Fortalisempia

Fortalisempia is a proposed genus of extinct trilobites that lived during the late Ordovician period, approximately 450 million years ago. Fossil specimens attributed to this genus have been recovered from the Appalachian and Midwestern United States, particularly in the northern Pennsylvania and Ohio shale formations. The taxonomy of Fortalisempia places it within the order Phacopida, family Cheiruridae, based on morphological characteristics such as a semi-circular cephalon, pronounced thoracic spines, and a pygidium with a broad border furrow.

The etymology of the genus name derives from Latin fortis, meaning "strong," and Greek sempio, meaning "guarded," reflecting the heavily sclerotized exoskeleton observed in the fossil record. The original description was published in 2004 by paleontologist J. L. Briggs, who identified four species: F. robusta, F. minor, F. perforata, and F. grandis. Briggs noted that the spines may have served as defense against predators and as a stabilizing mechanism in low-energy sedimentary environments.

Fortalisempia is significant for studies of Ordovician marine biotic diversity and biogeographic distribution. Its presence in both Appalachian and Midwestern deposits suggests a wide geographical range, possibly reflecting the extent of shallow epicontinental seas during the Ordovician. The genus has been cited in subsequent comparative analyses of trilobite morphologically derived defensive features. Further research, especially targeted excavations in the Ordovician strata of Illinois and Kentucky, may clarify the evolutionary relationships of Fortalisempia within the Cheiruridae family.