A new carcinosomatid eurypterid from the Siluro-Devonian of northern Vietnam

Abstract

A new carcinosomatid eurypterid, Rhinocarcinosoma dosonensis sp. nov., and Hughmilleria sp., are described from the Do Son Formation of the Do Son Peninsula, northern Vietnam. R. dosonensis is characterized by podomere 7 of prosomal appendage VI produced into an anterodistal spine, a metastoma with a cordate posterior margin, and an indented opisthosomal differentiation (i.e. preabdomen-postabdomen margin is concave). The Do Son Formation was originally interpreted as Late Devonian (Givetian/Frasnian) in age but the unit containing the eurypterid assemblage is now considered much older (Late Silurian). A deltaic palaeoenvironmental setting is interpreted from biotic associations and sedimentological evidence.