Comparison between a syntype tooth (A) and referred tooth (B) of Parotodus oligocaenus. Both are in labial view and are not to scale.
The hooked megatooth1, genus Parotodus Cappetta, 1980, currently contains three species: the early Eocene P. pavlovi (Menner, 1928), middle-late Eocene P. mangyshlakensis Kozlov in Zhelezko & Kozlov, 1999, and Miocene-Pliocene P. benedenii (Le Hon, 1871). A fourth species from the Oligocene, transitional between P. mangyshlakensis and P. benedenii, was identified by Ward et al. (2017). Ward et al. planned to name it as a new species, with a tooth from the Karatsu Formation of Japan as the intended holotype. They also referred teeth from the Boom Clay Formation of Belgium described by Leriche (1910) to this species. They refrained from naming it in their conference poster, a form of publication excluded by the Code (Article 9.10; ICZN, 1999), to avoid creating an unavailable name. To date, the formal description of this species by Ward et al. has not been published. This is fortuitous as there is an earlier available name that was overlooked.
van de Geyn (1937, p. 313) named the ‘premutation’ Isurus benedenii praemut. oligocaena for the teeth described by Leriche.
“Isurus benedeni [sic] praemut. oligocaena nov. praemut. mit als Typus die Art des belgischen Rupeliens (Leriche 1910)”
“Isurus benedeni [sic] praemut. oligocaena nov. praemut. with the type of the species from the Rupelian of Belgium (Leriche 1910)”
Although only mentioned once, it meets the requirements of the Code to be an available name. The explicit reference to Leriche’s prior work fulfills Article 13.1.2. The term premutation is not recognized in the Code. Since the name was a trinomen, was not stated to be infrasubspecific, and did not use a term like ‘aberration’ or ‘form’, it is to be regarded as a subspecies according to Article 45.6. van de Geyn did not designate a holotype, so all 15 teeth figured by Leriche (1910, pl. 16, figs. 1–15) are the syntypes following Article 73.2. Thus, Parotodus oligocaenus (van de Geyn, 1937) comb. nov. is the correct name for the Oligocene species of the hooked megatooth. To conform to Article 31.2, the original, feminine oligocaena is emended to the masculine oligocaenus to match the masculine –odus ending.
Notes
1Parotodus is often called the ‘false mako’ or ‘false-toothed mako’, but ‘hooked megatooth’ is proposed here as a more accurate common name. This acknowledges both its robust, curved teeth and its placement in Otodontidae.
References
- Cappetta, H. (1980). Modification du statut générique de quelques espèces de sélaciens crétacés et tertiaires. Palaeovertebrata, 10(1), 29-42.
- ICZN. (1999). International code of zoological nomenclature (4th ed.). International Trust for Zoological Nomenclature; Natural History Museum, London.
- Le Hon, H. (1871). Préliminaires d’un mémoire sur les poissons tertiaires de Belgique. Muquardt.
- Leriche, M. (1910). Les poissons tertiaires de la Belgique. III. Les poissons oligocènes. Mémoires du Musée royal d’Histoire naturelle de Belgique, 5, 229-363.
- Menner, V.V. (1928). Selyakhii paleogena Mangyshlaka, Emby i Vostochnogo Urala [Paleogene Selachii of Mangyshlak, Emba and eastern Urals]. Byulleten’ Moskovskogo Obshchestva Ispytateley Prirody, Otdel Geologicheskiy, 6(3-4), 292-338.
- van de Geyn, W.A.E. (1937). Das Tertiär der Niederlände mit besonderer Berücksichtigung der Selachierfauna. Leidse Geologische Mededelingen, 9(1), 177-361.
- Ward, D.J., Nakatani, D., & Bernard, E.L. (2017, December 17–19). A new species of Parotodus (Lamniformes: Otodontidae) from the Oligocene of Japan [Poster presentation]. 61st Annual Meeting of the Palaeontological Association, London, UK. https://doi.org/10.13140/RG.2.2.33171.58404
- Zhelezko, V.I., & Kozlov, V.A. (1999). Elasmobrankhii i biostratigrafiya paleogena Zaural’ya i Sredney Azii [Elasmobranchii and Palaeogene biostratigraphy of Trans Urals and Central Asia]. Russian Academy of Sciences, Urals Branch.
Incertae Sedis 