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Cryolophosaurus, new Antarctic sauropodomorph, and Poposaurus at GSA meeting



From: Ben Creisler
bcreisler@gmail.com

The abstracts for a few of the posters and presentations at the just
completed Geological Society of America meeting may be of interest to
the DML:

http://gsa.confex.com/gsa/htsearch.cgi?words=dinosaur&action=search&formaction=http%3A%2F%2Fgsa.confex.com%2Fgsa%2Fhtsearch.cgi&meetingid=93&dir=finalprogram&override=&restrict=gsa.confex.com%2Fgsa%2F2012NC%2Ffinalprogram%2F&passedyear=&passedmeeting=2012NC&exclude=%7C%2Fprogram%7C%2Fmeeting%7C%2Fsearch.html%7C%2Fprelim&config=gsa&method=and&format=builtin-long&sort=score

==

Section - 46th Annual Meeting (23–24 April 2012)
Paper No. 6-30
Presentation Time: 8:00 AM-11:40 AM

http://gsa.confex.com/gsa/2012NC/finalprogram/abstract_202648.htm

VERTEBRAL ANATOMY OF CRYOLOPHOSAURUS ELLIOTI, A THEROPOD DINOSAUR FROM
THE EARLY JURASSIC OF ANTARCTICA
CRANDALL, Jake R., Geology Department, Augustana College, 639 38th
Street, Rock Island, IL 61201, jake-crandall@augustana.edu

Fossil localities discovered in Antarctica in the early 1990’s and
early 2000’s have produced a nearly complete theropod dinosaur, the
fragmentary remains of a basal sauropodomorph dinosaur, a
dimorphodontid pterosaur humerus and a Bienotheroides clade
tritylodont tooth. Cryolophosaurus ellioti Hammer and Hickerson, 1994,
was discovered in the Early Jurassic Hanson Formation on Mt.
Kirkpatrick in the Beardmore Glacier region of the Central
Transantarctic Mountains at an altitude of approximately 4100 meters.
Cryolophosaurus is the most complete dinosaur yet discovered in
Antarctica and represents a theropod from an early critical period in
dinosaur evolution. Due to a very limited number of fossils from this
period we do not have a clear understanding of the phylogeny of these
early theropods. Cryolophosaurus is distinguished from all other
theropods by its possession of a distinct cranial crest and, at an
estimated body length of 6.5 meters and a weight of 465 kilograms,
Cryolophosaurus is the largest theropod known from the Early Jurassic.
Earlier studies indicate that Cryolophosaurus is related to a clade of
medium-bodied Early Jurassic theropods including ‘Dilophosaurus’
sinensis, Dracovenator regenti and Dilophosaurus wetherilli. This
clade challenges the previous understanding of the Coelophysoidea and
Ceratosauria, rendering both non-monophyletic. A morphological
description of the vertebral column of Cryolophosaurus is presented
here that includes many recently prepared new specimens collected in
2003 that were not included in the earlier analyses. The analysis
includes five cervical, six dorsal, two sacral and eleven caudal
vertebrae. The post-cranial skeleton of Cryolophosaurus preserves a
number of morphological characteristics that are useful in
interpreting its relationships and position within the phylogeny of
theropods.

North-Central Section - 46th Annual Meeting (23–24 April 2012)
General Information for this Meeting

Session No. 6--Booth# 30
Special Poster Session on Undergraduate Research (Posters)
Dayton Convention Center: Exhibit Hall 101/102
8:00 AM-11:40 AM, Monday, 23 April 2012

Geological Society of America Abstracts with Programs, Vol. 44, No. 5, p. 13


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North-Central Section - 46th Annual Meeting (23–24 April 2012)
Paper No. 6-38
Presentation Time: 8:00 AM-11:40 AM

http://gsa.confex.com/gsa/2012NC/finalprogram/abstract_203068.htm

A NEW BASAL SAUROPODOMORPH FROM THE EARLY JURASSIC HANSON FORMATION OF
ANTARCTICA
HELLERT, Spencer M., Geology, Augustana College, 639 38th St, Rock
Island, IL 61201, spencer-hellert@augustana.edu

The latest expedition to the Transantarctic mountains, Antarctica
(2010-2011), has yielded the remains of two possible new taxa from the
early Jurassic Hanson Formation. Earlier expeditions to the Mt.
Kirkpatrick region of the Transantarctics have produced a diverse
fossil assemblage including Cryolophosaurus ellioti, Glacialisaurus
hammeri, an undescribed pterosaur humerus, and a tritylodont
postcanine tooth. Here we describe the remains of a partial skeleton
of a basal sauropodomorph dinosaur discovered near the same locality
on Mt. Kirkpatrick, Antarctica. The material includes the anterior
portion of the left ilium, including a proportionally elongate
preacetabular process and the dorsal and anterior portions of the
acetabulum including the pubic peduncle. It also includes the
incomplete shaft and proximal end of the left ischium, including the
obturator process, but lacking the anterior extension, the distal end
of the left pubis, a nearly complete right pubis, and the last two
posterior dorsal vertebrae articulating with the first sacral
vertebra.

Based on plesiomorphic and derived characters, especially of the ilium
and vertebrae, this material represents a taxon within the family
Massospondylidae. Due to the size of the specimen and the lack of
fusion between the neural arches and the centra, the specimen appears
to be that of a juvenile animal. The material may represent that of a
juvenile Glacialisaurus hammeri, a taxon found in close proximity
though slightly lower in the section, however further investigation is
needed.

Although little is known about the temporal, spatial, and phylogenetic
relationships within basal sauropodomorphs, especially within the
Antarctic region, several recent discoveries from early Jurassic of
South America has helped elucidate some of these issues. The material
described herein is important for the understanding of biodiversity
and biogeographic implications of Antarctica during the Early Jurassic
and will aid in providing new data for the debate on basal
sauropodomorph phylogenetics.

North-Central Section - 46th Annual Meeting (23–24 April 2012)
General Information for this Meeting

Session No. 6--Booth# 38
Special Poster Session on Undergraduate Research (Posters)
Dayton Convention Center: Exhibit Hall 101/102
8:00 AM-11:40 AM, Monday, 23 April 2012

Geological Society of America Abstracts with Programs, Vol. 44, No. 5, p. 14

==

North-Central Section - 46th Annual Meeting (23–24 April 2012)
Paper No. 21-5
Presentation Time: 9:20 AM-9:40 AM

http://gsa.confex.com/gsa/2012NC/finalprogram/abstract_201327.htm

PEDAL DIGITAL AND PHALANGEAL PROPORTIONS OF THE “DINOCROC” POPOSAURUS GRACILIS
FARLOW, James O., Department of Geosciences, Indiana-Purdue Univ, Fort
Wayne, IN 46805, farlow@ipfw.edu, SCHACHNER, Emma R., Department of
Biology, University of Utah, Salt Lake City, UT 84112, and SARRAZIN,
John C., Department of Mechanical Engineering, University of Utah,
Salt Lake City, UT 84112
The Triassic suchian Poposaurus gracilis showed morphological
convergence with bipedal dinosaurs in an erect limb carriage and a
short forelimb/hindlimb length ratio, suggesting that, like non-avian
theropods and many ornithischians, Poposaurus was an erect, striding
biped. We investigated whether convergence between dinosaurs and
Poposaurus extended to relative lengths of the pedal digits, and of
the pedal phalanges.

We used two data sets in our analyses, employing both bivariate
comparisons and principal components analyses. One data set used our
own measurements as well as data from the literature of phalanges I1,
II1-II2, III1-III3, and IV1-IV3 (more distal phalanges, including
unguals, were not used in order to increase sample sizes of feet) of
Poposaurus, non-ornithodiran archosaurs, basal dinosauromorphs, basal
sauropodomorphs, non-avian theropods, bipedal ornithischians, and
ground birds. A second data set used only direct measurements from the
specimens of pedal digital and phalangeal lengths (including unguals)
of digits II-IV, and selected phalangeal widths, of Poposaurus,
non-avian theropods, and bipedal ornithischians. Data were
supplemented by photographs and published figures of specimens for
which measurements were not available.

Poposaurus is more like non-avian theropods and basal ornithopods than
non-ornithodiran archosaurs and most ground birds in the phalangeal
proportions of digits II-IV. It is similar to many dinosaurs as well
as crocodylians in the relative lengths of digits II and III, more
like dinosaurs (many saurischians and some ornithischians) than
non-ornithodirans in the relative length of digit IV, and more like
non-ornithodirans, prosauropods, and some ornithischians than
theropods in the length of digit I relative to the other pedal digits.
Poposaurus is more like non-avian theropods and basal euornithopods
(hypsilophodontids) than like other ornithischians in the relative
widths of digits II-IV. All told, the pes of Poposaurus is in most
features most like that of an unspecialized small theropod,
prosauropod, or hypsilophodontid. Its footprint would be similar to
larger ichnospecies of Anchisauripus, but possibly with a distinct
impression of digit I as well as digits II-IV.

North-Central Section - 46th Annual Meeting (23–24 April 2012)
General Information for this Meeting

Session No. 21
Vertebrate Paleontology
Dayton Convention Center: Room 203
8:00 AM-12:00 PM, Tuesday, 24 April 2012

Geological Society of America Abstracts with Programs, Vol. 44, No. 5, p. 61