Sex and the New Papers II

[Dann Pigdon <dannj@alphalink.com.au>]

Some free gems from the Proceedings of the Royal Society B:

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Manabu Sakamoto 2010 "Jaw biomechanics and the evolution of biting performance 
in theropod 
dinosaurs". Proceedings of the Royal Society B.

Abstract
Despite the great diversity in theropod craniomandibular morphology, the 
presence and distribution 
of biting function types across Theropoda has rarely been assessed. A novel 
method of 
biomechanical profiling using mechanical advantage computed for each biting 
position along the 
entirety of the tooth row was applied to 41 extinct theropod taxa. Multivariate 
ordination on the 
polynomial coefficients of the profiles reveals the distribution of theropod 
biting performance in 
function space. In particular, coelophysoids are found to occupy a unique 
region of function space, 
while tetanurans have a wide but continuous function space distribution. 
Further, the underlying 
phylogenetic structure and evolution of biting performance were investigated 
using phylogenetic 
comparative methods. There is a strong phylogenetic signal in theropod 
biomechanical profiles, 
indicating that evolution of biting performance does not depart from Brownian 
motion evolution. 
Reconstructions of ancestral function space occupation conform to this pattern, 
but phylogenetically 
unexpected major shifts in function space occupation can be observed at the 
origins of some 
clades. However, uncertainties surround ancestor estimates in some of these 
internal nodes, so 
inferences on the nature of these evolutionary changes must be viewed with 
caution. 

Free PDF:
http://rspb.royalsocietypublishing.org/content/early/2010/06/02/rspb.2010.0794.abstract

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Elizabeth R.Dumont 2010 "Bone density and the lightweight skeletons of birds" 
Proceedings of the 
Royal Society B.

Abstract
The skeletons of birds are universally described as lightweight as a result of 
selection for 
minimizing the energy required for flight. From a functional perspective, the 
weight (mass) of an 
animal relative to its lift-generating surfaces is a key determinant of the 
metabolic cost of flight. 
The evolution of birds has been characterized by many weight-saving adaptations 
that are 
reflected in bone shape, many of which strengthen and stiffen the skeleton. 
Although largely 
unstudied in birds, the material properties of bone tissue can also contribute 
to bone strength and 
stiffness. In this study, I calculated the density of the cranium, humerus and 
femur in passerine 
birds, rodents and bats by measuring bone mass and volume using helium 
displacement. I found 
that, on average, these bones are densest in birds, followed closely by bats. 
As bone density 
increases, so do bone stiffness and strength. Both of these optimization 
criteria are used in the 
design of strong and stiff, but lightweight, manmade airframes. By analogy, 
increased bone density 
in birds and bats may reflect adaptations for maximizing bone strength and 
stiffness while 
minimizing bone mass and volume. These data suggest that both bone shape and 
the material 
properties of bone tissue have played important roles in the evolution of 
flight. They also reconcile 
the conundrum of how bird skeletons can appear to be thin and delicate, yet 
contribute just as 
much to total body mass as do the skeletons of terrestrial mammals. 

Free PDF:
http://rspb.royalsocietypublishing.org/content/277/1691/2193.abstract


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Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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