The biostratigraphically important genus Hunnegraptus is recognized for the first time in the Marathon region, West Texas, based on restudy of the type material of Didymograptus novusBerry, 1960. The late Tremadoc Hunnegraptus Zone is the oldest unequivocally recognized graptolite zone in the Marathon region, underlain by faunas with nondiagnostic adelograptids. Hunnegraptus novus (Berry) shows a sicular bitheca, dichograptid stipes, and delayed first distal dichotomies as the most important rhabdosome characteristics. Hunnegraptus Zone faunas are more widely distributed in North America than previously realized and an immensely useful discovery for biostratigraphic correlation of this late Tremadoc time interval.

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