Partial articulated specimen of the Early Devonian putative chondrichthyanPolymerolepis whiteiKaratajūtė-Talimaa, 1968, with an anal fin spine

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ABSTRACT Polymerolepis whitei Karatajūtė-Talimaa, 1968 was described based on isolated polyodontode scales recovered from the Ukraine, and originally was thought to be heterostracan (Agnatha). Additional scales with neck canals were described years later, and as a result, P. whitei was reclassified as a bradyodont holocephalan because it had scales similar to those of Listracanthus Newberry & Worthen, 1870. Until now, no articulated body fossils were known, and so the classification of this taxon has remained uncertain and based only on the original authors opinion. New specimens of P. whitei from the Mackenzie Mountains, Northwest Territories, Canada, show articulated scale patches from the head, with the best specimen showing part of an anal fin, caudal peduncle, and caudal fin. This new material confirms that the original account of scale variation was accurate, but also that P whitei possesses an anal fin spine, a feature that, until recently, was thought to be a synapomorphy of acanthodian fishes amo...