Inverts and verts

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Phylogenetic investigations have constituted a major part of the work on 
(Cenozoic at least) radiolarians for some 40 years now.  Investigators of 
Mesozoic and Paleozoic radiolarians are also now able to formulate their 
nomenclatural systems to reflect phylogenetic relationships, to the extent 
that their fossil record permits.

One of us (WR) is old enough to have been struck many years ago by the 
cogency of the first article in the first issue of the journal 
Micropaleontology, in which Martin Glaessner (1955) stated in his abstract 
that "Taxonomy and ecology, biostratigraphy and ecology, and biostratigraphy 
and taxonomy of the foraminifera are closely related fields.  It is shown, 
with reference to examples and to modern work on other groups, that an 
approach to any one of these fields which does not take into account their 
interrelations is not in agreement with modern standards."  This is of 
course also true of fossil groups other than foraminifera, and those of us 
working on Cenozoic radiolarians are blessed with an abundance of material 
for pursuing phylogenetic, biostratigraphic and paleoenvironmental studies 
in combination (particularly since the commencement of deep-sea drilling).

When applying a taxonomic system to the Cenozoic radiolarians, we maintain a 
clear distinction in our heads (and in our publications) between species 
that can be placed in genera and families that reflect evolutionary 
relationships, and those whose relationships are not yet understood.  The 
latter, which still outnumber the former, are placed in genera and families 
according to gross morphological characters - usually approximating the 
system set up by Haeckel (1887) for the radiolarians collected by the 
Challenger Expedition.

Investigators continue replacing parts of this artificial Haeckelian 
taxonomy by genera and families reflecting true relationships.  Obviously, 
the stratigraphic record provides the concrete evidence on which 
phylogenetic relationships are based, and as the taxonomy becomes more 
natural a finer stratigraphic resolution is attainable.  And in recent 
years, paleobiogeographic variability of species, and close examination of 
the components of assemblages, are providing paleoenvironmental clues, and 
some indication as to how evolution proceeded in one environmental setting 
as compared to another.

In short, phylogenetics is alive and well in the fossil radiolarian business.


                                Bill Riedel and Annika Sanfilippo
W. Riedel
Scripps Institution of Oceanography
UCSD
La Jolla, CA 92093-0220

wriedel@ucsd.edu
phone (619) 534-4386
fax   (619) 534-0784