Rediscovery of the Type Specimens of the Sarcopterygian Fishes <i>Onychodus sigmoides</i> and <i>Onychodus hopkinsi</i> from the Devonian of Ohio, USA
Loren E. Babcock
John Strong Newberry described three species of the lobe-fin fish <i>Onychodus</i> (Osteichthyes, Sarcopterygii, Onychodontida) based on parasymphysial teeth, or tusks. Two species, <i>Onychodus sigmoides</i> Newberry, 1857 (type species of the genus) and <i>Onychodus hopkinsi</i> Newberry, 1857, were described from the “fish beds” in the Delaware Limestone (Middle Devonian, Eifelian) of Delaware, Ohio, USA; and one species, <i>Onychodus ortoni</i> Newberry, 1889, was described from the Ohio Shale, Huron Member (Upper Devonian, Famennian) of Perry Township, Franklin County, Ohio. In 1873, Newberry replaced the original species-group definition of <i>O. hopkinsi</i> with a definition based on teeth of different morphology from the West Falls Group (Upper Devonian, Frasnian) of Franklin, New York. Specimens of Newberry’s original <i>Onychodus</i> material, including the primary types, which were long assumed to be lost, have been rediscovered in a 19th-century collection. They show <i>O. hopkinsi</i> to be a junior synonym of <i>O. sigmoides</i> and clarify the species definition of <i>O. sigmoides</i>. <i>Onychodus sigmoides</i>, which is recognized from Middle Devonian strata of the Appalachian Basin in the United States and Canada, shows two end-member shapes of teeth on the parasymphysial whorl: procurved (arcuate) or nearly so proximally and recurved distally (anteriorly). Small teeth are commonly more slender than large teeth, which are robust. Parasymphysial teeth from the Upper Devonian of Ohio and New York are referred to <i>O. ortoni</i>.
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