Six genera are treated .in this section They are arranged alphabetically: Cavusgnathus, Diploognathodus, Gondolella, Idiognathodus Neognathodus and Streptognathodus with their -species arranged phylogenctically. These are, by and large, considered to be -the “platform” genera most useful for biostratigraphy. Strictly speaking, Diplognathodus lacks a platform hut appears to be closely related to taxa that bear true platforms and aIso shows an evolutionary pattern much like that of platform-bearing genera.
Three other genera are numerically important in these collections, but are not discussed in detail: Aethotaxis, Anahignathodus, and Idioprioniodus. Aethotaxis Baesemann, 1973, US a coomon and paleoecologically quite important conodont. It ranges through most orall of the, Pennsylvanian System and needs detailed monographic treatment considered to be beyond the scppe of this study. Anchignathodus Sweety 1970 (the Spathognathodus of authors), faces the same platform/nonplatform difficulty as Diplognathodus. The Pennsylvanian including Illinois basing species of Anchignatihodus have been studied in some detail by Merrill (1973a). Idioprioniodus Gunnell, 1933, is another nonplatforn conodont with great paleoecologic utility. Its apparatus composition has been, studied, based mostly on material from northwestern, Illinois, by Merrill and Merrill (1974), and studies about its spation are In process. Each of these genera is discussed briefly under the heading Multielement Taxonomy.
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“Pennsylvanian rocks exposed in Knox, Peoria, Fulton, and Schuyler Counties in northwestern Illinois include 11 major marine units. The oldest marine unit is late Atokan and the youngest is early Missourian; the remainders are Desmoinesian in age. Each unit has produced at least some conodonts, and the more than 200 samples produced an aggregate total in excess of 160,000 conodont specimens. These can be grouped into not fewer than 78 kinds, considered species in disjunct element taxonomy. At least 10 multielement genera and 40 multielement species are represented. Six new species: Diplognathodus illinoisensis, Neognathodus metanodosus, N. polynodosus, N. oligonodsus, N. anodus, and Gondolella pulchra are described. Although all marine beds were formed in shallow water, generally near shore, they represent the products of highly diverse environments. Conodont biofacies are sharply differentiated and mirror this diversity. Ecologic controls that effected conodont distribution are believed to have been salinity, energy, pH, and possibly biologic antagonism. Neognathodus is the most useful conodont genus for biostratigraphy in these rocks. Four zones and subzones are based on species of this genus and it has permitted relatively precise interregional correlations. Secondary zonations can be based on other genera that supplement the Neognathodus zonation and assist in identifying units. In decreasing importance these are Gondolella, the Idiognathodus-Streptognathodus plexus, and Diplognathodus.”