Normalograptus kufraensis, a new species of graptolite from the western margin of the Kufra Basin, Libya

Abstract

AbstractNormalograptus kufraensissp. nov. occurs as monospecific assemblages in the Tanezzuft Formation at the western margin of the Kufra Basin (Jabal Eghei), southern Libya. These graptolites have parallel-sided rhabdosomes with long, straight virgellae, climacograptid thecae and a full straight median septum.N. kufraensisis intermediate between Ordovician graptolites from theN. angustus(Perner) lineage and the younger sister speciesN. ajjeri(Legrand) andN. arrikiniLegrand.N. kufraensisdiffers from these taxa as follows: it is broader thanN. angustus; it has greater thecal spacing thanN. ajjeriorN. arrikini. A table comparing measurements ofN. kufraensiswith 44 otherNormalograptustaxa differentiates it from other members of this morphologically conservative group. Even thoughN. angustusandN. ajjeriare very long-ranging graptolites, a stratophenetic approach suggests that the specimens from Jabal Eghei may be of late Hirnantian or younger age. The faunal composition and preservation suggests these graptolites occupied the ‘cratonic invader’ biotope. The stratigraphic succession records deglacial flooding and fluctuating of redox in the Tanezzuft Formation, with the graptolites indicating a short-lived interval of anoxia.