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New papers in Senckenbergiana Lethaea and more
From: Ben Creisler email@example.com
New papers in Senckenbergiana Lethaea and more
I haven't seen these papers yet but the abstracts or
titles show up in online databases:
Henderson, D.M. & Weishampel, D.B. 2002. Convergent
evolution of the maxilla-dental-complex among carnivorous
archosaurs. Senckenbergiana-Lethaea. 82(1): 77-92.
AB: Archosaurs first appeared in the Late Permian, and
during the subsequent Mesozoic Era they evolved several
different clades of carnivores, all of which can trace
their origins back to a primitively carnivorous form.
Three aspects of the maxillary teeth of carnivorous
archosaurs were investigated for potential functional
correspondences with the form of their associated
maxillary bone: mean and maximal tooth lengths; medio-
lateral and antero-posterior tooth bending strengths; and
total external surface area of teeth. A fourth
investigation looked at the depth of the skull relative to
its length for any potential functional correspondence
with total tooth area or mean maxillary tooth length. All
linear and areal dimensions were normalized to correct for
size-related factors. A good correspondence was found
between long teeth and teeth with high bending strengths
and the amount of bone in the ventral region of the
maxilla; and this condition was observed to have evolved
independently in rauisuchians, at least three times in
theropod dinosaurs, and crocodylomorphs. No plausible
relationship was found between the total surface area of
the teeth and maxillary form. Working under the assumption
that larger predators will generally attack and dismember
larger prey, the observed changes in maxillary form are
interpreted as a biomechanical response for increasing
support of the teeth during a phylogenetic increase in
body size, and the concomitant increase in the size of
prey. A strong correlation also exists between normalized
maxillary tooth lengths (mean tooth length divided by
skull length) and skull aspect ratios (mean skull depth
divided skull length). It is proposed that increases in
the length of teeth, and the presumed increase in the
depth of penetration by the teeth, are associated with an
increased resistance to sagittal (dorso-ventral) bending
of the skull for all sizes of carnivorous archosaurs.
Carpenter, K. 2002. Forelimb biomechanics of nonavian
theropod dinosaurs in predation. Senckenbergiana-Lethaea.
AB: Theoretical models of theropod forelimb biomechanics
are often tainted with preconceived ideas. Actualistic
modeling using specimens and casts, coupled with CAT-scans
and dissections of extant vertebrate forelimbs,
demonstrates that forelimb motion in theropods is
considerably less than hypothetical models indicate. The
forelimbs of Coelophysis, cf. Coelurus. Allosaurus,
Deinonychus, and Tyrannosaurus were investigated. Motion
at the shoulder, elbow, wrist, and digits were analyzed
and compared with those of birds and crocodiles, then
motion of the entire forelimb was examined. The results
have considerable implications for forelimb use in
predation. Three models of predation are recognized: 1)
long armed grasper-Deinonychus, cf. Coelurus; 2) clutcher -
Tyrannosaurus; 3) combination grasper-clutcher-Allosaurus.
Analysis of the joints of Deinonychus show that the
forelimb could not fold avian fashion. The scapula of the
theropod Unenlagia was oriented incorrectly and differs
little from the standard theropod scapula.
Egi, N. & Weishampel, D.B. 2002. Morphometric analyses of
humeral shapes in Hadrosaurids (Ornithopoda, Dinosauria).
Senckenbergiana-Lethaea. 82(1): 43-58
AB: Variation in juvenile and adult humeral morphology
between the two subfamilies of Hadrosauridae (Ornithopoda,
Dinosauria) was examined. The sample consisted of five
hadrosaurine and four lambeosaurine genera and included
humeri from 28 to 65 centimeters in length. Nineteen
landmarks associated with articular surfaces and muscle
attachments were digitized from photographs of humeri in
posterolateral view, and the data were analyzed using
three morphometric techniques: Bookstein's coordinates,
Resistant-Fit Theta-Rho-Analysis, and Euclidean Distance
Matrix Analysis. Differences in humeral shape were greater
between adults of the two subfamilies than between the
juveniles, and the differences between adults and
juveniles were larger in lambeosaurines than in
hadrosaurines. Adult lambeosaurines exhibited lateral and
distal enlargement of the distal part of the deltopectoral
crest and relative shortening of the shaft distal to the
deltopectoral crest, resulting in the increased
performance of the shoulder muscles, particularly Mm.
pectoralis and deltoides clavicularis. The morphological
change of the humerus during growth seems to be closely
associated with the reduction of the humeral length
relative to antebrachium. The morphological variations in
hadrosaurid humeri relate to structural adaptations to
bear increased body size to some extent but also to a
behavioral specialization among some genera during growth.
Snively, E. & Russell, A. 2002.T he tyrannosaurid
metatarsus: Bone strain and inferred ligament function.
Senckenbergiana-Lethaea. 82(1): 35-42.
AB: Tyrannosaurid dinosaurs possess a metatarsus with an
arctometatarsalian proximal constriction of metatarsal
III, and strongly interlocking proximal articulations.
Bone and inferred ligament morphologies arc suggestive of
modes of locomotor energy transmission. CT scanning and
Finite Element Analysis (FEA) of Gorgosaurus libratus
metatarsals test two hypotheses of tyrannosaurid
arctometatarsus function: ligaments mediated transfer of
energy from the central metatarsal to the outer elements,
and ligaments arrested anterodorsal rotation of the distal
portion of the central metatarsal. The results have
implications for the use of FEA in functional morphology:
1) strain artifacts are identifiable under low-resolution
modeling, but higher resolution is better; and 2) bone
strain aids in testing hypotheses of ligament function.
Concentrations of bone strain energy under postulated
loading regimes for Gorgosaurus support the hypothesis of
axial energy transmission for the tyrannosaurid
metatarsus, and indirectly support the rotation damping
hypothesis. Palaeopathology provides a vital complement to
engineering tests of these hypotheses.
Stevens, K.A. 2002. DinoMorph: Parametric modeling of
skeletal structures. Senckenbergiana Lethaea. 82(1): 23-34
AB: A parametric approach towards modeling is advocated
for skeletal reconstructions. Three-dimensional digital
reconstructions are compared with conventional two-
dimensional illustrations, particularly silhouette
drawings. The advantages of the parametric system provided
by the DinoMorph<sup>TM</sup> software include: open
access to all data comprising the model and the rendering
algorithms for the independent verification of
reconstructions, tools for parametrically editing and
manipulating pose, bone, and joint geometry, visualization
of assemblies in three-dimensions from arbitrary
perspectives, multiple resolution models of skeletal
element morphology (from schematic to highly detailed),
and extensibility to support specific research objectives.
The system architecture and current capabilities are
described and illustrated.
Yao, Jinxian, Zhang, Yun & Tang, Zhilu, 2002. Small
spheres preserved in a therizinosauroid dinosaur's blood
vessels from northeast China. Acta Scientiarum Naturalium
Universitatis Pekinensis. (2002 Mar 20) 38(2): 221-225.
Caldwell, M.W 2002. From fins to limbs to fins: Limb
evolution in fossil marine reptiles.
AMERICAN JOURNAL OF MEDICAL GENETICS. (OCT 15 2002) 112
AB: Limb osteology and ontogenetic patterns of limb
ossification are reviewed for extinct lineages of
aquatically adapted diapsid reptiles. Phylogenies
including these fossil taxa show that paddle-like limbs
were independently derived, and that the varied limb
morphologies were produced by evolutionary modifications
to different aspects of the limb skeleton. Ancient marine
reptiles modify the limb by reducing the relative size of
the epipodials, modifying the perichondral and periosteal
surface of elements distal to the propodials, and evolving
extremes of hyperphalangy and hyperdactyly. Developmental
genetic models illuminate gene systems that may have
controlled limb evolution in these animals.