The Superciliaspididae, a new family of Early Devonian Osteostraci (jawless vertebrates) from northern Canada, with two new genera and three new species

Abstract

Three new species in two new genera of cornuate Osteostraci are described here based on specimens from the Early Devonian (Lochkovian) Man on the Hill (MOTH) locality in the Mackenzie Mountains, Northwest Territories, Canada. The new taxa share several characteristics with Superciliaspis gabrielsei. Glabrapelta gen. nov., and its two species, G. cristata sp. nov. and G. minima sp. nov., are based on four previously undescribed specimens. Dentapelta loefflerae gen. et sp. nov. is based on one newly recovered specimen, along with another specimen originally referred by earlier workers to ‘Cephalaspidinae indet.’ Together with Superciliaspis, these new genera are subjected to a phylogenetic analysis, building on earlier work by R. Sansom. The results indicate that all four species in three genera belong to a single clade that is here named as the new family Superciliaspididae. The Superciliaspididae are characterized by a long, narrow median field with a border of raised ridges of fused plates, by narrow and posteriorly pointing cornua, and by orbits close together. A laterally expanded pineal opening and raised orbital rims place the Superciliaspididae as sister to the clade Scolenaspididae + Zenaspididae in the Order Zenaspidida. Internal anatomy of the nasohypophysial opening confirms separate internal nasal and hypophysial ducts. To date, the Superciliaspididae have been found only at the MOTH locality in the Mackenzie Mountains of northern Canada, whereas related taxa are distributed more widely in North America, Spitsbergen and Europe.

http://zoobank.org/urn:lsid:zoobank.org:pub:F69DDE22-311A-4F2A-9B5D-8E59D13341E2

Keywords:

• Osteostraci
• cephalaspids
• MOTH
• agnathans
• Superciliaspis
• Devonian

Acknowledgements

For excellent collection and preparation of specimens we thank L. A. Lindoe. We also thank Z. Johanson of the Natural History Museum, London, E. J. Loeffler of the University of Bristol, and M. Currie of the Canadian Museum of Nature for access to specimens and information. We thank A. M. Murray of the University of Alberta for comments and discussion, and the reviewers of the manuscript for their helpful suggestions. This research was supported by NSERC Discovery Grant [A9180] to MVHW.