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Details on SVP 2002 Part 1



Another SVP down.  This summery will be a bit different from last years, as
the abstracts are freely available-
http://www.vertpaleo.org/meetings/Abstracts02.pdf .  It's a waste of both of
our time for me to write out details already in the abstracts.  Thus, my
summaries will be shorter.

Non-dinosaur stuff-

Weinbaum presented new information on Postosuchus.  Using the comparative
area of vertebral central articular faces along the column, they showed it
was bipedal.  This is substantiated by the tiny manus.  The braincase
actually resembles Allosaurus.  Chatterjea has a rather ornithomimid-like
pelvis, quite surprising and ironic considering the previously suggested
(and incorrect- Rauhut 1997, 2000) referral of Shuvosaurus to that taxon.  A
phylogeny was presented-
|--Aetosauria
`--Paracrocodylomorpha
   |--Poposauridae
   |  |--Lythrosuchus
   |  `--+--Poposaurus
   |     `--+--Sillosuchus
   |        `--Chatterjeea
   `--Paracrocodyliformes
      |--Rauisuchidae
      |  |--Rauisuchus
      |  `--+--Saurosuchus
      |     `--+--Batrachotomus
      |        `--Postosuchus
      `--Crocodylomorpha

And as for the dinosaurian talks I attended-

Forster presented a cladistic analysis of ceratopsids using 129 characters,
and Protoceratops and Zuniceratops as outgroups-
|--+--Avaceratops
|  `--+--+--Centrosaurus
|     |  `--Styracosaurus
|     `--+--Einiosaurus
|        `--+--Achelousaurus
|           `--Pachyrhinosaurus
`--+--+--Anchiceratops
   |  `--+--Arrhinoceratops
   |     `--+--Torosaurus
   |        `--+--Diceratops
   |           `--+--Triceratops prorsus
   |              `--Triceratops horridus
   `--+--Chasmosaurus mariscalensis
      `--+--Pentaceratops
         `--+--Chasmosaurus russelli
            `--+--Chasmosaurus irvinensis
               `--Chasmosaurus belli
She suggested Avaceratops may have been placed basally in part due to
ontogenetic characters, and noted only two steps are needed to make
Chasmosaurus monophyletic.

Harwell's  talk was informative, but frankly insulting to the viewers'
intelligence, with it's huge colorful cartoons and simplistic explanations.
The whole pont was that crocodiles can work well without pubic movement.
There is no pressure difference in the abdomen, 15% less liver movement and
10% less tidal volume.  So the fixed pubis of theropods would not have
hindered diaphragmatic breathing.  Fine, but you still have to show WHY they
would have it in the first place.

Kirkland has some wonderful specimens in the works.....

Lamanna et al. presented some new information on Paralititan.  Among the
info not in the abstract, the first caudal is procoelous, the manual
phalanges were absent (as in Opisthocoelicaudia and Epachthosaurus), and the
length was estimated at 20-25 meters.

I had a good discussion with Martin.  He's quite a nice guy, it's a shame
he's so wrong about almost everything dinobird-related.  Seems he officially
believes that maniraptorans are birds, but that other coelurosaurs are
unrelated.  He terms this the "Paulian hypothesis", though it's only similar
in thinking of maniraptorans as 2F and preferring the arboreal origin.  In
his mind, maniraptorans and other birds evolved from a Longisquama-like
creature.  And like Czerkas believes, some taxa (eg. Scansoriopteryx) are
just too hard to place as birds or dinosaurs until a more in depth study is
completed.  The same old ABSRD arguments were brought up (digit homology,
terrestrial theropods, Yixian feathers being collagen, etc.).  He referred
to both ichthyosaurs ( http://www.cmnh.org/dinoarch/2002Aug/msg00090.html )
and Psittacosaurus as having structures like those found in Sinosauropteryx
et al., which is just plain wrong of course.  In any case, he does have an
interesting eumaniraptoran that will be out soon.

Middleton's talk was concerned with theropod halluces.  He used
biomechanical studies to show the reversed hallux does not prevent birds
like starlings from moving efficiently terrestrially.  His main point was
that the neornithine reversed hallux is diffferent from the primitive
theropod type in having a strong twist in the first metatarsal.  I don't
recall him speaking about modern birds with unreversed halluces.  In any
case, every non-avian theropod he examined (including Coelophysis,
Allosaurus, alvarezsaurids, Caudipteryx, troodontids and Deinonychus) showed
a non-twisted morphology.  The Solnhhofen Archaeopteryx (the only one
preserved well enough), Rahonavis and Patagopteryx did too.  Confuciusornis,
Changchengornis, Concornis, Eoenantiornis, Sinornis and Liaoningornis
exhibited an intermediate semi-twisted condition, indicating a medial
direction.  Avisaurids apparently had an odd specialized hallux that was
hard to code.

Paul's talk on sauropod posture was interesting.  He countered Parrish and
Steven's horizontal neck theory by noting Apatosaurus' neck curved ventrally
through the ground if articulated in a neutral position.  He also noted that
a giraffe's neck articulates at a 45 degree angle when neutral, but varies
widely in life, including being vertical.

Peters and I talked a bit.  Seems he added Pterorhynchus to his matrix and
found it to be just basal to pterydactyloids, agreeing with the tentative
opinions of Holtz, Ford and Unwin.  Looks like a good concensus.  He was
unsure of what to make of Utahdactylus.

Sadleir and Chapman had an unconvincing talk in my opinion.  They used three
points on teeth (tip, proximal edge of each carina) to place them on a graph
showing the robustness (y axis) and amount of anterior/posterior "curvature"
present (x axis).  Unsurprisingly, theropod premaxillary teeth were less
curved, and the tooth row gets more curved posteriorly.  Varanids are
seemingly similar.  Crocodiles came out as a vertical line, which is of
course because they have more conical teeth.  Spinosaurs were said to be the
theropod exception.  Mosasaurs come out in a tight grouping.  They
attributed the differences in plots to theropods' and varanids' cranial
kinesis, but mosasaurs and spinosaurids are kinetic too.

Senter showed that including dinosaurs, Cosesaurus, Longisquama,
Megalancosaurus, crocodylians and birds in a single cladistic analysis (only
osteological characters) doesn't change the result that birds are
maniraptoran theropods.  Neither Megalancosaurus nor Longisquama even came
out as archosaurs (or saurians?), and were sister groups in some trees.
There were some odd results too, such as sauropods being the most basal
dinosaurs (George would be happy).  He tried coding bird hands as II-III-IV
to see if it changed the results, but it did not.  Stidham told me that if
the dinosaurs were all removed, birds still grouped with Marasuchus.  And if
it was removed, they grouped with more basal archosaurs, etc..  Apparently
almost all reptiles had to go before they claded with "avimorphs".  I think
he should have performed constrained analyses to test the amount of steps
needed for alternative placements for birds.

Stevens and Parrish said that giraffe necks had obvious articulations at the
base to show they are held vertically, and that sauropods don't have this
angling.  They also said that neutrally articulating Apatosaurus' neck made
it horizontal, not ventrally curved into the ground, and that the downard
kink in Diplodocus' neck reconstruction was due to distortion in that
specimen.  Cetiosaurus also articulated almost horizontally.  The
calculation of the nuchal ligament size that was needed to hold the neck and
tail up (which matched the space in the fossils), as well as the remains of
ossified ligaments between the forked neural spines of diplodocids was
excellent.  At the end, they argued the center of mass for diplodocids was
placed anterior to the hindlimbs and that the caudofemoralis would have to
be much too large if it were to support a bipedal diplodocid.  Paul later
brought up the bipedal abilities of virtually tailless elephants when I
asked him about the talks, which is a pretty good point.

Stidham discussed metatarsal fusion and its ontogeny in theropods.  He had a
horrible cladogram of (Coelophysis (Dilophosaurus "Syntarsus")) to map
fusion morphology on to.  Has this topology even been suggested in the lit?
He used x-rays to show that Avisaurus has distal tarsal fused to the
metatarsus, and suggested Archaeopteryx did too.  The small free elements
previously identified as distal tarsals in Archaeopteryx would then be
sesamoids.  He also used Iberomesornis as an example of this, but Sereno
(2000) showed that the supposed distal tarsals were part of the fused tarsal
cap.  Stidham used a juvenile "avisaurid" metatarsal from Utah(?) to show
that the distal tarsals fused to the metatarsals before the metatarsals fuse
to each other in enantiornithines.  Ornithurines differ in fusing the
metatarsals together, then fusing the tarsal cap to the tarsometatarsus.  He
believes this new developmental pathway allowed more niches to be filled
through greater diversification and specialiation of the pes.
Hesperornithids were used as an example, supposedly showing the speed at
which niches were filled after ornithurines evolved.  What he didn't show
was the highly specialized metatarsi of some enantiornithines (eg.
Yungavolucris, Lectavis), which I believe disprove his point.

Wilson and Upchurch discussed the identity of Titanosaurus.  Most species
were made nomina dubia, though I'll have to see the evidence for myself.
Supposedly indeterminate species included T. indicus, T. blanfordi, T.
falloti, T. lydekkeri, T. madagascariensis, T. nanus, T. rahiolensis(?), T.
robustus(?) and T. valdensis.  T. falloti was previously referred to
Tangvayosaurus, T. madagascariensis to Rapetosaurus and the new
saltasaurine, and T. valdensis to Iuticosaurus.  It's things like this that
make me doubt that all these taxa can be undiagnostic.  But we'll see.
"Titanosaurus" colberti was given a new genus name, and Laplatasaurus was
kept as a separate genus.  They presented a partial phylogeny-
|--Phuwiangosaurus
`--+--Venenosaurus
   `--+--Austrosaurus
      `--+--Andesaurus
         `--+--Malawisaurus
            `--+--Saltasauridae
Titanosauria was defined as Andesaurus plus Saltasaurus, while a new clade
name was given to Malawisaurus + Saltasaurus, referring to their armored
skin.
I got a chance to talk to Upchurch for quite some time.  Cetiosaurus is
looking to get a couple redescriptions.  First comes a redescription of a
referred specimen in Palaeontology, then next year is a revision of the
taxonomy and description of the holotype in JVP.  Cetiosauriscus is being
worked on too.  Sereno's (1999) basal placement of "Gyposaurus" sinensis is
based on elements that are missing and misidentified, in referred material
nonetheless.

More next time.....
The posters will be last, once I get my film back.

Mickey Mortimer