Trilobites are widespread in Lower Devonian deposits of north Gondwana, and some have been collected from two known sections of the Saoura Valley in SW Algeria, from the ‘Chefar el Ahmar’ Formation. This formation is considered to be from late Emsian to Frasnian in age, but only the lower parts of this formation have yielded trilobites. Nevertheless, no detailed studies have focused on their biodiversity and their morphological variability. New occurrences of phacopids including Barrandeops chattertoni sp. nov., Geesops fabrei sp. nov., Austerops legrandi sp. nov. and Phacops boudjemaai sp. nov. are described from this area and comparisons are made with closely allied species. These new occurrences have been integrated into analyses of intra- and inter-specific variability and biodiversity.

A diverse fauna of phacopid trilobites is described from the Late Devonian (middle Frasnian to early Famennian) of the northern Canning Basin, Western Australia. One new genus and four species in two genera are described from zones 11, 13a and 13b of the middle and late Frasnian: Trimerocephaloides sinevisus gen. nov. and sp. nov., T. ? linguiformis sp. nov., Acuticryphops acuticeps (Kayser, 1889) and A. klapperi sp. nov. Late Frasnian phacopines are either blind, as shown for the first time in Trimerocephaloides sinevisus, or show trends to decreasing eye size up to the Frasnian–Famennian ‘Kellwasser’ mass extinction event. This evolutionary trend in Acuticryphops is demonstrated to have been global at this time. One new genus and six species of early Famennian phacopids are described, from the Upper triangularis, crepida and rhomboidea zones: Houseops gen. nov. with the new taxa H. canningensis sp. nov., H. beckeri sp. nov. and H. sp. A, Babinops planiventer Feist & Becker, 1997, B. minor sp. nov., Trimerocephalus tardispinosus Feist & Becker, 1997 and T. mimbi sp. nov. In contrast to European sections where exclusively blind phacopids are known in earliest Famennian sites, initial recovery following the mass extinction event in Canning peri-reefal environments is characterized by oculated forms. These trilobites must have evolved from conservative ancestors with normal eyes that had succeeded in surviving the Kellwasser biocrises in reef-related shallow water niches. Thus the origin of post-event phacopids from shallow water environments is demonstrated for the first time. Descendant lineages show increasing eye size, increased cephalic vaulting and effacement during the early Famennian.