[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: New Cretaceous bird and other papers
On Sat, 16 Feb 2002 email@example.com wrote:
> Phylogenetic analyses indicate an early split between
> Accipitridae and Falconidae, which, according to molecular
> dating of other avian divergence times, can be assumed to
> have taken place in the late Cretaceous 65-83 MYA.
If these clades split at this time, and they both appear and behave in a
broadly similar way now, doesn't this mean that they appeared and behaved
in a broadly similar way then--that there were falcon-like neornithines in
the Cretaceous? I mean, if they were both generic bird-things back then,
why would they share so mant things today? Please be gentle.
> Christiansen-P. 2002. Mass allometry of the appendicular
> skeleton in terrestrial mammals.
> JOURNAL OF MORPHOLOGY. FEB 2002; 251 (2) : 195-209.
> AB: Most analyses on allometry of long bones in
> terrestrial mammals have focused on dimensional allometry,
> relating external bone measurements either to each other
> or to body mass. In this article, an analysis of long bone
> mass to body mass in 64 different species of mammals,
> spanning three orders of magnitude in body mass, is
> presented. As previously reported from analyses on total
> skeletal mass to body mass in terrestrial vertebrates, the
> masses of most appendicular bones scale with significant
> positive allometry. These include the pectoral and pelvic
> girdles, humerus, radius+ulna, and forelimb. Total
> hindlimb mass and the masses of individual hindlimb bones
> (femur, tibia, and metatarsus) scale isometrically.
> Metapodial mass correlates more poorly with body mass than
> the girdles or any of the long bones. Metapodial mass
> probably reflects locomotor behavior to a greater extent
> than do the long bones. Long bone mass in small mammals
> (<50 kg) scales with significantly greater positive
> allometry than bone mass in large (>50 kg) mammals,
> probably because of the proportionally shorter long bones
> of large mammals as a means of preserving resistance to
> bending forces at large body sizes. The positive
> allometric scaling of the skeleton in terrestrial animals
> has implications for the maximal size attainable, and it
> is possible that the largest sauropod dinosaurs approached
> this limit.