Retiolitid graptolites from the collection of Hermann Jaeger III. Paraplectograptus, Gothograptus and their relatives

Abstract

The graptolite collection of Hermann Jaeger at the Museum für Naturkunde in Berlin, Germany includes a number of Paraplectograptus and Gothograptus specimens. The material provides another glimpse into the dramatic changes affecting retiolitine graptoloids across the Lundgreni Extinction Event of the mid Homerian (Wenlock, Silurian) which led to the demise of most earlier groups of retiolitines. The material indicates that the diversity of the pre-extinction retiolitines might have been larger than is already known through the recognition of previously unknown constructional details in earlier Gothograptus and Paraplectograptus species. Especially, Gothograptus shows a much higher diversity in the pre-extinction interval than previously recognized. In the Pristiograptus parvus/Gothograptus nassa Biozone interval Gothograptus re-emerged with new species and Semigothograptus is shown to have survived unchanged, indicating that these two genera represent survivors of the extinction event. A number of new genera originated and diversified in the Pristiograptus dubius/Gothograptus nassa to Colonograptus praedeubeli/deubeli Biozone interval, but their evolutionary relationships with earlier taxa are still only partly understood. Paraplectograptus hermanni sp. nov., Gothograptus berolinensis sp. nov. and Gothograptus osgaleae sp. nov. are described as new. Several species are described in open nomenclature due to the lack of sufficiently well preserved material.