About graptolite genus Lithuanograptus once more

Abstract

A new genus of graptolites named Lithuanograptus has been found in Lithuania and studied by the present author (Paškevičius, 1972, 1976) in the Silurian Llandovery cyphus zone of the Rasytė Formation and the following 4 species have been described: L. fusiformis Pašk., L. obuti Pašk., L. minimus Pašk. and L. serus Pašk. Loydell (1992) treated this genus as a junior synonym of Metaclimacograptus and attributed the species of L. minimus and L. serus to this genus. The author of the present paper agrees to the attribution of these species to the genus Metaclimacograptus. Nevertheless, a genotype L. fusiformis of Lithuanograptus and its species L. fusiformis and L. obuti differ significantly from Metaclimacogratus by fusiform rhabdosome, massive virgella and structure of thecae – a flattened geniculum surrounding and fully covering the thecal excavations, types of medial and interthecal septa and other features. Therefore, the author considers Lithuanograptus with L. fusiformis and L. obuti being separate genus and species. Moreover, the paper presents the holotypes of the mentioned two species with the material, diagnosis, age and detection sites.