The Ludlow (Late Silurian) neocucullograptid fauna from the southern Tien Shan, Kyrghizstan

A diverse Ludlow monograptid fauna has been studied from complete sections of the Kursala and Pulgon formations in the Peshkaut and Tashbulak Valleys and on Kyk Mountain in south Fergana, Kyrghizstan, Central Asia. The Kursala Formation is 150 m thick and consists mostly of mudstone interbedded with sandstone and calcarenite; it ranges in age from the lundgreni/testis to the transgrediens Biozones of the graptolite-bearing, terrigenous Ludlow succession of the southern Tien Shan. Closely-spaced collections, made at 10-30 cm intervals, have led to the establishment of a high-resolution biozonation within this part of the Late Silurian, consisting of the progenitor/ colonus, scanicus/chimaera, linearis, tenuis, podoliensis and formosus/spineus Biozones; this serves as the correlation standard for the Ludlow of Central Asia. New data have been gathered on the taxonomy and stratigraphic ranges of members of the Egregiograptus and Polonograptus plexuses, as well as of some specialized bohemograptids. The strati graphically well-controlled, succession of graptolite assemblages is important in Ludfordian (late Ludlow) biostratigraphy, the interpretation of the evolutionary dynamics and in phyletic reconstructions of the neocucullograptid fauna. Eighteen species and subspecies of Lobograptus, Bohemograptus, Egregiograptus and Polonograptus are described, including pandemic forms; new taxa are Bohemograptus decorus sp. nov., Egregiograptus dimitrii sp. nov., Egregiograptus klishevichi sp. nov., Egregiograptus rinellae sp. nov., Bohemograptus garratti singularis subsp. nov. and Bohemograptus praecornutus brevis subsp. nov.