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

Re: So here it is... my paper, open for discussion (very long; try to view it in maximum window breadth)

> Congratulations on getting your paper published!  The aquatic hypothesis
is very interesting....


> As for putting Unenlagia in the same family as Archaeopteryx, I'd like to
know what characters they share that other
> deinonychosaurs lack.

Apparently none. The sideways-facing glenoids have turned out to be normal
among dromaeosaurids, and your analysis has found the vertical pubis to be
most parsimoniously a reversal. I have no idea why this should have
occurred, though. Anyway, this part of the phylogeny is based on "old"
papers and websites.

> > Sometime it is mentioned that the latter three taxa (troodontids and
tyrannosaurs: Currie,
> > 1995, oviraptorosaurs: Sues, 1997 contra Norell et al. 2000) have a
separate exit for the
> > cranial nerve V1, which normally exits the braincase through a large
foramen together with V2 > and V3. Dromaeosaurus
> > (Currie, 1995) and Archaeopteryx (Elzanowski & Wellnhofer, 1996)
> > exhibit the primitive condition.
> The derived state is also present in Allosaurus

Sure?!? *Allosaurus*?!?

> and Carpenter and Currie (2000) code oviraptorids as having the primitive

Any chance for a typo in their matrix? :-]

> This shows the character distribution is more complex than presented.

A few years ago, state of the art was that nerve arrangements change very
rarely in evolution (probably because selectionary pressures can hardly be
imagined) and that birds have that separate exit, while all other tetrapods

> > Arctometatarsalians and oviraptorosaurs also share pneumatised quadrates
and articulars not
> > occuring in Archaeopteryx (Elzanowski & Wellnhofer, 1996) and
Dromaeosaurus (Currie,
> > 1995).
> Caudipteryx lacks a pneumatic quadrate, as do Shuvuuia and Confuciusornis.
This character would thus be more
> parsimoniously interpreted at convergently evolving in
arctometatarsalians, oviraptorids and ornithurines.  Pneumatic
> articulars are much rarer among theropods.  They are present in
Tyrannosaurus, Erlikosaurus and Bagaraatan.  They are
> certainly absent in Chirostenotes, Deinonychus and Gobipteryx, and
probably in Archaeopteryx.  I also see no evidence of > a foramen in
Confuciusornis. I'm not sure where segnosaurs or Bagaraatan go in your
phylogeny, but as Chirostenotes and > Gobipteryx lack this feature (and I
don't know the condition in Caudipteryx and oviraptorids), the assertion
oviraptorosaurs > and pygostylians can be united with it is weakened.

Maybe I can "explain this away" that the actual character here is not the
hole in the bone, but the presence of the air sac, which may or may not
invade the bone due to ontogenetic age or whatever. Of course, this is
hardly falsifiable...
        *Bagaraatan* doesn't go anywhere in my phylogeny, because I lack
information. Segnosaurs... well, I've put them into Sauropodomorpha with the
usual arguments, but this placement has become difficult to defend. Either
way, one arrives at about 50 synapomorphies and 50 convergences, as someone
stated onlist a few years ago on this topic (now in www.dinosauria.com).

> > Osmólska & Maryanska (1997) note that oviraptorid quadrates are
double-headed, i. e. they
> > have an additional contact to the braincase, and they are much more
pneumatised than in
> > arctometatarsalians (Osmólska & Maryanska, 1997).
> Oviraptorids have double-headed quadrates, but the basal oviraptorosaur
Caudipteryx lacks this character.

What are double-headed quadrates good for, anyway?

> > Oviraptorosaurs (Sues, 1997) (including Caudipteryx <and
Protarchaeopteryx?>) also share
> > with alvarezsaurids (Novas, 1997) rather short tails that are not
stiffened distally, a condition
> > seen in no other theropods. <...>
> True.  Caudipteryx has an especially short tail, only slightly longer than
that of Confuciusornis.  Yandangornis and
> segnosaurs also have relatively short tails.


The tail of *Avimimus* is rather short too, AFAIK.

> > Pneumatic features also fit this picture: Archaeopteryx is no more
extensively pneumatised
> > than dromaeosaurids, i. e. cervical and dorsal vertebrae as well as
their ribs are pneumatised
> > (Britt et al., 1998). In oviraptorosaurs (Currie, 1995) and
alvarezsaurids (Novas, 1997),
> > pneumatic foramina (or depressions) occur as far back as the middle of
the tail! (In recent
> > turkeys (Britt et al., 1998), the sacral and free caudal vertebrae are
pneumatised, in ostriches
> > (Britt et al., 1998) the caudals are not.)
> There is a difference between the lateral depressions found in the dorsals
(confuciusornithids, enantiornithines) and caudals
> (Patagonykus, enantiornithines) of some maniraptorans and the pleurocoels
(pneumatic foramina) found in the sacrals and
> caudals of caenagnathids and oviraptorids.

Which (other than grade)?

> Patagonykus is the only alvarezsaurid known to have such depressions, they
are absent in Alvarezsaurus and Parvicursor.
> No alvarezsaurid has sacral or caudal pleurocoels.  On the other hand, the
dromaeosaurid Achillobator has pleurocoel-like > foramina on its proximal
caudals, while Variraptor and Ornithodesmus have pleurocoels in the first
two sacral vertebrae.
> Also, the basal oviraptorosaurs Caudipteryx and Microvenator lack caudal
pleurocoels.  This again suggests parallel
> development to any birds which have such excavations.


> > With the description of Nomingia (Keesey, 2000, /genera/nomingia.html),
the pygostyle has
> > joined the list of maniraptoran (see cladogram) synapomorphies (no
alvarezsaurid tail end is
> > known, Caudipteryx and Protarchaeopteryx could have pygostyles <just
discussed>, judging
> > from photographs (Ackerman, 1998), the resolution of which is too coarse
to be certain)."
> While Nomingia does have a pygostyle, Caudipteryx and oviraptorids do not.
Another reference (Zhou et al., 2000) can be > added to the list of experts
who have verified this fact (Zhou and Wang 2000, Ji et al. 1998).

Oviraptorids don't (secondarily?), but Caudipteryx has something very much
like one (maybe it really has one only 3 vertebrae long).

> Oviraptorosaurs are sort of like the basal diapsids/archosauromorphs of
the birds-aren't-dinosaurs group.  Put them
> together (short tail and reversed hallux of Caudipteryx; pygostyle of
Nomingia; elongate radius of Microvenator; caudal
> pneumaticity of caenagnathoids; fused jaw elements and absent coronoid of
caenagnathids; double-headed quadrate and
> triradiate palatine of oviraptorids) and you get a perfect pygostylian
sister group, but look at them separately and the
> picture's not so clear.

I haven't addressed the radius of *Microvenator* (I didn't know about it,
and animals like *Sinornithosaurus*, *Bambiraptor* or -- *Archaeopteryx*
would decidedly look like better candidates here) and the jaws of
caenagnathids (AFAIK there isn't much fusion, if any, in alvarezsaur jaws,
and I have mentioned in the paper that *Oviraptor* has a tiny separate
        How surely identified are the ornithoid *Deinonychus* eggshells? Are
there embryos inside (_inside_, not outside like the ?nest-parasitizing
*Velociraptor* chicks in the oviraptorid nest)?

> > A single bird synapomorphy, according to Elzanowski & Wellnhofer (1996),
has been left to
> > Archaeopteryx: the triradiate palatines. I think that it is most
parsimonious to explain this
> > feature by convergence <ô surprise>, though I have no idea why this
should have occurred."
> Well, even though my analysis currently supports Archaeopteryx as a basal
deinonychosaur, I'll play devil's advocate.
> Besides the reversed hallux, Archaeopteryx shares the following characters
with pygostylians not seen in dromaeosaurids,
> oviraptorosaurs or arctometatarsalians.
> - reduced olfactory lobes

As *A.* lived at the seashore, where there aren't too many things to sniff,
I'll suspect convergence.

> - less than nine caudal vertebrae with transverse processes
> - very short anterior chevrons, none taller than anteroposteriorly long

What's the condition in *Microraptor* and *Rahonavis* (wherever the latter

> - manual digit I doesn't extend past manual phalanx II-1

> - phalanges on third manual digit reduced (III-1 and III-2 sutured, not
jointed; possibly ancestral to the pygostylian
> condition of having two non-ungual phalanges on digit III)

Sutured??? Really sutured??? And your phylogeny supports this as being
reversed in dromaeosaurids???

> - proximodorsal ischial process

I'll try to have a few looks at theropod pelves, about which I don't really
know much.

> - tibia subequal in width and length in proximal view

Sounds like size-related to me.

> > Birds down to Alvarezsauridae have prokinesis (Chiappe, Norell & Clark,
> > confuciusornithids have akinetic skulls (Hou et al., 1999), which is
probably secondary
> > because the jugals don't have ascending processes.
> While the akinetic skulls of confuciusornithids could very well be
secondary, they do possess ascending processes on their
> jugals (Chiappe et al., 1999).

What's that ref, the JVP paper on *Changchengornis*?

> > '[a]nd in spite of the fact that dromaeosaurids are often proclaimed to
be the most birdlike of
> > the theropods <...>, they lack many of the theropod-avian synapomorphies
found in other
> > theropod families, and have too many specialisations to be plausible
avian ancestors'
> Unlike those conservative oviraptorosaurs ;-)

Well, as no-one has proclaimed them as avian _ancestors_, at least since the
advent of cladistics, they can have as many specialisations as they want,
and so can oviraptorosaurs.

[snip: origin of feathers]

> While I can easily picture non-dinosaurian dinosauriformes (Marasuchus,
Lagerpeton) and smaller maniraptorans
> (Microraptor, mononykines, Archaeopteryx, enantiornithines) being at least
partially insectivorous, basal theropods,
> sauropodomorphs and ornithischians were too large to have depended on
insects as their main food source.

So far no feathered sauropodomorphs and ornithischians have been found, so
secondary loss in these groups is possible. For theropods (or coelurosaurs
only), the fossil record is still lamentable, and compsognathids aren't very

> Also, new evidence suggests feathers may not have developed from scales,
while the structure of Sinosauropteryx's
> integumentary filaments suggest feathers evolved by adding branching
filaments, not splitting scales.

Hm. I'll wait for the *Protopteryx* paper.

> Your aquatic hypothesis is quite interesting.  Seems defendable, but on
the other hand difficult to test.

Of course, given the present knowledge of the fossil record. However, this
situation isn't any better for the other hypotheses...

> >         "Arctometatarsalians did the same, but they changed to
long-distance pursuing, as
> > indicated by their feet. They were already present at the same time as
dromaeosaurids -
> > there are the troodontid Koparion, some ornithomimid teeth <and that
Kimmeridgian finger
> > from Great Britain -- thanks to the list I mention it in the published
> Jurassic ornithomimid teeth?  What might the reference for this be?

I'm sure to have read this in _The complete dinosaur_. Where in this thick
book I don't know, however :-( .

> >       Still true. :-( Is it likely that a mobile scapula-coracoid joint
can evolve twice (or be a
> > misinterpretation)? In this case Rahonavis could belong to
Archaeopterygiformes... MORE
> > FOSSILS!!!
> The mobile scapulocoracoid joint of Rahonavis is certainly present.
What's odd however is the absence of this character in > confuciusornithids.
This could easily support a convergence or loss.

Oho! ~:-\ Well, a convergence would (like its tail) support referring *R.*
to Archaeopterygiformes.

> >         Neotheropoda or earlier: furcula? (not ossified - like the
sternum - in e. g.
> > compsognathids, attached to the scapula by ligaments and therefore
frequently falling off
> > before burial, which explains its rare preservation [Makovicky & Currie,
1998]; the ventral ends
> > of the clavicles of Sinornithoides and probably Carnotaurus are broken -
perhaps the middle
> > part of a furcula has broken away [Mortimer, 2000 <in the List archives,
can't find it now; it is
> > properly cited in the published version>])
> I'm actually referenced in a bibliography?

At least, you are referenced in print.

> Adam Yates should get the real credit though, as I heard the idea >from
> http://www.cmnh.org/fun/dinosaur-archive/2000Apr/msg00601.html
> I never even mentioned the Carnotaurus furcula.  That came from Thomas
> http://www.cmnh.org/fun/dinosaur-archive/2000Apr/msg00635.html .


Should I forward this post to the editor of the Dinosaur Society Quarterly
(for an Errata page or something?)

Thanks for the good critique!