The well preserved Llandovery biserial and uni-biserial graptoloid fauna of the Mugodzhary Range of the Kos-Istek region of western Kazakhstan gives an unusual insight into the biodiversity of Llandovery assemblages. Sixty-three taxa are described, of which twenty-one are left in open nomenclature, assigned to the families Glyptograptidae, Akidograptidae, Dimorphograptidae and Metaclimacograptidae fam . novo There are thirteen new species: Glyptograptus bulbus, Neodiplograptus korinevskii, Hirsutograptus longispinus, H. villosus, Victorograptus morosus, Parapetalolithus dignus, Rivagraptus inconstans, R. rozmanae, R. sentus, Corbograptus enigmatica, Metaclimacograptus khabakovi, Me. khvorovi and Me. orcus. Five new genera and a new subgenus are erected on the basis of Uralian material: Hirsutograptus, Victorograptus, Parapetalolithus, Rivagraptus, Corbograptus, and the subgenus Pseudorthograptus (Dimorphograptoides). Two other new genera are erected, Persculptograptus and Sudburigraptus, based on material from Wales and Alaska respectively. The type material of the genera Comograptus and Dittograptus, from Norilsk, Siberia, is redescribed. The diverse graptolite assemblages of the Kos-Istek region have enabled accurate attribution of faunas to biozones of Rhuddanian to early Telychian age.
The multispinose biserial graptoloids evolved in three main lineages: (l), Normalograptus to Hirsutograptus; (2) , Pseudorthograptus (Pseudorthograptus) mutabilis to P. (Dimorphograptoides) and to P. (P.) obuti, P. (P.) insectiformis and P. (P.) inopinatus; P. (P.) obuti to Corbograptus, Dittograptus and Victorograptus; P. (P.) mu tab ilis / obuti to Petalolithus; (3), Sudburigraptus to Rivagraptus cyperoides, R. rozmanae, R. senlUS, R. inconstans and R. bellulus ; and Rivagraptus to Agetograptus.