Re: New paper: Theropod forelimb evolution & Archie is not a "Rosetta stone"

[dinoboygraphics@aol.com]

I gotta say: "Duh".

But good to see it published.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

-----Original Message-----
From: tijawi@yahoo.com
To: dinosaur@usc.edu
Cc: tijawi@yahoo.com
Sent: Wed, 29 Apr 2009 8:05 pm
Subject: New paper: Theropod forelimb evolution & Archie is not a 
"Rosetta stone"







Dececchi, TA and Larsson, HCE. (2009) Patristic evolutionary rates 
suggest a
punctuated pattern in forelimb evolution before and after the origin of 
birds.
Paleobiology 35: 1-12


Abstract: "The evolution of powered flight has traditionally been 
associated
with the origin of birds, the most successful clade of modern 
tetrapods, as
exemplified by the nearly 10,000 species alive today. Flight requires a 
suite of
morphological changes to skeletal anatomy to create a light vet 
resistant
framework for an airfoil and advanced nervous motor control. Given the 
level of
morphological integration necessary to create a suitable aerofoil, the 
origin of
flight may be intuitively assumed to be coupled with high evolutionary 
rates of
wing-related morphologies. Here we show that the origin of birds is 
associated
with little or no evolutionary change to the skeletal anatomy of the 
forelimb,
and thus _Archaeopteryx_ is unlikely to be the "Rosetta Stone" for the 
origin of
flight it was once believed to be. Using comparative statistics and 
time-series
analyses on a data set constructed from all known forelimb skeletal 
anatomy of
non-avian theropod
 dinosaurs and a diverse assemblage of early birds, we demonstrate 
three focused
peaks of rapid forelimb evolution at Tetanurae, Eumaniraptora, and
Ornithothoraces. The peaks are not associated with missing data and 
remain
stable tinder multiple perturbations to the phylogenctic arrangements. 
Different
regions of the forelimbs are demonstrated to have undergone 
asynchronous periods
of evolutionary peaks and stasis. Our results evince a more complicated 
stepwise
mode of forelimb evolution before and after the origin of Aves than 
previously
supposed."


The paper pours cold water on the centrality of _Archaeopteryx_ to the 
evolution
of flight, but offers oblique support for non-avian eumaniraptorans 
being
secondarily flightless.  However, I'm not exactly sure how the clades 
'Paraves'
and 'Eumaniraptora' are defined here: the former is treated as more 
inclusive
than the latter, and the Supplementary Material link (which the main 
text
suggests might contain this info) takes me to the wrong site.

Among other things, the authors argue that the number of shared derived
characters between small deinonychosaurs (microraptorines) and 
_Archaeopteryx_
are not so much due to flight capability but to similar prey-capture 
behaviors.
Nevertheless, the authors also claim that non-avian eumaniraptorans had
"facultative" flight ability, which was refined later in 
Ornithothoraces, when
powered light became "central" to the ecomorphology of birds.  I think 
this is
the point, anyway.


Cheers

Tim