[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

The Lion, the Witch and the New Papers

(Apologies in advance if any of these have been mentioned already.  I only have 
the first and the last.)

Butler RJ, and Barrett PM. (2008) Palaeoenvironmental controls on the 
distribution of Cretaceous herbivorous dinosaurs.  Naturwissenschaften. 2008 
Jun 26. [Epub ahead of print] 

Abstract: "Previous attempts to determine palaeoenvironmental preferences in 
dinosaurs have generally been qualitative assessments based upon data from 
restricted geographical areas.  Here, we use a global database of Cretaceous 
herbivorous dinosaurs to identify significant associations between clades and 
broad palaeoenvironmental categories ('terrestrial', 'coastal', 'marine').  
Nodosaurid ankylosaurs and hadrosaurids show significant positive associations 
with marine sediments, while marginocephalians (Ceratopsia, 
Pachycephalosauria), saurischians (herbivorous theropods, Sauropoda) and 
ankylosaurid ankylosaurs are significantly positively associated with 
terrestrial sediments.  These results provide quantitative support for the 
hypothesis that some clades (Nodosauridae, Hadrosauridae) were more abundant in 
coastal and/or fluvial environments, while others (e.g. Marginocephalia, 
Ankylosauridae) preferentially inhabited more distal environments."

Lingham-Soliar T, and Wesley-Smith J. (2008) First investigation of the 
collagen D-band ultrastructure in fossilized vertebrate integument. Proc Biol 
Sci. 2008 Jun 24. [Epub ahead of print]

Abstract: "The ultrastructure of dermal fibres of a 200Myr thunniform 
ichthyosaur, _Ichthyosaurus_, specifically the 67nm axial repeat D-banding of 
the fibrils, which characterizes collagen, is presented for the first time by 
means of scanning electron microscopy (SEM) analysis.  The fragment of material 
investigated is part of previously described fossilized skin comprising an 
architecture of layers of oppositely oriented fibre bundles.  The wider 
implication, as indicated by the extraordinary quality of preservation, is the 
robustness of the collagen molecule at the ultrastructural level, which 
presumably contributed to its survival during the initial processes of 
decomposition prior to mineralization.  Investigation of the elemental 
composition of the sample by SEM-energy dispersive X-ray spectroscopy indicates 
that calcite and phosphate played important roles in the rapid mineralization 
and fine replication of the collagen fibres and fibrils.  The exceedingly small 
sample used in
 the investigation and high level of information achieved indicate the 
potential for minimal damage to prized museum specimens; for example, 
ultrastructural investigations by SEM may be used to help resolve highly 
contentious questions, for example, 'protofeathers' in the Chinese dinosaurs."

(In this context, I would say the choice of the term "highly contentious" is 
itself highly contentious.)

Witzmann F, Asbach P, Remes K, Hampe O, Hilger A, and Paulke A. (2008) 
Vertebral pathology in an ornithopod dinosaur: a hemivertebra in 
_Dysalotosaurus lettowvorbecki_ from the Jurassic of Tanzania.  Anat Rec 
(Hoboken). 2008 Jun 5. [Epub ahead of print]

Abstract: "A vertebral fragment of the Late Jurassic ornithopod dinosaur 
_Dysalotosaurus lettowvorbecki_ from Tanzania is described.  It consists of a 
hemivertebra that is co-ossified with a complete vertebral centrum. The 
hemivertebra causes a hyperkyphotic posture of the vertebral column with an 
angle of approximately 35 degrees between the end plates of the vertebra, that 
is, a dorsal bending of the vertebral column.  Associated with this is a 15 
degrees lateral bending, which suggests a scoliosis.  Micro-CT scans reveal 
thickening of the cortical bone in the hemivertebra and the complete vertebral 
centrum as compared to a "normal" vertebra.  This can be interpreted as a 
reaction of the bone to the abnormal direction of forces arising from the 
defective configuration of the vertebral column.  No signs of vertebral 
fracture are present.  The arrangement of the Foramina venosa and the 
trapezoidal outline of the complete centrum that is co-ossified with the 
hemivertebra indicate that
 the hemivertebra in _Dysalotosaurus_ developed early in embryogenesis probably 
by "hemimetameric segmental shift", that is, a defect of the fusion of the 
paired vertebral anlagen.  This finding illustrates that hemivertebrae 
represent a fundamental defect of the vertebrate ontogenetic program."

Rounding off with some nice biomechanical work (then again, I'm biased).

Moreno K, Wroe S, Clausen P, McHenry C, D'Amore DC, Rayfield EJ, and Cunningham 
E. (2008)  Cranial performance in the Komodo dragon (_Varanus komodoensis_) as 
revealed by high-resolution 3-D finite element analysis.  J Anat. 212 (6): 

Abstract: "The Komodo dragon (_Varanus komodoensis_) displays a unique hold and 
pull-feeding technique.  Its delicate 'space-frame' skull morphology differs 
greatly from that apparent in most living large prey specialists and is 
suggestive of a high degree of optimization, wherein use of materials is 
minimized.  Here, using high-resolution finite element modelling based on 
dissection and in vivo bite and pull data, we present results detailing the 
mechanical performance of the giant lizard's skull.  Unlike most modern 
predators, _V. komodoensis_ applies minimal input from the jaw muscles when 
butchering prey.  Instead it uses series of actions controlled by postcranial 
muscles.  A particularly interesting feature of the performance of the skull is 
that it reveals considerably lower overall stress when these additional 
extrinsic forces are added to those of the jaw adductors.  This remarkable 
reduction in stress in response to additional force is facilitated by both 
internal and
 external bone anatomy.  Functional correlations obtained from these analyses 
also provide a solid basis for the interpretation of feeding ecology in extinct 
species, including dinosaurs and sabre-tooth cats, with which _V. komodoensis_ 
shares various cranial and dental characteristics."

The i’m Talkathon starts 6/24/08.  For now, give amongst yourselves.