Deep-sea (250-1,550 m) Benthic Thanatocoenoses from the Southern Tyrrhenian Sea
283
known from the Northeast Atlantic (e.g. Waren
1991, Bouchet and Waren 1993; Salas 1996).
The common serpulid Filogranula stellata
shows a similar geographical and bathymetric
distribution in the Northeast Atlantic and all
through the Mediterranean (Zibrowius 1977; Ben
Eliahu and Fiege 1996).
Among bryozoans, only Setosella folini is
comparable in depth distribution with the species
mentioned above, although it is much rarer. This
species is known from a single Western
Mediterranean site in 550 m (Calvet 1907).
Conversely, it is frequent in the Northeastern
Atlantic. including the Ibero-Moroccan Gulf,
from 700 down to 3,700 m (Jullien 1882;
Harmelin and d'Hondt 1992). The single shallower record (200 m) by Harmelin (1977) is from an
upwelling area in the Canary Islands.
A small group of species deserves remarks
about biogeography. The molluscs Pyramidella
minuscula and R octaviana (stn 37) in the
Mediterranean, are only known from deep shelf
and upper slope (Di Geronimo 1973). Also
Akrytogira conspicua (stns 7, 10,44) and Alvania
elegantissima (stns 14, 23, 28, 29, 30, 35, 39), are
only known from Mediterranean waters, the former in 100-2,400 (Waren 1992), the latter in 400800 (Oliverio et al. 1992). Diaphana cf. marshalli
(stns 8, 10) shows morphological differences from
the Northeast Atlantic specimens and could be
provisionally assumed as a distinct Mediterranean
species. Another species (from stn 28), recently
described as Haliella tyrrhena (Di Geronimo and
La Perna in press), is very similar to an Atlantic
species. Among bryozoans, Characadoma mamillatum (stns 35,36,39), an euribathyc species present with its deep morphotype. is known only
from the Mediterranean (Rosso 1999). The serpulid Hyalopomatus variorugosus, known
throughout the Mediterranean (Ben Eliahu and
Fiege 1996; Sanfilippo 1998), is unknown from the
Atlantic, except for a single unpublished record
(see Sanfilippo 1998). It is also worth stressing the
occurrence of Gemellipora eburnea (stn 14), a
widely distributed species (Lagaaij and Cook
1973; Rosso and Di Geronimo 1998), so far
unrecorded from the Recent Mediterranean.
Discussion
The deep Mediterranean faunas appear markedly
impoverished compared to the Northeast Atlantic
ones, especially when the numerous euribathyc
species are excluded from the deep bathyal
assemblages. Most euribathyc species actually
show closer relations (taxonomic, ecological,
etc.) to the shelf benthos, rather than to the
deep-sea one. Marked differences are also evident
from the Lower-Middle Pleistocene bathyal
assemblages, recently studied by Barrier et aL
(1996), Di Geronimo and La Perna (1996, 1997),
Di Geronimo et al. (1996. 1997), Rosso and Di
Geronimo {1998}. The Pleistocene assemblages
are more similar to the Recent Atlantic ones than
to Recent Mediterranean ones. The Pleistocene
assemblages comprise many species presently
occurring only in the Atlantic, and extinct species
with marked Atlantic, or Oceanic in general. taxonomic affinities. Atlantic species in the
Mediterranean Pleistocene are the molluscs
Calliotropis ottoi (Philippi), Fissurisepta rostrata
Seguenza, Puncturella noachina (Linnaeus),
Torellia delicata (Philippi), Mitrolumna smithi
(Dauntzenberg and Fisher) and many others (see
Di Geronimo and La Perna 1997; Di Geronimo et
al. 1997), the bryozoans Euginoma verrniformis
Jullien, Caberea ligata Jullien, Scrupocellaria jullieni Hayward, Sertulipora guttata Harmelin and
d'Hondt (Rosso 1990; Di Geronimo et a1. 1997;
Rosso and Di Geronimo 1998), the serpulids
Neovernilia falcigera (Roule) and Vitreotubus
digeronimoi Zibrowius (Zibrowius 1979;
Zibrowius and Ten Hove 1987; Di Geronimo et al.
1997). The extinct species are mostly represented
by molluscs, such as Fissurisepta papillosa
Seguenza, Solariella marginulata (Philippi),
Austrotindaria pusio (Philippi). Bathyspinula
excisa (Philippi), Thestyleda cuspidata (Philippi),
Katadesmia conlusa (Seguenza), Cadulus ovulum
(Philippi), etc., all markedly abundant within the
Pleistocene communities {Di Geronimo and La
Perna 1997; Di Geronimo et al. 1997}. The
Pleistocene bryozoans Tervia barrieri Rosso.
Heliodoma angusta Rosso, Characadoma reclinatum Rosso and C. rostratum Rosso have been
recently described and added to the extinct stock
(Rosso 1998,1999). Most of these extinct species
might have been palaeoendemics. However, most
of the Recent species were also present in the
Pleistocene. Preliminary data suggest a decrease
in the species number of about one half.
In spite of such evident differences in composition, species dominance and diversity, the
Recent molluscan assemblages are structurally
comparable with the Pleistocene ones, in terms
283
known from the Northeast Atlantic (e.g. Waren
1991, Bouchet and Waren 1993; Salas 1996).
The common serpulid Filogranula stellata
shows a similar geographical and bathymetric
distribution in the Northeast Atlantic and all
through the Mediterranean (Zibrowius 1977; Ben
Eliahu and Fiege 1996).
Among bryozoans, only Setosella folini is
comparable in depth distribution with the species
mentioned above, although it is much rarer. This
species is known from a single Western
Mediterranean site in 550 m (Calvet 1907).
Conversely, it is frequent in the Northeastern
Atlantic. including the Ibero-Moroccan Gulf,
from 700 down to 3,700 m (Jullien 1882;
Harmelin and d'Hondt 1992). The single shallower record (200 m) by Harmelin (1977) is from an
upwelling area in the Canary Islands.
A small group of species deserves remarks
about biogeography. The molluscs Pyramidella
minuscula and R octaviana (stn 37) in the
Mediterranean, are only known from deep shelf
and upper slope (Di Geronimo 1973). Also
Akrytogira conspicua (stns 7, 10,44) and Alvania
elegantissima (stns 14, 23, 28, 29, 30, 35, 39), are
only known from Mediterranean waters, the former in 100-2,400 (Waren 1992), the latter in 400800 (Oliverio et al. 1992). Diaphana cf. marshalli
(stns 8, 10) shows morphological differences from
the Northeast Atlantic specimens and could be
provisionally assumed as a distinct Mediterranean
species. Another species (from stn 28), recently
described as Haliella tyrrhena (Di Geronimo and
La Perna in press), is very similar to an Atlantic
species. Among bryozoans, Characadoma mamillatum (stns 35,36,39), an euribathyc species present with its deep morphotype. is known only
from the Mediterranean (Rosso 1999). The serpulid Hyalopomatus variorugosus, known
throughout the Mediterranean (Ben Eliahu and
Fiege 1996; Sanfilippo 1998), is unknown from the
Atlantic, except for a single unpublished record
(see Sanfilippo 1998). It is also worth stressing the
occurrence of Gemellipora eburnea (stn 14), a
widely distributed species (Lagaaij and Cook
1973; Rosso and Di Geronimo 1998), so far
unrecorded from the Recent Mediterranean.
Discussion
The deep Mediterranean faunas appear markedly
impoverished compared to the Northeast Atlantic
ones, especially when the numerous euribathyc
species are excluded from the deep bathyal
assemblages. Most euribathyc species actually
show closer relations (taxonomic, ecological,
etc.) to the shelf benthos, rather than to the
deep-sea one. Marked differences are also evident
from the Lower-Middle Pleistocene bathyal
assemblages, recently studied by Barrier et aL
(1996), Di Geronimo and La Perna (1996, 1997),
Di Geronimo et al. (1996. 1997), Rosso and Di
Geronimo {1998}. The Pleistocene assemblages
are more similar to the Recent Atlantic ones than
to Recent Mediterranean ones. The Pleistocene
assemblages comprise many species presently
occurring only in the Atlantic, and extinct species
with marked Atlantic, or Oceanic in general. taxonomic affinities. Atlantic species in the
Mediterranean Pleistocene are the molluscs
Calliotropis ottoi (Philippi), Fissurisepta rostrata
Seguenza, Puncturella noachina (Linnaeus),
Torellia delicata (Philippi), Mitrolumna smithi
(Dauntzenberg and Fisher) and many others (see
Di Geronimo and La Perna 1997; Di Geronimo et
al. 1997), the bryozoans Euginoma verrniformis
Jullien, Caberea ligata Jullien, Scrupocellaria jullieni Hayward, Sertulipora guttata Harmelin and
d'Hondt (Rosso 1990; Di Geronimo et a1. 1997;
Rosso and Di Geronimo 1998), the serpulids
Neovernilia falcigera (Roule) and Vitreotubus
digeronimoi Zibrowius (Zibrowius 1979;
Zibrowius and Ten Hove 1987; Di Geronimo et al.
1997). The extinct species are mostly represented
by molluscs, such as Fissurisepta papillosa
Seguenza, Solariella marginulata (Philippi),
Austrotindaria pusio (Philippi). Bathyspinula
excisa (Philippi), Thestyleda cuspidata (Philippi),
Katadesmia conlusa (Seguenza), Cadulus ovulum
(Philippi), etc., all markedly abundant within the
Pleistocene communities {Di Geronimo and La
Perna 1997; Di Geronimo et al. 1997}. The
Pleistocene bryozoans Tervia barrieri Rosso.
Heliodoma angusta Rosso, Characadoma reclinatum Rosso and C. rostratum Rosso have been
recently described and added to the extinct stock
(Rosso 1998,1999). Most of these extinct species
might have been palaeoendemics. However, most
of the Recent species were also present in the
Pleistocene. Preliminary data suggest a decrease
in the species number of about one half.
In spite of such evident differences in composition, species dominance and diversity, the
Recent molluscan assemblages are structurally
comparable with the Pleistocene ones, in terms