Early Cambrian Trilobites from the Shackleton Limestone of the Central Transantarctic Mountains

Abstract

We document and describe the trilobite faunas of the Lower Cambrian Shackleton Limestone. The faunas include taxa of Atdabanian, Botomian and possible Toyonian ages and have affinities with those known previously from Gondwana or peri-Gondwana terranes. The geographic distribution of these organisms reveals a large measure of faunal connectedness around the margin of this vast supercontinent in Early Cambrian time. This connectedness extended even to taxa that inhabited shallow-water carbonate shelf environments, because the Shackleton Limestone accumulated in a variety of shallow subtidal and peritidal settings along the ocean-facing margin of the East Antarctic craton, subsequent to a Neoproterozoic rifting event. Although the fossilized Shackleton Limestone fauna is dominated by archaeocyathans, trilobites are common locally. We describe the remains of 35 trilobite taxa from 32 collecting localities. One species, H. granulosa , is assigned to the new genus Holyoakia; the remaining new species are Pagetides (Discomesites) spinosus, Lemdadella antarcticae, Kingaspis (?) convexus, Yunnanocephalus longioccipitalis , and Onchocephalina (?) spinosa.