About thirty-five thousand identifiable conodonts were recovered
from samples of Middle and Upper Ordovician sedimentary
rocks of Minnesota. One section was sampled in detail
for each formation except the Glenwood, which was
sampled at three localities in east-central and southeastern
Thirty-three form species or groups of form species <Ire
described as biological or natural species. Form species
comprising a natural species are associated by similarities
in stratigraphic range, abundance ratios, size, and secondary
Problems stemming from the presently used invalid dual
nomenclature can be solved by applying the name of the
earliest described form species to the natural species according
to the rules of zoological nomenclature.
The Middle and Upper Ordovician strata of Minnesota can
be subdivided into ten biostratigraphic zones on the basis of
the stratigraphic distribution of conodonts. An increase in
European elements at the expense of American mid-continent
elements in the Galena and Dubuque Formations represents a
major shift in conodonts with respect to pre-Galena faunas.
SP-04 The Middle and Upper Ordovician Conodont Faunas of Minnesota.
Minnesota Geological Survey.
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