Early Middle Cambrian<i>Albertella</i>Biozone trilobites of the Pioche Shale, southeastern Nevada

Abstract

Thirty-four species of trilobites belonging to 21 genera are recognized in the Albertella Biozone within the Grassy Spring Member (new name) of the Pioche Shale of southeastern Nevada. Genera include Pagetia, Poliella, Kootenia, Olenoides, Albertella, Albertellina, Albertelloides, Delamarella, Mexicaspis, Paralbertella, Ptarmiganoides, Ursinella, Zacanthoides ?, Amecephalites, Mexicella, Nyella, Onchocephalites ?, Pachyaspis, Panacus, Plagiura , and Volocephalina. Two new corynexochid genera and species, Delamarella brevispinaspis and Ursinella major , are described. The existing corynexochid genus Albertella is revised to include two new species, A. fritzi and A. highlandensis. A new species, Albertelloides kitai , is described. Two new ptychopariid genera, Amecephalites and Panacus , plus four new ptychopariid species, Amecephalites sundbergi, Mexicella granulata, Panacus palmeri , and Volocephalina variosa , are described and Nyella immoderata Palmer is revised. In addition, the Albertella Biozone is divided into three new subbiozones, the lower Albertellina aspinosa Subbiozone, the middle unnamed subbiozone, and the Albertella highlandensis Subbiozone.