Morphometric Data - An Invariant Approach to Statistical Analysis of Shapes - page 27

morphologically divergent characters, that non-homologous structures
can develop from homologous anlagen, and that the molecular mecha-
nisms of development may be put to use in varying contexts producing
novel morphologies (Müller and Wagner, 1996). Resolution of these pos-
sibilities in any particular case requires careful evaluation of
molecular mechanisms, developmental programs, and morphological
similarity.
It is obvious from the above classification that there are landmarks
that could be shared among organisms on more than one of the biolog-
ical bases outlined above. The particular orientation of the research
and the research question that is being posed will dictate the actual
choice of landmarks. The choice of which specific landmarks should be
used in a study is arbitrary but should be made on the basis of the sci-
entific question being posed.
2.3 Collection of landmark coordinates
Landmark coordinates are the location of points in space recorded
along X- and Y-axes in two-dimensions and along X-, Y-, and Z- axes in
three-dimensions. Landmark coordinate data can be collected directly
from whole specimens, from serially sectioned specimens, or from
images of specimens. The following is not meant to be a comprehensive
review of available techniques and equipment, but rather a listing and
description of some of the types of devices already used in biological
research and available to the scientific community. We mention by
name only those instruments with which we have had personal expe-
rience or with which we have had personal contact with users. Parts of
this discussion follow a paper prepared by Luci Kohn (1994), present-
ed at the Morphometrics workshop held during the International
Conference of Vertebrate Morphology, Chicago, 1994.
2.3.1 Commonly used devices for collection of
landmark coordinate data from whole specimens
Diagraph
The diagraph is a machine that allows collection of landmark coordi-
nate data using only paper and pencil. A stable vertical stand anchors
necessary parts of this device. The object to be digitized is immobilized