REVIEW OF LATE SILURIAN SPATHOGNATHODONTID CONODONT TAXA OF THE SOUTH-CENTRAL UNITED STATES

Spathognathodontid conodonts were widespread and common species during the late Silurian and early Devonian, yet this group is taxonomically poorly understood owing to the conservative shape of the carminate P₁ elements and the tendency to develop intergrading morphologies. Taxonomic revisions of the family undertaken within the last decade have split the genus Ozarkodina into six or more separate genera, but controversy remains, particularly regarding the remscheidensis/eosteinhornensis group. Study of collections from the south-central United States (Henryhouse and Haragan Formations, south-central Oklahoma; Frame Formation, west Texas; Bainbridge Formation, south-eastern Missouri; Decatur and Ross Formations, western Tennessee) has provided additional data to help both in the resolution of taxa and establishment of geographic and biostratigraphic ranges. Taxa identified in this region include multiple morphotypes of “Ozarkodina” (New Genus W of Murphy et al.) eosteinhornensis, Ozarkodina martinssoni auriformis, the Ozarkodina snajdri-crispa transition, which crosses the Ludlow-Pridoli boundary interval, “Ozarkodina” planilingua, and an unnamed taxon the P₁ of which resembles that of the younger species Zieglerodina remscheidensis. Comparisons with collections and published descriptions from Europe, Australia, and elsewhere in North America suggest that the Silurian and Devonian Spathognathodontidae may have some unutilized potential for correlation worldwide; however, the application of species of this group to resolve and precisely correlate the Silurian-Devonian boundary does not appear to be possible.