Pontogeneus priscus Leidy, 1852

Martínez-Cáceres, Manuel, Lambert, Olivier & Muizon, Christian de, 2017, The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru, Geodiversitas 39 (1), pp. 7-163 : 13

Pontogeneus priscus Leidy, 1852

HOLOTYPE. — ANSP 13668 , isolated middle cervical centrum.

TYPE LOCALITY AND HORIZON. — The original description indicates that the holotype is “from the Eocene formation of Ouachita, Louisiana ” ( Leidy 1852: 52). Recently, Uhen (2005) pointed out the possibility that it comes from the vicinity of the Caldwell Parish, Louisiana, where the upper Eocene Jackson Group (Eargle 1959) is exposed.

DISCUSSION

Leidy (1852) created the taxon Pontogeneus priscus based on an isolated cervical vertebra ( Fig. 4 ), figured by Kellogg (1936) and interpreted as a fifth cervical. Uhen (2005) recognized it as a more anterior cervical (C3 or C4) and considered both genus and species as nomina nuda because the original description was not diagnostic and the vertebra could belong to a small specimen of Basilosaurus (indeed, the centrum is quite similar in size to that of UM-WH74, a small Basilosaurus isis ). However, it can be evaluated that the vertebarterial foramina in the holotype of P. priscus are proportionally larger than in Basilosaurus ( Fig. 4 ). Such a feature is diagnostic for the genus Cynthiacetus (Martínez-Cáceres & Muizon 2011) . Because of this character Pontogeneus priscus could have closer affinities with Cynthiacetus than with Basilosaurus (as proposed by Gingerich 2015). However, such a holotype (the centrum of an isolated cervical vertebra) is not regarded as diagnostic enough to characterize a basilosaurid taxon and it is suggested here that the binome Pontogeneus priscus should only refer to the cervical vertebra described by Leidy (1852). Therefore, the genus name and the species name should be regarded as a Basilosauridae or a Pelagiceti incertae sedis and restricted to the type specimen of P. priscus .

Figures

FIG. 4. — Comparison of the middle cervical vertebrae in large basilosaurids: A, MMNS VP455, third cervical vertebra of Cynthiacetus maxwelli; B, UM-WH74, third cervical vertebra of Basilosaurus isis; C, ANSP 13668, holotype of Pontogeneus priscus, probably a C3 or C4 (from Kellogg 1936); D, MffNB uncatalogued, third cervical vertebra of Cynthiacetus sp. (referred to Zeuglodon brachyspondylus by Dames [1894]). Note the large vertebrarterial foramina in C. maxwelli and P. priscus as compared to B. isis.