Abstract

Despite being reported widely from basal Sunwaptan strata, Dellea? punctataPalmer, 1965, is known from only four figured cranidia. New material from Nevada, Utah and Oklahoma, including librigenae and pygidia, indicate that specimens assigned previously to D.? punctata are best interpreted as a complex of related species that are assigned to a new genus, Bartonaspis. This genus is diagnosed by punctate sculpture, a pair of fossulae at the anterior corners of the glabella, and by a subelliptical pygidium with a short convex axis composed of three segments. Three new species, B.fredericksoni, B.palmeri, and B. wilsoni, are described and B. punctata (Palmer) is restricted to its holotype. Bartonaspis is known only from the Irvingella major Zone, and its first appearance defines the base of the Sunwaptan Stage. DelleaWilson, 1949, is related to Bartonaspis and is differentiated from it primarily by pygidial morphology. In contrast to Bartonaspis, the pygidium of Dellea has an axis composed of four, rather than three, segments and a narrow concave border.

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