Pseudocryptic species of the Middle Cambrian trilobite Eodiscus Hartt, in Walcott, 1884, from Avalonian and Laurentian Newfoundland

Abstract

Two species of the Middle Cambrian trilobite Eodiscus Hartt, in Walcott, 1884, E. punctatus (Salter, 1864) and E. scanicus (Linnarsson, 1883), have been reported from several paleocontinents. However, in their respective type areas of Avalonian Britain and Baltica (Sweden), both species are poorly documented from moulds preserved in siliciclastic mudstone that are variably compacted and distorted. Moreover, variation in such characters as surface sculpture between putative occurrences suggests that widespread use of these names may mask species differentiation within and between paleocontinents. Detailed examination of Eodiscus sclerites that are exquisitely preserved in full relief in limestone from the Manuels River Formation of Avalonian Newfoundland and the Shallow Bay Formation of Laurentian Newfoundland demonstrates the presence of multiple species that are distinct from both E. punctatus and E. scanicus. We interpret them as a group of pseudocryptic species that are comparable to groups that are now identified routinely among modern invertebrates. New species are E. confossus, E. tuberculus, and E. coloholcus. At the current state of knowledge, E. punctatus and E. scanicus are best restricted to their respective types.