Article Abstracts

[Miles Constable at Edmn <ConstableM@mail.edm.ab.doe.ca>]

Pardon my absence, I have been busy with that other stuff called work.

Gilinsky, N.L., Bennington, "Estimating numbers of whole individuals from 
collections of body parts: A taphonomic limitation of the paleontological 
record. Paleobiology, Spring 1994, 20, 2, 245-258.
"Paleoecologists have long sought to obtain estimates of the sizes of 
extinct populations. However, even in ideal cases, accurate counts of 
individuals have been hampered by the fact that many organisms disarticulate 
after death and leave their remains in the form of multiple, separated 
parts. We here analyze the problem of estimating numbers of individuals from 
collections of parts by developing a general counting theory that elucidates 
the major contributing variables. We discover that the number of unique 
individuals of a particular species that are represented in a fossil. 
collection can be described by an intricate set of relationships among (1) 
the number of body parts that were recovered, (2) the number of body parts 
that were possessed by organisms belonging to that species, and (3) the 
number of individuals of that species that served as the source of the parts 
from which the paleontological sample was obtained (the size of the 
''sampling domain''). The ''minimum number of individuals'' and ''maximum 
number of individuals'' methods currently used by paleontologists to count 
individuals emerge as end members in our more general, counting theory. The 
theory shows that the numbers of individuals of a species that are 
represented in a sample of body parts is fully tractable, at least in a 
theoretical sense, in terms of the variables just mentioned. The bad news is 
that the size of the ''sampling domain'' for a species can never be known 
exactly, thus placing a very real limit on our ability to count individuals 
rigorously. The good news is that one can often make a reasonable guess 
regarding the size of the sampling domain, and can therefore make a more 
thoroughly informed choice regarding how to estimate numbers of individuals. 
By isolating the variables involved in determining the numbers of 
individuals in paleontological samples, we are led to a better appreciation 
of the limits, and the possibilities, that are inherent in the fossil 
record."

Barrick, R.E., Showers, W.J. "Thermophysiology of Tyrannosaurus rex: 
Evidence from oxygen isotopes" Science, July 8, 1994, 265, 5169, 222-224.
"The oxygen isotopic composition of vertebrate bone phosphate (delta(p)) is 
related to ingested water and to the body temperature at which the bone 
forms. The delta(p) is in equilibrium with the individual's body water, 
which is at a physiological steady state throughout the body. Therefore, 
intrabone temperature variation and the mean interbone temperature 
differences of well-preserved fossil vertebrates can be determined from the 
delta(p) variation. Values of delta(p), from a well-preserved Tyrannosaurus 
rex suggest that this species maintained homeothermy with less than 4 
degrees C of variability in body temperature. Maintenance of homeothermy 
implies a relatively high metabolic rate that is similar to that of 
endotherms."

Benton, M.J. "Palaeontological Data and Identifying Mass Extinctions". 
Trends in Ecology & Evolution, May, 1994, 9, 5, 181-185.
"It is often assumed that mass extinctions may be read directly from the 
fossil record. However, recent work on the Cretaceous-Tertiary (K-T) 
boundary has shown the difficulty of doing this. For example, it is hard to 
tell whether the stratigraphic ranges of taxa are complete or not, and what 
the shape of an extinction really is. Range completeness may be assessed by 
(1) a statistical approach to the relative completeness of ranges of taxa, 
and (2) tests based on collecting effort near the ends of ranges. Tests 
carried out recently suggest that the record is good in parts and getting 
better. Hence, palaeontologists ought to be able to document the nature of 
extinction events ever more precisely."