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Reisz and Sues, 2001. Longisquama does not have
feathers. JVP 21(3) 92A.
A great talk, showing conclusively that
Longisquama's dorsal scales are not branched, but are instead hollow on the
sides. Wonderful magnified slides showed this, though there was still at
least one disbeliever. :-)
Clarke, Gautheir, Norell and Ji, 2001. The origin
and significance of a propatagium in flying dinosaurs. JVP 21(3)
41A.
Argued cf. Sinornithosaurus lacked a propatagium,
while Confuciusornis had one. The condition in Archaeopteryx is
uncertain. Notes that wing area estimates of Archaeopteryx assume the
presence of such a structure, whose absence would decrease the area by
4%.
Dial, 2001. On the origin and ontogeny of avian
flight: Wing-assisted incline running. JVP 21(3) 45A.
Definitely one of the best talks at SVP, argued
birds may have started flying when ancestors ran up sloped/vertical
surfaces. The wings act to keep the bird close to the surface, as spoilers
do on race cars. Much more complex than my simple explanations of course.
It was all demonstrated with meticulous studies of birds of all ages running up
surfaces of various materials and angles. Nice video was shown, including
adorable little chicks. Looks like a good competitor with the arboreal
jumping hypothesis.
Tumarkin, Chinsamy and Dodson, 2001. Trauma in
birds: Is it reflected as interruptions in osteogenesis? JVP 21(3)
109A.
Neornithines don't have lines of arrested growth
(LAGs) in their bone cross sections, indicating they grow continuously.
Enantiornithines and more basal theropods do have such structures. The
confusion is with Patagopteryx, which has one LAG in the cross section that's
been taken. This is odd and has been suggested to be due to a pathology,
such as trauma or nutritional deprivation. To solve the problem, the most
time-consuming and complex method was chosen. Take a cross section of
another Patagopteryx individual you say? Why would we do that when we can look
through numerous museum specimens of living birds that died after trauma and
examine them for LAGs, while attempting to account for interspecies variation,
ontogeny and different types of trauma? And the end result of it all- Eh,
we're still unsure. A lot of uneccessary work in my opinion.
Wharton, 2001. The evolution of the avian brain.
JVP 21(3) 113A.
Work on braincase anatomy to determine characters
important in avian evolution. This holds quite a bit of promise to give us
more braincase characters for our coelurosaur phylogenies. For instance,
Bambiraptor, Archaeopteryx and pygostylians have reduced optic lobes, unlike
Troodon, Tyrannosaurus and Allosaurus. This supports troodontids being
outside the Eumaniraptora.
The last day had the following talks, but no
dinosaur related posters-
Sampson and Forster, 2001. Parallel evolution in
hadrosaurid and ceratopsid dinosaurs. JVP 21(3) 96A.
Witmer, 2001. The position of the fleshy nostril in
dinosaurs and other vertebrates and its significance for nasal function. JVP
21(3) 115A.
Henderson, 2001. Tension, tendons and trellises: A
predictive model for the orientation of ossified tendons and vertebral structure
in iguanodontian dinosaurs. JVP 21(3) 60A.
Krauss, 2001. An analysis of the feeding habits of
herbivorous dinosaurs through an examination of phytoliths trapped on tooth
grinding surfaces. JVP 21(3) 69A.
A great idea, Krauss intended to determine which
plant types hadrosaurs and ceratopsids ate, then see if there is any distinction
between the clades. It turns out to be more complicated than one would
like- plant types are extremely difficult to equate with phytolith morphologies
and ceratopsids and hadrosaurs show no discernable difference in taste (contra
the abstract).
Hill, Witmer and Norell, 2001. A new juvenile
specimen of Pinacosaurus grangeri: Ontogeny and phylogeny of ankylosaurs. JVP
21(3) 61A.
A Pinacosaurus skull from Ukhaa Tolgod (Campanian)
in Mongolia. The holotype actually has three pairs of narial openings, not
two like originally supposed. The sequential appearence of secondary
dermal ossification can be determined with this specimen, the holotype, the
previously described juvenile and P. mephistocephalus. A phylogeny was
presented-
|-Stegosauria
|-+-Emausaurus | `-Scelidosaurus `-+-+-Pawpawsaurus | `-+-Silvisaurus | `-+-Sauropelta | `-+-Panoplosaurus | `-+-Edmontonia | `-Animantarx `-+-Gargoleosaurus `-+-Gastonia `-+-Minmi `-+-Pinacosaurus `-+-Talarurus `-+-+-Tsagigantea | `-Shamosaurus `-+-+-Tarchia | `-Saichania `-+-Euoplocephalus `-+-Ankylosaurus `-Nodocephalosaurus Interesting that Minmi is an ankylosaurid and
Polacanthidae is paraphyletic. Unlike Carpenter's analysis, the families
Ankylosauridae, Nodosauridae and Polacanthidae were not assumed to be
monophyletic a priori.
Norman, 2001. The anatomy and systematic position
of Scelidosaurus harrisonii Owen, 1861. JVP 21(3) 84A.
Unfortunately, Norman could not present his
talk. Some characters noted in the abstract include- cranial dermal
ossicles; supraorbital horns; reduced antorbital fenestra and fossa; ossified
epipterygoid; cervical dermal rings; laterally tilted, dorsoventrally compressed
preacetabular blade; partially closed acetabulum; pendent fourth trochantor;
enlarged greater trochantor confluent with femoral head. Says new evidence
suggests it is a basal ankylosaur, not outside of Eurypoda. Carpenter says the
same thing in The Armored Dinosaurs, but doesn't discuss the previously
suggested eurypodan synapomorphies.
Makovicky, 2001. Evolutionary history of basal
Neoceratopsia. JVP 21(3) 77A.
A phylogenetic analysis of neoceratopsians was
performed with 122 characters and 23 taxa. Kulceratops, Microceratops and
Turanoceratops were found to be nomina dubia, so not included.
Graciliceratops is said to be a metataxon (ack!). The holotype of
Asiaceratops (a maxilla) is said to be indeterminate, but some referred remains
are diagnostic. There is an unnamed Jurassic taxon (IVPP V
12722) from Hebei, China that comes out as the sister group to
Chaoyangsaurus. There is also an undescribed form from the Two Medicine
Formation. Montanaceratops' nasal horn was shown to be a misidentified
jugal.
|-+-Chaoyangsaurus
| `-IVPP V 12722 `-+-Psittacosaurus `-+-Archaeoceratops `|-Asiaceratops |-+-Montanaceratops | `-+-Leptoceratops | `-Udanoceratops `-+-ZPAL MgD-I/156 `-+-+-Bagaceratops | `-Protoceratops `-+-Zuniceratops `-+-|-Anchiceratops | |-Triceratops | `-+-Chasmosaurus | `-Pentaceratops `-+-Avaceratops `-+-Centrosaurus `-+-Styracosaurus `-+-Achelousaurus `-Pachyrhinosaurus Notice Montanaceratops is fairly low, in the
Leptoceratopsidae. Avaceratops is a ceratopsid, contra Penkalski and
Dodson (1999).
Goodwin and Horner, 2001. How Triceratops got its
horns: New information from a growth series on cranial morphology and ontogeny.
JVP 21(3) 56A.
A growth series of Triceratops shows the nasal horn
is formed by an epinasal ossification that fuses almost completely with the
nasals by adult size. The postorbital horns develop before the nasal horn,
start out small and forward pointing, grow longer and curve backward, then take
on the recurved morphology typical of adults. Nice photos of a tiny
juvenile skull.
Chapman, Snyder, Jabo and Anderson, 2001. On a new
posture for the hormed dinosaur Triceratops. JVp 21(3) 39A-40A.
Computer modeling let the authors make miniature
versions of the bones and articulate a virtual skeleton to determine
Triceratops' posture. The result- the forelimbs are intermediate between
sprawled and vertical.
Rauhut, Lopez-Arbarello, Puerta and Martin, 2001.
Jurassic vertebrates from Patagonia. JVP 21(3) 91A.
Taxa from the Canadon Asfalto Formation
(Callovian-Oxfordian) of Argentina were discussed. Piatnitzkysaurus was
discovered here, but there is also a new tetanurine with possible coelurosaur
affinities. It's known from a partial skeleton with the following
characters- anterior cervical pleurocoels more posteroventrally located than in
Piatnitzkysaurus; deep lateral sacral fossae; reduced cnemial crest on
tibia. The skeletal reconstruction was shown, so hopefully this taxon will
be published soon.
Patagosaurus is actually a chimaera, with referred
specimen MACN Ch934 being another taxon. Bonaparte didn't distinguish
specimens in his 1986 description, so sorting out this mess will be
difficult. The new taxon has dorsal vertebrae with distally expanded
neural spines, round neural canals and vertical lateral neural pedicle edges,
all unlike Patagosaurus. In addition, its ilium has a shorter pubic
peduncle and rounded preacetabular blade. Other sauropod specimens include
a partial articulated skeleton, large humerus and possibly brachiosaurid
femur. The Canodon Asfalto sauropods (also including Volkheimeria and
Tehuelchisaurus) were entered into Upchurch's and Sereno and Wilson's matrices
to find the following topologies-
Upchurch's 1998
|-Vulcanodon
`-+-Volkheimeria `-+-+-Cetiosaurus | `-Patagosaurus `-+-Barapasaurus `-+-Euhelopodidae `-+-MACN Ch934 `-+-Lapparentosaurus `-+-Haplocanthosaurus `-+-Tehuelchisaurus `-Neosauropoda Sereno and Wilson's
1998
|-Vulcanodon `-|-Volkheimeria |-Shunosaurus `-+-Omeisaurus `-+-Patagosaurus `-+-MACN Ch934 `-+-Diplodocoidea `-+-Haplocanthosaurus `-+-Camarasaurus `-|-Tehuelchisaurus |-Brachiosaurus `-+-Euhelopus `-Titanosauridae At least, I think that's what the topologies
were. I actually didn't note where they placed neosauropods in Upchurch's,
so I assume it was at the tip. Note that a Cetiosaurus+Patagosaurus clade
also appears in Upchurch and Barrett's new cladogram, but Tehuelchisaurus is the
sister group to Omeisaurus in the latter. Also, Patagosaurus and
Omeisaurus switch places in this version of Sereno and Wilson's phylogeny and
Wilson's new SVP phylogeny. Volkheimeria seems very basal, while MACN
Ch934 is fairly derived, if not neosauropod.
Well, that's it. I have some more photos,
including that new tall-crested oviraptorid, but they aren't developed
yet. I'll be sure to post once they are.
Mickey
Mortimer |