A tale of two holotypes: Rediscovery of the type specimen of Edestus minor

Abstract

Edestus is a Carboniferous chondrichthyan genus known mainly from its triangular, serrated teeth. A maximum of around ten teeth are joined at their bases to form tooth whorls. Edestus minor Newberry, 1866, was described on the basis of a single, isolated tooth. A tooth whorl containing seven teeth, described and figured by Hitchcock in 1856, but not named by him, was later referred to E. minor by Newberry, who came to regard it as the holotype. However, the isolated tooth remains the holotype, since it is the sole specimen upon which the original description was based. The distinction is not trivial, because the crown of the holotype of E. minor differs from those present in Hitchcock's specimen. Edestus mirus Hay, 1912, was designated as a new species, based on differences from the Hitchcock specimen, although the crowns are not distinguishable from those of the holotype of E. minor. Thus, E. mirus is almost certainly a junior synonym of E. minor, while the Hitchcock specimen may require a new name. If so, it should probably be referred to Edestus minusculus Hay, 1910. Recently, the holotype of E. minor was located at the American Museum of Natural History, where it had not been recognized as a type specimen. Published documents as well as nineteenth- century museum labels provide some insight into this tangled nomenclatural history.