Onchidella carpenteri ( Binney, 1861 )

Dayrat, Benoît, Zimmermann, Sara & Raposa, Melissa, 2011, Taxonomic revision of the Onchidiidae (Mollusca: Gastropoda: Pulmonata) from the Tropical Eastern Pacific, Journal of Natural History 45 (15 - 16), pp. 939-1003 : 967-970

Onchidella carpenteri ( Binney, 1861) nom. dub.

Onchidium carpenteri Binney 1861: 154 . — Tryon 1868: 317, pl. 18, fig. 39. — Binney and Bland 1869: 307–308, figs 544–545.

Onchidella carpenteri . – Fischer and Crosse 1878: 697–698 [as Oncidiella (?) carpenteri ]. — Binney 1885: 163, fig. 150.

Type material

The original description mentioned five syntypes: maximum size (preserved) of 5/ 3 mm, leg. and collecting date unknown. The syntypes were supposedly from the collections of the National Museum of Natural History, Washington, DC, but they could not be found there. They are likely lost. Type locality: Strait of Juan de Fuca (see Discussion). Type material condition unknown, although Binney and Bland (1869) mentioned that the syntypes were dry and destroyed .

Remarks on the original description

The brief original description is reproduced here in its entirety: ONCHIDIUM CARPENTERI . Among the mollusca from the Straits of De Fuca, Mr Carpenter has detected five specimens of a shelless mollusk, which evidently belong to the genus Onchidium . Being preserved in alcohol it is difficult to obtain any more satisfactory specific characters than the following: The body is oblong, with its extremities circularly rounded; the upper surface is regularly arched; below, quite near the edge, the border of the mantle is readily distinguished, most of the under surface is occupied by the broad, distinct, locomotive disk; the body is uniformly smoke-coloured; in size the individuals vary considerably, the length of the largest being 5, the extreme breadth 3 millimetres.

Discussion

To say the least, the case of O. carpenteri is complicated. Here it is regarded as a nomen dubium. In order to justify this nomenclatural decision, two key issues need to be addressed: (1) the number of specimens identified by Binney as O. carpenteri ; (2) the type locality of O. carpenteri .

In the brief original publication, the type locality is unambiguously cited as the Strait of Juan de Fuca, which is at the north-western border between Canada and the United States, more specifically between Vancouver Island and Washington State. Based on the original description, it might seem that P.P. Carpenter collected the specimens. However, P.P. Carpenter was actually working at the Smithsonian, and it is more likely that he studied some material available in the collections. In fact, Binney and Bland (1869) indicated that it was unknown who had sent the specimens to the Smithsonian .

The problems start with Tryon (1868), who mentioned O. carpenteri from “Lower California ”, i.e. Baja California, without any explanation. Tryon seems to be the first author who made a mistake about the known distribution of O. carpenteri (the Strait of Juan de Fuca is not in Baja California). Maybe the mistake came from the fact that, in the same one-page article where he described carpenteri, Binney (1861) also described a new species of Pedipes from “St Lucas Peninsulae Californiae” which is, indeed, in Baja California. Another explanation is that Tryon actually had access to Binney and Bland’s (1869) manuscript because Tryon’s figure of O. carpenteri ( Tryon 1868) is the same as Binney and Bland’s (1869) figure 544. Tryon could have been influenced by Binney and Bland’s (1869) mention of Cape San Lucas as a locality for O. carpenteri .

Indeed, Binney and Bland (1869) reproduced the original description in its entirety. They did not mention any new material, but added two black-and-white drawings of the original specimens (their figures 544–545). As material available in the collections of the Smithsonian, they mentioned four specimens from “De Fuca”. However, they also indicated that their figure 545 was drawn from “one of specimens collected at Cape San Lucas”, which is in Baja California. Binney (1883) later addressed the confusion generated by the mention of Cape San Lucas for a species then supposedly only known from the frontier between Canada and the US, by admitting that “The locality, Cape San Lucas, is doubtful. It is so referred, probably by mistake...”

Two years later, however, Binney (1885) wrote that Onchidella carpenteri was distributed from “Strait of Fuca to Gulf of California ”. It could mean one of two things. First, that Binney had changed his mind and thought that Cape San Lucas was indeed one of the type localities or even the type locality. Second, that he had received new material from the Gulf of California which he had identified as O. carpenteri . The correct answer very likely is the second one. Indeed, to our knowledge, the only specimens that had become available in the last years of the 1870s from the western coast of North America were those collected by W.J. Fisher from the Gulf of California. Stearns (1879) originally described those specimens as O. carpenteri , which explains why, in 1885, Binney could assume that his species O. carpenteri was distributed from the Strait of Juan de Fuca all the way down to the Gulf of California.

A few years later, Binney (1890) published two new figures of an alcohol-preserved specimen of Onchidella carpenteri with no locality data. Those two drawings look completely different from the drawings published earlier by Binney (1885) for O. carpenteri . According to Stearns (1894), Binney made those two new drawings based on a specimen collected by W.J. Fisher (not P. Fischer) from the Gulf of California (and which Binney had received from Dall, who had also received some specimens from W.J. Fisher).

Cooper (1892) mentioned some specimens of Onchidella carpenteri collected by [John] Xantus from Cape San Lucas. However, his identification was based on the assumption that O. carpenteri was “doubtfully reported from lat. 48 ◦ north ”. However, according to Binney (1861, 1883), O. carpenteri was originally described from there.

Unfortunately, Stearns (1894) changed his mind and decided that the material collected by W.J. Fisher from the Gulf of California was a different species, mainly because O. carpenteri , for which only the five original specimens had ever been recorded, was a very tiny species (5 mm maximum in length) compared to the specimens collected from the Gulf of California (17.2/12.2 mm on average). Stearns decided to refer to those specimens as Onchidella binneyi , to honour Binney.

No other mention of O. carpenteri found in the literature was based on new material. According to P. Fischer [not W.J. Fisher] and Crosse ( Fischer and Crosse 1878, translated here): “Only one species is cited from the Pacific coast of Mexico: Oncidiella Carpenteri, W. G. Binney. ” Also, in their translation of Binney’s description of O. carpenteri, Fischer and Crosse (1878) claimed that its habitat was “Cape San Lucas, at the extremity of Lower California (P. Carpenter)”. However, Carpenter was most likely not the collector (see above) and the locality mentioned in the original description was Juan de Fuca, which is not in Lower California. Finally, the long anatomical description of Onchidella by Fischer and Crosse is based on specimens of Onchidella celtica , not O. carpenteri (for which Fischer and Crosse did not have any additional material).

The erroneous idea that O. carpenteri was distributed in the Gulf of California was perpetuated in all subsequent literature, and, again, without new material ( Watson, 1925; Hoffmann, 1928; Labbé, 1934). Hoffmann (1928) even wrote that the type locality was “Straits of De Fuca [Golf von Californien]”. Watson (1925) made the same mistake in his map of all known Onchidella species , and placed O. carpenteri off southern California (and not in the Strait of Juan de Fuca). Labbé (1934) erroneously cited O. binneyi Stearns, 1894 as a synonym of O. carpenteri Binney, 1894 (with a wrong date), but he did not examine any specimens and only mentioned it from the Gulf of California.

Later, Abbot (1954) still regarded O. carpenteri as a valid species distributed from Puget Sound to Lower California. Marcus (1961) indicated that O. carpenteri differed from O. borealis , but could not be distinguished from O. binneyi . However, this statement was due to the fact that Marcus (1961) regarded O. carpenteri mainly as a “southern species”, and he was still referring to specimens of O. binneyi as O. carpenteri . Finally, Marcus and Marcus (1967) suggested that, perhaps, O. carpenteri (type locality Strait of Juan de Fuca) could be a synonym of O. borealis (type locality Alaska), but still thought that O. carpenteri was present in the Gulf of California.

In summary, Binney’s type locality of O. carpenteri was the Strait of Juan de Fuca, at the border between Canada and the United States. None of the records of O. carpenteri from the Gulf of California were based on new material, but simply on an erroneous placement of the Strait of Juan de Fuca on a map. The fact that Binney and Bland (1869) listed, by mistake, Cape San Lucas (which is in the Gulf of California) as a locality for O. carpenteri did not help, although Binney (1883) clearly corrected that mistake. Finally, the identification of the material collected by W.J. Fisher from the Gulf of California as O. carpenteri was a misidentification, and all those specimens were later referred to as O. binneyi (see that species).

For several reasons, O. carpenteri is a nomen dubium. First, the type material is lost. Second, the original description is extremely brief, largely incomplete, and no additional material was described. Third, given their size (maximum 5 mm long), those specimens were very young and likely immature. Fourth, the type locality, although clearly in the Strait of Juan de Fuca, has remained extremely confused in the literature (because authors erroneously thought that Juan de Fuca was in Baja California). In any case, there is only one species of Onchidella from California to Alaska ( Onchidella borealis ), and it is very likely that the description of O. carpenteri was simply based on young specimens of O. borealis .