A new species of Waengsjoeaspis (Cephalaspidomorpha, Osteostraci) from the Early Devonian of northwestern Canada, with a redescription of W. nahanniensis and implications for growth, variation, morphology, and phylogeny

ABSTRACT

The Lower Devonian (Lochkovian) Man On The Hill (MOTH) Lagerstätte preserves a large diversity of early vertebrates fossils, including several species of osteostracan. Waengsjoeaspis nahanniensis had previously been named on the basis of material from MOTH and is redescribed herein. The genus Waengsjoeaspis Janvier was originally established in 1985 for two species from Spitsbergen. In addition, the new species Waengsjoeaspis platycornis is recognized. Both species from MOTH lack barbs on their cornual processes. The new species differs from W. nahanniensis in proportions of the cornual processes and of the median field. New specimens from MOTH clarify the condition of the infraorbital sensory line, the mouth, and other morphological features within the genus, and confirm that the dermoskeleton grew like that of Superciliaspis by separate ossification of tesserae, fusion of tesserae to form larger units, and centrifugal growth of these units. The new observations are consistent with the earlier phylogenetic placement of Waengsjoeaspis within a clade basal to the Benneviaspidida and add to the considerable diversity of osteostracans at this important locality.

ACKNOWLEDGMENTS

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 and 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, along with D. Elliott and R. Sansom for their helpful reviews of an earlier version of the manuscript. This research was supported by NSERC Discovery Grant A9180 to M.V.H.W.

Handling editor: Martha Richter