A photo of a yellow anaconda in its natural habitat, by Walter S. Prado (Wikimedia Commons, CC0 1.0).
Constantine Rafinesque was an infamously eccentric naturalist and one of the most prolific taxonomists of all time, having named thousands of plant and animal taxa. He was also an early cryptozoologist, publishing the first ever attempt at a scientific classification of sea serpents in 1817 (Rafinesque, 1817). This article also contains descriptions of more mundane sea snakes, with one species in particular standing out. Rafinesque named it Pelamis1 curis and it was not actually found in the ocean. Instead, it hailed from the jungles of Paraguay and was originally reported as the “curiyú” by explorer Félix de Azara (Azara, 1809).
“Pelamis curis. (Curiyu. Azara trav. Vol. I. p. 226.) Spotted and variegated, of black and yellowish white. It measures over 10 feet, and is of the size of the leg; it lives in the lakes and rivers of Paraguay, north of the 31st degree of latitude. It goes sometimes on land (and shrubs), but moves heavily thereon; it has a dreadful aspect, but does not bite; it lives on fishes, young otters, apereas and copibaras.”
It is clear that it was not a sea snake and thus not a true species of Pelamis/Hydrophis. Instead, the coloration, size, location, and diet all match the yellow anaconda (Waller et al., 2007). “P.” curis meets the requirements of Article 12 of the Code (names before 1931; ICZN, 1999), so it is the oldest available name for the yellow anaconda. The next oldest and currently used name is Eunectes notaeus, which was coined by Edward Drinker Cope 45 years later (Cope, 1862). However, “P.” curis was never used as a valid name after 1899, so it is a nomen oblitum according to Article 23.9 of the Code. As a result, E. notaeus remains the correct name for the yellow anaconda.
Notes
1The genus Pelamis is now considered a junior synonym of Hydrophis (Sanders et al., 2013).
References
- Azara, F., de. (1809). Voyages dans l’Amérique méridionale. Tome premier. Dentu.
- Cope, E.D. (1862). Synopsis of the species of Holcosus and Ameiva, with diagnoses of new West Indian and South American Colubridae. Proceedings of the Academy of Natural Sciences of Philadelphia, 14, 60–82.
- ICZN. (1999). International code of zoological nomenclature (4th ed.). The International Trust for Zoological Nomenclature; The Natural History Museum, London.
- Rafinesque, C.S. (1817). Dissertation on water snakes, sea snakes and sea serpents. The American Monthly Magazine and Critical Review, 1(6), 431–435.
- Sanders, K.L., Lee, M.S.Y., Mumpuni, Bertozzi, T., & Rasmussen, A.R. (2013). Multilocus phylogeny and recent rapid radiation of the viviparous sea snakes (Elapidae: Hydrophiinae). Molecular Phylogenetics and Evolution, 66(3), 575-591. https://doi.org/10.1016/j.ympev.2012.09.021
- Waller, T., Micucci, P.A., & Alvarenga, E. (2007). Conservation biology of the yellow anaconda (Eunectes notaeus) in northeastern Argentina. In R.W. Henderson & R. Powell (Eds.), Biology of the boas and pythons (pp. 340-362). Eagle Mountain Publishing.
Incertae Sedis 
