ORTHAMBONITES AND RELATED ORDOVICIAN BRACHIOPOD GENERA

In a revised diagnosis, Orthambonites is restricted to a small group o f late lower Ordovician (latest Arenig-Llanvirn equivalent) brachiopod s from Baltoscandia. Orthambonites rotunda is proposed as the formal t ype species of the genus to replace Orthambonites transversa which is considered a nomen dubium. Revision of Orthis calligramma suggests in turn that it is a senior subjective synonym of O. rotunda, and thus be comes the effective type species of Orthambonites. Many species includ ed previously within the genus are assigned to Paralenorthis, and to t hree new genera - Sulevorthis, Sivorthis, and Shoshonorthis. Krattorth is is defined as a new related genus. Neotypes are proposed for O. rot unda and Sulevorthis lyckholmiensis. A lectotype is designated for Ort his callactis, the type species of Orthis, which is discussed briefly in order to clarify past confusion with Orthambonites.