Olenellus
Olenellus is an extinct genus of redlichiid trilobites, with species of average size (about 5 centimetres or 2.0 inches long). It lived during the Botomian and Toyonian stages (Olenellus-zone), 522 to 510 million years ago, in what is currently North-America, part of the palaeocontinent Laurentia.[4]
Olenellus means small Olenus, after a genus belonging to the Ptychopariida, to which the type species O. thompsoni was originally assigned. The name Olenus refers to a mythological figure who was turned to stone by the gods. The names of the species have the following derivations.
Olenellus is the only genus currently recognised in the subfamily Olenellinae. The sister group called the Mesonacinae consists of the genera Mesonacis and Mesolenellus.[1]
"Paedeumias" was previously regarded as a genus related to Olenellus[5] or a subgenus being part of Olenellus.[6] Recent analysis shows that there is a group of species formerly assigned to Olenellus (Paedeumias) nested within Olenellus (O. clarki, O. nevadensis, O. parvofrontatus, O. roddyi and O. transitans). However, this group is more closely related to the majority of the remainder of Olenellus species than to O. agellus and O. romensis. This implies that either two new monophyletic subgenera need to be erected, or Olenellus (Paedeumias) and Olenellus (Olenellus) need to be dropped as subgenera, the latter being proposed by Lieberman.[1]
O. thompsoni is found in the middle Upper Olenellus-zone of Vermont (Franklin County, Parker Slate, Georgia).[6]
O. chiefensis has been collected from the final layer of the Upper Olenellus-zone of Nevada (Pioche Formation).[3]
