refs; no systematics

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

Greetings, everybody.

Here are some new references of subjects of interest to the lists, and no
major classification revisions among them!

First, the biggie (thanks to Chris Nedin to alerting me to this paper!):
Nikhakht, N. & J. C. McLachlan. 1999. Restoring avian wing digits. Proc. R.
Soc. Lond. B. 266: 1101-1104.

Experimental manipulation of developing chicken embryos: "element 5" of the
bird wrist (thought by many developmental biologists to be metacarpal V or a
rudimentary digit V) grows into a small metacarpal with rudimentary
phalanges when fibroblast growth factor 4 is added to the distal tip of the
wing bud.  "Element 5" is lateral to the minor metacarpal (mc III of some,
mc IV of others), so it would be either mc IV or mc V (respectively).
However, some specimens show the beginnings of yet another (fifth...)
metacarpal element, lateral to "element 5".  Make of that what you will...

Now, some biomechanical stuff:
Blob, R. W. & A. A. Biewener. 1999.  In vivo locomotor strain in the
hindlimb bones of _Alligator mississipiensis_ and _Iguana iguana_:
implications for the evolution of limb bone safety factor and non-sprawling
limb posture.  J. Exper. Biol. 202: 1023-1046.

Part of Rich Blob's dissertation work, looking at the evolution of limb
postures and behaviors.  For the first time sprawlling diapsids have their
limb bone strain analysed in life (previous work was on mammals and birds
with parasagittal gaits).  Some of the primary data Blob is using in his
study of the transition from the sprawling to the parasagittal gait in the
evolution of therapsids (and ultimately applicable to the rise of the same
gait in archosaurs).

Irschick, J. D. & B. C. Jayne.  1999.  Comparative three-dimensional
kinematics of the hindlimb for high-speed bipedal and quadrupedal locomotion
of lizards.  J. Exper. Biol. 202: 1047-1065.

Cool stuff I saw at SICB in January (sitting next to Jim Farlow, who found
it pretty cool, too): work on the locomotion of lizards at high speeds
rather than low speeds (as previously done).  At high speeds, the lizards
examined were digitigrade runners; the tail of _Callisaurus draconoides_ and
(especially) _Uma scoparia_ is flexed at the proximal end and held upwards
(in _Uma_ it is held at a 90 degree angle), something to think about when
reconstructing running dromaeosaurids...  The Froude number (a dimensionless
quantity used to compare motion of different sized objects) for the lizards
examined ranged from 5.4 to 8.0; by comparison, the world-class human
sprinters run at a Froude number of about 3.2

In a similar vein...
Bonine, K. E. & T. Garland, Jr.  1999.  Sprint performance of phrynosomatid
lizards, measured on a high-speed treadmill, correlates with hindlimb
length.  J. Zool., Lond. 248: 255-265.

After lots of measurements, they found that interspecific variation in
maximal speed is positively correlated with hindlimb span, but not
significantly related to either body mass or body temperature.
(Incidentally, their fastest running taxon was _Cnemidophorus tigris
marmoratus_, with a mean maximal sprint running speed of 6.17 m/s, or about
13.8 mph).

Biknevicius, A. R. 1999.  Body mass estimation in armoured mammals: cautions
and encouragements for the use of parameters from the appendicular skeleton.
J. Zool., Lond. 248: 179-187.

Compared body mass to various femoral measurements for a variety of
dasypodids, manids, and caviomorphs (that's armadillos, pangolins, and
various large bodied rodents such as agoutis and American porcupines and
capybaras).  Found that femoral proportions were a good predictor of body
mass *within* groups, but not *across* groups (e.g., using the armadillo
regression line doesn't accurately predict pangolin body mass).

One of the cautions: "How, then, should one proceed when body mass estimates
are desired for animals that are unusual morphologically?  Unless there is a
compelling phylogenetic reason for doing so (i.e., recent ancestry), choice
of another highly derived group for use in constructing predictive equations
is not recommended: just because a mammal has an armoured integument does
not mean that its body mass is estimated best with equations based on
_another_ group of armoured mammals."

Later,

                        Thomas R. Holtz, Jr.
                        Vertebrate Paleontologist
Deptartment of Geology                  Director, Earth, Life & Time Program
University of Maryland                  College Park Scholars
College Park, MD  20742       
Webpage: http://www.geol.umd.edu        Phone:301-405-4084
Email:tholtz@geol.umd.edu               Fax:  301-314-9661