Biostratigraphical significance of the Devonian Sinoleperditiini (Ostracoda)

摘要

The Tribe Sinoleperditiini (Ostracoda), which is mainly distributed in South China and its adjacent areas, is a single natural group of the Leperditiidae, characterized by the development of a trailing chevron muscle scar. This tribe is known only from the Devonian and ranges through most of the Devonian. The evolutionary trends within the Sinoleperditiini have been well documented and are exemplified by changes in the trailing chevron muscle scar. The main evolutionary change is a tendency of the trailing chevron muscle scar to extend ventrally through time, as demonstrated by the increasing ratio (th/ah) of the vertical height of the trailing chevron muscle scar (th) to that of the adductor muscle scar (ah). The recent discovery of a sinoleperditiine assemblage (th/ah values available) in the middle-upper Lower Emsian Shanglun Formation allows to propose a sinoleperditiine biostratigraphical sequence for the Devonian. This sequence contains 11 assemblages (th/ah value available for each assemblage), which cover all the 7 Devonian stages and some substages. This sequence is particularly useful for correlating and dating Devonian rocks in the littoral clastic, lagoonal and restricted or semirestricted carbonate platform facies where these ostracodes are most abundant and other fossils are uncommon.