Early Devonian cephalaspids (Vertebrata: Osteostraci: Cornuata) from the southern MacKenzie Mountains, N.W.T., Canada

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Abstract
A diverse and well-preserved vertebrate fauna occurs in Early Devonian rocks of the Delorme Formation in the southern Mackenzie Mountains, Northwest Territories, Canada. The osteostracans of this fauna include the new cornuate species Waengsjoeaspis nahanniensis and Diademaspis? mackenziensis. Specimens of the latter species had been described in 1976 by Dineley and Loeffler as “Cephalaspis sp. indet.” The cornuate originally described as “?Cephalaspis gabrielsei” Dineley and Loeffler, 1976 is here assigned to the new genus Superciliaspis and more fully described. Other taxa include a possible example of Parameteoraspis sp. and several other indeterminate cornuates. Only dermal bone has been preserved, but preservation of its external and internal surfaces is excellent. Conspecific osteostracan specimens demonstrate a wide variety of overall proportions, due to differing amounts and directions of compaction. Some preferential orientation of corpses on bedding planes has been seen and several examples of both single-species and multiple-species mass-death aggregations occur.