Agastograptus robustus Obut and Zaslavskaya, 1983, the type species of the genus Agastograptus is herein recognized as a species of Plectograptus. Large proximal lateral orifices are one of the significant characters of Plectograptus. P. robustus differs from the type species, Plectograptus macilentus Törnquist, 1887, in possessing paired apertural processes. Other species of Agastograptus have been assigned to three different genera: Spinograptus, S. clathrospinosus (Eisenack, 1951), S. munchi (Eisenack, 1951), Neogothograptus, N. balticus (Eisenack, 1951), and Cometograptus, C. nevadensis (Berry and Murphy, 1975). The main diagnostic feature used for Agastograptus, the spinoreticular paired apertural processes, is recognized as a species feature, characteristic mostly for Spinograptus, whereas the generic features are the arrangement of the proximal end, ventral walls, and ancora sleeve of the rhabdosome. Therefore the genus Agastograptus is a synonym of Plectograptus.

Key words: Graptolithina, Retiolitidae, Agastograptus, Silurian, taxonomy

Anna Kozłowska−Dawidziuk [akd@twarda.pan.pl], Instytut Paleobiologii PAN, ul. Twarda 51/55, PL−00−818Warszawa, Poland.