TERMINAL EARLY CAMBRIAN EXTINCTION OF THE OLENELLINA - DOCUMENTATION FROM THE PIOCHE FORMATION, NEVADA

The extinction of the Olenellina on Laurentia can be located within ce ntimeters in the C-shale or uppermost Combined Metals Limestone member s of the Pioche Formation in eastern Nevada. Olenellid species diversi ty beneath the extinction boundary is not diminished. One of the riche st Laurentian intervals for articulated olenellids is in the 50 centim eters of shale immediately below the extinction boundary at Ruin Wash. Additional morphological information about some of the species comes from a silicified fauna 1.8 m below the extinction boundary at Hidden Valley. The olenellid fauna from the 2-meter interval below the extinc tion boundary is described. Questions about current generic and subgen eric relationships are discussed. Among general observations, intraspe cific variability unrelated to size or taphonomic effects is minimal f or most species; at least two species may have been capable of enrollm ent; and visual surfaces of one species show no evidence of facets. Ne w species include: Olenellus (Olenellus?) fowleri, Olenellus (Paedeumi as) chiefensis, Olenellus (Paedeumias) terminatus, Bolbolenellus brevi spinus, and Nephrolenellus geniculatus. Olenellus (Olenellus) gilberti Meek and Olenellus (Olenellus) howelli Meek are revised.