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2 The University of Kansas Paleontological Contributions—Paper 99
INTRODUCTION
During preparation of descriptions of
Cambrian and lowermost Ordovician conodont
genera for the revision of Part W of the
Treatise on Invertebrate Paleontology, it
became clear that considerable taxonomic
revision of these genera was needed. It is the
purpose of this paper to clarify the generic
classification of a number of Upper Cambrian
and Lower Ordovician conodonts. Most of
the changes involve description of new genera
with previously named type species, the
changes being necessary because of recognition
that these species belong to previously
unrecognized conodont apparatuses.
Of the new genera, three are paraconodonts.
Albiconus has a previously undescribed
type species. It is the last known
paraconodont genus to appear and is probably
represented by a one-element apparatus.
Nogamiconus is established for several species
of probable one-element apparatuses. Mziellerodus
is proposed to replace Muellerina
Szaniawski, 1971, which is preoccupied by
Muellerina Bassiouni, 1965, an ostracode.
Several primitive euconodont genera considered
here are also based on one-element apparatuses.
One such genus, Proconodontus
Miller, 1969, is redefined and two new
species, P. posterocostatus and P. tenuiserratus,
are described. Clavollannilus Furnish,
1938, Hirsutodontus Miller, 1969, and
Teridontus, n. gen., also include one-element
apparatuses.
Simple cones of the new euconodont genus
Monocostodus form a primitive symmetry
transition by variation in the lateral and
posterior position of a single costa.
Several genera are based on two-element
apparatuses. These include the related new
genera Cambrooistodus and Eoconodontus,
which possess similar noncostate apparatuses,
and differ from Sein iacontiodus Miller, 1969,
and LI taliconus, n. gen., which possess similar
costate apparatuses. Cordylodus Pander,
1856, is extensively revised and is interpreted
to include a two-element denticulate apparatus
similar to those of Cambrooistodus
and Eoconodontus.
The apparatus of Fryxellodontus Miller,
1969, was originally interpreted as a three- or
four-element symmetry-transition series. Designation
of holotypes for the two species
described by Miller (1969) was improper and
lectotypes are designated here.
Examination by electron microscopy of
the holotype of Nericodus capillarnention
LindstrOm, 1955, has shown it to be a broken
element. The obscure species, which is known
only from this specimen and a few additional
fragments, may be related to Hirsutodontus.
The geographic and stratigraphic occurrences
for most species are referenced where
appropriate; unreferenced occurrences are
from my research collections. Biostratigraphic
ranges of taxa are listed for most North
American occurrences, and are given (Fig. 1)
in terms of either trilobite zones (Winston &
Nicholls, 1967; Longacre, 1970; Stitt, 1977) or
conodont zones and faunal units (Miller,
1975, 1978; Ethington & Clark, 1971).
Illustrated specimens have been placed in
the collections of the National Museum of
Natural History, Washington, D.C., and are
identified by numbers with the prefix
"USNM."
Acknowledgments. I have been involved
in taxonomic studies of Cambrian and
Lower Ordovician conodonts for more than a
decade, and in that time have received assistance
from many persons and several institutions.
These persons include S. M. Bergstrom,
D. L. Clark, J. R. Derby, E. C. Druce, R. L.
Ethington, P. W. Goodwin, L. F. Hintze, D. J.
Kennedy, V. E. Kurtz, Ed Landing, J. L.
Mason, L. L. Miller, K. J. Muller, J. E. Repetski,
A. J. Rowell, J. H. Stitt, M. E. Taylor,
and the late W. C. Bell. Special thanks go to
D. L. Clark and R. A. Robison for providing
help and special encouragement in completing
this study. Financial assistance for graduate
research was provided by National Aeronautics
and Space Administration, Geological
Society of America, Society of Sigma Xi, and
the University of Wisconsin, together with
support from National Science Foundation
grants to D. L. Clark. Subsequent financial
support was granted by Research Corporation,
University of Utah Faculty Research
Fund, Southwest Missouri State University
Faculty Research Fund, and a National
Science Foundation grant to V. E. Kurtz and
myself.