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Dinosaur stuff at Society for Integrative and Comparative Biology meeting

From: Ben Creisler

The Society for Integrative and Comparative Biology meeting also had a
number of papers related to dinosaurs and archosaurs, etc. Some of
this research has been published in part or has been mentioned at
other conferences, but mentioning it again won't hurt I guess.


P3. 197 WHITNEY, M*; CURRY ROGERS, K; BAGLEY, B;Macalester College,
University of MInnesota;rogersk@macalester.edu

Bone Histology and Primary Growth Rates in Hatchling Titanosaurs from
Madagascar: New Insights from Micro-Computed Tomography.

The smallest post-hatching juvenile sauropods are only a little less
than half of known adult size and leave details of the earliest stages
of sauropod ontogeny poorly understood.  Here we report on two partial
skeletons of hatchling Rapetosaurus krausei, a titanosaur from the
Upper Cretaceous Maevarano Formation of Madagascar, that provide new
data on primary early stage growth rates in sauropods.  The skeletons
come from two localities and greatest length ratios for appendicular
elements confirm that there are only two individuals present,that
there is no significant allometry in Rapetosaurus postcranial
ontogeny, and that each individual is less than 15% adult size.  The
smaller specimen includes sacral and caudal vertebrae, pubis, femur,
tibia (12. 7 cm long), fibulae,metatarsal I, humeri, metacarpal III,
and a phalanx.  The larger specimen includes caudal vertebrae, tibia
(17. 9 cm long), and metacarpals I and IV.  We employed an X5000
high-resolution dual-head 225kV microfocus X-ray CT system located in
the Department of Earth Sciences, University of Minnesota to garner
bone histological data on earliest stage growth rates in these
juveniles.  We achieved an effective pixel pitch of 36 – 48 microns
for the larger samples and 14 – 28 microns forsub-volumes.  We
collected 2-D radiographs and reconstructed these data to produce a
3-D volume for visual analysis and slices of the 3-D volume for
quantitative analysis.  Primary bone growth in Rapetosaurus is highly
vascularized woven and fibrolamellar bone with mid-diaphyseal
remodeling.  These results support the hypothesis that intensive
remodeling observed in the bones of older juvenile Rapetosaurus may be
dictated, at least in part, by resource limitations during periods of
drought/ecological stress recorded in the Maevarano Formation.

Very similar presentation and abstract


P3. 91 LEARY, B; KAVANAGH, KD*; Univ.  of MassachusettsDartmouth;

Pedal Digit IV Proportions Reveal Body-Size Associated Constraint on
Dinosaur Foot Morphology.

The proportions of the pedal phalanges of tetrapods have been found to
correlate with foot function.  Plotting the phalangeal proportions of
birds in morphospace not only allows us to discriminate functional
groups, but also reveals a restricted range of variation in which many
potential morphologies are unrepresented.  Additionally, we observe
some striking examples of convergent evolution.  We observed that
digit IV is effective in discriminating functional groups in birds.
We applied this knowledge to the pedal phalanges of 30 non-avian
theropods and bipedal ornithischians to identify functional groups and
explore the range of variation in the ancestors of modern birds.
Analyses revealed that  (1) the phalanges proportions of all dinosaurs
sampled fall within a subset of the range of variation observed in
birds, (2) ornithischian dinosaurs fall exclusively within the range
of terrestrial, non-perching birds (e. g.  running, walking,
swimming);  exhibiting in most cases, extreme proximodistal gradient
patterning, (3) non-avian theropods fall  within a range spanning from
terrestrial birds to highly arboreal taxa, but extreme raptorial
morphologies are conspicuously absent (PCA) and (4) the phalanx
proportions of non-avian theropods are strongly correlated with body
length. We conclude that (1) the emergence of modern birds may have
been preceded by a shift in pedal morphology to accommodate arboreal
lifestyles, (2) the range of variation available to modern birds was
also available to non-avian theropods, (3) non-avian theropods can be
grouped into 2 distinct functional groups:  terrestrial and arboreal,
(4) while the ability to develop elongate distal phalanges exists in
non-avian theropods, phalanx proportions may be constrained by larger
body sizes.


S. ; ROWE, T. B. ; NORELL, M. A. ; ABZHANOV, A. ;Harvard, Univ.
Auton.  de Madrid, Max Planck Inst.  Evol. Anthro. , NYCOM, Univ.
Tex, Aus. , Amer.  Mus.  Nat.  Hist., Harvard ;

The evolution and development of the archosaurian head and the origin
of the bird skull.

The bird skull is a highly specialized structure that has diverged
considerably from the ancestral cranial plan of the archosaurian
"ruling reptiles," whose modern representatives are  birds and
crocodilians.  We investigated the developmental mechanisms underlying
this divergence on several scales.  On a broad scale, we propose that
the heterochronic mechanism of progenetic paedomorphosis explains many
seemingly disparate transitions from a more ancestral archosaurian
skull to an avian skull.  The bird lineage was juvenilized in several
steps relativeto ancestral forms, an insight obtained using a
geometric morphometric analysis that included both phylogenetic and
ontogenetic  breadth.  Early avialans in particular clustered with the
juveniles and embryos of other archosaurs, with more crownward taxa
moving farther and farther backward along atrajectory corresponding to
ontogenetic progression. Definitionally, these results describe
paedomorphosis, but the particular mechanism of progenesis was
strongly supported by corresponding decreases in body size and in time
to sexual and somatic maturity.  Furthermore, some modularity exists
in the heterochronic transformations here identified, notably in that
the premaxilla, which forms the distinctive bird bill, grows
peramorphically against a global paedomorphic background in which the
orbits and brain become relatively larger and the maxillary region
smaller.  Given a broad evolutionary developmental mechanism for major
changes in skull  form toward birds, we have subsequently undertaken
investigations of the specific molecular mechanisms behind the
transformations elucidated by our phylogenetic/ontogenetic
morphometric work, with some success in testing hypotheses of gene
function using manipulation of model organisms.


142. 6 HOLLIDAY, CM*; GANT, CA; NESBITT, SJ; University ofMissouri,
University of Washington; hollidayca@missouri.edu

Form, function, and evolution of archosaur mandibular symphyses.

Archosaurs radiated into numerous trophic niches during the Mesozoic,
resulting in a diversity of cranial adaptations and feeding behaviors.
 The mandibular symphysis is a poorly understood cranial joint which
may offer significant insight into cranial development and function,
feeding ecology, and evolution in these vertebrates.  Using imaging,
histology, and dissection data from extant and fossil sauropsids, we
investigated the anatomy and evolution of archosaur symphyses with a
focus on Alligator mississippiensis and crocodyliforms. Adapting
Scapino’s classification scheme, character complexes of specific
clades were identified and their evolution was mapped using a current
phylogeny of archosauriforms.  During ontogeny, alligators rapidly
develop a complex, interdigitated, Class III symphysis coupled with
fused Meckel’s cartilages.  This morphology is a derived for
mesoeucrocodylians as protosuchians possess non-interdigitated Class
II symphyses. Extinct taxa with the simple Class I condition (e. g.
,proterochampsids, rauisuchians), rugose Class II (aetosaurs,
silesaurids,  derived dinosaurs), and interdigitating Class III
symphyses (e. g. , phytosaurs, crocodyliforms, basal birds) and
finally fused Class IV (Neoaves) build the joints in expected ways,
though they differ in contributions of bony elements and Meckel’s
cartilage.  Optimization of the different classes of symphyses across
archosauromorph clades indicate that major iterative transitions from
plesiomorphic  Class I to derived, rigid Class II-IV symphyses and
beaks occurred alongthe lines to phytosaurs, aetosaurs, poposauroids,
crocodyliforms, pterosaurs, ornithischians, and birds.  These
transitions in symphyseal morphology appear to correlate with changes
in dentition, the origin of beaks, and potentially inferred diet.


99. 5 MUSSER, JM*; WAGNER, GP; PRUM, RO; Yale University,Yale
University, Yale Systems biology Institute, Yale University,Peabody
Museum of Natural History; jacob. musser@yale.edu

The Homology of Feathers and Scales: Using New High-throughput Methods
to Address a Classic Question.

Feathers are an important anatomical innovation that evolved in the
ancestors of birds and facilitated the evolution of flight,greater
thermoregulation, and other facets of modern avian life. However, the
molecular basis for the evolution of feathers is poorly understood,
and the homology of feathers to other skin derivatives, especially
scales, remains contentious.  Here, we take a new approach to
answering these questions by comparing transcriptomes from different
stages of developing feathers, different avian and reptilian scales,
and claws.  We performed mRNA-seq on different stages of skin
appendage development collected from two distantly related birds,
Chicken (Gallus gallus) and Emu (Dromaius novaehollandiae), and from
American Alligator (Alligator mississippiensis), a member of the
extant clade most closely related to birds.  Comparison of  these
transcriptomes allows us to investigate the homology of feathers and
scales at different developmental stages.  Further,they allow us to
identify candidate regulatory molecules,including transcription
factors and members  of signaling pathways, which underlie feather
novelty.  Finally,  to complement our transcriptome data, we used
immunohistochemistry to compare patterns of expression and subcellular
localization of the transcription cofactor beta-catenin, the earliest
known molecule expressed in feathers.  Our preliminary evidence
suggests beta-catenin is also present in early developing avian scales
and alligator scales, suggesting these skin appendages use similar
molecular pathways at the beginning of their development.  Together,
our data presents a new and comprehensive look at the homology of
feathers and scales and the molecular basis of feather novelty.


P3. 201 TSAI, H. T. *; HOLLIDAY, C. M. ; Univ.  of Missouri,Columbia;
hptkr7@mail. missouri.edu

Anatomy of archosaur hip joint soft tissues and its significance for
interpreting hindlimb function.

Reconstructing the appendicular joint anatomy of archosaurs is
critical for understanding their posture, locomotor behavior,ecology,
and evolution.  Soft tissue significantly contributes to the shape and
size of archosaur joints, such that fossil archosaurs often exhibit
incongruent bony articular surfaces. This study infers the amount of
soft tissue once present in archosaur hip joints via congruence tests,
as well as investigates the hip joint cartilage anatomy of archosaurs.
Differences in the mediolateral depth, as well as dorsoventral and
craniocaudal diameters of the femoral head and the acetabulum are used
to test for congruence of the hip joint in each axis.  Hip joints of
suchians and basal dinosaurs (i. e. Shuvosaurus and Coelophysis) are
more congruent along the craniocaudal axis than those of derived
non-avian dinosaurs (i. e.  hadrosaurids, sauropods, tetanurans).
Furthermore, non-avian dinosaurs exhibit mediolaterally longer femoral
articular surface than the depth of the acetabulum, whereas basal
suchians exhibit mediolaterally wider acetabulum than the femoral
articular surface.  Dissections and histology of extant archosaur hip
joints show that articular cartilage exhibits localized morphological
differences associated with assumed loading regimes.  These results
indicate that an increased amount of femoral articular cartilage is
associated with the medial rotation of the proximal femur during
non-avian dinosaur evolution, which impact our hypotheses of femoral
regional homology and hip joint function.


75. 4 FARMER, CG*; SCHACHNER, ER; SARRAZIN, JC;University of Utah; cg.

Structure & Function in Sauropsid Lungs.

The lung is among the most diverse organs in the vertebrate body but
the functional underpinnings and evolutionary history of this
diversity are poorly understood.  Because gas exchange in the lungs is
the first step in the oxygen cascade, this organ plays a key role in
the ability of organisms to sustain vigorous exercise and is therefore
inextricably linked with ecomorphological diversification.  We have
been using integrative approaches to study structure-function
relationships in a range of vertebrates with the aim of understanding
the evolutionary history of this organ.  We are currently focusing on
the potential role innovations in lung structure played during one of
the greatest and most controversial radiations in vertebrate history,
that of the Archosauria (e. g. , pterosaurs,dinosaurs, crocodilians).


114. 3 HEERS, A M*; DIAL, K P; University of Montana;ashmheers@gmail.com

Wings versus legs: mechanistic underpinnings of variation in locomotor
strategies among birds.

Among the 10,000 species of living birds and their extinct dinosaurian
ancestors, relative musculoskeletal investment in wings versus legs is
highly diverse, varying both across species and throughout ontogeny.
Such variation likely has profound effects on locomotor performance
and many related aspects ofbird ecology, including habitat
preferences, foraging strategies, migration patterns, and parental
care.  During aerial locomotion, high leg investment may hinder wing
performance. Likewise, high wing investment may hinder leg performance
during terrestrial locomotion.  Given these potential relationships
between body modules, do tradeoffs between wings and legs influence
locomotor ontogeny and evolution? To explore this question and better
understand the ecological ramifications of how wings and legs function
both independently and cooperatively during ontogeny and evolution, we
used published and new data to compare wing and leg morphology and
locomotor performance (i) across adult birds of different species and
(ii) during ontogeny, in three precocial anseriform-galliform species
with distinctly different sequences of locomotor development.  Our
findings suggest  that birds with high wing investment may have
reduced mass-specific leg performance and rely on wing-dominated
locomotor behaviors, while birds with high leg investment may have
reduced wing performance and rely on leg-dominated locomotor
behaviors.  For example, among adults, wing and leg investment are
negatively correlated.  Similarly, ontogenetic increases in wing
investment and performance can compromise leg investment and
performance, and vice versa.  Collectively,these results provide new
insight into the mechanistic underpinnings of variation in locomotor
strategies among birds,and suggest that performance tradeoffs between
different body modules may be important during ontogeny and evolution.


P3. 94 SCHACHNER, ER*; LYSON, TR; FARMER, CG; University of Utah,
Smithsonian Institution;eschachner@gmail.com

Pulmonary anatomy and the evolution of turtles.

A fundamental question in evolutionary morphology is theorigin of the
structural diversity in the amniote lung.  A second,and equally as
contentious question within biology is the phylogenetic position of
turtles.  Recent studies have placed turtles outside of Diapsida based
upon paleontological characters; however, several recent
molecular-based analyses place them as a sister group to archosaurs.
Pulmonary anatomy has long been used as a phylogenetic character for
many vertebrates (e. g. , varanids, chamaeleonids, anguimorph lizards,
and rodents), yet there remains to be any detailed investigation into
the pulmonary anatomy of turtles with the aim of contributing to the
phylogenetic debate.  The anatomy of the primary, secondary, and
tertiary pulmonary bronchi of multiple genera of turtles were
visualized as 3D surface models using computed tomography (CT).  This
method provides a novel way to analyze the respiratory system in situ,
which will further elucidate the unusual morphology of turtle lungs as
well as contribute to the discussion on the evolution of Testudines.


18. 5 ANGIELCZYK, KD*; SCHMITZ, L; Field Museum of Natural History,
Claremont McKenna, Pitzer, and ScrippsColleges;

Reconstructing the Diel  Activity Patterns of Fossil Nonmammalian Synapsids.

The majority of extant mammals are nocturnal, and it has been assumed
that this trait characterized the earliest mammals.  It also has been
hypothesized that the shift to nocturnality caused a fundamental
reorganization of the circadian system in mammals.  However, the diel
activity patterns (DAP) of the nonmammalian synapsid ancestors of
mammals have never been examined in detail, even though this could
provide insight into whether nocturnality is characteristic of mammals
or a deeper lineage, and whether nocturnality evolved multiple times
among synapsids.  Eye dimensions are correlated with light
sensitivity, and eye shape can be used to effectively discriminate
amniotes of different DAP.  Orbit and scleral ring dimensions are
reliable skeletal proxies for eye shape, and canbe used to extend
reconstructions of DAP into the fossil record. Extant mammals lack
scleral rings, but they are present,although infrequently preserved,
across much of nonmammalian synapsid diversity.  We compiled a data
set of 40 specimens from 28 synapsid species.  We used previously
published data on scleral ring and orbit dimensions of extant
squamates and avians with known DAP to establish classification rules
with a linear discriminant analysis.  Using prior probabilities
derived from proportions of DAP among extant amniotes, we classified
fossil synapsids (species averages) into diurnal, nocturnal, and
cathemeral categories. Our results suggest that diurnality was the
most common DAP in the analyzed sample.  However, nocturnality was
present in several clades, including Varanopidae, Sphenacodontidae,
Therocephalia, and Cynodontia.  Nocturnality likely evolved multiple
times within synapsids, with its earliest appearance in the


Midwestern University, UT Austin, SmithsonianInstitution, University
of Lethbridge; mhallx1@midwestern.edu

The relationship between scleral ring morphology and activity pattern
in birds and dinosaurs.

Activity pattern, the time of day when an animal is awake and active,
is highly associated with that animal’s ecology.  Extinct bird and
dinosaur activity patterns are presently poorly understood but would
provide important contributions toward understanding their
paleoecologies.  Soft-tissue studies of eyeball measurements show that
extant birds exhibit characteristic eye shapes associated with their
activity pattern. Specifically, nocturnal bird eyes are optimized for
visual sensitivity with a relatively large corneal diameter and
diurnal bird eyes are optimized for visual acuity with a relatively
large axial diameter.  Orbit morphology reflects eyeball shape and
activity pattern can be interpreted from measurements of the scleral
ring plus the orbit.  Recent studies utilizing a new statistical
technique suggest that measurements of the scleral ring even without a
complete orbit are sufficient to make activity pattern interpretations
for fossil birds and dinosaurs. Here, we analyze scleral ring
measurements of over 500 species of extant birds and lizards within a
phylogenetic context, and apply the results to interpret dinosaur
scleral rings.  Several factors preclude reliable interpretation of
activity pattern from measurements of the scleral ring, and we
conclude that these measurements are not sufficient to interpret
activity pattern.  Instead, more measurements of the orbit are
required, especially orbit depth, to infer activity pattern with any