Here's the second part of the SVP dinosaur
presentations.
Clarke and Norell report a new ornithurine very
close to Neornithes from Ukhaa Tolgod in Mongolia. It's a nearly complete
skeleton and presumedly different than the "Protoavis-skulled" coelurosaur at
the Fighting Dinosaurs exhibit (which has troodontid
synapomorphies).
Coria, Chiappe and Dingus report their new
carnotaurine abelisaurid from the Anacleto Member of the Rio Colorado Formation
of Argentina. It's 30% smaller than Carnotaurus and is almost
complete. It differs from Carnotaurus in that it has a- longer and lower
snout, maxillary fenestra, "swells" instead of horns, reduced coracoid process,
slender and craniocaudally compressed humerus with well-defined condyles, open
haemal canals. It's the sister group of Carnotaurus based on- cranially
projected cervical epipophyses, proximal and mid-caudals with
hyposphene-hyantra, frontal protuberances, broad coracoid, large hemispherical
humeral head, very short radius and ulna. Traces of soft tissue are
preserved around the pelvis.
Darrough, Armstrong-Hall and Fix discussed
hadrosaur vertebrae, phalanx and tooth remains from the Cretaceous Chronister
site in Missouri.
A new Bathonian tracksite from England has 42 well
preserved continuous trackways. Two-thirds are Brontopodus, while the
others are Megalosauripus. The latter are 60 cm in length and at least one
was running. The many parallel tracks suggests herding behavior.
This was presented by Day, Burton and Norman.
The Early Maastrichtian Williams Fork Formation in
Colorado preserves seven saurischians and five ornithischians, including
Pentaceratops. Diem and Archibald presented this mostly mammalian
talk.
Eberth, Currie, Coria, Garrido and Zonneveld gave
more details regarding the unnamed large carcharodontosaur bonebed in the Rio
Limay Formation (Huincul Member) of Argentina. Although the cause of
death is unknown, the fact that six individuals died here at the same ime
suggests a pre-mortem community and/or social structure.
Erickson and Curry Rogers used Developmental Mass
Extrapolation to reconstruct growth curves for dinosaurs and concluded they were
comparable to extant marsupials.
Evans, Prasad and Manhas announced small theropod
and ornithopod remains from the Early-Middle Jurassic Kota Formation of
India. These are the first ornithopod remains from that
subcontinent.
Theropod teeth from the Prince Creek Formation of
Alaska (Middle Maastrichtian) were examined by Fiorillo and Gangloff. They
concluded that species diversity is less than that in Judith River, Aguja
and Hell Creek Formations. Troodon dominates the fauna, unlike in
Judith River.
Forster and O'Connor describe new avian remains
from the Maeverano Formation of Madagascar. Two distal humeri are assigned
to Rahonavis, while two partial humeri and an ulna are assigned to Vorona.
This is based on morphological and morphometric evidence. Additional
remains include a dentary, furcula, tibia, coracoid, two types of synsacra and
three types of humeri. These are from enantiornithines with derived
features (ten sacral vertebrae, well-developed bicipital crests, enlarged
ventral tubercles, large coracobrachialis scars) and most are small, although
one moderately large synscarum is present.
Galton and Upchurch present a paper on the
confusing state of sacral transformation in prosauropods. The
plesiomorphic condition is to add a third sacral from the caudal series.
This is present in Marasuchus, Sauropoda, Saturnalia, Thecodontosaurus,
Ammosaurus, Melanorosaurus, Euskelosaurus, Plateosaurus and Sellosaurus.
The apomorphic condition of adding a sacral from the dorsal series is
present in Riojasaurus, Jingshanosaurus, Massospondylus, Yunnanosaurus,
Lufengosaurus, ?Sellosaurus and "Gyposaurus" sinensis. Why Sellosaurus is
mentioned twice I'm not sure. A 135 character, 16 genera cladistic
analysis indicates the apomorphic condition developed more than once and
reversed as well.
Gauthier and Gishlick report on the manus of
Compsognathus. "Metacarpal I" is really phalanx I-1. The mystery
element above the skull is a very short metacarpal I. There is a
collateral ligament pit on metacarpal III, but no preserved phalanges.
Thus, there may have been a third digit or not.
Gimenez describes the skin impressions of
Tehuelchesaurus, which originate from the thorax and scapular regions. The
skin is covered with tubercular scales with two diferent patterns- semi-smooth
and hexagonal scales (3x2.5 cm) alternating with smaller ones (2x1.5
cm) in small roseate patterns; rhomboidal scales (2-4 mm).
Gishlick studied the forelimb of Deinonychus and
concludes that it was poorly designed for quadrupedal climbing. This is
because the wrist flexes in the lateral plane, unlike scansorial animals, which
have wrists that flex in the dorsoventral plane. The arm would pull a
dromaeosaurid into the surface it was climbing instead of up it, and the
laterally folding wrist would twist the claws out of the surface they were
clinging to.
Grellet-Tinner reports on the titanosaurid
eggshells from Auca Mahuevo. The membrana testacea (organic eggshell
membrane) is preserved. The eggs contain radiating acicular calcite
crystals in the mammillary layer, like those of Deinonychus and Oviraptor.
Troodon shows blocky calcite crystals in the same area. Thus, the former
condition is considered symplesiomorphic for Saurischia.
Happ and Morrow describe soft tissue of Triceratops
from a specimen (SUP9713) found in the Hell Creek Formation of Montana. A
mineralized layer on the supraorbital horn core contains a mass of vessel
traces. These traces are mineralized with ferruginous hollow tubular
structures. Arteries and veins are 2.3-5.8 mm in diameter, while
arterioles and venules are .16-1.3 mm. In the braincase, solid tubular
structures passing through the exoccipital exit through the jugular
foramen. These are probably cranial nerves IX, X, XI and the jugular
vein. In addition, a solid ovate structure is preserved in the typanic
cavity.
Hartman concludes that lengthening of primary and
caudal feathers in maniraptorans provided pitch control and stability to short
duration leaps on to prey (as has been hypothesized for dromaeosaurids).
He thinks this shows that wing and caudal feathers may have evolved in a
terrestrial context.
Henderson reports on the hindlimb changes
associated with size increase in ornithopods. These include- increase in
angle between digits II and IV; increased robustnes of digit IV; equalization of
lengths of digits II-IV. Theropods do not show these changes, which is
said to be due to their saurischian pelvis. Although birds show convergent
changes, ornithopods were "hip walkers" and changed for balance reasons.
Birds are "knee walkers" that modified their foot structure for propulsion
reasons.
Hernandez-Rivera and Delgado-De Jesus describe skin
impressions from two hadrosaurs from the Cerro del Pueblo Formation (Late
Campanian) of Mexico. One hadrosaur is preserved as a nearly complete
skeleton that has impressions from the tail, limbs and hip. Another
is preserved as skin impressions without an associated skeleton.
Holtz presented a phylogenetic analysis of
neotheropods. He advocates the inclusion of poorly preserved taxa that
show novel character combinations, as (although there are often more most
parsimonious trees) they can produce trees with combinations of taxa not seen in
more inclusive analyses. He also warns that using more derived members of
the outgroup can alter the results of an analysis. Finally, he warns
against excluding characters a priori. Unfortunately, details of the
analysis are not presented :-(
There are still more talks to be covered, so
look for updates later this week.
Mickey Mortimer
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