THE NAUTILUS 118(1): 1-42, 2004
Pagel
The deep-sea Buccinoidea (Gastropoda: Neogastropoda) of the
Scotia Sea and adjacent abyssal plains and trenches
M. G. Harasewych
Department of Systematic Biology
National Museum of Natural Histoiy
Smithsonian Institution
Washington, DC 20013-7012 USA
Yuri I. Kantor
Severtzov Institute
Russian Academy of Sciences
Leninski Prospect 33,
Moscow 117071 RUSSIA
ABSTRACT
Four new genera and species of buccinoidean gastropods, Spi-
kebuccinum stephaniae new genus, new species; Drepanodon-
tus tatyanae new genus, new species; Muffinbuccinum cath-
erinae new genus, new species; and Germonea rachelae new
genus, new species, are described from the Scotia tectonic
plate and adjacent abyssal plains. Only Bathydomus obtectus
Thiele, 1912, Tromina bella abyssicola Clarke, 1961 and T.
abyssorum Lus, 1993, had previously been reported from abys-
sal depths off Antarctica. The latter two species were proposed
in the genus Tromina, subsequently shown to belong to the
family Muricidae. Therefore, a new genus, Lusitrornina is pro-
posed for these abyssal and hadal buccinoidean species. Anal-
yses of the taxonomic placement, geographical and bathymetric
distribution, and diversity of the 29 buccinoidean genera pres-
ently known from Antarctica and the Magellanic Province have
shown that the abyssal (>2200 m) buccinoidean fauna of the
region shares no genera with the sublittoral or bathyal faunas.
None of die sl\ abyssal genera conform readily to the subfam-
ilies represented by the sublittoral or bathyal faunas. Credible
sister taxa and likely origins for some abyssal genera occur on
the adjacent continental slope. For others, closest relatives may
be found on abyssal plains beyond the Antarctic convergence.
Generic diversity decreases with increasing depth for both the
bathyal and abyssal buccinoidean faunas, while bathymetric
range tends to increase. For abyssal buccinoideans, maximum
generic diversity occurs between 2600 and 3200 meters. The
proportion of monotypic genera in the Antarctic and Magel-
lanic Provinces is extraordinarily high (48.3%), and may be an
artefact of low sampling density exacerbated by difficulties in
differentiating closely related species. Neither gigantism nor
dwarfism is evident in the abyssal buccinoidean fauna. Rather,
the range in sizes narrows with increasing depth. Genera in-
habiting the base of the continental slope are smaller than
those of either the upper slope or continental rise. In the abys-
sal zone, maximum shell size is reached near the boundaiy of
the continental rise and abyssal plain, and subsequently de-
creases with increasing depth.
INTRODUCTION
The Buccinoidea are the most geographically wide-
spread and ecologically diverse clade 'within the Neo-
gastropoda. First appearing during the Early Cretaceous
[Valanginian] (Tracey et al., 1993), these predatory snails
have radiated to occupy most benthic marine habitats
ranging from the tropics to the poles and from the in-
tertidal zone to hadal depths (Clarke, 1962). Several
members of the families Nassariidae and Buccinidae
have even invaded fresh water (Kantor and Kilburn,
2001; Brandt and Temcharoen, 1971).
Buccinoideans are readily distinguished by their usu-
ally weakly sculptured, conical to fusiform shells, their
distinctive rachiglossan radula with multicuspid lateral
teeth, long to very long proboscis, as well as by the ab-
sence of a rectal gland and accessory salivary glands.
Their relationships to other Neogastropoda, however,
have been variously interpreted, ranging from basal to
derived (e.g., Ponder, 1974; Ponder and Waren, 1988;
Ponder and Lindberg, 1996; Kantor, 1996; Harasewych
et al., 1997). While a number of authors have attributed
different taxonomic ranks to Buccinoidea and its com-
ponent higher taxa (e.g., Powell, 1929; Thiele, 1929;
Wenz, 1938; Ponder, 1974; Ponder and Waren, 1988),
there is little disagreement as to the monophyly or com-
position of the group. We had earlier briefly reviewed
the history of the higher classification of buccinoideans
(Harasewych and Kantor, 1999), which is based primarily
on differences in shell, opercular and radular morphol-
ogies applied to regional faunas (e.g., Powell, 1929,
1951, Southern Oceans; Habe and Sato, 1973, Northern
Pacific; Bouchet and Waren, 1985, Northeastern Atlan-
tic). We continue to retain provisionally the use of Buc-
cinulidae and its subdivisions, as defined by Powell
(1951), without necessarily endorsing their taxonomic
rank, for the antiboreal members of the Buccinoidea,
pending the availability of sufficient anatomical and/or
molecular data for a meaningful phvlogenetic revision of
the higher taxa of Buccinoidea on a global basis. The
subfamilial assignments of presently known buccino-
idean genera that occur south of die Antarctic Conver-
gence, as well as those from the Magellanic Province are
reviewed (Appendix 1) and, in some cases, revised.
Our continuing studies of the Buccinoidea represent-
ed in the collections assembled by the United States
Antarctic Program (USAP) have revealed a number of
BioStor
