Happy Fossil Friday!
Today we’re looking at Agorophius pygmaeus, one of the first named odontocetes from North America. Agorophius has a long, complicated history – and it starts right here, in Charleston!
Agorophius pygmaeus was discovered in the 1840’s at Middleton Place, a plantation in West Ashley. It was found in the Ashley Limestone, and was originally named Zeuglodon pygmaeus, from a partial braincase and single tooth.
It was heavily studied throughout the 19th century, but the holotype specimen was lost sometime before 1907 when Frederick True attempted to locate it. However, some 140 years later, Ewan Fordyce re-discovered the tooth of the holotype specimen in the collections of the Harvard Museum of Comparative Zoology in 1980, and was able to match it to the illustrations from the original publication. However, the partial skull has never been found again.
This missing holotype has wreaked havoc in odontocete taxonomy; Agorophius exhibited many uniquely transitional features and many authors have discussed the “Agorophiidae;” for a long time, Agorophius was one of the only early odontocetes known. The loss of the holotype caused “taxonomic paralysis” – naming of new genus and species was on hold as new specimens couldn’t be compared to the original, else risk bloat and naming new species when they were actually just new specimens of an already named genus or species.
A new paper recently published by Stephen Godfrey et al. (2016) refers two new skulls to Agorophius pygmaeus, one from the Chandler Bridge Formation (23-24 Ma) and another from the older Ashley Formation (~26-29 Ma); both of these specimens include basicrania and earbones, and are somewhat more complete than the lost holotype.
However, neither specimen has teeth, and the only surviving part of the type specimen is a tooth – this means that the identification is based on the original illustrations; various authors have debated whether or not this is kosher. Ultimately, illustrations of Agorophius are extremely detailed and better than many photographs of fossil cetaceans in papers published in the last few decades, and as such are accepted as a means for identification.
This recent paper is a significant leap forward in the study of early odontocetes; CCNHM also has material that is referable to Agorophius or even Agorophius pygmaeus, and gives CCNHM researchers & affiliates a “green light” toward studying our own Agorophius and dwarf agorophiid specimens.
Stephen J. Godfrey, Mark D. Uhen, Jason E. Osborne and Lucy E. Edwards (2016). A new specimen of Agorophius pygmaeus
(Agorophiidae, Odontoceti, Cetacea) from the early Oligocene Ashley Formation of South Carolina, USA. Journal of
Paleontology, 90, pp 154-169 doi:10.1017/jpa.2016.4 [Link]
Fordyce, R. E., 1981, Systematics of the odontocete whale Agorophius
pygmaeus and the Family Agorophiidae (Mammalia: Cetacea): Journal of
Paleontology, v. 55, no. 5, p. 1028–1045. [Link]