New early Devonian styginid trilobites from Victoria, Australia, with revision of some spinose styginids

Abstract

A distinctive new genus (Xyoeax) and two new species (Xyoeax eponcus, Scutellum sudorum) of styginid trilobites are described from the late Early Devonian (Emsian) Murrindal Limestone of eastern Victoria, Australia. Limited material of a third styginid species not belonging to any named genus is also described from the same locality. Xyoeax is considered to be closely related to Ancyropyge Clarke, 1891, and Weberopeltis Maksimova in Moore, 1959, and less closely related to Kolihapeltis Prantl and Pribyl, 1947. Weberopeltis is revised and newly diagnosed. Several species previously assigned to Weberopeltis are transferred to the new genus Exastipyx, which is considered to be related to Cornuscutellum Snajdr, 1960. Ancyropyge, Exastipyx, Weberopeltis, and Xyoeax all have pygidia with long pleural spines derived by reduction of the pleural field between the pleural ribs, whereas Kolihapeltis and Cornuscutellum lack pygidial spines. Pygidial morphology of Xyoeax type has thus arisen independently in separate styginid lineages. The type species of Altaepeltis Maksimova, 1968 is established as Weberopeltis bublitchenkoi Maksimova, 1960, by monotypy.