Upper Homerian and Gorstian (Silurian) Retiolitidae (Graptolithina) from Lithuania and Latvia

A well preserved retiolitid fauna isolated from upper Homerian and Gorstian (Silurian) strata is documented for the first time from boreholes in Lithuania and Latvia. The faunal assemblage corresponds very closely to species of retiolitoids recovered from the Polish part of the East European Platform. The retiolitoids described provide new data on biostratigraphic ranges as well as on some aspects of morphology. Rudimentary transverse rods in Spinograptus spinosus, S. clathrospinosus and Neogothograptus balticus are described for the first time in post-lundgreni retiolitoids. The described material includes ten species belonging to five genera: Gothograptus nassa, Papiliograptus papilio, Spinograptus spinosus, S. clathrospinosus, S. munchi, Neogothograptus purus purus, N. balticus, N. alatiformis, Plectograptus toernquisti and Pl. mobergi.