Type Crania of the Devonian Placoderm Macropetalichthys from North America: Resolving Key Nomenclatural and Stratigraphic Conundrums

Macropetalichthys rapheidolabis Norwood and Owen, 1846 (Placodermi: Petalichthyida), type species of Macropetalichthys Norwood and Owen, 1846, was based on a single cranial roof from the Devonian of southeastern Indiana. Poor preservation, and later destruction, of the holotype has complicated subsequent studies. J.S. Newberry (1873) redefined Macropetalichthys using remains from the Devonian of Ohio. A neotype for M. rapheidolabis, from the Delaware Limestone (Middle Devonian, Eifelian) of Columbus, Ohio, is designated from Newberry’s studied specimens. The genus Agassichthys Newberry, 1857 was erected to receive two species: A. sullivanti Newberry, 1857 and A. manni Newberry, 1857. Newberry (1889) designated a lectotype for A. sullivanti from the Columbus Limestone (Middle Devonian, Eifelian) of Columbus, Ohio; once thought lost, it has been rediscovered. Agassichthys sullivanti is designated as the type species of the genus. A lectotype for A. manni Newberry, 1857, is selected from among the syntypes collected from the Delaware Limestone (Middle Devonian, Eifelian) of Delaware, Ohio. Agassichthys is a junior subjective synonym of Macropetalichthys. With a neotype of M. rapheidolabis on which to directly base taxonomic comparisons, A. sullivanti and A. manni are considered junior subjective synonyms.