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

Re: Recoded Aves introduces a lot of fog?

David Marjanovic wrote-

> Why Bagaraatan here?

You know, it's only been included in four phylogenetic analyses I know of.
In my 2000-2001 analyses, it was the most basal paravian, less derived than
alvarezsaurids, troodontids, dromaeosaurids and birds.  In Holtz's 2000 GAIA
analysis, it was the sister group of a clade containing tyrannosauroids,
compsognathids and maniraptoriformes.  In Rauhut's 2000 thesis, it was in a
trichotomy with enigmosaurs and paravians.  In Longrich's 2001 SVP analysis,
it was in a trichotomy with alvarezsaurids and an enigmosaur-paravian clade.
So the majority consensus is that it's very close to the enigmosaur-paravian
divergence.  The AMNH team doesn't appear to be including it yet.  If Tom
Holtz is reading this, perhaps he will tell us where it came out in his SVP

> Very strange places for both *Yandangornis* and *Sapeornis*. The latter is
> almost obviously the sister group of Pygostylia.

The precise relationships of Yandangornis, Sapeornis and confuciusornithids
are quite uncertain at this point.  As I wrote previously-
Yandangornis is more derived than Sapeornis based on-
fibula does not reach calcaneum; phalanx II-2 longer than II-1?; reduced
manual unguals.  It's less derived than Sapeornis based on- cervical centra
not heterocoelous; absence of pygostyle?.  Problems arise because I don't
trust the accuracy of the skeletal reconstruction of Yandangornis in the
original description, so phalangeal lengths are suspect.  Most authors don't
differentiate the semi-heterocoelous state from either amphicoelous or
heterocoelous, but aren't more likely to choose one of the extremes when
describing the intermediate condition (eg. Confuciusornis has been described
as having amphicoelous and heterocoelous cervicals by different authors, but
truly has an intermediate state).  Finally, the very distal end of
Yandangornis' tail isn't preserved, so it may have had a small
Nomingia-style pygostyle, like Sapeornis.  Also, there are a couple
characters in Yandangornis (olecranal fossa; phalanx II-2 longer than II-1?;
reduced manual unguals) and Sapeornis (ulna longer than humerus; scapular
shaft tapering distally) that are more derived than confuciusornithids.

> Has the same distinctive shape of metatarsal III as Pygostylia,
> and *Yandangornis*... OK, it's not so distinctive, at least
> almost has it likewise, at least in caudal view, but *H.* is certainly not
> troodontid.

Remember, resemblence of Sinornithoides' metatarsus is caudal view to that
of pygostylians' in cranial view is no more meaningful than if one taxon's
pubis resembled another's scapula. :-)

Jaime Headden wrote-

> Alternatively, most birds have the large external mandibular fenestra,
> especially phorusrhacoids, by which a parallel I mean too draw in the near
> future.

But not basal birds.  In confuciusornithids and the Spanish nesling yes, but
Archaeopteryx, Eoenantiornis, Gobipteryx, perhaps Sinornis, Hesperornis and
others go so far as to lack any external mandibular fenestra.

> Basal oviraptorosaurs, contra to Mickey, also possess the invasive
> posterior surangular "prong," and the pubic concavity of the enigmosaur
> complex is not so easily ruled out: >snip<

Caudipteryx zoui has a small dorsal process, but only one of the two
Caudipteryx sp. nov. specimens has it.  And Chirostenotes certainly doesn't.
The whole "anteriorly concave pubis" character needs some work.  I just got
done with character 94 in my revision, that's character 223.  So it will be
a while.

> ovate foramen magnum taller than wide

That's not even present in Nothronychus, Erlikosaurus and Chirostenotes (and
Citipati sp. according to Norell et al.).

> It becomes then as easy as saying that ornithomime and tyrant
> dinosaurs are sister groups because they have similar hindlimbs. Which
> does not meet up with the recently presented evidence of the last two
> years, though Holtz (2001) has supported somewhat Arctometatarsalia on
> compeletly different grounds.

Um, five of Holtz's (2000) seventeen tyrannosauroid + ornithomimosaur
synapomorphies were hindlimb characters.  I wouldn't call that "completely
different grounds".  Of course, his 2001 analysis excludes tyrannosauroids
from Arctometatarsalia.

> Incidentally ... there's more data indicating *Caudipteryx* is an
> oviraptorosaur thanb presently exists for *Microvenator*.

Because Caudipteryx is far more complete than Microvenator. :-)

Mickey Mortimer