Article: Orthambonites and related Ordovician brachiopod genera
Valdar Jaanusson and Michael G. Bassett
In a revised diagnosis, Orthambonites is restricted to a small group of late lower Ordovician (latest Arenig-Llanvirn equivalent) brachiopods from Baltoscandia. Orthambonites rotunda is proposed as the formal type 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 becomes the effective type species of Orthambonites. Many species included previously within the genus are assigned to Paralenorthis, and to three new genera - Sulevorthis, Sivorthis, and Shoshonorthis. Krattorthis is defined as a new related genus. Neotypes are proposed for O. rotunda and Sulevorthis lyckholmiensis. A lectotype is designated for Orthis callactis, the type species of Orthis, which is discussed briefly in order to clarify past confusion with Orthambonites.