NINADIACRODIUM: A NEW LATE CAMBRIAN ACRITARCH GENUS AND INDEX FOSSIL.

The acritarch Ninadiacrodium gen. nov. is erected to include forms with a basically triangular outline,but with a clearly bipolar arrangement of processes. It belongs to the 'diacrodian' dade; these are morphotypes with ornament and/or processes at the two opposite poles of the central body. They were extremely abundant and highly diverse during the Late Cambrian and Early Ordovician. The new genus includes the two widely-cited species Ninadiacrodium caudatum (Vanguestaine 1973) comb. nov. and Ninadiacrodium dumontii (Vanguestaine 1973) comb. nov. Both taxa are emended here. Ninadiacrodium is easily recognizable due to its elongate triangular shape, but is clearly differentiated from Veryhachium Deunff 1954, which appears in the Ordovician. Ninadiacrodium is apparently confined to the Late Cambrian, and has a global distribution. It is therefore an index fossil for the Late Cambrian. [ABSTRACT FROM AUTHOR]