Agnostida

The Agnostida were a highly specialized order of trilobites, extinct marine arthropods. These small, blind creatures, typically only about 6 millimeters long, are characterized by having just two thoracic segments and a large tail segment. The anterior and posterior regions of their bodies were often so similar that distinguishing them was difficult.12

Agnostids are significant as fossils for correlating rock strata from the Early Cambrian to the Late Ordovician periods (approximately 540 to 438 million years ago). Unlike most other trilobites, which were endemic to specific regions, many agnostid species had wide intercontinental distributions, making them valuable for global biostratigraphic zonation, particularly in the upper half of the Cambrian System. Their specialized appendages suggest they may have been pelagic, living in the open sea rather than on the seafloor.13