A new acanthodian from the Pennsylvanian of Utah, U.S.A., and the distribution of otoliths in gnathostomes

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Abstract
A new acanthodiform acanthodian is described from the lowermost Pennsylvanian of Utah. The specimen is a primitive acanthodid, as is indicated by the posterior position of pelvic fin spine, and is named Utahacanthus guntheri, gen. et sp. nov. It is characterized by opposing dorsal and anal fin spines, relatively shorter pelvic and dorsal fin spines compared to other Acanthodidae, and strongly developed gill rays. Utahacanthus, in common with some other acanthodians, possessed three otoliths. A comparative analysis of gnathostome otoliths results in the postulation of aragonite as the basic mineral of otoliths for all gnathostomes, and of three otoliths as a feature common to all teleostomes including acanthodians. Many parallel characters apparently occur involving the mineral composition of statoconia and otoliths. The number of otoliths is reduced within osteichthyans from three (actinopterygians) to two (dipnoans) to one (actinistians), and finally to statoconia (reversal in tetrapods).

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