New in Paleobiology - myrmercophagous Mononykus & origin of flight stroke

[Tim Williams <twilliams_alpha@hotmail.com>]

Two topics that have been frequently addressed on the DML...  (I'm looking 
forward to reading the papers, though I've only seen the abstracts so far.)

Senter, P. (2005).  Function in the stunted forelimbs of _Mononykus 
olecranus_ (Theropoda), a dinosaurian anteater.  Paleobiology 31(3): 
373-381.

Abstract: "_Mononykus olecranus_, a theropod dinosaur from the Upper 
Cretaceous of Mongolia, exhibits reduced forelimbs with a single functional 
digit.  These bizarre forelimbs have aroused great curiosity as to the 
behavior of the animal, but until now no functional study on the forelimbs 
of _Mononykus_ has been undertaken.  Here I show that the orientation and 
range of motion in the forelimb elements of _Mononykus_ are such that the 
humeri sprawl laterally, the antebrachia are held subvertically, the palms 
face ventrally, and intramanual movement is restricted to subparasagittal 
motion.  This is a radical departure from the typical theropod condition, in 
which the palms face medially and intramanual movement is transverse.  The 
results of this study confirm that the forelimbs of _Mononykus_ could not 
have been used to grasp prey or dig burrows, but were well suited for 
scratch-digging or hook-and-pull movements such as are used by extant 
anteaters and pangolins to open tough insect nests.  _Mononykus_ likely 
occupied a niche equivalent to that of an anteater or pangolin, an unusual 
niche for a dinosaur."


Gatesy, S.M. and Baier, D.B. (2005). The origin of the avian flight stroke: 
a kinematic and kinetic perspective.  Paleobiology 31(3): 382-399.

Abstract. "Flying birds flap their wings to generate aerodynamic forces 
large enough to overcome weight and drag.  During this behavior, the 
forelimbs are displaced and deformed in a complex, coordinated sequence of 
movements collectively known as the "flight stroke."  Despite an influx of 
relevant fossil material and new functional insights from extant birds, the 
historical origin of the avian flight stroke remains poorly resolved.  
Potential behavioral precursors have been identified primarily on the basis 
of kinematic resemblance-similarity of movement irrespective of underlying 
mechanisms.  We discuss fundamental issues of motion analysis that are 
frequently overlooked by paleontologists, and conclude that a purely 
kinematic approach is insufficient.  Consideration of kinetics, the forces 
responsible for motion, offers a more complete picture of flight stroke 
evolution.  We introduce six kinetic components that interact to determine a 
limb's trajectory.  Phylogenetic mapping reveals that forelimb loading 
patterns have undergone at least two major transitions on the line from 
basal archosaur to modern bird.  Using this kinematic and kinetic 
perspective, we offer four specific criteria to help constrain and evaluate 
competing scenarios for the origin of the avian flight stroke."