The Lower Cambrian Fossil Tommotia

The genera Tommotia Missarẑevskij 1970 (1966) and Camenella Missarẑevskij 1966 from the Lower Cambrian Tommotian Stage of the Siberian Platform represent different skeletal parts of the same organism and are consequently synonymous. Tommotia is selected as the valid name. Tommotia baltica n.sp. is described from the Lower Cambrian zone of Mobergella holsti of the Kalmarsund area in the southern part of the Baltic Sea. The Lower Cambrian families Tommotiidae Missarzevskij 1970 (1969) and Tannuolinidae Fonin & Smirnova 1967 show important similarities in their basic structure and are brought together in the new order Mitrosagophora, characterized by a composite outer skeleton with two types of skeletal elements, termed ‘mitral’ and ‘sellate’, each occurring in symmetrical pairs. The group is of uncertain systematic position but may have affinities with the Machaeridia. The Scandinavian zone of Mobergella holsti is correlated with the Siberian zone of Dokidocyathus lenaicus and Majatheca tumefacta, the uppermost zone of the Tommotian Stage.