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RE: New article in Nature



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> christopher robert noto
>
> Here's the complete ref as was mentioned on the AP news earlier:
>
> Dinosaurian growth rates and bird origins
> KEVIN PADIAN, ARMAND J. DE RICQLS & JOHN R. HORNER
> http://www.nature.com/nlink/v412/n6845/abs/412405a0_fs.html
>
> Haven't had a chance to read it yet, but the results sound exciting.
>
> Chris
>
>
Actually, there are THREE papers on dinosaur growth in the latest Nature!

There's the above, and:
Bone histology: Evolution of growth pattern in birds
ANUSUYA CHINSAMY AND ANDRZEJ ELZANOWSKI Nature 412, 402 - 403 (2001)

AND

Dinosaurian growth patterns and rapid avian growth rates
GREGORY M. ERICKSON, KRISTINA CURRY ROGERS & SCOTT A. YERBY Nature 412,
429 - 433 (2001)

In the latter, Erickson et al. demonstrate that non-avian dinosaurs are
weird relative to other groups of vertebrates, in that their growth rate
increases allometrically faster (greater slope) than those of other groups
of vertebrates.  Predicted growth rates for small guys (like _Shuvuuia_) are
around marsupial rates (and twice those of non-dinosaurian reptiles);
medium-sized dinosaurs (_Syntarsus_, _Massospondylus_) range between
marsupial and placental/precocial bird rates; big dinos (_Maiasaura_) grows
at eutherian/precocial bird rates, and bigass dinos (_Apatosaurus_) at rates
as high or higher than eutherians, but below altricial birds.

Padian et al. give a progress report on their work, which shows that the
moden avian bone growth conditions and growth rates are a series of
step-wise changes, including (curiously) a slowdown in growth rate in basal
Mesozoic birds (in other words, they seem to reach adult size longer than it
would take a similar sized non-avian dino to reach the same size).  In part
they think this may be due to the peculiar heterochrony of birds:
pygostylian birds are not classically neotenic relative to other theropods
because their body shape is NOT that of a juvenile theropod.  Instead, they
have a highly apomorphic form.

Chinsamy & Chiappe examine bone histology of _Rahonavis_ and _Gobipteryx_,
among others.  They find evidence for "superprecociality" similar to that of
modern megapodes in enantiornithines: that is, these guys seem to have had
an early onset of flight.

Interesting stuff.  Need to sit down and digest it more.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796