Olenus (trilobite)

Olenus is a genus of Upper Cambrian ptychopariid trilobite.
Distribution.
"Olenus" can be found in the British Isles, India, Norway, Sweden, Denmark, Newfoundland, Texas, South Korea, and Australia.
Ecology.
Fossils of "Olenus" are commonly found in dark mudstones, which were deposited on the seafloor in environments with low oxygen levels. The very wide side lobes (or pleurae) are thought to have shielded extended gills, which would have helped the animal absorb the maximum amount of oxygen possible in such an environment. Evidence also suggests that "Olenus" and its relatives may have developed a symbiotic relationship with sulfate-reducing bacteria, either by feeding on them or by absorbing nutrients directly from them.
Description.
Size: Up to 1.5 in (4 cm) long. It had up to 15 thoracic segments, with a narrow axis and wide pleurae.