some new papers

[Jay <sappororaptor@yahoo.com>]

Ancestor-descendant relationships and the reconstruction of the Tree of Life.
Beno&icirct Dayrat, pages 347-353.
Abstract:
not availible 

Evolutionary modifications of ontogeny: heterochrony and beyond. Mark Webster,
Miriam Leah Zelditch, pages 354-372.
Abstract:
Consideration of the ways in which ontogenetic development may be modified to 
give morphological
novelty provides a conceptual framework that can greatly assist in formulating 
and testing
hypotheses of patterns and constraints in evolution. Previous attempts to 
identify distinct modes
of ontogenetic modification have been inconsistent or ambiguous in definition, 
and incomprehensive
in description of interspecific morphological differences. This has resulted in 
a situation
whereby almost all morphological evolution is attributed to heterochrony, and 
the remainder is
commonly either assigned to vague or potentially overly inclusive alternative 
classes, or
overlooked altogether.

    The present paper recognizes six distinct modes of ontogenetic change, each 
a unique
modification to morphological development: (1) rate modification, (2) timing 
modification, (3)
heterotopy, (4) heterotypy, (5) heterometry, and (6) allometric repatterning. 
Heterochrony,
modeled in terms of shape/time/size ontogenetic parameters, relates to 
parallelism between
ontogenetic and phylogenetic shape change and results from a rate or timing 
modification to the
ancestral trajectory of ontogenetic shape change. Loss of a particular 
morphological feature may
be described in terms of timing modification (extreme postdisplacement) or 
heterometry, depending
on the temporal development of the feature in the ancestor. Testing hypotheses 
of the operation of
each mode entails examining the morphological development of the ancestor and 
descendant by using
trajectory-based studies of ontogenetically dynamic features and 
non-trajectory-based studies of
ontogenetically static features.

    The modes identified here unite cases based on commonalities of observed 
modification to the
process of morphological development at the structural scale. They may be 
heterogeneous or
partially overlapping with regard to changes to genetic and cellular processes 
guiding
development, which therefore require separate treatment and terminology. 
Consideration of the
modes outlined here will provide a balanced framework within which questions of 
evolutionary
change and constraint within phylogenetic lineages can be addressed more 
meaningfully.

Function in the stunted forelimbs of Mononykus olecranus
(Theropoda), a dinosaurian anteater. Phil Senter, pages 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.

The origin of the avian flight stroke: a kinematic and kinetic perspective.
Stephen M. Gatesy, David B. Baier, pages 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.

Integrating ichnofossil and body fossil records to estimate locomotor posture
and spatiotemporal distribution of early sauropod dinosaurs: a stratocladistic
approach. Jeffrey A. Wilson, pages 400-423. 
Abstract:
Fossil vertebrate distributions are typically based on body fossils, which are 
often poorly
sampled at the margins of their true temporal and spatial ranges. Because 
vertebrate ichnofossils
can be preserved in great abundance and in different environments than 
vertebrate body fossils,
inclusion of ichnofossil data may improve sampled ranges. However, if 
ichnofossils are to serve as
an independent source of distributional data, then their attribution to a body 
fossil group (i.e.,
trackmaker identification) cannot rely on temporal and spatial coincidence. 
Ichnofossils
identified by synapomorphies can act as an independent source of distributional 
data that can
modify spatial, temporal, and character distributions, which in turn may 
influence hypotheses of
locomotor evolution.

In this paper I evaluate the spatial, temporal, and character distributions of 
early sauropod
dinosaurs by using a combined ichnofossil and body fossil data set. Sauropod 
ichnofossils
supplement the spatiotemporal distributions of early sauropods and provide 
important information
on early sauropod foot posture that is rarely preserved or can only be inferred 
from body fossils.
The presence of derived features in early-appearing ichnofossils challenges 
previous hypotheses of
character transformation, implying either parallelism, reversal, or ghost 
lineages.

Stratocladistics can be used to resolve conflicting character and temporal 
distributions from body
fossils and ichnofossils. Stratocladistic analysis of a combined ichnofossil 
and body fossil data
set suggests a richer, more widely distributed diversity of early sauropods 
than currently
recognized in body fossils and suggests that several locomotor characters 
originated much earlier
than implied by body fossils.


The above issue is now available for the Paleontological Journals Online

Journal: Paleobiology (0094-8373)
 Volume: 31
  Issue: 3

Jay

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