Abstract
ABSTRACT A new weigeltaspid heterostracan, Orthogoniaspis amnicus nov. sp. represents the first weigeltaspid reported from the Early Devonian Peel Sound and Snowblind Bay formations, Nunavut, Canadian Arctic. One partially articulated specimen shows for the first time that while the main plates of the dorsal shield abutted each other the orbital, pineal and rostral plates were separated by bands of tesserae. The similarity of this arrangement to that of the corvaspids, particularly the presence of dorsal lateral plates and bands of tesserae separating the anterior plates suggests a sister-group relationship, as no other heterostracans share this arrangement. Arctic weigeltaspids range from the late Ludlow to the late Lochkovian (O. amnicus nov. sp.), which is earlier than the related European taxa suggesting an Arctic centre of development for the weigeltaspids, as has been suggested for other heterostracan taxa.
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