page_title: Olenellus
section_title: Description
hierarchical_section_title: Olenellus / Description
caption_attribution_description: English: An Olenellus nevadensis trilobite, Family Olenellidae, Order Redlichiida, 22mm measured along the axis, collected from the Latham Formation, near Cadiz, California, USA, from the end of the Lower Cambrian (Toyonian), genae and L4 damaged
context_page_description: Olenellus is an extinct genus of redlichiid trilobites, with species of average size. It lived during the Botomian and Toyonian stages, 522 to 510 million years ago, in what is currently North-America, part of the paleocontinent Laurentia.
context_section_description: As with most early trilobites, Olenellus has an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As part of the suborder Olenellina, Olenellus lacks dorsal sutures. Like all other members of the superfamily Olenelloide, the eye-ridges emerge from the back of the frontal lobe (L4) of the central area of the cephalon, that is called glabella. Olenellus also shares the typical character of whole family Olenellidae that the frontal (L3) and middle pair (L2) of lateral lobes of the glabella are partially merged. This creates two very typical, isolated slits. It can be distinguished from the other two genera in the family, Mesolenellus and Mesonacis, because the angle in the back rim of the cephalon is less than 15°, making the head approximately semi-circular. The genal spines are reaching back no further than the 6th thorax segment, making them 4-5 times as long as the most backward lobe of the glabella (occipital ring or L0)1. The thorax is 4-4½ times wider that the axis, measured at the 3rd segment. The base of the spine on the 15th thorax segment is almost as wide as the axis itself.
caption: Olenellus nevadensis
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