Megistaspis

Megistaspis (Greek for "largest shield") is a genus of asaphid trilobites that lived throughout the Early and Middle Ordovician. Megistaspis was common throughout the Early and Middle Ordovician of Baltoscandia, but specimens have also been found in Australia, France, Germany, Morocco, and the United States. Appendages and a digestive system of M. hammondi have been preserved; it likely served as a mixed detritivore, producing Cruziana rugosa trace fossils. Meanwhile, Megistaspis hyorrhina may have burrowed below the sediment, using a swelling on the head to detect pressure changes. Megistaspis is also notable as it displays a large degree of morphological variation as a result of environmental conditions like ocean depth and substrate. The genus plays an important part in the biostratigraphy of Ordovician Baltoscandia, with several biozones being named after Megistaspis species.