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GSA dinosaur papers



From: Ben Creisler
bcreisler@gmail.com


Since the abstracts for 2013 GSA meeting are now public on the GSA
website and not embargoed that I can determine, I would point out a
number dinosaur-related papers that may be of interest:

GSA Paper No. 194-8
GRIFFIN, Christopher T. and NESBITT, Sterling J. [2013]
HOW TO GROW A DINOSAUR: THE HISTOLOGY AND FEMORAL ONTOGENY OF THE
MIDDLE TRIASSIC (?LATE ANISIAN) DINOSAURIFORM ASILISAURUS KONGWE AND
IMPLICATIONS FOR THE GROWTH OF EARLY DINOSAURS.
https://gsa.confex.com/gsa/2013AM/webprogram/Paper232986.html

The ontogeny of dinosaurs and their closest relatives is poorly
understood due to the lack of ontogenetic series from the same
species-level taxon. The large numbers of skeletal elements of the
silesaurid Asilisaurus kongwe recently recovered from the Anisian of
Tanzania provides an opportunity to closely examine the ontogenetic
trajectory of the earliest known member of Ornithodira and one of the
closest relatives to Dinosauria. We examined the histological tissues
and the appearance of muscle scars over a series of different lengths
of long bone elements. Five femora, as well as three tibiae, a fibula,
and a humerus were thin sectioned to examine osteological tissues. No
annual lines of arrested growth (LAG) are present in any of the
specimens, and it is likely that A. kongwe did not lay down LAGs,
although all specimens thin sectioned may be <1 year old. The woven
bone present in the cortex is similar to that of the earliest
dinosaurs in all elements sectioned. We also observed muscle scar
appearance and shape change throughout an ontogentic series of femora
(n = 26) of different lengths (73.8 to 177.2 mm). Femoral muscle scars
develop at different ontogenetic stages, and we hypothesize that the
majority of femora follow a similar developmental trajectory, e.g. the
anterior trochanter and trochanteric shelf develop separately and
roughly simultaneously, but fuse later in ontogeny in the most common
developmental path. However, we did observe developmental polymorphism
in the order of appearance and shape of muscle scars, e.g. there is
high morphological variability in the fourth trochanter throughout
most of the series, and although fusion of the trochanteric shelf and
the anterior trochanter is only common in larger specimens, it is
present in the second smallest specimen and conspicuously lacking in
one of the largest specimens.
The ontogenetic pattern of Asilisaurus femora provides a baseline for
understanding growth in early dinosaurs. This developmental trajectory
provides an alternate explanation for the robust/gracile dichotomy
found in early dinosaurs (e.g. Coelophysis, Syntarsus) that commonly
has been interpreted as sexual dimorphism. The shared femoral scar
features found in Asilisaurus and early dinosaurs suggest this
ontogenetic pathway may be pleisiomorphic for Dinosauria.

===
GSA Paper No. 126-21
MORI, Hirotsugu, and DRUCKENMILLER, Patrick [2013]
LASER-ABLATION MC-ICP-MS ANALYSIS OF ALASKAN EDMONTOSAURUS (LATE
CRETACEOUS, PRINCE CREEK FORMATION) TO TEST ARCTIC DINOSAUR MIGRATION
HYPOTHESES.
https://gsa.confex.com/gsa/2013AM/webprogram/Paper228359.html

During the Late Cretaceous, the Arctic had a rich dinosaurian fauna,
in spite of a sub-freezing winter temperatures. This Late Cretaceous
Arctic dinosaurian fauna includes not only theropods (including cf.
Troodon), but also multiple juvenile individuals of the hadrosaurid
Edmontosaurus sp. Discovery of dinosaurs from a high paleolatitude
(~82° N) has been of interest for many researchers, because this
suggests their metabolic rate was high enough to withstand the
coldness. However, one counter hypothesis is that they migrated to the
south during winter challenges, including low temperatures and
darkness. To test this migration hypothesis, we analyzed and compared
the strontium isotope ratio (87Sr/86Sr) of Edmontosaurus and cf.
Troodon teeth. 87Sr/86Sr in animal’s body reflects that of the local
sediment, and we assumed that Troodon were non-migratory, and
therefore used cf. Troodon teeth as a proxy of the 87Sr/86Sr signal of
the Late Cretaceous sediment. We analyzed seven Edmontosaurus teeth,
five of which were extracted from two maxillae, and three isolated
Trodon teeth. Since their enamel is very thin (~30 - 90 µm), we
adapted laser-ablation MC-ICP-MS. To assess the alteration of the
isotope signal due to diagenesis, we also compared the strontium
signals between the dentine plus bone. We found the enamel preserves
statistically significantly different 87Sr/86Sr value from those of
dentine and bone, suggesting the enamel retains its original strontium
signal. However, we did not find difference in the mean 87Sr/86Sr
values between the Edmontosaurus and cf. Troodon teeth. The older
teeth of the Edmontosaurus also have the same means as the younger
teeth. Therefore, the Liscomb Bonebed Edmontosaurus were likely not
migratory.

===


GSA Paper No. 406-5
SMITH, Nathan D., HAMMER, William R.,and MAKOVICKY, Peter J. [2013]
NEW DINOSAURS FROM THE EARLY JURASSIC HANSON FORMATION OF ANTARCTICA,
AND PATTERNS OF DIVERSITY AND BIOGEOGRAPHY IN EARLY JURASSIC
SAUROPODOMORPHS
https://gsa.confex.com/gsa/2013AM/webprogram/Paper232923.html

The Early Jurassic Hanson Formation of Antarctica has yielded
unprecedented insight into the evolution of high-latitude vertebrate
faunas during the early Mesozoic. To date, the Hanson fauna includes
the theropod dinosaur Cryolophosaurus ellioti, the sauropodomorph
dinosaur Glacialisaurus hammeri, a pterosaur, and a 'Bienotheroides
clade' tritylodont. New U-Pb zircon dates of ~194 Ma help constrain
faunal age. Our recent expedition collected new material of
Cryolophosaurus and Glacialisaurus, as well as several new
sauropodomorph specimens. One individual is a nearly complete juvenile
skeleton, and the other includes several vertebrae and pelvic
material. The two specimens may represent distinct species, and differ
in the curvature of the iliac preacetabular process, the concavity of
the proximal pubes, and the shape of the femoral head.
Phylogenetic analysis of 57 taxa and 353 characters recovers the three
Antarctic sauropodomorphs as distantly related to each other, and the
new specimens as more closely related to Sauropoda than to
Massospondylidae. Previous studies posited that some Early Jurassic
sauropodomorph regional faunas were phylogenetically overdispersed
(taxa from a given fauna are more distantly related to each other than
expected by chance), but such patterns have not been tested
quantitatively. We analyzed aspects of Early Jurassic sauropodomorph
faunal structure using phylogenetic comparative methods and a
time-sliced dataset with several branch length estimations. The
phylogenetic diversity represented in the Antarctic sauropodomorph
fauna is as high or higher than that of the other five Early Jurassic
regional faunas analyzed. We found no significant support for
phylogenetic overdispersion of sauropodomorphs in Early Jurassic
regional faunas, though analyses generally recovered Antarctica as
having the most evenly dispersed fauna. These results provide
additional support for prevalent dispersal across Pangaea during the
Early Jurassic. The presence of three distantly related
sauropodomorphs in Antarctica also implies that although endemism in
Antarctic vertebrates increased from the Early Triassic to Early
Jurassic, climatic and/or physiographic barriers did not prevent
dispersal into Antarctica during the Early Jurassic.

==


GSA Paper No. 36-23
MOSSBRUCKER, Matthew T.,  BAKKER, Robert T. and MARSH, Adam D. [2013]
MISSING MUZZLE FOUND: NEW SKULL MATERIAL REFERABLE TO APATOSAURUS AJAX
 (MARSH 1877) FROM THE MORRISON FORMATION OF MORRISON, COLORADO.
https://gsa.confex.com/gsa/2013AM/webprogram/Paper231547.html

In 1877, the first giant Jurassic dinosaurs were discovered in
Morrison, Colorado by Arthur Lakes. Although North America did not
produce the first sauropodomorph dinosaur, Apatosaurus ajax was the
first sauropod that provided insight into the form of the most iconic
family of long-necked dinosaurs. Crowning the neck with the correct
skull proved challenging, particularly for the type sample of
Apatosaurus, as only the rear of the skull had been identified --
until now.
>From Lakes' Quarry 5, the most productive Morrison Formation sandstone
quarry, we have recovered a virtually uncrushed, disarticulated but
associated diplodocid maxilla and premaxillae. We assign these
specimens to Apatosaurus ajax because the general proportions are most
like Apatosaurus as described by Berman and McIntosh and differ from
those of other diplodocids. A. ajax appears to be the only Apatosaurus
species documented from the sample area.
The new Quarry 5 maxilla - premaxilla is broader across the muzzle
than in Diplodocus, and agrees with that of Apatosaurus louisae. The
undistorted new maxilla suggests a deeper eye/cheek region than
previously reconstructed for A. louisae. Another feature linking the
new maxilla to that of A. louisae is the proportionately large
antorbital fenestra with an anterior end far deeper and blunter than
that of Diplodocus.
The proportions of the Quarry 5 specimen are unique in the extreme
depth of the anterior end of the antorbital fenestra, indicating that
A. ajax was more derived in this feature than Apatosaurus louisae and
to a lesser extent, Apatosaurus excelsus. A partial dentary with
erupted teeth from Quarry 5 was assigned to Diplodocus lacustris in
1884; however the specimen was excavated in the same sandstone and
within 10 m of the new apatosaur muzzle. Hence we refer the jaw to A.
ajax. With this new partial snout, combined with the paired quadrates
and braincase from the 1877 excavation at Morrison’s Quarry 10, we can
more accurately reconstruct the skull of the first known species of
Apatosaurus. With further preparation, these specimens from Quarry 5
help to illuminate the distinction between Apatosaurus ajax and other
diplodocids.

==


GSA Paper No. 219-1
SUAREZ, Celina, TRIESCHMANN, Ben, YOU, Hailu, and LI, Da-Qing [2013]
PALEOECOSYSTEM OF THE EARLY CRETACEOUS LANZHOU-MINHE BASIN, NW CHINA
REVEALED FROM TOOTH ISOTOPIC COMPOSITION OF LANZHOUSAURUS MAGNIDENS.
https://gsa.confex.com/gsa/2013AM/webprogram/Paper229596.html

Stable isotopic analyses of tooth enamel phosphate and carbonate were
collected from a maxillary and dentary tooth of the advanced
iguanodontid Lanzhousaurus magnidens from the early Cretaceous Hekou
Group, NW China. A long isotopic record representing over a year is
available for these teeth, as Lanzhousaurus teeth are the largest
herbivorous dinosaur teeth ever discovered (~10cm). O isotopic
composition was collected to determine the isotopic composition of
drinking water and seasonality of the early Cretaceous Lanzhou-Minhe
basin of Northwest China. Tooth carbonate C and O isotopic composition
was used to determine Lanzhousaurus diet and therefore dominant plant
type. Isotopic composition of tooth phosphate (delta18Op) ranged from
+18.72 to +22.64‰ V-SMOW and averaged +20.30‰ for the dentary and
+16.79‰ to +23.37‰ and averaged +21.62‰ for the maxilla. Seasonal
variability was observed and typically ranged 1 to 2‰, but was as much
as ~4‰. A long term increasing trend in isotopic composition was also
observed. Isotopic composition of tooth enamel carbonate oxygen
(delta18Oco3) currently analyzed on the dentary ranged between +26.01
and +22.59 ‰ V-SMOW. Carbon isotopic composition ranged from -5.39 to
-6.57‰ V-PDB. delta18Op and delta18OCO3 of individual samples are
linearly correlated (r2 = 0.72) suggesting little diagenetic
alteration of enamel carbonate. Based on physiological equations and
testing a range of relative humidities from 50 to 70%, isotopic
composition of drinking water ranged between an average delta18O value
of -9.2‰ for 50% relative humidity to -5.2‰ for 70% relative humidity.
Estimated plant diet delta13C values suggest a dry C3 dominated
ecosystem and ranged between -24.57‰ and -23.39‰ and averaged -24.00‰.
These values will be compared to additional water isotope proxies
(turtle delta18Op) as well as bulk and picked organic C from the
surrounding sediment. These values will help determine if
Lanzhousaurus was consuming meteoric water or high elevation water
derived from the nearby mountains, revealing a clearer picture of the
terrestrial ecosystem of the early Cretaceous Lanzhou-Minhe Basin.