A new cyathaspid (Agnatha, Heterostraci) with an articulated oral cover from the Late Silurian of the Canadian Arctic

ABSTRACT

A new genus and species of cyathaspid heterostracan, Capitaspis giblingi, gen. et sp. nov., is described from the Late Silurian (Pridolian) Upper Member of the Somerset Island Formation, Northwest Territories, Canada. The new species is most closely related to Pionaspis in the subfamily Cyathaspidinae, family Cyathaspididae, showing similarity in the presence of distinct central, anterior, and lateral epitega and in overall size and proportions, but differing in details of the ridge pattern. The unique specimen of the new taxon has an articulated oral cover that consists of a series of postoral and oral plates. Because the oral cover is almost unknown for cyathaspids, this specimen increases our knowledge of the range of oral structures in this family beyond the simple structures known for Poraspis and Anglaspis.

ACKNOWLEDGMENTS

Field work support from an NERC grant and assistance and logistic aid at Resolute, Cornwallis Island, from the Polar Continental Research Project are gratefully acknowledged. My thanks go to M. Gibling who provided invaluable help in the field, K. Soehn for helpful comments, and E. Mark-Kurik and A. Blieck who provided insightful and useful reviews. J. Wittke carried out the SEM imaging.

Handling editor: Martha Richter