decide that propubic-mesopubic-opisthopubic must be based on
the angles the three elements make that compose the pelvis, wouldn't they
just make things more complicated? For instance, there is in no way possible
to say when something is mesopubic based on angles, it would become
something like a grade thing. But how would this seperation would be like?
>From exactly what angles do we deceide when a pelvis is mesopubic or not.
No, I fail to see why this simplified seperation needs to be altered when it
is still in good shape. Like they say: never change a winning team.

>I personally think troodontids + eumaniraptorans were primitively
>opisthopubic, with reversals in derived troodontids, Achillobator,
>Archaeopteryx and Rahonavis.  Unenlagia also reversed somewhere in there,
>but exactly where it goes I'm uncertain.  I think it's less likely that
>paravians or all maniraptorans were primitively opisthopubic, but it is
>possible.

Opisthopubic pelves was probably an ancestral character which was later
reversed in the Troodontids, Oviraptorids, some Dromeosaurs for unknown
reasons. This would make the opisthopubic pelvis an ancestral character and
therefore pretty useless in creating a tree about the Maniraptoriforms. But
what you are implying with the segment "I think it's less likely that
paravians or all maniraptorans were primitively opithopubic", does this mean
this family is polyphyletic or anything? I am an advocate for HP G.S. Paul's
theory that maniraptorids are secondarily flightless, meaning that
Maniraptors evolved from an opisthopubic ancestor the likes of
Archaeopteryx. Both Sinornithosaurus and Sinovenator are very much like
Archaeopteryx, leading me to expect that the latter could be their sort of
ancestor or sister group, and these two genera are the basal most genera
known for two of the major families that comprimise the Maniraptors. Where
Ovi's fit in is a complete mystery and are probably not closely related to
either the Dromeosaurids or Troodontids. Their universally accepted
similarities to Therizinosaurids, with the Early Jurassic representative
Eshanosaurus, leads me to suspect that Ovi's evolved the semi-lunate carpal
convergently. Or.....Archaeopteryx is not the first of a new breed of
animal, but more an intermediate step and related to an animal from the
Upper Triassic. Speculation, speculation, speculation....

The exact way in which to deal
>with these situations is often subjectively decided.  For instance should
>"posterior tooth serrations enlarged" be coded as absent in a taxon with
>serrationless teeth?  We can't tell the size of the serrations when they
>were not present, or does that mean they are infinitely small?  In this
>example I probably should have coded Hesperornis as "?" for "manual
>phalanges III-2, III-3 and III-4 absent".

That's what I would do

>
>Mickey Mortimer

Rutger Jansma