Busycon Taxonomic Travail
Note: Whelk DNA sequencing since this article was published suggests that all living sinistral whelks of the western Atlantic are conspecific [of the same species], Busycon perversum (Linnaeus, 1758) being the oldest available nomen.
| For many amateur conchologists,
the hobby of shell collecting includes personally collecting a
specimen and then assigning its proper Latin name through the use
of one or more of the so-called "popular shell books"
such as Abbott and Dance's 1986 Compendium Of Shells
- trusting the knowledge and judgment of the book's author(s).
However, even to an amateur, occasionally something just doesn't look right, and a little research can be eye-opening and lead to brief look into the tangled web of taxonomy. Such was the case with the left-handed whelk called by some Busycon perversum pulleyi Hollister, 1958 (the official name of the Texas State Shell), which bears much more than a casual resemblance to what has been traditionally called Busycon contrarium (Conrad, 1840) (the Lightning Whelk).
In his 1958 thoroughly-researched revision of the Genus Busycon, Solomon Hollister compared the lectotype of B. contrarium (a Miocene fossil) to Recent shells to which this name had been applied. This comparison showed significant differences in both size and sculpture, and he concluded that the two were different species. Therefore, he proposed B. sinistrum as the name for the Recent species. In the same work he described B. pulleyi as a species similar in general appearance to B. sinistrum, but differing from it by the "spire being higher, more turreted" and that "the beads of the early whorls do not evanesce but transform into spines which become stronger on further growth of the shell." The holotype of Busycon perversum (Linnaeus, 1758) (Perverse Whelk), with its swollen mid-whorl ridge, was shown to be similar in general appearance to what is now called B. carica eliceans (Montfort, 1810) (Kiener's Whelk), although the latter is dextral. Its distribution was limited to the Bay of Campeche, Mexico.
So what are the proper names for the Texas State Shell and the Recent species traditionally called B. contrarium? Contemporary shell books differ. Despite Hollister's persuasive evidence that the name B.contrarium should not be applied to the Recent species, acceptance of this by popular shell book authors has been spotty.
Dr. Jean Andrews in her 1971 Sea Shells Of The Texas Coast sets the tone for the general Busycon taxonomic muddle which exists to date. The name B. contrarium was used for what appears to be Hollister's B. pulleyi, with a range from "South Carolina to Florida and the Gulf States." She then added that it is "more spiny, more turreted, and with a higher spire than B.sinistrum Hollister" (virtually the exact diagnoses used by Hollister to separate B. pulleyi from B. sinistrum). Finally, she added that "Hollister (1958) calls this shell B. sinistrum and the type found in Texas B. pulleyi." Interestingly, Dr. Andrews didn't treat a Lightning Whelk of any name in her 1994 Field Guide To Shells Of The Florida Coast despite the fact that is the most common large gastropod found along the Florida coast.
Dr. R. Tucker Abbott in his 1974 American Seashells noted that the Miocene fossil described by Conrad has characteristics (rounded shoulders) seen in living colonies near Sarasota, Florida and continued use of the name B. contrarium for Recent shells. Abbott further stated "some authorities feel that the common Lightning Whelk should be called perversum Linnaeus, an idea not without technical merit." In his remarks concerning B. perversum pulleyi, Dr. Abbott noted that it "occurs from Breton Sound, Louisiana, to Texas and to the north Mexican coast" and remarked that "in the northeast part of its range, this subspecies blends in with contrarium, giving rise to the possibility that this complex is one species, namely perversum."
Dr. William Emerson and Morris Jacobson in their 1976 Guide To Shells, concurred with Hollister that B. contrariun is an extinct species but used the name B. perversum for the sinistral shells found from New Jersey* to Campeche, Mexico and the name B. kieneri (Philippi, 1848) for the shells Hollister called B. perversum (the two were synonomized by Hollister and by Abbott). However, Emerson and Jacobson further commented that Dr. Thomas Pulley considers B. kieneri to be a variant of what they called B. perversum, because intergrades existed.
Dr. Abbott and S. Peter Dance in the 1986 Compendium Of Shells didn't address B. sinistrum at all but continued use of the name B. contrarium for Hollister's B. sinistrum and B. perversum for the Bay of Campeche shell.
Most recently, Drs. Abbott and Percy Morris in the 1995 Shells Of The Atlantic & Gulf Coast, remarked that B. contrarium is also called B.sinistrum.
So, where has all this review led us? To no definitive conclusion, it would seem - with variation and intergrades being the keys. If one accepts the proposition that the sinistral species found in North Carolina is the same species found in the Bay of Campeche, although quite different in appearance, sculpture, etc., (and that B. contrarium is an extinct fossil species), then B. perversum would be the proper name. If one accepts a majority of Hollister's diagnoses, B. sinistrum (his name for the Recent species related to B. contrarium), would then be appropriate, and B. perversum is a separate species found in the Bay of Campeche. If one accepts B. contrarium as the proper name for the sinistral species found from North Carolina to the Gulf States (not an extinct species), then B. contrarium is your moniker. Regardless of ones acceptance, it appears that B. pulleyi does not rate species status, but is an allopatric subspecies or form.
If by now you get the idea that shell book authors, no matter how learned, simply don't have all the answers, then your diagnosis is correct.
* Shells collected north of Cape Hatteras, North Carolina appear to be referable to Busycon laeostomum Kent, 1982, but that is another story. An Obscure Whelk - Busycon laeostomum Kent, 1982 (Shell-O-Gram, July-August, 1996)
Abbott, R. Tucker 1974. American Seashells (Second Edition), Van Nostrand Reinhold Co., New York, NY, 663 pp.
Abbott, R. Tucker and Dance, S. Peter 1986. Compendium Of Seashells, American Malacologists, Inc., Melbourne, FL, 411 pp.
Abbott, R. Tucker and Morris, Percy A. 1995. Shells Of The Atlantic & Gulf Coasts & The West Indies, Houghton Mifflin Co., Boston, MA, 350 pp.
Andrews, Jean 1971. Sea Shells Of The Texas Coast, University Of Texas Press, Austin, TX, 298 pp.
Andrews, Jean 1994, A Field Guide To Shells Of The Florida Coast, Gulf Publishing Company, Houston, TX, 182 pp.
Emerson, William K. and Jacobson, Morris K. 1976. The American Museum Of Natural History Guide To Shells, Alfred A. Knopf, New York, NY, 482 pp.
Hollister, Solomon C. 1958. A review of the genus Busycon and its allies, Pt. 1, Palaeontographica Americana, 4, no. 28, pp. 1-126.