Let me throw in my two Pfennige on this thread.
Gary Rosenberg is absolutely right in stating that Neverita fossata (Gould,
1847) represents the form of Neverita duplicata (Say, 1822) which Phil Poland
nicely figured as Neverita spec. on the Jacksonville Shell Club's home page.
However, if this form really proves to be separable from N. duplicata (see
discussion below), then the oldest available name for it would actually be
Neverita delessertiana (Recluz in Chenu, 1843). Although Recluz merely
published a figure with a name in the plate legend, this at the time was
considered a valid description of a new species. The book wherein this
description appeared (Illustrations Conchyliologiques, by J.-C. Chenu, Paris,
1843) is exceedingly rare which might explain why this name has been
overlooked by many workers. In volume four of this work Recluz figured "Natica
duplicata Say" (plate 4, figs. 1, 3) as well as "Natica delessertiana Recluz"
(plate 4, figs. 5 and 6). Figure 5 shows in two different views a specimen
resembling a fairly typical N. duplicata, while figure 6 shows a specimen
(also in two views) which features the deeply excavated umbilical channel
described by Gould as characteristic for N. fossata. Thus, while "fossata"
clearly is the better descriptive name (meaning "dug out", which is really
what the umbilical channel of this form looks like), the name "delessertiana"
clearly predates Gould's name by four years, making N. fossata a junior
synonym of N. delessertiana.
A complicating factor, at least at first glance, might be considered the fact
that Recluz did not state a locality for N. delessertiana, leaving up to
speculation the possibility that the specimen might be from the Indopacific or
some other region, where similar species of Neverita are known to occur.
However, Tryon in his "Manual of Conchology" (vol. 8, 1886, p. 34) includes
N. delessertiana in the synonymy of N. duplicata Say, albeit without citing
any knowledge of the supposed type locality. Interestingly, he states: "N.
delessertiana, Recluz, combines the typical form [of N. duplicata] with that
described by Gould as N. fossata. The latter is scarcely entitled to even
varietal rank; it is distinguished by the umbilicus being more decidedly
striate and bounded by an acute ridge, but these features, common, perhaps
predominant in Florida specimens, seem to shade away with the more northern
distribution."
The question of type locality was put to rest only recently, when Alan Kabat,
Yves Finet and Kathie Way published a paper entitled "Catalogue of the
Naticidae (Mollusca: Gastropoda) described by C.A. Recluz, including the
location of the type specimens" which appeared in Apex, vol. 12(1), pp. 15-26,
1997. The authors examined the type material of N. delessertiana preserved in
the Geneva Museum of Natural History and reported: "Possible syntypes, MHNG
20803 (2 specimens; probably the figured specimens) and MHNG 20804 (2
specimens)" with a label reading "Hab. la Louisiana sur le bords du Missisipi,
Marguier". Thus, the specimens clearly are from the southern coast of the
U.S., ruling out that N. delessertiana might be based on an Indopacific
specimen.
Just to round off this taxonomical excursion into the synonymy of the "N.
duplicata complex", Philippi in 1851 also recognized the existence of a
variant, deeply excavated form of N. duplicata and named it "Natica
texasiana", with Galveston, TX as the type locality [Philippi, R.A. (1851)
Zeitschr. Malakozool. 5, edition for 1848, pp. 158-159]. He later figured the
species (Systematisches Conchylien-Cabinet, Die Gattungen Natica und Amaura,
1850, pl. 12, fig. 10). His figure looks much like the picture Phil Poland
posted and which shows an extreme form of umbilical excavation. Thus, in
principle we have a third name to choose from should this form turn out to
represent a distinct species. However, this third name clearly is just another
junior synonym of Neverita delessertiana (Recluz in Chenu, 1843), and is even
junior to Neverita fossata (Gould, 1847).
Apart from the taxonomic intricacies delineated above, the more profound
question (and the one Phil Poland raised originally) is whether the excavated
form of N. duplicata Say is merely a variant without taxonomic status or
whether it can be consistently differentiated from N. duplicata sensu strictu,
thus raising it to subspecific or even specific status. I have examined
numerous N. duplicata in my collection for the slate of characters Phil has
used to separate the two forms/species, and find that I can always find
"crosssover" specimens, with features from both character lists. Specifically,
Phil stated that N. duplicata has an evenly rounded umbilical area, is squat
in shape, grayish and can get rather large (above 60 mm), while N. spec. is
said to have an excavated umbilical area, a globose form, a brownish
coloration and a fairly small size (generally below 45 mm).
I have specimens from Lejeune, NC which are at the same time excavated and
squat, while others from the same locality are evenly rounded and globose.
From Cape Cod, MA and from Cocoa, FL I have specimens which are excavated but
greyish. From Cape Canaveral, FL as well as from Lynn Harbor, MA and Margate,
NJ I have evenly rounded specimens which are globose rather than squat.
Furthermore, the degree of excavation of the umbilical area varies widely,
with some specimens having barely noticeable striations while others show a
deeply sunken-in umbilical area. Thus, I have to agree with the statement of
Tryon more than 100 years ago (see above); my personal conclusion is that the
morphological evidence at hand neither warrants nor justifies separation into
two species. Neverita duplicata just happens to be a very variable species,
including, by the way, some interesting ecophenotypic variations in the color
of the callus which have been shown to depend on the diet of the animals.
Naturally, compelling evidence such as a large lot of specimens from a single
locality ("sympatrical specimens") which show statistically significant
morphological differences might change my view on this subject.
It might be interesting to note that other species within the genus Neverita
show similar variability in general shape and umbilical features. The common
Indopacific species Neverita didyma (Roeding, 1798) includes an excavated form
which was named N. lamarckii (Recluz in Chenu, 1843) but is now considered a
mere variant (Cernohorsky, 1972). Similarly, the U.S. west coast species
Neverita reclusiana (Deshayes, 1839) includes a high-spired, globose form
(among many other forms) with a slightly excavated umbilical area which at
times has been called N. alta (Arnold, 1903), but which now is considered to
be a mere form of N. reclusiana [Marincovich, L. (1977) Bull. Amer. Paleont.
70].
Michael Hollmann
N.B.: On a less serious note: I am just happy that Neverita is not a genus
within the Conidae or Cypraeidae. If that were the case N. duplicata, N.
didyma, and N. reclusiana most certainly would all have been divided up into
at least 10-15 "species" each......
******************************************
Dr. Michael Hollmann
Goerdelerweg 17
D-37075 Goettingen
GERMANY
Tel.: (home) (49)-551-22356
Tel.: (work) (49)-551-3899-437
FAX: (work) (49)-551-3899-644
e-mail: [log in to unmask]
****
|
