Cladistic analysis of plicated Thalassiosira (Bacillariophyceae)

Nineteen Thalassiosira species informally referred to as the plicated Thala ssiosira were examined in a cladistic analysis. The species range in age fr om 17 Ma to modern, representing the earliest known members of the group an d its most recent members. Two most parsimonious cladograms were discovered , generally agreeing with the occurrence of species in the fossil record. C haracter distributions support all described species in the context of the phylogenetic species definition, and important features diagnosing these sp ecies are presented. The group's fossil record and use of its species as bi ostratigraphic and ecological indicators are discussed. Results of the clad ogram are also used to detail potential nomenclatural modifications of both Thalassiosira itself and within the plicated Thalassiosira, and an outline of this future research is presented.