EARLY CAMBRIAN TRILOBITES FROM THE SHACKLETON LIMESTONE OF THE CENTRAL TRANSANTARCTIC MOUNTAINS

We document and describe the trilobite faunas of the Lower Cambrian Sh ackleton Limestone. The faunas include taxa of Atdabanian, Botomian an d possible Toyonian ages and have affinities with those known previous ly from Gondwana or peri-Gondwana terranes. The geographic distributio n of these organisms reveals a large measure of faunal connectedness a round the margin of this vast supercontinent in Early Cambrian time. T his connectedness extended even to taxa that inhabited shallow-water c arbonate shelf environments, because the Shackleton Limestone accumula ted in a variety of shallow subtidal and peritidal settings along the ocean-facing margin of the East Antarctic craton, subsequent to a Neop roterozoic 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 local ities. One species, H. granulosa, is assigned to the new genus Holyoak ia; the remaining new species are Pagetides (Discomesites) spinosus, L emdadella antarcticae, Kingaspis (?) convexus, Yuananocephalus longioc cipitalis, and Onchocephalina (?) spinosa.