Bilateralsuodatus

Bilateralsuodatus is a genus of extinct trilobite arthropods that lived during the Upper Ordovician period, approximately 450 million years ago. Fossils attributed to this genus have been reported from the Appalachian Basin of North America and the Carpathian region of Eastern Europe, indicating a wide geographic range during the late Ordovician. Bilateralsuodatus is classified within the family Olenellidae, order Redlichiida, a group characterized by a large glabella and a relatively primitive morphology.

The generic name derives from Latin bilateralis, meaning “two‑sided”, and sudatus, meaning “furrowed” or “swollen”, referencing the distinctive bilateral furrow pattern on the cephalic border of the exoskeleton. The type species, Bilateralsuodatus sinuosa, was first described by A. K. Nielsen in 1984 on the basis of specimens collected from the Coosawhatchie Formation in South Carolina. Additional species have since been identified from strata in Switzerland and Poland.

Morphologically, Bilateralsuodatus trilobites possess a broad cephalon with two prominent longitudinal furrows extending from the anterior to the posterior margin. The glabella is comparatively low, and the eyes, if present, are reduced. The pygidium is small and lacks spines, corroborating a planktonic or nektonic lifestyle rather than a strictly benthic mode of life. The rostral spines, when present, point forward.

Biostratigraphically, Bilateralsuodatus is valuable because its species exhibit rapid evolutionary turnover and a well‑defined stratigraphic range, allowing geologists to correlate late Ordovician strata across disparate regions. The genus is often cited in studies of the Great Ordovician Biodiversification Event, serving as an index fossil for marine transgressive sequences.