Agnostid trilobites are tiny compared to their better known and larger relatives from the Paleozoic seas. Agnostids survived for almost exactly one hundred million years, living from the Early Cambrian (beginning 542 million years ago) to the late Ordovician Period (which ended 443 million years ago). Largely due to their diminutive size, agnostid trilobites have defied attempts to properly interpret their affinities, environmental preferences, behavior, and feeding strategies (McMenamin 2010).