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Re: New Cretaceous bird and other papers




On Sat, 16 Feb 2002 bh480@scn.org 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.  
> 
>