AN UNUSUAL EOCENE VOLUTID GASTROPOD FROM PARIS BASIN, FRANCE

On a collecting trip in 1987 to Le Guépelle, in the Paris Basin of northern France, I found a nicely preserved specimen of a late middle Eocene (approximately 40 million-year old) shallow-marine gastropod. I did not realize until later, just how rare this specimen is. After spending considerable time and effort trying to identify it, my identification can only be tentative. This is because of the incompleteness of the data known about this species.

Athleta labrella? (Lamarck, 1802). Three views: front, right side (turned slightly), and back, respectively. Height 5 cm, width 4 cm. Specimen collected by R. Squires at the Le Guépelle quarry, Paris Basin, northern France.

My attempt to identify, with certainty, this fossil volutid took a lot twists and turns (which is not unusual in the world of paleontologic taxonomic research). I am aware that such details are not interesting to everyone. So, if you do not want to go down this “rabbit hole,” I understand. For those who are curious or somewhat curious, please continue to read the following text.

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After some searching, I finally found pictures that look just like “my” gastropod in the classic work by Cossmann and Pissarro (see images below). They identified this Paris Basin, France species as the volutid Athletla labralla (Lamarck, 1802). [Note: Some researchers reported that this work was published in 1803, even though the original paper by Lamarck can be found online, in a publication that was is dated as 1802].

Front and back views of a specimen of Athleta labralla found at Le Guépelle, northern France and figured by Cossmann and Pissarro (1910–1913, pl. 44, figs. 202-10 (two views).

I looked at Lamarck’s (1802, p. 479) original work. He referred to his species both as Voluta labrelle [in French] and as Voluta labrella [in Latin]. He had this species from Grignon in northern France [but not from Le Guépelle, where I and Cossmann and Pissarro found our specimens]. In the literature, the last letter of the word “labrelle” has been changed to read “labrella.” This is in keeping with the rule that the endings of Latinized species names have to agree with the gender of the genus name (e.g., the genus name Volta is feminine, thus the species name has to be spelled as labrella).

Lamarck’s description (in Latin) of his species is very short, but he did mention that the shell is carinate, which refers to the prominent shoulder on the last whorl. Although he provided drawings of his species, they were not available, until Palmer (1977, p. 33, figs. 15a, b) found his “lost figures” [which were referred to by Lamarck as “velins,”] and published them.

Voluta labrella from Palmer’s 1977 publication: p. 13, vélin 2, figs. 15a, b, of Lamarck’s drawings of his species 

When I saw Lamarck’s drawings of Voluta labrella (in Palmer’s publication, figs. 15a, b), I was quite surprised. As you can clearly see, the aperture of his specimen has a very pronounced indentation (“spout-like”) on the posterior corner of its outer lip side. I know of no other volutid, fossil nor modern, with such a similar feature. It seems very likely that Lamarck greatly enhanced this feature. Otherwise, his drawings are similar to the morphology of the specimens found by  Cossmann and Pissarro and by me. Until the actual specimen illustrated by Lamarck is found and photographed, I have to remain very skeptical that Lamarck’s species is the same as the one illustrated by me (in this post) and the species illustrated by by Cossman and Pissarro.

Note: Although Lamarck assigned his species to genus Voluta, this genus name has undergone considerable change in its meaning, with many new volutid genera having been added to cover the myriad of morphologic differences among these gastropods. Although the genus name Voluta is still valid today, it is now used in a greatly restricted manner than when early workers, like Lamarck, used it. In summary, Lamarck’s species does not belong in genus Voluta.

Based on the information available, I identify my specimen and the one that Cossmann and Pissarro figured, as being the same species, which is undoubtedly a volutid and most likely belongs to genus Athleta but questionably belongs to species labrella. 

Athleta is a very diverse genus and specimens are very common in middle Eocene rocks in northern France and southern England. Specimens typically have a very spinose spire and a spinose last-whorl shoulder (carina). Thus Lamarck’s labrella is quite atypical. The northern Europe Athleta athleta (shown below) looks most similar to Lamarack’s species, yet A. athleta is spiny. 

In closing, I am inclined to believe that labrella specimens could represent Athleta that lived in unusual (localized?) paleoenvironmental conditions. Also, photographic images and a more detailed description of labrella are sorely needed, including growth stages (juvenile vs. adult) information, in order to resolve the paleontologic status of Lamarck’s species.   

Front and back views of Athleta athleta (Solander), from Barton-on-Sea, Bartonian age, southern England. Specimen 4.3 cm high, 3 cm wide, found by John Quayle, 1986 and donated to the author. This species somewhat resembles Athleta labrella.

References Cited:

 

Squires, R.L. 1987. Eocene molluscan paleontology of the Whitaker Peak area, Los Angeles and Ventura Counties, California. Contributions in Science, no. 388, 93 pp.

Lamarck, J.B.P.A. de Monet. 1802. Mémoires sur Annales du Muséum National d’Histoire Naturelle. Tome Premier. Paris. 507 pp. 

Cossmann, M. and Pissarro, G. 1910-1913. Iconographie complete des coquilles fossiles de l’Eocene des environs de Paris. Vol. 2 (Gastropodes, etc.), 65 pls., Paris.

Palmer, V.W. 1977. The unpublished vélins of Lamarck (1802–1809). Illustrations of fossils of the Paris Basin Eocene. Paleontological Research Institution, New York. 67 pp., 52 pls.