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

Details on SVP 2001Friday Talks 2 and Saturday Talks

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-
| `-Scelidosaurus
  | `-+-Silvisaurus
  |   `-+-Sauropelta
  |     `-+-Panoplosaurus
  |       `-+-Edmontonia
  |         `-Animantarx
              | `-Shamosaurus
                | `-Saichania
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.
| `-IVPP V 12722
     | `-+-Leptoceratops
     |   `-Udanoceratops
     `-+-ZPAL MgD-I/156
         | `-Protoceratops
             | |-Triceratops
             | `-+-Chasmosaurus
             |   `-Pentaceratops
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
    | `-Patagosaurus
        `-+-MACN Ch934
Sereno and Wilson's 1998
      `-+-MACN Ch934
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