Mark Wilson January 16th, 2015
Why another one of those strange twisty gastropods from the Pliocene of Cyprus for our Fossil of the Week? Because this one fooled me for years. Above is a pair of images of a specimen of the vermetid gastropod Petaloconchus intortus (Lamarck, 1818) from the Nicosia Formation (Pliocene) of central Cyprus. It is encrusting a branch of the coral Cladocora. Ever since 1996 I’ve cataloged this and other such Cypriot specimens as serpulids, a type of polychaete worm that constructs adherent calcareous tubes like these. In fact, I placed on Wikipedia an image of the specimen below as a serpulid example.
Last week an anonymous editor on Wikipedia changed the caption on my image from “serpulid worm tube” to “Petaloconchus“. I did some research and yes, he or she was correct. I’ve since remade the image and updated all the Wikipedia pages where it appeared. This is not the first time I’ve posted a fossil image online and been corrected, and I hope it’s not the last. Such feedback and criticism is a major advantage of online science, and I learn a great deal.
In my research on Petaloconchus, I found a delightful Journal of Paleontology paper by Stephen Jay Gould in which he defines a new subspecies of Petaloconchus sculpturatus and discusses the genus and its evolution in classic Gouldian ways (Gould, 1994). He, for example, found this quote by Myra Keen (1961, p. 183):
The Vermetidae (worm gastropods) probably hold a record among molluscs for the degree of confusion they have promoted, both in collections, and in the literature; for they have been misconstrued at every level from subspecies to phylum.
I’m happy to see I’m not the only one who has had trouble with vermetid gastropods. Even in Gould’s (1994, p. 1035) taxonomy of his new subspecies we see some of the issues with Petaloconchus:
Etymology.–alaminatus to recognize key feature of the absent internal laminae. The Linnean name is a paradox, as Petaloconchus means laminate shell (the supposed, but inadequate, definition of the genus), while the subspecific name alaminatus negates this characteristic feature. But who ever denied either nature’s complexity or evolution’s capacity to eliminate structures?
Petaloconchus was named in 1843 by Henry Charles Lea (1825-1909), an American historian and political activist — an unexpected description of someone who named a snail. Lea came from a family deeply embedded in early American politics, and his father, Isaac Lea (1792-1886) was a prominent naturalist. Henry was clearly a prodigy in many endeavors. Note that his paper describing Petaloconchus and other fossils was completed when he was just 18 years old. In 1847, as a young man of 22, he suffered a mysterious nervous breakdown. During his long convalescence he read French medieval history, which turned his interests to the humanities. He eventually became a renowned historian of the Spanish Inquisition. (No one expects the Spanish Inquisition.)
Original image of Petaloconchus sculpturatus by Lea (1843).
Above are some real serpulid worm tubes from the Pliocene of Cyprus, although I’m open to corrections!
Aguirre, J., Belaústegui, Z., Domènech, R., de Gibert, J.M., and Martinell, J. 2014. Snapshot of a lower Pliocene Dendropoma reef from Sant Onofre (Baix Ebre Basin, Tarragona, NE Spain). Palaeogeography, Palaeoclimatology, Palaeoecology 395: 9-20.
Bradley, E.S. 1931. Henry Charles Lea. A Biography. Philadelphia, University of Pennsylvania Press, 418 pages.
Carpenter P. 1857. First steps toward a monograph of the recent species of Petaloconchus, a genus of Vermetidae. Proceedings of the Zoological Society of London 24: 313-317.
Gould, S.J. 1994. Petaloconchus sculpturatus alaminatus, a new Pliocene subspecies of vermetid gastropods lacking its defining generic character, with comments on vermetid systematics in general. Journal of Paleontology 68: 1025-1036.
Keen, A.M. 1961. A proposed reclassification of the gastropod family Vermetidae. Bulletin of the British Museum (Natural History), Zoology, 7:183-213.
Lea, H.C. 1843. Descriptions of some new fossil shells, from the Tertiary of Petersburg, Virginia. Transactions of the American Philosophical Society 9: 229-274. [The volume was actually published in 1846.]