Middle Telychian (Llandovery, Silurian) graptolites and biostratigraphy of the Howgill Fells, England, based upon the collections of DWR Wilson housed in the Lapworth Museum of Geology, University of Birmingham

摘要

Examination of D.W.R. Wilson's PhD graptolite collection from the Howgill Fells, housed in the Lapworth Museum of Geology, University of Birmingham, reveals a high diversity (23 species) of middle Telychian graptolites from the uppermost Streptograptus crispus and Streptograptus sartorius (and possibly lowermost Monoclimacis griestoniensis) biozones. The collections include the first British records of Pseudoplegmatograptus hexagonalis and Pristiograptus pergratus. The stratigraphical range of P. pristinus is extended upwards, into the sartorius Biozone. One specimen of Stimulograptus clintonensis shows remarkable dorsal rhabdosome curvature proximally. Torquigraptus is particularly diverse in the sartorius Biozone with at least six species present: one new species, T. wilsoni, is described and two probable new species, one of which is very similar to the lower Telychian T. cavei, are left in open nomenclature.