New Caledonia: The major centre of biodiversity for volutomitrid molluscs (Mollusca: Neogastropoda: Volutomitridae)

Abstract

Recent deep-sea explorations in the South Pacific have documented around New Caledonia the most diverse fauna of gastropods of the family Volutomitridae anywhere in the world. Fourteen species (nine new, two remaining unnamed) are recorded, all essentially confined to the 250–750 m depth range. The high number of species in the New Caledonia region does not appear to be an effect of sampling intensity, but appears to result from four factors: regional spatial heterogeneity, frequency of hard substrates, syntopy, and a historical heritage shared with Australia and New Zealand, which until now ranked as the major centre of volutomitrid diversity. In the New Caledonia region, volutomitrids show a marked preference for hard bottoms and up to three species may co-occur in the same dredge haul. Many species appear to have extremely narrow geographical distributions within the region (e.g. a single seamount or a single submerged plateau); conversely, Microvoluta
joloensis, the only non-endemic volutomitrid present in New Caledonia, ranges from the Mozambique Channel to Tonga.

Full text

Systematics and Biodiversity 1(4): 467–502 Issued 9 June 2004
DOI: 10.1017/S1477200003001282 Printed in the United Kingdom C
The Natural History Museum
Philippe Bouchet
Mus´eum National d’Histoire
Naturelle, 55 rue Buffon,
75005 Paris, France
Email: pbouchet@mnhn.fr
Yuri I. Kantor
A.N. Severtzov Institute of
Problems of Evolution of
Russian Academy of Sciences,
Leninski prosp. 33,
Moscow 117071, Russia
submitted March 2003
accepted July 2003
New Caledonia: the major centre
of biodiversity for volutomitrid molluscs
(Mollusca: Neogastropoda:
Volutomitridae)
Abstract Recent deep-sea explorations in the South Pacific have documented
around New Caledonia the most diverse fauna of gastropods of the family Vo-
lutomitridae anywhere in the world. Fourteen species (nine new, two remaining
unnamed) are recorded, all essentially confined to the 250–750 m depth range.
The high number of species in the New Caledonia region does not appear to
be an effect of sampling intensity, but appears to result from four factors: re-
gional spatial heterogeneity, frequency of hard substrates, syntopy, and a historical
heritage shared with Australia and New Zealand, which until now ranked as the
major centre of volutomitrid diversity. In the New Caledonia region, volutomitrids
show a marked preference for hard bottoms and up to three species may co-
occur in the same dredge haul. Many species appear to have extremely narrow
geographical distributions within the region (e.g. a single seamount or a single
submerged plateau); conversely, Microvoluta joloensis, the only non-endemic vo-
lutomitrid present in New Caledonia, ranges from the Mozambique Channel to
Tonga.
Key words Bathyal, benthos, tropical, Gastropoda, anatomy, new species, Pacific
Ocean, New Caledonia
Introduction
The Volutomitridae constitute a small group of neogastropods
with maximum diversity in the southern hemisphere, espe-
cially in cold waters in the Antarctic, southern Australia and
New Zealand. A few species are known from high northern
latitudes in the Pacific and Atlantic Oceans. Volutomitrids
have lowest diversity at low latitudes, and then only in deeper
waters. A couple of species of Volutomitra have been des-
cribed from 200–600 m in the tropical South-West Pacific
(Cernohorsky, 1982; Bouchet & Kantor, 2000b), but these
represent only the tip of the iceberg of a New Caledonia di-
versity of 14 species, the most diverse fauna of volutomitrids
anywhere in the world. In the present paper, we review the com-
position of the family and describe the taxa from the tropical
South-West Pacific, consisting mostly of undescribed species
of Volutomitra and Microvoluta.
The mitriform shell of the Volutomitridae, with 2–5
columellar plaits, is superficially similar to that of the Mitridae
and Costellariidae. The family is characterized anatomically
by the wishbone-shaped central tooth of the radula, and needle-
like lateral teeth, when present. The anterior part of the digest-
ive tract differs from that of any other neogastropod in the
mid-oesophagus being very elongated, convoluted, and broad,
its posterior part being extremely muscular; in the valve of
Leiblein being well anterior to the nerve ring; and in the gland
of Leiblein being very small and tubular. A single accessory
salivary gland is present (Ponder, 1998; Kantor & Harasewych,
1992).
The standard monographic reference on the family is
Cernohorsky (1970b) who recognized six genera and 88 spe-
cies (Recent and fossil), with at that time four genera and
24 species in Recent faunas; six genera and 41 Recent species
are currently known. The oldest fossil species unambiguously
assignable to the Volutomitridae is from the lower Paleocene
of Denmark, with one doubtful species in the Upper Creta-
ceous of North America (Tracey et al., 1993). In Europe, the
diversity of the family peaks in the Paleogene (essentially in
the Eocene) where it lived in shallow to sublittoral depths,
and almost faded out from the fossil record in the lower Mio-
cene (Lozouet, 1999). By contrast, the Volutomitridae remain
present throughout the fossil record in the Neogene of New
Zealand, where they mainly lived in bathyal environments
(Beu & Maxwell, 1990).
467

468 Philippe Bouchet & Yuri I. Kantor
Figure 1 Standard orientation of protoconch and measurements taken. A, Shell in the standard position with protoconch-teleoconch
transition (marked by dotted line). Measurements taken on protoconch: D1, D2, PRE. Measurements taken on teleoconch: TL1 to TL6.
See Material and Methods for description and references. B, count of whorls numbers.
Material and methods
The present paper is based on the vast material collected re-
cently by expeditions in the New Caledonia area (Richer de
Forges, 1990, 1993; Richer de Forges & Chevillon, 1996),
Wallis and Futuna (Richer de Forges & Menou, 1993), Vanuatu
(Richer de Forges et al., 1996) and Fiji (Richer de Forges et al.,
2000a, b). Unless otherwise stated, this material is stored in
the Mus´
eum National d’Histoire Naturelle, Paris (MNHN),
and paratypes have been distributed to the Museum of New
Zealand Te Papa Tongarewa, Wellington (NMNZ) and the
Australian Museum, Sydney (AMS). No MNHN museum
number is allocated to individual lots, but the material re-
ported in this paper is unambiguously designated (and retriev-
able) through the combination of expedition acronym, e.g.
BATHUS 3, and station number, e.g. DW1435. This informa-
tion is present on labels accompanying individual lots. In the
lists of material examined, lv refers to live-taken specimens
and dd to empty shells.
Standard shell measurements were taken: shell length,
SL; last whorl length, BWL; aperture length, AL; shell dia-
meter, SD. For the purposes of species discrimination, we
used a number of protoconch and teleoconch measurements
following those defined and described in detail by Tursch &
Germain (1985, 1986), and proven to be operational. Meas-
urements taken from camera lucida drawings being more ac-
curate than those made directly on the shell with the aid of
an ocular micrometer, protoconchs were drawn with a camera
lucida in standard position, with the protoconch-teleoconch
transition facing the observer (Fig. 1); standard measurements
taken from the drawings. Instead of protoconch diameter, we
used D2, which equals the diameter of the protoconch + 1/4of
the first teleoconch whorl. PRE represents the exposed height
of the protoconch and is referred to in the text as protoconch
elevation. The number of protoconch and teleoconch whorls
was counted with an accuracy of 1/8 whorl, and the number
of axial ribs was counted on the first three teleoconch whorls.
(It should be noted that the method used for counting num-
ber of protoconch whorls, or measuring protoconch diameter,
is usually not specified in the literature, making comparisons
difficult).
Radulae and jaws were studied with SEM after cleaning
in diluted bleach, mounting on glass slides, air drying and
coating with gold-palladium. Two species of Microvoluta were
embedded in paraffin, serially sectioned at 8 µm, and stained
with Masson triple stain.
Composition of the family
In his monograph the Volutomitridae, Cernohorsky (1970b)
recognized six genera, two of which were known only as
fossils. Since then, several changes and additions have taken
place in the generic composition of the family. Latiromitra
Locard, 1897 (treated by Cernohorsky as a subgenus of Vo-
lutomitra) has been recognized as a genus of Turbinellidae
Ptychatractinae (Bouchet & War´
en, 1985; Harasewych, 1987;
Bouchet & Kantor, 2000a), Wai m a t e a Finlay, 1927 has been
synonymized with Volutomitra (Maxwell, 1992), and Kilburn
(1974) described the monotypical genus Magdalemitra.
Finally, Petuch (1987) described two Recent species of
Conomitra, a genus previously known only as fossil. As a
result, six Recent genera are currently recognized: Volutomitra
H. and A. Adams, 1853; Conomitra Conrad, 1865; Microvoluta
Angas, 1877; Paradmete Strebel, 1908; Peculator Iredale,
1924; and Magdalemitra Kilburn, 1974.
At species level, Cernohorsky recognized 88 species, of
which 24 were Recent. In the last 30 years, the latter total was
increased to 41 Recent species, and the present paper adds
a further nine (and describes but does not name two more),
thus bringing the total number of Recent named species of
Volutomitridae to 50 (Appendix).

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 469
Generic diagnoses
Generic definitions in the Volutomitridae are based on concho-
logical characters and, in many cases, the allocation of species
to genera seems somewhat arbitrary. The review below repres-
ents the current state of the art, rather than a full re-evaluation
of the validity of the Recent genera; the latter would necessit-
ate examination of fossil material, which is beyond the scope
of this paper.
Genus Volutomitra H. and A. Adams, 1853
Type species: Mitra groenlandica Beck in M¨
oller, 1842
(by subsequent designation, Fischer, 1884). Recent, North
Atlantic.
Diagnosis: Shell of small to large size for the family (6.6–
47 mm), shape from fusiform-ovate to fusiform-elongate, with
low to medium-high spire. Protoconch large, attaining at least
1.6 mm in diameter and consisting of 1.75–2.5 smooth whorls.
Axial sculpture of weak axial ribs or absent, spiral sculp-
ture indistinct in most species, of very low inconspicuous
striae, of narrow distinct cords in a few species (V. erebus,
V. bayeri). Aperture high (from about 60 to 70% of shell
length), smooth inside. Columellar plaits well developed and
broadly spaced, 3–5 in number, with second adapical strongest
in most species. Shell colour from white under olivaceous or
brown periostracum to beige and pinkish spotted, with brown
zigzag lines in a few species.
Operculum vestigial, present in juveniles, absent in
adults.
Chitinous jaw present, in the shape of closed or semi-
closed funnel. Lateral radular teeth vestigial.
Distribution: Recent: northern and central-western Atlantic,
northern and north-western Pacific, Hawaii, Australia, New
Zealand, New Caledonia, 10 to 1570 m. Fossil: Eocene to
Miocene, New Zealand (Cernohorsky, 1970b; Beu & Maxwell,
1990).
Genus Conomitra Conrad, 1865
Type species: Mitra fusoides Lea, 1833 (subsequent designa-
tion, Dall, 1889). Eocene, southeastern United States.
Diagnosis: Shell of small to medium size for the family (10–
18 mm), shape from biconical to elongate-fusiform, with angu-
late shoulder in most species, with medium-high to high spire.
Protoconch consisting of about 2 smooth whorls. Axial sculp-
ture well developed, consisting of narrow closely spaced axial
ribs, spiral sculpture well developed, consisting of distinct
cords, forming reticulated structure while crossing axial ribs.
Aperture medium-high (about 60% of shell length), narrow,
smooth inside. Columellar plaits 4, well developed, second
adapical strongest. Colour white to pale tan with dots and
zigzag lines, spiral colour bands present in some species.
Animal not known.
Distribution: Recent: Caribbean, 35 to 90 m. Fossil: Paleocene
to late Miocene; Europe, USA, Australia, New Zealand.
Remarks: The genus includes only three Recent species, which
form the basis for the diagnosis above. None of them has been
described anatomically, but their general shell morphology
leaves no doubt as to their placement in the Volutomitridae.
Cernohorsky (1970b) classified in Conomitra about 40 fossil
species, ranging from stout and biconical, similar to Peculator,
to elongate, similar to Microvoluta. The generic allocation of
a number of them probably requires reconsideration.
Genus Paradmete Strebel, 1908
Type species: Paradmete typica Strebel, 1908 (by application
of ICZN Art. 68.3) [=Volutomitra fragillima Watson, 1882].
Recent, Antarctic and sub-Antarctic.
Diagnosis: Shell of small to medium size for the family (7–
25 mm), shape from fusiform elongate to stout, nearly turri-
form, with low to medium-high spire. Protoconch medium-
sized to large (0.8–2.7 mm in diameter), consisting of about
2.5 smooth whorls. Axial sculpture ranges from very weak
axial ribs, marked only in the subsutural zone, to clearly
defined ones, extending towards the shell base; spiral sculp-
ture ranges from very low and inconspicuous striae to rather
narrow, but distinct, cords. Aperture high (60–70% of shell
length), narrow to broad, smooth inside. Columellar plaits 2–4
in number, from very poorly pronounced to rather distinct.
Operculum present in the adults of most species, but
absent in at least one.
Chitinous jaw present, but morphology not described in
detail. Lateral radular teeth relatively large and stout.
Distribution: Recent only. Antarctic and sub-Antarctic seas,
30 to 810 m.
Remarks: Although Paradmete, and especially its type species
P. fragillima, is rather similar conchologically to Volutomitra
(and was treated as a subgenus by Cernohorsky, 1970b), it
differs from it by the less pronounced columellar plaits, more
developed lateral radular teeth, and different shape of the cent-
ral tooth (see below).
Genus Microvoluta Angas, 1877
Type species: M. australis Angas, 1877 (by monotypy). Re-
cent, southeastern Australia.
Diagnosis: Shell of very small to small size for the family (3.8–
14.5 mm), shape from biconical to elongate-fusiform, nearly
turriform in some species, with medium-high to high spire.
Protoconch small (diameter 630–820 µm) in most species and
consisting of about 1.5–2.1 smooth whorls. Axial sculpture
well developed in most species, consisting of closely spaced
axial ribs, often producing knobs on shoulder; spiral sculpture
poorly developed, usually of very low inconspicuous striae.
Aperture from low to medium high (rarely reaching 60% of
shell length), narrow, smooth or lirate inside (within the same
population of some species). Columellar plaits 3–5 in number,
well developed in most species, second adapical strongest.
Shell colour white in most species, banded, blotched and/or
streaked with brown in a few species.

470 Philippe Bouchet & Yuri I. Kantor
Operculum absent in adults.
Chitinous jaw present, in the shape of horse-shoe plate
with long lateral flaps. Lateral radular teeth relatively large and
stout.
Distribution: Recent: Atlantic: central eastern Atlantic,
Caribbean; South Africa; Indo-Pacific: western and south-
west Pacific, from Japan and the Philippines to Australia and
New Caledonia, Fiji, Wallis and Futuna, and Tonga; New
Zealand; 50 to 1900 m (shell only). Fossil: Miocene-Pliocene,
Australia and New Zealand (Cernohorsky, 1970b; Beu &
Maxwell, 1990).
Remarks: Microvoluta is a well defined genus, distinguished
from other genera by its small elongated shell with attenuated
spire, and different jaw morphology.
Genus Peculator Iredale, 1924
Type species: Peculator verconis Iredale, 1924 (by monotypy).
Recent, southern Australia.
Diagnosis: Shell of small size for the family (6.5–12 mm),
stout, shape biconical, with low spire. Protoconch consisting of
about 1.5–2 smooth whorls. Axial sculpture poorly developed,
consisting of thickened growth lines and, in some species,
narrow and low ribs; spiral sculpture poorly developed, of
low closely spaced striae. Aperture high (60–70% of shell
length), narrow, smooth or lirate inside. Columellar plaits 3–4
in number, well developed and broadly spaced, first or second
adapical largest. Shell colour pale brown, with paler spots in
some species.
Operculum vestigial, present in adults.
Chitinous jaw may be present, shape unknown. Lateral
radular teeth vestigial.
Distribution: Recent: Australia and New Zealand, now New
Caledonia, in 6 to 260 m. Fossil: Eocene to Pliocene,
Australia and New Zealand (Cernohorsky, 1970b; Beu &
Maxwell, 1990).
Remarks: Peculator is a well defined genus, distinguished from
other genera by its small, stout, biconical shell with low spire
and narrow aperture.
Genus Magdalemitra Kilburn, 1974
Type species: Magdalemitra gileosum Kilburn, 1974 (by ori-
ginal designation).
Diagnosis: Shell of medium size for the family (19 mm),
shape cylindrical, pupoid, with a low, blunt and tumid spire.
Protoconch unknown. Axial sculpture of riblets on first
teleoconch whorl only; spiral sculpture consisting of striae
on the first teleoconch whorl and on the shell base. Aperture
narrow, columellar plaits 4, adapical largest. Colour brown
with darker subsutural band.
Animal not known.
Distribution: Monotypical genus, known only from the Recent
of South Africa, from Port Alfred to Embotyi, Pondoland.
Remarks: The single known species presents a unique combin-
ation of columbellid shell shape and columellar plaits. Pending
an examination of the radula and anatomy, the allocation of
Magdalemitra to the family Volutomitridae remains uncon-
firmed. A position in the Costellariidae also is possible (R.N.
Kilburn, pers. comm.).
Species descriptions
Class Gastropoda
Unranked group Caenogastropoda
Order Neogastropoda Wenz, 1938
Family Volutomitridae Gray, 1854
Genus Volutomitra H. and A. Adams, 1842
Volutomitra glabella Bouchet and Kantor, 2000 (Fig. 2)
Volutomitra glabella Bouchet & Kantor, 2000b: 182–187,
figs.1A–H;2A,C,D,E;3;4.
Type material: Holotype and 3 paratypes in MNHN, 1 para-
type each in NMNZ and AMS.
Type locality: South of New Caledonia, Norfolk Ridge,
Banc Eponge, 24◦57S, 168◦21E, 517–559 m [SMIB 10, sta.
DW205].
Material examined: 33 lots (about 115 specimens) from north
of New Caledonia and 2 lots (2 specimens) from south of
New Caledonia (list of material in Bouchet & Kantor, 2000).
Dimensions of the largest specimen: shell height 25.0 mm,
diameter 12.0 mm, last whorl height 19.1 mm, aperture height
16.5 mm.
Distribution: North and South of New Caledonia, on hard
bottoms, alive in 258–525 m, shells in 190–613 m.
Remarks: This distinctive species differs from its sympatric
congeners by usually reaching a much larger adult size (al-
though the sizes of the largest V. vaubani [18.2 mm] and of
the smallest adult V. glabella [17.0 mm] slightly overlap),
and by its broader shell with a lower spire. Even at
comparable sizes, young or small V. glabella are readily
separated from any other Volutomitra of the region by their
significantly larger and more elevated protoconch (Table 3).
Volutomitra vaubani Cernohorsky, 1982
(Figs3,4,5,10A)
Volutomitra (Waimatea) vaubani Cernohorsky, 1982: 999,
pl. IV, figs 23–28.
Type material: Holotype and 5 paratypes in MNHN.
Type locality: South of New Caledonia, 22◦49S, 167◦12E,
395 m [R/V Vauban 1978–79 sta. 15].
Material examined: 22 lots (194 specimens) from north of
New Caledonia and 13 lots (88 specimens) from south of New
Caledonia.
North of New Caledonia. LAGON, R/V Alis: sta. 444,
Atoll de Surprise, 18◦15S, 162◦59E, 300–350 m, 1 lv [co-
occurring with V. glabella].

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 471
Figure 2 Volutomitra glabella. A–B, Holotype, South of New Caledonia, SMIB 10, sta. DW205, SL 24.0 mm; C, Paratype, BATHUS 4, sta.
DW941, SL 18.5 mm; D–E, Paratype, BATHUS 4, sta. DW923, SL 19.8 mm; F, Juvenile paratype, BATHUS 4, sta. DW941, SL 14.0 mm.
MUSORSTOM4,R/VVauban: sta. DW156, 18◦54S,
163◦19E, 525 m, 1 dd [co-occurring with V. z i c z a c ,n.sp.].–
Sta. DW164, 18◦33S, 163◦13E, 255 m, 5 dd. – Sta. DW197,
18◦51S, 163◦21E, 550 m, 1 dd [co-occurring with V. z i c z a c ,
n. sp.].
BATHUS 4, R/V Alis: sta. DW914, 18◦49S, 163◦15E, 600–
616 m, 40 dd. – Sta. DW923, 18◦52S, 163◦24E, 470–502 m,
6 dd, 1 lv [co-occurring with V. z i c z a c , n. sp.]. – Sta. DW927,
18◦56S, 163◦22E, 444–452 m, 2 lv, 9 dd.
South of New Caledonia.R/VVauban 1978–79: sta. 15,
22◦49S, 167◦12E, 395 m, 2 lv (holotype and paratype). –
Sta. 16, 22◦46S, 167◦12E, 390–400 m, 4 lv (paratypes).
BIOCAL, R/V Jean-Charcot: sta. DW43, 22◦46S, 167◦15E,
400 m, 4 dd. – Sta. DW44, 22◦47S, 167◦14E, 440–450 m,
39 lv + dd. – Sta. DW46, 22◦53S, 167◦17E, 570–610 m, 4 lv,
27 dd.
MUSORSTOM4,R/VVauban: sta. DW212, 22◦47S,
167◦10E, 375–380 m, 7 dd. – Sta. DW223, 22◦57S,
167◦30E, 545–560 m, 2 dd. – Sta. DW230, 22◦52S,
167◦12E, 390–420 m, 1 dd.
SMIB 2, R/V Vauban:sta.DW1,22
◦53S, 167◦13E, 438–
444 m, 7 lv, 1 dd. – Sta. DW4, 22◦53S, 167◦13E, 410–417 m,
1 dd. – Sta. DW5, 22◦56S, 167◦14E, 398–410 m, 2 dd. –
Sta. DW8, 22◦54S, 167◦13E, 435–447 m, 3 dd. – Sta. DW9,
22◦54S, 167◦15E, 475–500 m, 3 dd. – Sta. DW12, 22◦53S,
167◦14E, 445–460 m, 1 lv.
SMIB 3, R/V Vauban:sta.CP4,24
◦54S, 168◦22E, 530 m,
Banc Eponge, 1 dd. – Sta. DW29, 22◦47S, 167◦12E, 405 m,
8 dd.
SMIB 8, R/V Alis: sta. DW189, 23◦18S, 168◦06E, 400–
402 m, Banc Antigonia, 1 lv. – Sta. DW190, 23◦18S,
168◦05E, 305–310 m, Banc Antigonia, 4 lv. – Sta. DW197–
199, 22◦51S, 167◦12E, 408–436 m, Ile des Pins, 5 lv.
BATHUS 2, R/V Alis: sta. DW719, 22◦48S, 167◦16E, 444–
445 m, 42 lv, 13 dd. – Sta. DW721, 22◦54S, 167◦17E,
525–547 m, 5 lv. – Sta. DW729, 22◦52S, 167◦12E, 400 m,
7 dd.
NORFOLK 1, R/V Alis: sta. DW1734, 22◦53S, 167◦12E,
403–429 m, 5 lv. – Sta. DW1735, 22◦52S, 167◦12E, 415–
445 m, 4 lv, 1 dd. – Sta. DW1736, 22◦51S, 167◦12E, 383–
407 m, 3 dd. – Sta. DW1737, 22◦52S, 167◦12E, 343–
400 m, 4 lv, 1 dd. – Sta. DW1738, 22◦51S, 167◦10E, 340–
381 m, 1 dd. – Sta. DW1739, 22◦51S, 167◦12E, 404–
448 m, 1 lv, 2 dd. Dimensions of the largest specimen (SMIB
8, sta. 197–199) (Fig. 3C): shell height 18.2 mm, dia-
meter 8.0 mm, last whorl height 13.6 mm, aperture height
12.0 mm.

472 Philippe Bouchet & Yuri I. Kantor
Figure 3 Volutomitra vaubani. A–D, South of New Caledonia. A–B, holotype, SL 13.5 mm; C, SMIB 8, sta. 197–199, SL 18.2 mm; D, BIOCAL, sta.
DW46, SL 12.2 mm. E–G, North of New Caledonia. E, BATHUS 4, sta. DW914, SL 14.6 mm; F–G, BATHUS 4, sta. DW927, SL 13.2 mm.
All shells at the same scale.
Distribution: Off north and south of New Caledonia and
Norfolk Ridge, alive in 310–570 m, shells in 255–600 m
(Fig. 4).
Remarks: Considerable new material collected since the
original description of V. vaubani showsthatitisavery
variable species, with individual as well as geographical
variation.
In the north of New Caledonia, V. vaubani occurs sym-
patrically and, occasionally, syntopically (see Discussion at
the end of the paper for terminology) with V. z i c z a c ,n.sp.
(Fig. 4 – arrows indicate stations of co-occurrence) and/or
V. glabella Bouchet & Kantor, 2000b, and there is no doubt
that three species of Volutomitra are involved in that region.
There, it differs from V. z i c z a c , n. sp. by its less convex
and more shouldered whorls, its colour pattern that never
forms axial zigzag lines, and by having a strong subsutural
groove extending on all whorls including the last adult whorl
(Fig. 5). Apart from these constant differences, V. vaubani
is quite variable in terms of axial sculpture and colour.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 473
Figure 4 Geographical and bathymetrical distribution of
Volutomitra vaubani. Arrows indicate stations where the
species is syntopic with V. ziczac, n. sp. Each column
represents 10 specimens (lv or dd). Isobath 1000 m.
Some populations have almost no axial sculpture on the last
whorl (Fig. 5E), while others have strong, sharp axial ribs
(Fig. 5C). These axially sculptured populations have uniform
yellowish-beige shells, while the smooth forms vary from
white to yellowish-beige with brown blotches, especially at
the shoulder.
In the south of New Caledonia, the populations vary ex-
tensively, from specimens with a low spire and convex whorls
(resembling V. z i c z a c , n. sp., in outline) to specimens with a
higher spire and shouldered whorls (resembling the northern
form described above – Fig. 3D); however, they are connected
by intermediates. A single species of Volutomitra appears to be
present in that region, and the name vaubani can be applied to it
without ambiguity. The question is whether this southern form
is conspecific with one of the northern species (and then which
one?) or whether it represents a separate species. All south-
ern populations of vaubani are uniformly coloured, yellowish-
beige, except one population from BIOCAL sta. DW46 where
some specimens have a pattern of zigzag brown axial lines
and it is tempting to connect these with V. z i c z a c ,n.sp.
(Fig. 3D). However, this similarity appears to be superficial: in
V. z i c z a c , n. sp., the brown axial lines are extremely oblique,
with very angular changes of direction, whereas in the speci-
mens from BIOCAL sta. DW46 they are not so oblique, with
more obtuse changes of direction. Instead, the strongly sculp-
tured forms of southern Volutomitra vaubani share with the
northern populations described above the presence of a strong
subsutural groove and axial ribs extending over the whole
height of the last whorl. We hypothesize that these populations
are conspecific.
To summarize, the zigzag pattern that appears to be so
characteristic of Volutomitra ziczac, n. sp., may occur occa-
sionally in southern populations of V. vaubani. In the north
of New Caledonia, where the two species co-occur, a zigzag
pattern is never observed in V. vaubani; this may be interpreted
as character displacement.
Volutomitra ziczac,n.sp.(Figs.5B,D,G,6,7,11A,C)
Type material: Holotype (lv) and 3 paratypes in MNHN.
Type locality: North of New Caledonia, 18◦55S, 163◦24E,
370–405 m [BATHUS 4, sta. DW925].
Material examined: 17 lots (59 specimens) from north of New
Caledonia.
North of New Caledonia. MUSORSTOM 4, R/V Vauban:sta.
DW156, 18◦54S, 163◦19E, 525 m, 3 dd [co-occurring with
V. vaubani]. – Sta. DW181, 18◦57S, 163◦22E, 350 m, 4 dd,
3 lv. – Sta. DW196, 18◦55S, 163◦24E, 450 m, 3 lv [radula ex-
amined, Fig. 11A]. – Sta. DW197, 18◦51S, 163◦21E, 550 m,
1 dd [co-occurring with V. vaubani].
HALICAL1, R/V Alis: sta. DW01, 18◦56S, 163◦24E, 380–
400 m, 2 dd. – Sta. DW04, 18◦55S, 163◦24E, 350–365 m,
1 dd.
BATHUS 4, R/V Alis: sta. DW923, 18◦52S, 163◦24E,
470–502 m, 3 dd [co-occurring with V. vaubani]. – Sta.
DW924, 18◦55S, 163◦24E, 344–360 m, 7 dd. – Sta. DW925,
18◦55S, 163◦24E, 370–405 m, 4 lv (holo- and paratypes),
2 dd. – Sta. DW926, 18◦57S, 163◦25E, 325–330 m, 5 dd. –
Sta. DW929, 18◦52S, 163◦23E, 502–516 m, 3 dd. – Sta.
DW931, 18◦55S, 163◦24E, 360–377 m, 2 dd. – Sta. DW932,
19◦08S, 163◦29E, 170–190 m, 1 dd. – Sta. DW942, 19◦04S,
163◦27E, 264–270 m, 6 dd.
SMIB 6, R/V Alis: sta. DW118, 18◦58S, 163◦26E, 290–
300 m, 1 lv. – Sta. DW121, 18◦58S, 163◦26E, 315 m, 1 dd.
LAGON, R/V Alis: sta. 1152, 18◦58S, 163◦24E, 335 m, 1 lv,
6 dd [co-occurring with V. glabella].
Distribution: Off north of New Caledonia, alive in 300–450 m,
shells in 190–550 m.
Description (holotype): Shell solid, glossy, elongate-ovoid,
width 48% of height, consisting of c. 2.0 protoconch and
5.5 teleoconch whorls. Protoconch slightly eroded in holo-
type, rather large, bulbous, diameter 1090 µm, exposed height
730 µm, first whorl convex, smooth, second whorl with flat
sides, protoconch-teleoconch transition indistinct. Teleoconch
whorls convex with tightly impressed suture, ramp slightly
concave, nearly flat, exposed part below periphery more con-
vex. Sculpture consisting on early teleoconch whorls of strong
straight ribs, crossed by 2 spiral cords on the 2nd and 3rd
whorls, intersection forming knobs. On later whorls the sculp-
ture become less distinct, although one cord is visible on all
teleoconch whorls. Eighteen axial ribs on first whorl, 17 on
second, 17 on third; axial ribs gradually becoming obsolete on
last whorl, which has only indistinct undulations at shoulder.
Spiral sculpture of very indistinct, closely spaced narrow cords,
14 more distinct on siphonal canal. Last whorl high, 74% of
total shell height. Aperture height 68% of shell height, nar-
rowly elongate, smooth inside, outer lip simple. Columella
with narrow, thin callus, with 4 widely spaced plaits, abap-
ical one smallest. Siphonal canal short, straight. Colour of
shell pinkish brown, with irregularly spaced, brownish, zic-
zac chevrons covering entire subadult and adult shell surface.

474 Philippe Bouchet & Yuri I. Kantor
Figure 5 Syntopic specimens of Volutomitra vaubani (A,C,E,F)andV. ziczac n. sp. (B, D, G). A–B, MUSORSTOM 4, sta. DW156, SL 12.5 mm
(A), 17.5 mm (B). C–D, MUSORSTOM 4, sta. DW197, SL 12.2 mm (C), 13.8 mm (D). E–G, BATHUS 4, sta. DW923, SL 12.1 mm (E),
12.5 mm (F), 15 mm (G). All shells at the same scale.
Dimensions (holotype): Shell height 14.2 mm, diameter
6.8 mm, last whorl height 10.5 mm, aperture height 9.7 mm.
Largest specimen (paratype): shell height 16.2 mm, diameter
7.8 mm, last whorl height 12.1 mm, aperture height 11.2 mm.
Anatomy: A specimen from MUSORSTOM 4, sta. DW196
has been studied anatomically. It had a shell height of 15.9 mm,
diameter 7.8 mm, last whorl height 12.2 mm, aperture height
10.2 mm. Its anatomy is very similar to that described
and illustrated for Volutomitra glabella (Bouchet & Kantor,
2000b).
External anatomy: Body consists of 5 whorls, mantle
spans one whorl, nephridium 0.3 whorl, and digestive gland
3.5 whorls. Body yellowish and lacking specific pigment-
ation. Operculum absent. Foot with ovate sole, folded
lengthwise. Columellar muscle thick anteriorly, consisting
of 1.5 whorls, with four deep grooves, corresponding to
columellar plaits. In its posterior part, in the place of at-
tachment to columella, muscle is split into separate branches,
each inserting between columellar plait. Mantle edge rather
thick, while central part of mantle is extremely thin and
transparent. Mantle covers head base. Head narrow and small,

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 475
Figure 6 Volutomitra ziczac, n. sp. A–C, holotype, SL 14.2 mm. D, paratype, SL 16.2 mm. E, paratype, SL 14.5 mm. F, HALICAL 1, sta. DW01, SL
13.8 mm. G, BATHUS 4, sta. DW 926, SL 12 mm. All shells at the same scale.
with very short conical tentacles and large eyes. The spe-
cimen was a mature male and has a penis typical for Vo-
lutomitridae, long and flattened with open seminal groove
running along inner side of penis to its tip. Seminal papilla
absent.
Mantle: Mantle complex very similar to that of Vo-
lutomitra glabella. Anal gland seen through mantle as short
black strip.
Digestive system: Foregut anatomy is in all details similar
to that of V. glabella and differs only in its slightly longer valve
of Leiblein and significantly (c. 2×) longer anterior (i.e. part
between the proboscis and the valve) oesophagus. The probos-
cis, being less contracted, is relatively longer (about 2.0 mm,
or 20% of aperture height), conical, and occupies about 2/3 of
the rhynchocoel length. Mouth opening circular. The large un-
paired ventral proboscis retractor is attached to the anterior part
of the rhynchodaeum (proboscis sheath) and to the bottom of
the cephalic haemocoel in its posterior part. Small semi-closed
funnel-shaped chitinous jaw (Fig. 11C) lines anterior surface of
buccal cavity (on the illustration the jaw is partially uncoiled,
but in its natural position it is very similar to that of Volutomitra
glabella – Fig. 11D). Radula (Fig. 11A) long, c. 3.0 mm, or

476 Philippe Bouchet & Yuri I. Kantor
Figure 7 Geographical and bathymetrical distribution of
Volutomitra ziczac, n. sp. Arrows indicate stations where
the species is syntopic with V. vaubani. Each column
represents five specimens (lv or dd). Isobath 1000 m.
29% of aperture length; forming part long and comprising 20%
of the whole radular length. It is of typical morphology for
Volutomitridae and consists of wishbone-shaped central teeth
with rather long central cusp, having a deep groove on its dorsal
surface, into which cusp of the previous row interlocks. Width
of central tooth is about 24 µm (0.24% of aperture length).
Median cusp/total tooth length ratio 42%. Part of radula in
the sublingual pouch is remarkably long and comprises 1/3 of
entire membrane length. In its posterior part it is embraced
by muscular convoluted rod, which protrudes beyond rear of
proboscis. In studied specimen anterior part of the radula was
protruding through the jaw. Stomach relatively small and ad-
joins nephridium. Its shape is very similar to, although more
sharply curved, than that of V. glabella. Due to the condition
of preservation, we were not able to study its inner structure.
The digestive gland is bilobate, although less clearly so than
in V. glabella.
Remarks: The separation between Volutomitra ziczac and
V. vaubani is discussed under the latter species. In the north
of New Caledonia, the occurrences of Volutomitra ziczac and
V. vaubani are essentially parapatric, with a narrow zone of
overlap, about 6 km broad. Although in allopatric populations,
some specimens of V. z i c z a c (BATHUS 4: sta. DW923, sta.
DW926, see Fig. 6G) may superficially resemble V. vaubani
in shell outline (e.g. specimens in Fig. 3F–G), the two species
are strikingly different in the zone of co-occurrence (Fig. 5).
Etymology: With reference to the colour pattern of brownish,
zic-zac chevrons.
Genus Microvoluta Angas, 1877
Microvoluta joloensis Cernohorsky, 1970
(Figs 8, 9, 10E, 11B, 12, 13H, 14, 18)
Microvoluta joloensis Cernohorsky, 1970a: 103–104,
figs. 8–10. – Cernohorsky, 1970b: 121–122, pl. 15,
figs. 8–10, 12.
Type material: National Museum of Natural History,
Smithsonian Institution, holotype (USNM 288396) and 50
paratypes.
Type locality: Philippines, Sulu Sea, off Cagayan Island,
09◦38.5N, 121◦11E, 929 m [U.S. Bureau of Fisheries sta.
5423].
Material examined: A total of 66 lots (507 specimens), of
which 37 lots (303 specimens) from the New Caledonia region.
SW Indian Ocean, northern Mozambique channel.
BENTHEDI, R/V Suroit: sta. DR05, 12◦32S, 47◦40.2E, 150–
135 m, 1 dd. – Sta. DR08, 11◦29.2S, 47◦18.2E, 250 m, 1 lv,
2 dd. – Sta. DS10, 11◦28.5S, 47◦57.7E, 440 m, 1 lv, 4 dd. –
Sta. DR104, 11◦26.4S, 47◦22.3E, 330–350 m, 2 lv. – Sta.
DS120, 11◦30S, 47◦24.7E, 335–390 m, 3 lv, 1 dd. – Sta.
DS122, 11◦32S, 47◦23.2E, 615–625 m, 1 dd. – Sta. DS128,
11◦32S, 47◦23.2E, 600 m, 1 dd.
Coral Sea.Nova Bank. MUSORSTOM 5, R/V Coriolis:sta.
306, 22◦08S, 159◦21E, 375–415 m, 1 dd.
North of New Caledonia. MUSORSTOM 4, R/V Vauban:
sta. DW159, 18◦46S, 163◦16E, 585 m, 8 dd. – Sta. DW161,
18◦39S, 163◦11E, 550 m, 4 dd. – Sta. DW197, 18◦51S,
163◦23E, 550 m, 3 dd, 1 lv.
BATHUS 4, R/V Alis: sta. DW895, 20◦15S, 163◦52E, 315–
350 m, 1 dd. – Sta. DW914, 18◦49S, 163◦15E, 600–616 m,
170 dd. – Sta. DW923, 18◦52S, 163◦24E, 470–502 m, 1 lv. –
Sta. DW926, 18◦57S, 163◦25E, 325–330 m, 1 dd.
South of New Caledonia. BIOCAL, R/V Jean-Charcot:sta.
CP26, 22◦40S, 166◦27E, 1618–1740 m, 2 dd. – Sta. CP27,
23◦06S, 166◦26E, 1850–1900 m, 1 dd. – Sta. CP30, 23◦09S,
166◦41E, 1140 m, 1 dd. – Sta. DW56, 23◦35S, 167◦12E,
695–705 m, 2 dd. – Sta. KG73, 22◦13S, 167◦29E, 1285 m,
7 dd. – Sta. CP75, 22◦19S, 167◦23E, 825–860 m, 2 dd [co-
occurring with M. cryptomitra, n. sp.]. – Sta. DW77, 22◦15S,
167◦15E, 440 m, 4 dd [co-occurring with M. amphissa,
n. sp.].
SMIB 2, R/V Vauban: sta. DW21, 22◦40S, 167◦41E, 460–
500 m, 1 dd. – Sta. DW23, 22◦31S, 167◦37E, 410–420 m,
1 dd.
BIOGEOCAL, R/V Coriolis: sta. KG210, 22◦44S, 166◦31E,
1190 m, 3 dd. – Sta. DW253, 21◦32S, 166◦29E, 310–315 m,
12 dd.
BATHUS 1, R/V Alis: sta. CP651, 21◦42S, 166◦40E, 1080–
1180 m, 2 dd.
MUSORSTOM 4, R/V Vauban: sta. CC246, 22◦08S,
167◦11W, 410–420 m, 12 dd. – Sta. CC247, 22◦09S,
167◦13W, 435–460 m, 9 lv. – Sta. CC248, 22◦09S, 167◦10W,
380–385 m, 1 dd.
HALIPRO 1, R/V Alis: sta. CP866, 21◦26S, 166◦17E, 550–
600 m, 2 dd.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 477
Figure 8 Microvoluta joloensis.North of New Caledonia. A–B, MUSORSTOM 4, sta. DW161, 550 m, SL of both shells 11.2 mm. C, specimen
with lirate aperture, MUSORSTOM 4, sta. DW159, 585 m, SL 11.0 mm. D, specimen with well developed axial ribs, BATHUS 4, sta.
DW914, 600–616 m, SL 9.4 mm. Loyalty Islands. E–G, BIOCAL, sta. DW79, 1320–1380 m, SL 9.8 mm (E), 8.4 mm (F), 5.0 mm (G).
Southern New Caledonia. H, BIOCAL, sta. CP30, 1140 m, SL 5.9 mm. SW Indian Ocean. I, BENTHEDI, sta. DS120, 335–390 m, SL
9.6 mm. Norfolk Ridge. J, BATHUS 3, sta. DW825, 597–605 m, SL 14.2 mm, specimen with spiral grooves and axial ribs on last whorl,
extending to shell base. All shells at the same scale.
Norfolk Ridge. BATHUS 3, R/V Alis: sta. DW824,
23◦19S, 168◦00E, 601–608 m, 1 dd. – Sta. DW825, 23◦22S,
168◦00E, 597–605 m, 2 dd.
Loyalty Ridge. BIOCAL, R/V Jean-Charcot: sta. DW79,
20◦40S, 166◦52E, 1320–1380 m, 4 dd [co-occurring with M.
cryptomitra, n. sp.]. – Sta. DW80, 20◦32S, 166◦48E, 900–
980 m, 2 dd.
BIOGEOCAL, R/V Coriolis: sta. CP232, 21◦34S, 166◦27E,
760–790 m, 4 dd. – Sta. CP260, 21◦00S, 166◦58E,

478 Philippe Bouchet & Yuri I. Kantor
Figure 9 Microvoluta joloensis.North of New Caledonia. A, specimen intermediate between typical North New Caledonian form and biconical
form, BATHUS 4, sta. DW914, 600–616 m, SL 8.9 mm. Southern New Caledonia. B, biconical form, HALIPRO 1, sta. CP866,
550–600 m, 8.7 mm. C, specimen with finely reticulated sculpture, MUSORSTOM 4, sta. CC247, 435–460 m, SL 11.2 mm. I, biconical
specimen, MUSORSTOM 4, sta. CC246, 410–420 m, SL 7.8 mm. Fiji. D–E, elongated specimens, BORDAU 1, sta. DW1485, 700–707 m,
SL 9.7 mm (D), 8.8 mm (E). F, biconical specimen, BORDAU 1, st. DW1432, 477–493 m, SL 10.1 mm. G, specimen with strongly
reticulated sculpture, BORDAU 1, st. DW1479, 450–460 m, SL 12.2 mm. SW Pacific, Wallis and Futuna Islands. H, biconical
specimen, MUSORSTOM 7, sta. DW601, 350 m, SL 10.0 mm. Loyalty Ridge. J, strongly elongated form, BATHUS 3, sta. DW790, SL
8.0 mm. All shells at the same scale.
1820–1980 m, 1 dd. – Sta. DW313, 20◦59S, 166◦59E, 1600–
1640 m, 1 dd.
MUSORSTOM 6, R/V Alis: sta. DW410, 20◦38S, 167◦07E,
490 m, 2 dd. – Sta. DW468, 21◦06S, 167◦33E, 600 m, 8 dd
[co-occurring with M. cryptomitra, n. sp.]. – Sta. DW479,
21◦09S, 167◦55E, 310 m, 11 dd. – Sta. DW485, 21◦23S,
167◦59E, 350 m, 1 dd.
BATHUS 3, R/V Alis: sta. DW790, 23◦49S, 169◦48E, 685–
715 m, 13 dd [co-occurring with M. respergens,n.sp.].–Sta.
DW825, 23◦22S, 168◦00E, 597–605 m, 1 dd.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 479
Figure 10 A, Volutomitra vaubani, protoconch; southern New Caledonia, BIOCAL, sta. DW46. B, D, Microvoluta cythara,n.sp.,Chesterfield
Plateau, MUSORSTOM 5, sta. 362. B, inner shell surface of the last whorl showing liration. D, protoconch. C, Microvoluta amphissa,
n. sp., southern New Caledonia, BIOCAL, sta. DW46, protoconch. E, Microvoluta joloensis, north of New Caledonia, BATHUS 4, sta.
DW914, protoconch.
SW Pacific. Wallis and Futuna. MUSORSTOM 7, R/V Alis:
sta. DW523, 13◦12S, 176◦16W, 455–515 m, 17 lv,
18 dd. – Sta. DW524, 13◦12S, 176◦16W, 300 m, 1 lv. –
Sta. DW527, 13◦24S, 176◦15W, 540–560 m, 1 dd. – Sta.
DW585, 13◦10S, 176◦13W, 415–475 m, 1 dd. – Sta. DW586,
13◦11S, 176◦13W, 510–600 m, 2 dd. – Sta. DW601, 13◦19S,
176◦17W, 350 m, 31 dd. – Sta. DW604, 13◦21S, 176◦08W,
415–420 m, 6 dd. – Sta. DW608, 13◦22S, 176◦08W, 440–
458 m, 2 dd.
SW Pacific, Bank Waterwitch. MUSORSTOM 7, R/V Alis:
st. DW535, 12◦30S, 176◦41W, 340–470 m, 1 dd. – Sta.
DW537, 12◦30S, 176◦41W, 325–400 m, 1 dd. Bank Combe:
st. DW540, 12◦27S, 177◦28W, 600 m, 1 dd. – Sta. DW541,
12◦27S, 177◦26W, 500–505 m, 2 dd.
Fiji.BORDAU1,R/VAlis: sta. CP1392, 16◦49S, 179◦54W,
545–651 m, 1 dd. – Sta. DW1408, 16◦02S, 179◦30W, 550–
561 m, 9 dd. – Sta. DW1432, 17◦20S, 178◦44W, 477–
493 m, 8 dd, 4 lv. – Sta. DW1479, 20◦58S, 178◦45W, 450–
460 m, 5 dd. – Sta. DW1485, 19◦03S, 178◦30W, 700–707 m,
15 dd. – Sta. DW1486, 19◦01S, 178◦26W, 395–540 m,
19 dd. – Sta. DW1488, 19◦01S, 178◦25W, 500–516 m,
39 dd. – Sta. DW1492, 18◦43S, 178◦23W, 430–450 m, 1 dd.
Tonga.BORDAU2,R/VAlis: st. DW1585, 18◦33S,
173◦57W, 578 m, 1 lv. – Sta. CP1642, 21◦05S, 175◦23W,
532 m, 1 lv.
Distribution: Indian Ocean: NW of Madagascar; Western
Pacific: Philippines, New Caledonia region (Coral Sea, New
Caledonia proper, Norfolk and Loyalty Ridges), Fiji, Wallis
and Futuna, Tonga. Alive in 250–578 m, shells to 1900 m.
Remarks: We interpret Microvoluta joloensis as a highly
variable species, with variation appearing to reflect envir-
onmental conditions more than the very extensive horizontal
distribution. Under our taxonomical extension of M. joloen-
sis, there is more variation between populations within the
New Caledonia region (Table 1) than between any other parts
of its geographical range. Another interpretation of the vari-
ation observed would be to recognize several species with
discrete bathymetrical zonation. However, live-taken samples
are too few to adequately document the fine distribution of
the different morphs, and we have chosen a conservative ap-
proach in terms of number of species. Cernohorsky (1970a)
had also interpreted considerable differences in shape, colour
and sculpture among Philippines populations as within-species
variation.

480 Philippe Bouchet & Yuri I. Kantor
Figure 11 A, C, Volutomitra ziczac n. sp., MUSORSTOM 4, sta. DW196. A, dorsal view of radular ribbon. C, jaw (unfolded). D, Volutomitra
glabella, jaw. B, Microvoluta joloensis, MUSORSTOM 7, sta. DW601, lateral view of radular membrane. E–G, Microvoluta amphissa
n. sp., antero-lateral (E) and dorsal views of the jaw (G). F, microscupture of the jaw surface. Abbreviations: ct central tooth, lt lateral
tooth.
Figure 12 Geographical distribution of Microvoluta joloensis in the South-West Pacific. Isobath 500 m.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 481
Figure 13 A–G, Microvoluta respergens, n. sp. A–F, Loyalty Ridge, BATHUS 3, sta. DW790. A–C, holotype, SL 9.3 mm; D, paratype, 8.6 mm; E,
paratype, SL 9.6 mm; F, juvenile, 5.8 mm. G, Southern New Caledonia, BATHUS 2, sta. CP743, SL 8.5 mm. H, Microvoluta joloensis,
same station as A–F, SL 8.0 mm. All shells at the same scale.
Specimens from the western Indian Ocean are rather uni-
form (Fig. 8I), and are characterized by oval to slightly bicon-
ical shell shape, whorls with adpressed suture, well developed
axial ribs with subsutural bulge, extending to the shell base on
the last whorl, very poorly developed spiral threads, usually
lirate inside aperture of adults (smooth in juveniles). Colour
whitish, some specimens with irregular very pale brownish
spots under the suture and in some specimens forming irregu-
lar spiral bands or broken axial lines.
The variation around New Caledonia (Table 1) appears to
be depth-related. In general, specimens collected north of New
Caledonia (Fig. 8A–C) and in two samples from the Loyalty Is-
lands in 300–600 m are characterized by elongate-oval shells,
with generally smoothened axial ribs on the last and penul-
timate whorls in adults, as well as poorly developed spiral
sculpture. However a large sample (BATHUS 4, sta. DW914),
containing about 170 shells, shows all transitions from spe-
cimens with a nearly smooth last whorl to specimens with

482 Philippe Bouchet & Yuri I. Kantor
Range (µm) Average (µm) σn
North of New Caledonia
protoconch diameter (D2) 780–880 840 36 6 Fig. 9E
protoconch elevation (PRE) 700–830 750 46 6
last whorl/shell height 0.60–0.67 (adults) 0.63 0.02 10
up to 0.68 ( juv.)
diameter/height 0.38–0.47 0.41 0.03 10
aperture height/shell height 0.49–0.58 0.53 0.03 10
largest adult shell height 11.2 mm, diameter 4.2 mm
last whorl height 6.8 mm, aperture height 5.7 mm
South of New Caledonia, 300–400 m
protoconch diameter (D2) 640–720 690 40 4
protoconch elevation (PRE) 420–500 470 35 4
last whorl/shell height 0.68–0.72 0.70 0.02 4
diameter/height 0.42–0.48 0.45 0.03 4
aperture height/shell height 0.58–0.62 0.60 0.02 4
largest adult shell height 7.4 mm, diameter 3.1 mm
last whorl height 5.0 mm, aperture height 4.4 mm
South and East of New Caledonia, 700–1800 m
protoconch diameter (D2) up to 1140 965 80 10
largest adult shell height 9.6 mm, diameter 3.8 mm
last whorl height 5.4 mm, aperture height 4.5 mm
Table 1 Biometric characteristics of selected populations of Microvoluta joloensis in the New Caledonia region.
strong axial ribs, extending over all the shell surface (Fig. 8D),
to specimens with a nearly biconical shell (Fig. 9A). The spiral
groove in the subsutural zone is also rather variable, being dis-
tinct and rather deep in some specimens, while nearly obsolete
in others. On some specimens with better pronounced axial
ribs, these tend to form rounded low swellings on the shoulder.
All intermediates between a completely smooth aperture and
rather strongly lirate were also observed in this sample.
Specimens from south of New Caledonia (Fig. 9B, I)
at depths of 300–400 m (shells to 600 m: HALIPRO 1, sta.
CP866) are rather constant in shell shape and are characterized
by a rather small biconical shell (juveniles in particular have
strongly biconical shells) with flat whorls, axial ribs depressed
at periphery, and spiral sculpture of indistinct spiral grooves.
Shell colour greyish-white with indistinct pale brown colour
marks. Number of axial ribs on the first whorl ranges 12–
16 (average 13.5, σ=1.9, n =4), on second 12–17 (average
14.5, σ=2.1, n =4), on third whorl 15–17 (average 16.3,
σ=1.0, n =4). Protoconch diameter is smaller than in the
northern form. Although extreme specimens from the northern
and these southern populations may seem strikingly different,
all intermediates between them can be found.
In populations from deeper water (400–600 m), the shell
is biconical, with high, shouldered whorls, almost canaliculate
suture, one strong spiral groove delimiting subsutural node,
others grooves more shallow, and the spiral cords are stronger
and produce a reticulated shell surface (Figs 8J, 9C). Extreme
specimens of these populations may again look very different,
but can be connected by intermediates with specimens of pop-
ulations from shallower water. Shells of this form attain the
largest size for M. joloensis: shell height 14.2 mm, diameter
5.4 mm, last whorl height 8.8 mm, aperture height 7.1 mm
(BATHUS 3, sta. DW825; Fig. 8J). One population from
Loyalty Ridge (MUSORSTOM 6, sta. DW479, 310 m) has
a rather distinct shell colour, pale brownish irregular spots in
the upper part of the whorls and, in some specimens, narrow
but distinct, strongly oblique, zigzag lines on the periphery and
shell base.
In still deeper water (700–1800 m) in the south and east
of New Caledonia, in the Loyalty Basin, and off the Loyalty
Islands, a rather distinct form (Figs 8E–H) is characterized
by slender, biconical to elongate-oval shell, with fewer axial
ribs forming a strong subsutural bulge. Ribs are better de-
veloped on adapical teleoconch whorls, but fade on 4th and
later whorls, where they are pronounced only at shoulder and
periphery. Spiral sculpture is absent from most specimens
and the shell is glossy. Subadult shells from these popula-
tions look quite different from adults ones due to their shorter
last whorl, but the morphology of early teleoconch whorls
is identical. This form resembles late Miocene fossils, such
as Microvoluta marwicki (Vella, 1954) (illustrated by Beu &
Maxwell, 1990, pl. 27o) and M. nodulata Maxwell, 1988, from
deep-water deposits in New Zealand. This deep-water form
appears rather distinct, and is only poorly connected by inter-
mediates with forms from more shallow water. However, as we
did not find it co-occurring with any other form of M. joloensis,
and as specimens of M. joloensis from intermediate depths, in
500–700 m, show a tendency to larger protoconch diameter
with increasing depth, we interpret it as a deep-water morph of
M. joloensis.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 483
Figure 14 Morphometric comparison of Microvoluta joloensis (䊉,
populations from north New Caledonia) and M.
respergens,n.sp.(
䊏). PRE =exposed height of
protoconch; D2 =diameter of protoconch and first 1/4
teleoconch whorl (see Fig. 1); SFF =number of axial folds
on first three teleoconch whorls.
An isolated population from a seamount on the Loyalty
Ridge (BATHUS 3, sta. DW 790) is characterized by a
very slender shell (diameter/shell length ratio 0.36–0.47)
with strong knobs on the subsutural rim (Fig. 9J). Because
it resembles most some elongated forms of M. joloensis,we
also interpret it conservatively as a local variation of the latter;
molecular data might either prove or disprove this hypothesis.
The numerous lots from Fiji, Wallis and Futuna, and
Tonga show a variation most similar to that observed in
populations from 400–600 m off southern New Caledonia.
Practically all forms, from elongated ones (Fig. 9D, E) to
biconical (Fig. 9F, H) and strongly reticulated ones (Fig. 9G),
can be found in every archipelago (except Tonga, where the
only two shells are of the biconical type).
Radula and jaw of 2 specimens with biconical shell
(Wallis and Futuna, MUSORSTOM 7, sta. DW 601; south-
ern New Caledonia, MUSORSTOM 4, sta. CC246) have been
examined. The radula is typical for Volutomitridae (Fig. 11B);
median cusp/total tooth length ratio 0.56–0.62; lateral teeth
rather well developed and long. Jaw is in all details similar to
that of M. amphissa (Fig. 11E–G – see below).
Microvoluta respergens, n. sp. (Figs 13, 14, 15)
Type material: Holotype (dd) and 6 paratypes (dd) MNHN; 1
paratype (dd) NMNZ, 1 paratype (dd) AMS.
Type locality: Loyalty Ridge, 23◦49S, 169◦48E, 685–715 m
[BATHUS 3, sta. DW790].
Material examined: A total of six lots (30 specimens).
Loyalty Ridge. BIOGEOCAL, R/V Coriolis: sta. DW289,
20◦36S, 167◦00E, 830–840 m, 1 dd.
BATHUS 3, R/V Alis: sta. DW786, 23◦54S, 169◦49E,
699–715 m, 8 dd. – Sta. DW790, 23◦49S, 169◦48E, 685–
715 m, 10 dd (holotype and paratypes) [co-occurring with
M. joloensis]. – Sta. DW793, 23◦47S, 169◦49E, 731–
751 m, 2 lv, 3 dd. – Sta. DW794, 23◦48S, 169◦49E,
751–755 m, 1 lv.
Southern New Caledonia. BATHUS 2, R/V Alis: sta. CP743,
22◦36S, 166◦26E, 713–950 m, 5 dd.
Distribution: South of New Caledonia and Loyalty Ridge,
alive in 750 m, shells in 715–830 m. Except for one sample
from SW of New Caledonia, all other specimens come from a
single seamount (unnamed seamount labelled ‘J’ on ZONECO
maps) on the Loyalty Ridge.
Description (holotype) (Fig. 13A–C): Shell solid, glossy,
semitransparent, slender, fusiform, width 38% of height,
consisting of 1.875 protoconch and 6.0 teleoconch whorls. Pro-
toconch large, diameter (D2) 800 µm, high, elevation 710 µm.
Whorls convex, first whorl globose, smooth, semitransparent,
protoconch-teleoconch transition indistinct, marked by very
weak orthocline rib. First half of first teleoconch whorl prac-
tically smooth. Teleoconch whorls convex, with impressed su-
ture, slightly angulated at shoulder, without subsutural sul-
cus. Sculpture consisting of strong, widely spaced, arched
but nearly orthocline ribs, forming large rounded knobs on
shoulder; ribs equally well developed on all teleoconch whorls,
11 on first, 19 on second, 16 on third, 14 ribs on last whorl,
where they extend to shell base. Last whorl short, 58% of total
shell height. Aperture low, height 47% of shell height, narrowly
elongate, angulated at anterior fifth, where reflected outer lip
is flaring; smooth inside, except for a spiral lira correspond-
ing in its position to the row of shoulder knobs. Columella
without callus, with 4 rather low columellar plaits, adapical
one smallest. Siphonal canal moderately long, slightly curved
to right and backward. Colour of the shell uniformly greyish-
white.
Dimensions (holotype): Shell height 9.3 mm, diameter
3.5 mm, last whorl height 5.4 mm, aperture height 4.4 mm.
Largest adult (paratype): Shell height 9.6 mm, diameter
3.8 mm, last whorl height 5.4 mm, aperture height 4.5 mm.
Remarks:Microvoluta respergens, n. sp. is only moderately
variable in shell shape, degree of prominence of shoulder
knobs and in protoconch elevation. Diameter/height ratio in
adults ranges 0.38–0.43 (average 0.41, σ=0.02, n =6), last
whorl/shell height ratio 0.57–0.60 (average 0.58, σ=0.01,
n=6), aperture height/shell height ratio 0.47–0.50 (average
0.48, σ=0.01, n =6). Number of axial ribs on the first whorl
ranges 12–15 (average 12.9, σ=1.3, n =7), on second 15–19
(average 16.9, σ=1.6, n =7), on third whorl 12–16 (aver-
age 14.6, σ=1.8, n =7). Protoconch diameter ranges 770–
890 µm (average 820, σ=50, n =7), protoconch elevation
620–720 µm (average 670, σ=40, n =7). Subadults are much
less slender (diameter/height ratio 0.47) (Fig. 13F) and with
proportionately higher last whorl (last whorl/shell height ratio
0.61).
The general shell morphology of Microvoluta res-
pergens, n. sp. resembles that of M.joloensis, especially
specimens from north of New Caledonia. However, M. res-
pergens, n. sp. differs in having fewer, stronger axial ribs,
in having a distinctly angulated outer aperture lip, as well

484 Philippe Bouchet & Yuri I. Kantor
Figure 15 Geographical distribution of Microvoluta cryptomitra n. sp., Microvoluta cythara,n.sp.,Microvoluta dolichura,n.sp.,and
Microvoluta respergens, n. sp. Isobath 500 m.
as in having slightly less elevated protoconch (as shown
on scatter plot, Fig. 14). Microvoluta respergens,n.sp.and
M. joloensis have been taken together at BATHUS 3 sta. DW
790, where they differ markedly (compare Figs 13A and H).
Etymology:Respergere (Latin) – to pour, by reference to the
shape of the outer lip of the aperture.
Microvoluta cythara,n.sp.
(Figs 10B, D, 15, 16A–G, M, 17, 18)
Type material: holotype (lv) and 11 paratypes (2 lv and 9 dd)
MNHN; one paratype (dd) NMNZ, 1 paratype (dd) AMS.
Type locality: Coral Sea, Chesterfield plateau, 19◦53S,
158◦40E, 410 m [MUSORSTOM 5: sta. 362].
Material examined: A total of six lots (40 specimens).
Coral Sea, Chesterfield plateau. MUSORSTOM 5, R/V
Coriolis: sta. 337, 19◦54S, 158◦38E, 412–430 m, 1 dd. –
Sta. 339, 19◦53S, 158◦38E, 380–395 m, 3 dd. – Sta. 361,
19◦53S, 158◦38E, 400 m, 1 lv, 5 dd. – Sta. 362, 19◦53S,
158◦40E, 410 m, 3 lv, 12 dd (holotype and paratypes). – Sta.
378, 19◦54S, 158◦38E, 355 m, 2 dd. – Sta. 379, 19◦53S,
158◦40E, 370–400 m, 5 lv (1 specimen sectioned), 8 dd.
Distribution: Coral Sea, Chesterfield plateau, alive in 400–
410 m, shells from 355 m.
Description (holotype) (Fig. 16A–C): Shell solid, glossy,
elongate-fusiform, nearly biconical, width 43% of height, con-
sisting of 2.0 protoconch and 5.0 teleoconch whorls. Proto-
conch diameter (D2) 800 µm, protoconch elevation 605 µm,
whorls convex, smooth, protoconch-teleoconch transition
indistinct. Teleoconch whorls convex with adpressed suture
and strong subsutural sulcus, whorls distinctly concave below
subsutural sulcus and becoming convex at periphery. Sculpture
consisting of strong sigmoid opisthocline ribs, crossed by very
indistinct low spiral striae; 12 ribs on first whorl, 14 on second,
17 on third; axial ribs gradually becoming obsolete on last
whorl, last whorl with only indistinct ribs in last half. Rather
strong internal spiral lirae visible through semitransparent shell
(Fig. 10B), 11 in aperture. Last whorl height 64% of total shell
height. Aperture height 54% of shell height, narrowly elong-
ate, with spiral lirae inside, becoming obsolete at the lip, outer
lip distinctly deflected in adapical fifth. Columella without
a callus, with 4 widely spaced plaits, abapical one smallest.
Siphonal canal moderately long, straight. Colour of the shell
uniformly glossy white.
Dimensions (holotype): Shell height 10.1 mm, diameter
4.3 mm, last whorl height 6.5 mm, aperture height 5.5 mm.
Largest specimen (paratype) (Figs 16F–H): shell height
10.5 mm, diameter 4.5 mm, last whorl height 6.5 mm, aperture
height 5.7 mm.
Anatomy: Two specimens have been studied anatomically.
One dissected specimen (MUSORSTOM 5, sta. 362) had a
shell height of 7.7 mm, diameter 3.7 mm, last whorl height
5.4 mm, aperture height 4.8 mm. One specimen (MUSOR-
STOM 5, sta. 379; SL 9.6 mm) was sectioned. The description
is based mainly on the dissected specimen, with some details
added from the sectioned one.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 485
Figure 16 A–G, M, Microvoluta cythara, n. sp. A–D, F–G, M, MUSORSTOM 5, sta. 362. A–C, M, holotype, SL 10.1 mm; D, paratype, SL 7.7 mm;
F–G, paratype, SL 10.5 mm. E, MUSORSTOM 5, Sta. 379. E, SL 8.5 mm. H–L, Microvoluta dolichura,n.sp.,CORAIL2,Sta.DE16.H–J,
L, holotype, SL 10.1 mm; K, paratype, SL 10.2 mm. Scale bar 5 mm (A–K) and 0.5 mm (L–M).
External anatomy: The body consists of about 2.5 whorls
(1.5 whorls were retrieved from the shell), the mantle spans
slightly over 0.5 whorl, the nephridium about 0.3 whorl. The
body is yellowish-white and lacks pigmentation; it carries nar-
row spiral grooves, corresponding to the lirae on the internal
shell surface. Operculum absent. The foot has an ovate sole,
folded lengthwise. The siphon is short, simple, slightly pro-
truding beyond the mantle edge (Fig. 17A, B – s). The columel-
lar muscle is thick, consisting of 1.75 whorls, with three deep
grooves, corresponding to columellar plaits. Abapical muscle
branch completely detached from the rest. Mantle very thin
and semitransparent, covering head base. Head medium-sized,
with short conical tentacles and large eyes.
Mantle: Ctenidium occupying slightly more than half
of mantle length, curved and separated into two parts. An-
terior part (close to mantle edge) narrow, with lamellae having

486 Philippe Bouchet & Yuri I. Kantor
Figure 17 Anatomy of Microvoluta cythara, n. sp., male, MUSORSTOM 5, sta. 362. A–B, Body removed from the shell. C, Anterior view of the
head-foot, mantle cut along the left side, pulled aside and reflected. D, Anterior digestive system, oesophagus uncoiled, proboscis
sheath removed to show the proboscis. Abbreviations: aoe anterior oesophagus, col.m columellar muscle, ct ctenidium, dg
digestive gland, gl gland of Leiblein, mmoe muscular posterior part of the mid oesophagus, moe mid oesophagus, ne nephridium,
nr nerve ring, os osphradium, pen penis, per pericardium, poe posterior oesophagus, pr proboscis, prp propodium of the foot, s
siphon, sg salivary gland, st stomach, tcephalic tentacle, vl valve of Leiblein, vpr ventral proboscis retractor.
narrow base, hanging freely into the cavity. Posteriorly, the
ctenidium becomes much wider and consists of triangular
lamellae. Osphradium large, slightly wider than ctenidium,
asymmetrical, with the right side being at least 1.5×broader
than the left. Hypobranchial gland poorly developed, covering
partially the rectum and pallial gonoduct. Rectum very narrow,
anal gland not seen on dissection.
Digestive system: Proboscis preserved in semi-protracted
position, moderately long, about 0.76 mm, or 16% of aper-
ture height, cylindrical and protruded through mouth opening
(Fig. 17C – pr). In the sectioned specimen, the proboscis in re-
tracted position occupies most of rhynchocoel length. Probos-
cis walls thin, lumen between proboscis wall and thick-walled
oesophagus broad and filled by large, oval, probably glandular

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 487
Figure 18 Morphometric comparison of Microvoluta cythara,n.sp.(䊏) and two populations of Microvoluta joloensis (䊉). A, biconical
population from south of New Caledonia. B, population from north of New Caledonia. PRE =exposed height of protoconch; D2 =
diameter of protoconch and first 1/4 teleoconch whorl (see Fig. 1); D =shell diameter; SL =shell height.
cells. Proboscis and oesophagus walls connected by numerous
transverse muscle fibres. Oesophagus wall thick (about twice
as thick as proboscis wall) and muscular. Proboscis and oeso-
phagus probably act as muscular pump. Large unpaired ventral
proboscis retractor (Fig. 17D – vpr) attached to posterior part
of the rhynchodaeum (proboscis sheath) and bottom of ceph-
alic haemocoel. Anteriormost part of proboscis invaginated
inside, so that circular fold is situated around narrow mouth
opening. The small horse-shoe-shaped chitinous jaw lines the
anterior dorsal surface of the buccal cavity and is in all details
similar to that of Microvoluta amphissa (Fig. 11E–F). Dorsal
edge of jaw sharp and serving as cutting edge. Radula about
1.2 mm long, or 25% of aperture length. Lateral teeth simple,
needle-shaped. Width of central tooth about 18 µm (0.32% of
aperture length). Median cusp/total tooth length ratio 0.47. In
its posterior part, the radular sac is embraced by a muscular
convoluted rod, which lies completely within the protracted
proboscis. Subradular cartilages paired, not fusing in anterior
part, but connected with transverse muscle, and running along
the entire proboscis length.
Morphology of oesophagus very similar to that de-
scribed for other Volutomitridae (Ponder, 1972; Arnaud &
van Mol, 1979; Kantor & Harasewych, 1992; Bouchet &
Kantor, 2000b). Anterior oesophagus (between proboscis and
valve of Leiblein) relatively short and thin. Valve of Leiblein
(Figure 17D – vl) well demarcated and distinguished by a
more whitish colour than rest of oesophagus. Position of tor-
sion is situated at posterior part of the valve of Leiblein.
This is expressed in rotation of ventral channel of the valve,
which is seen as a dark strip through the wall of the valve.
Soon after the valve, the mid-oesophagus widens consider-
ably and forms two loops before passing through the circum-
oesophageal nerve ring. Posterior part of mid-oesophagus
(Fig. 17D – mmoe) becoming extremely thick and convo-
luted until the entrance of the gland of Leiblein, which is small
and tubular (Figure 17D – gL). Posterior oesophagus (after
opening of the gland) becoming very narrow and thin-walled.
Stomach relatively small, adjoining nephridium (Fig. 17B –
st), nearly U-shaped, but with a small caecum, similar in shape
to that of Volutomitra glabella (Bouchet & Kantor, 2000b)
and Peculator hedleyi (Ponder, 1972). Salivary glands large,
fused, consisting of few acini, very large in diameter. Access-
ory salivary gland rather long, coiled and protruding beyond
the base of the retracted proboscis. Duct very narrow, running
along ventral proboscis wall to open near mouth.
The dissected specimen was an immature male with a
rather short simple penis with open seminal groove (Fig. 17C –
pen).
Remarks:Microvoluta cythara, n. sp. is rather constant
in shell shape, with diameter/height ratio 0.43–0.48 (av-
erage 0.44, σ=0.02, n =7), last whorl/shell height ratio
0.62–0.71 (average 0.67, σ=0.04, n =7), aperture
height/shell height ratio 0.54–0.61 (average 0.58, σ=0.03,
n=7). Number of axial ribs on the first whorl 12–15 (average
13.4, σ=1.3, n =7), on second 14–17 (average 15.7, σ=1.1,
n=7), on third whorl 16–20 (average 17.6, σ=1.3, n =7).
Protoconch diameter (D2) ranges 800–840 µm (average 818,
σ=17, n =7), protoconch elevation 520–640 µm (average
580, σ=46, n =7).
M.cythara, n. sp. has some similarities to M. joloensis,
especially its biconical outline, but is readily distinguished
from it by the concave profile of the whorl above the peri-
phery, the larger and more elevated protoconch, and the more
numerous axial ribs on the spire whorls (Fig. 18).
Etymology: After the turrid genus Cythara, to which it bears
a superficial resemblance; used as a noun in apposition.
Microvoluta dolichura, n. sp. (Figs 15, 16H–L)
Type material: holotype (dd) and 4 paratypes (dd) MNHN.
Type locality: Coral Sea, Lansdowne-Fairway Bank, 20◦48S,
160◦56E, 500 m [CORAIL 2: sta. DE16].
Material examined: Only the type lot (five specimens).
Distribution: Known only from the type locality, Coral Sea,
Lansdowne-Fairway Bank, dead in 500 m.

488 Philippe Bouchet & Yuri I. Kantor
Description (holotype) (Fig. 16H–J): Shell solid, glossy,
narrow-fusiform, nearly biconical, width 39% of height, con-
sisting of 1.75 protoconch and 6.5 teleoconch whorls. Proto-
conch diameter (D2) 710 µm, protoconch elevation 710 µm,
whorls convex, smooth, first whorl swollen, strongly raised,
protoconch-teleoconch transition very indistinct. Teleoconch
whorls convex with adpressed suture and strong subsutural
sulcus, whorls distinctly concave below subsutural sulcus.
Sculpture consisting of strong sigmoid opisthocline ribs,
crossed by two strong spiral cords located between the sulcus
and periphery, the lower cord forming a prominent shoulder,
and very indistinct low spiral striae; 12 ribs on first whorl, 14
on second, 16 on third; axial ribs well pronounced on entire last
whorl, 15 in total. Eleven rather strong, closely spaced, spiral
cords on the canal. Moderately developed internal spiral lirae
visible through semitransparent shell (Fig. 10J), 8 in aperture.
Last whorl height 60% of total shell height. Aperture height
49% of shell height, narrowly elongate, with spiral lirae in-
side, becoming obsolete at the lip, outer lip simple, fragile.
Columella without a callus, with 4 widely spaced plaits, abap-
ical one smallest. Siphonal canal moderately long, narrow,
straight. Colour of the shell uniformly glossy white.
Dimensions: Shell height 10.1 mm, diameter 3.9 mm,
last whorl height 6.1 mm, aperture height 4.9 mm. Largest spe-
cimen (paratype) (Fig. 16K): shell height 10.2 mm, diameter
3.9 mm, last whorl height 6.4 mm, aperture height 5.4 mm.
Remarks:Microvoluta dolichura, n. sp. is rather constant
in shell shape, with diameter/height ratio 0.37–0.39 (n =3),
last whorl/shell height ratio 0.60–0.63 (n =4), aperture
height/shell height ratio 0.49–0.54 (n =4). Number of axial
ribs on the first whorl 11–13 (average 12, σ=1, n =5), on
second 13–16 (average 14.4, σ=1.1, n =5), on third whorl
15–16 (average 15.6, σ=0.5, n =5). Protoconch diameter
(D2) ranges 700–750 µm (average 730, σ=20, n =5), pro-
toconch elevation 670–780 µm (average 720, σ=50, n =5).
The number, strength and position of the spiral cords situated
below the subsutural sulcus vary from 1 to 3, and these are
better developed in the holotype than in other specimens. In
the illustrated paratype, there are three, closely spaced, but less
developed.
From Microvoluta cythara, n. sp., also found in the Coral
Sea but allopatric, M.dolichura, n. sp. is readily distinguished
by its higher spire, by its narrower shell, by the presence of the
spiral cords below the subsutural sulcus, and by the smaller
but much more elevated protoconch (Fig. 16L, M).
Etymology: From the Greek words dolichos (adjective), mean-
ing long, and uros, meaning tail, by reference to the attenuated
spire and siphon of the shell.
Microvoluta cryptomitra, n. sp. (Figs 15, 19A–E)
Type material: holotype and 3 paratypes in MNHN.
Type locality: Coral Sea, Chesterfield plateau, 21◦19S,
158◦00E, 975 m [MUSORSTOM 5: sta. 322].
Material examined: A total of four lots (nine specimens).
Coral Sea, Chesterfield plateau. MUSORSTOM 5, R/V
Coriolis: sta. 322, 21◦19S, 158◦00E, 975 m, 4 dd (holo- and
paratypes).
South of New Caledonia. BIOCAL, R/V Jean-Charcot:sta.
CP75, 22◦19S, 167◦23E, 825–860 m, 3 dd [co-occurring with
M. joloensis].
Loyalty Islands. BIOCAL, R/V Jean-Charcot: sta. DW79,
20◦40S, 166◦52E, 1320–1380 m, 1 dd [co-occurring with
M. joloensis].
MUSORSTOM 6: sta. DW468, 21◦06S, 167◦33E, 600 m,
1 dd [co-occurring with M. joloensis].
Distribution: Coral Sea (Chesterfield plateau), south off New
Caledonia, and Loyalty Islands, shells only in 600–1320 m.
Description (holotype) (Fig. 19A–B): Shell fragile, glossy,
high-fusiform, width 37% of height, consisting of 1.625
protoconch and 5.5 teleoconch whorls. Protoconch not large,
diameter (D2) 840 µm, raised, exposed height 750 µm, whorls
convex, smooth, protoconch-teleoconch transition marked by
orthocline axial rib. Teleoconch whorls slightly convex with
adpressed suture, weak subsutural sulcus, whorl profile con-
cave below sulcus and shoulder. Sculpture consisting of strong,
widely spaced, nearly orthocline ribs, equally well developed
on all teleoconch whorls, and forming pointed knobs at
shoulder, crossed by very indistinct low spiral striae; 11 ribs
on first whorl, 9 on second, 8 on third, 8 on last. Shell base and
canal with 6 low, but distinct, closely spaced spiral cords. Last
whorl height 59% of total shell height. Aperture height 48%
of shell height, narrowly elongate, outer lip simple. Columella
without callus, with 3 widely spaced plaits, abapicalmost smal-
lest. Siphonal canal moderately long, straight. Colour of the
shell uniformly white.
Dimensions: Shell height 9.4 mm, diameter 5.5 mm, last
whorl height 4.5 mm, aperture height 3.5 mm. The holotype
is the largest and best-preserved specimen, although drilled in
the penultimate whorl.
Remarks:Microvoluta cryptomitra, n. sp. is rather constant in
shell shape, protoconch size, dimensions and axial sculpture.
The spiral sculpture is slightly more variable, from nearly
obsolete in one paratype, to eight, very distinct, and more
widely spaced cords in another.
M.cryptomitra, n. sp. is readily distinguished from its
congeners by the narrow shell with a tall spire, and by its axial
ribs forming knobs at the shoulder. In general outline it strongly
resembles some species of Belomitra (Buccinidae), but is
separable instantly by the much more developed columellar
plaits.
Etymology: After the buccinoid genus Cryptomitra, one of
the synonyms of Belomitra (Buccinidae), to which it bears a
superficial resemblance; used as a noun in apposition.
Microvoluta sp. (Figs 19F, 21)
Material examined: North of New Caledonia.
MUSORSTOM 4, R/V Vauban: sta. DW196, 18◦55S,
163◦24E, 450 m, 1 dd.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 489
Figure 19 A–E, Microvoluta cryptomitra, n. sp. A–C, MUSORSTOM 5, sta. 322. A–B, holotype, SL 9.4 mm; C, paratype, SL 9.2 mm. D, BIOCAL,
sta. DW79, SL 8.6 mm. E, BIOCAL, sta. CP75, SL 9.2 mm. F, Microvoluta sp., north of New Caledonia, MUSORSTOM 4, sta. DW196, SL
6 mm. Scale bar for Figs A–E, Fig. F not at the same scale.
A single, worn specimen (Fig. 19F) is characterized by
a solid, oval shell with a rather high last whorl, nearly flat
teleoconch whorls, weak axial ribs, obsolete on the last two
whorls, and a very weak subsutural sulcus.
Dimensions: Shell height 6.0 mm, diameter 2.9 mm, last
whorl height 4.1 mm, aperture height 3.6 mm.
This specimen represents an unknown species, but the
lack of adequate material precludes formal description.
Microvoluta engonia,n.sp.(Figs20E–G,21,22)
Type material: holotype and 2 paratypes in MNHN.
Type locality: West coast of New Caledonia, 21◦07S,
164◦28E, 320–344 m [BATHUS 4, R/V Alis: sta. DW887].
Material examined: The type lot (3 specimens) is the only
known material.
Description (holotype) (Fig. 20E–F): Shell very small, rather
solid, semitransparent, glossy, biconical, width 54% of
height, consisting of 1.625 protoconch and 3.75 teleoconch
whorls. Protoconch small (although large by comparison with
teleoconch), diameter (D2) 620 µm, moderately raised, ex-
posed height 450 µm, whorls convex, smooth, semitrans-
parent. Protoconch-teleoconch transition marked by narrow,
weak, orthocline rib. Teleoconch whorls with impressed su-
ture, strongly angulated at periphery, without subsutural
sulcus. Whorl profile slightly concave between suture and
periphery and slightly convex below periphery. Sculpture
consisting of strong, slightly prosocline ribs, producing strong
rounded swellings at periphery; 10 ribs on first, 11 on second,
12 on third and last whorl, becoming obsolete on shell base.
Last whorl high, height 68% of total shell height. Aperture
height 55% of shell height, narrowly elongate, outer lip without
internal lirae, simple. Columella without callus, with 4 widely

490 Philippe Bouchet & Yuri I. Kantor
Figure 20 A–D, Microvoluta echinata, n. sp., BATHUS 2, sta. DW754. A–B, holotype, SL 5.7 mm; C, paratype, SL 4.5 mm; D, paratype, SL
4.5 mm. E–G, Microvoluta engonia, n. sp., BATHUS 4, sta. DW887. E–F, holotype, SL 3.75 mm; G, paratype, SL 3.8 mm. All shells at
the same scale.
spaced sharp plaits, abapical one smallest. Siphonal canal
moderately long, straight. Colour of the shell uniformly off-
white.
Dimensions: shell height 3.75 mm, diameter 2.04 mm,
last whorl height 2.54 mm, aperture height 2.06 mm. Largest
specimen: shell height 3.80 mm, diameter 2.0 mm, last whorl
height 2.62 mm, aperture height 2.12 mm.
Remarks: With only three specimens from a single popu-
lation at hand, it is difficult to evaluate the variability of
Microvoluta engonia, n. sp. Diameter/height ratio 0.53–0.54,
last whorl/shell height ratio 0.68–0.69, aperture height/shell
height ratio 0.55–0.56. Number of axial ribs on the first whorl
is constantly 10, on second 10–11, and on third whorl 10–12.
Number of protoconch whorls is rather variable from 1.625 to
2.125. Protoconch diameter ranges 610–670 µm, protoconch
elevation 440–480 µm.
Microvoluta engonia,n.sp.resemblesM. echinata,n.sp.
in shell outline and sculpture pattern, but differs from it in the
absence of a subsutural sulcus, and in having a slightly broader
shell (Fig. 22).
Etymology: From the Greek engonia, angular, with reference
to profile of the whorls; used as a Latin adjective.
Microvoluta echinata, n. sp. (Figs 20A–D, 21, 22)
Type material: holotype (dd) and 5 paratypes (dd) in MNHN.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 491
Figure 21 Geographical distributions of Microvoluta echinata,n.sp.,M. engonia,n.sp.,M. amphissa,n.sp.,Microvoluta sp., and Peculator
sp. Isobath 500 m.
Type locality: South of New Caledonia, 22◦23S, 166◦13E,
577–780 m [BATHUS 2: sta. DW754].
Material examined: A total of three lots (24 specimens).
South of New Caledonia. BATHUS 2, R/V Alis:sta.
DW754, 22◦23S, 166◦13E, 577–780 m, 6 dd (holotype and
paratypes). – Sta. DW755, 22◦22S, 166◦14E, 495 m, 2 dd. –
Sta. DW761, 22◦19S, 166◦11E, 490–500 m, 15 dd.
Description (holotype): Shell small, fragile, semitransparent,
glossy, biconical, width 46% of height, consisting of 1.75
protoconch and 4.8 teleoconch whorls. Protoconch medium-
sized, diameter (D2) 680 µm, moderately raised, exposed
height 550 µm, whorls semitransparent, convex, smooth.
Figure 22 Morphometric comparisons of Microvoluta echinata,n.sp.(䊏)andMicrovoluta engonia,n.sp.(䊉). TL1 =diameter of first
teleoconch whorl; TL2 =diameter of second teleoconch whorl; TL3 =height of first teleoconch whorl; TL4 =height of second
teleoconch whorl (see Fig. 1); BWL =height of last whorl; SL =shell height ratio.
Protoconch-teleoconch transition marked by strong orthocline
rib and change in shell transparency. Teleoconch whorls with
impressed suture, strongly angulated at periphery, subsutural
sulcus better pronounced on last and penultimate whorls.
Whorl profile slightly concave above periphery, slightly con-
vex below periphery on adapical teleoconch whorls, and nearly
flat between shoulder and periphery on penultimate and last
whorls. Sculpture consisting of strong, slightly prosocline
ribs, producing strong rounded swellings at periphery and on
shoulder of last and penultimate whorls, and extending to-
wards shell base of last whorl; 9 ribs on first whorl, 8 on
second, 10 on third. Last whorl height 55% of total shell height.
Aperture height 47% of shell height, narrowly elongate, outer
lip thin, simple, without internal lirae. Columella without

492 Philippe Bouchet & Yuri I. Kantor
callus, with 3 sharp plaits, central one strongest. Siphonal canal
short, straight. Colour of the shell uniformly off-white.
Dimensions: Shell height 5.70 mm, diameter 2.60 mm,
last whorl height 3.15 mm, aperture height 2.70 mm. Largest
specimen (paratype): shell height 5.90 mm, diameter 2.58 mm,
last whorl height 3.42 mm, aperture height 2.76 mm.
Remarks:Microvoluta echinata, n. sp. is rather constant in
shell shape. Diameter/height ratio 0.46–0.55 (average 0.49,
σ=0.04, n =5), last whorl/shell height ratio 0.58–0.67 (av-
erage 0.62, σ=0.04, n =5), aperture height/shell height ratio
0.47–0.56 (average 0.50, σ=0.03, n =5). Number of axial
ribs on the first whorl 7–10 (average 8.4, σ=1.0, n =5),
on second 8–10 (average 9.4, σ=0.8, n =5), and on third
whorl constantly 10. Protoconch diameter (D2) 670–730 µm
(average 700 µm, σ=20, n =5), protoconch elevation 520–
565 µm (average 540 µm, σ=20, n =5). One of the speci-
mens has a lirate aperture.
For a comparison with M. engonia, n. sp., see under that
species.
Etymology: The Latin adjective echinatus,-a,-um, meaning
spiny, with reference to the sculpture.
Microvoluta amphissa, n. sp. (Figs 10C, 11E–G, 21, 23)
Type material: Holotype and 15 paratypes MNHN, 4 para-
types NMNZ, 4 paratypes AMS.
Type locality: Norfolk Ridge, Bank Eponge, 24◦55S,
168◦22E, 508–532 m [SMIB 8: sta. DW146–147].
Material examined: A total of 21 lots (454 specimens).
South of New Caledonia and Norfolk Ridge.SMIB8,R/V
Alis: sta. DW146–147, 24◦55S, 168◦22E, 508–532 m, about
170 dd and lv (from which the type material has been selec-
ted). – Sta. DW148, 24◦56S, 168◦21E, 510 m, 11 dd. – Sta.
DW169, 23◦37S, 167◦42E, 447–450 m, 1 dd.
BIOCAL, R/V Jean-Charcot: sta. DW33, 23◦10S, 167◦10E,
675–680 m, 12 dd. – Sta. DW46, 22◦53S, 167◦17E, 570–
610 m, about 50 dd, 12 lv. – Sta. DW48, 23◦00S, 167◦29E,
775 m, 2 dd [co-occurring with M. mitrella]. – Sta. DW49,
23◦03S, 167◦32E, 825–830 m, 1 dd. – Sta. DW51, 23◦05S,
167◦45E, 680–700 m, 118 dd and lv. – Sta. DW66,
24◦55S, 168◦22E, 505–515 m, about 50 dd, 12 lv. – Sta.
DW77, 22◦15S, 167◦15E, 440 m, 1 dd [co-occurring with
M. joloensis].
BATHUS 2, R/V Alis: sta. DW720, 22◦52S, 167◦16E, 530–
541 m, 29 dd and lv. – Sta. DW721, 22◦54S, 167◦17E, 525–
547 m, 27 dd and lv.
BATHUS 3, R/V Alis: sta. DW809, 23◦39S, 167◦59E, 650–
730 m, 2 dd and 2 lv. – Sta. DW810, 23◦40S, 167◦59E, 850–
900 m, 3 dd.
CHALCAL 2, R/V Alis: sta. DW72, 24◦55S, 168◦22E,
527 m, 2 dd. – Sta. DW76, 23◦40S, 167◦45E, 470 m, 7 lv,
3 dd.
BERYX 11, R/V Alis: sta. DW09, 24◦52S, 168◦22E, 635–
680 m, 4 dd. – Sta. DW10, 24◦53S, 168◦21E, 565–600 m,
5lv.
NORFOLK 1, R/V Alis: sta. DW1692, 24◦56S, 168◦21E,
24◦56S, 168◦21E, 507–967 m, 3 lv, 10 dd. – Sta. DW1697,
24◦39S, 168◦38E, 569–616 m, 2 lv, 14 dd. – Sta. DW1704,
23◦45S, 168◦16E, 400–420 m, 1 lv.
Distribution: South of New Caledonia and Norfolk Ridge,
alive in 420–680 m, shells to 850 m.
Description (holotype) (Fig. 23A–C): Shell small, fragile,
semitransparent, glossy, fusiform, width 39% of height,
consisting of 2.0 protoconch and 4.25 teleoconch whorls.
Protoconch medium-sized, diameter (D2) 570 µm, moder-
ately raised, exposed height 530 µm, whorls convex, smooth,
semitransparent (Fig. 10C). Protoconch-teleoconch transition
marked by strong opisthocline rib. Teleoconch whorls con-
vex, evenly rounded, with impressed suture, and without
subsutural sulcus. Sculpture consisting of strong, narrow,
widely spaced, arcuate, nearly orthocline ribs, equally well
developed on all teleoconch whorls and on last whorl ex-
tending nearly to canal; 14 ribs on first whorl, 12 on second,
11 on third and last whorls. Last whorl 62% of total shell
height. Aperture height 52% of shell height, narrowly elong-
ate, outer lip thin, simple. Columella without callus, with 4
sharp, closely spaced plaits, middle ones strongest. Siphonal
canal short, curved backwards. Colour of the shell uniformly
off-white.
Dimensions: Shell height 6.16 mm, diameter 2.37 mm,
last whorl height 3.84 mm, aperture height 3.21 mm. Largest
specimen (BATHUS 3, sta. 809): shell height 7.47 mm, dia-
meter 3.47 mm, last whorl height 5.20 mm, aperture height
4.47 mm.
Radula and jaw of two specimens were examined. Rad-
ula is in all respects similar to that of other Microvoluta spe-
cies, differing from M. joloensis in having less developed,
shorter lateral teeth. Median cusp /total tooth length 0.57–0.63.
Jaw (Fig. 11E–G) chitinous, with porous surface (Fig. 11G)
(this may be an artefact of bleaching), rather thin, its vent-
ral edge on transverse sections sharp and acting as a cutting
edge.
Remarks: Diameter/height ratio ranges 0.38–0.50 (average
0.46, σ=0.03, n =22), last whorl/shell height ratio 0.57–0.72
(average 0.67, σ=0.03, n =22), aperture height/shell height
ratio 0.47–0.66 (average 0.57, σ=0.04, n =22). Number of
axial ribs on the first whorl 11–15 (average 12.8, σ=1.2,
n=11), on second 10–14 (average 12.0, σ=1.5, n =11), and
on third whorl 10–15 (average 12.3, σ=1.3, n =11). Proto-
conch diameter ranges 710–790 µm (average 770 µm, σ=20,
n=11), protoconch elevation 480–580 µm (average 540 µm,
σ=30, n =11).
Microvoluta amphissa forms rather distinct morphs, that
are never syntopic. One morph (to which the holotype be-
longs) is characterized by a slightly more slender shell, by
its evenly rounded whorls, by its slightly wider and more ar-
cuate axial ribs and by the absence of a shoulder angulation.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 493
Figure 23 Microvoluta amphissa, n. sp. A–D, SMIB 8, sta. DW146–147. A–C, holotype, SL 6.2 mm; D, paratype, SL 5.5 mm. E–F, morphotype
with pronounced subsutural sulcus. E, BIOCAL, sta. DW46, SL 4.5 mm; F, BIOCAL, sta. DW51, SL 6.5 mm. G, deep-water
morphotype, BATHUS 3, sta. DW809, SL 7.4 mm. H, specimen transitional between deep-water morphotype and morphotype with
pronounced sulcus, BATHUS 3, sta. DW809, SL 7.0 mm. I, specimen transitional between morphotype of type locality and
morphotype with pronounced sulcus, CHALCAL 2, sta. DW76, SL 5.7 mm. All shells at the same scale.
This morph was found in abundance at depths of 440–532 m.
Another morph has a stouter shell with less well developed
axial ribs, which form rounded swellings at the shoulder
(Fig. 23E–F). These swellings are connected by a single spiral
cord, best seen in the rib interspaces. This morph was abundant
at stations in slightly deeper water, in 547–680 m. Few inter-
mediate specimens have been found, and then only at stations
with a small number of specimens (CHALCAL2, sta. DW76 –
Fig. 23I). At even greater depth (730–850 m), the shell may
be even stouter and slightly larger (Fig. 23G), with less
pronounced, even obsolete, shoulder swellings, but intermedi-
ate specimens co-exist in the same station (Fig. 23H). Attempts
to distinguish these three morphotypes morphometrically with
the use of all shell parameters failed. This, in addition with the
occasional occurrence of shells with intermediate characters,
leads us to consider them conspecific.

494 Philippe Bouchet & Yuri I. Kantor
Figure 24 A–C, Peculator sp., BIOCAL, sta. DW38. A–B, SL 4.6 mm; C, SL 4.8 mm. D–G, Microvoluta mitrella, n. sp., BIOCAL, sta. DW48. D–E,
holotype, SL 10.0 mm; F, paratype, SL 8.9 mm; G, paratype, 10.5 mm. Scale bar for Microvoluta mitrella only.
Microvoluta amphissa, n. sp. is well distinguished from
its congeners by the combination of small adult size, well
developed axial ribs, and absence of a pronounced subsutural
sulcus.
Etymology: After the columbellid genus Amphissa,towhichit
bears a superficial resemblance; used as a noun in apposition.
Microvoluta mitrella,n.sp.(Fig.24D–G)
Type material: Holotype and three paratypes in MNHN.
Type locality: South of New Caledonia, 23◦00S, 167◦29E,
775 m [BIOCAL: sta. DW48].
Material examined: Only the type material [co-occurring with
M. amphissa,n.sp.].
Description (holotype): Shell large, glossy, elongate-oval,
width 43% of height, consisting of 1.75 protoconch and
4.125 teleoconch whorls. Protoconch very large, diameter
(D2) 1250 µm, raised, exposed height 940 µm, whorls evenly
convex, smooth. Protoconch-teleoconch transition indistinct.
Teleoconch whorls convex with impressed suture, rounded
shoulder and without subsutural sulcus. Sculpture consisting
of strong, straight, slightly prosocline ribs, equally developed
on all teleoconch whorls, on last whorl extending towards shell
base; 12 ribs on first whorl, 11 on second, 13 on third and last

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 495
whorls, crossed by spiral cords, 11 low and rounded cords
on shell base and canal, 4 abapicalmost strongest. Last whorl
high, height 70% of total shell height. Aperture smooth inside,
height 60% of shell height, narrowly elongate, outer lip thin,
simple. Columella without a callus, with 4 plaits, abapical one
indistinct. Siphonal canal moderately long, curved backward.
Colour of the shell uniformly off-white.
Dimensions: shell height 10.0 mm, diameter 4.3 mm, last
whorl height 7.0 mm, aperture height 5.9 mm. Largest speci-
men (Fig. 24G): shell height 10.5 mm, diameter 5.0 mm, last
whorl height 6.6 mm, aperture height 5.6 mm.
Remarks: The small number of specimens of Microvoluta
mitrella at hand is rather constant in shell shape and outline.
Diameter/height ratio 0.43–0.47, last whorl/shell height ratio
0.63–0.70, aperture height/shell height ratio 0.54–0.59. The
number of axial ribs on one paratype (Fig. 24F) 13 on first
whorl, 14 on second and third whorls. The protoconch is in-
tact in only one of the three paratypes and its size, diameter
1280 µm, elevation 880 µm, is very similar to that of the holo-
type.
Microvoluta mitrella is readily distinguished from its con-
geners by its very large protoconch.
Etymology: After the columbellid genus Mitrella,towhichit
bears a superficial resemblance; used as a noun in apposition.
Genus Peculator Iredale, 1924
Peculator sp. (Figs 21, 24A–C)
Material examined: South of New Caledonia. BIOCAL, R/V
Jean-Charcot: sta. DW38, 23◦00S, 167◦29E, 360 m, 3 dd.
Three worn, but very distinctive, shells strongly resemble in
general shell shape and sculpture pattern the Recent species of
Peculator. Shell height up to 4.8 mm, rounded with very low
spire, indistinct subsutural sulcus, closely set axial ribs and
rather distinct spiral striation. Diameter/height ratio 0.55–0.57,
last whorl/shell height ratio 0.72–0.74 shell height, aperture
height/shell height ratio 0.63–0.65.
This finding represents the first occurrence of the genus
outside Australia and New Zealand, but we prefer to leave the
species unnamed in view of the rather poor state of the speci-
mens.
Discussion
An overview of the volutomitrid fauna of the world known be-
fore the present paper, totaling 41 species (Appendix), reveals
two major, and two minor, centres of species richness. One
major centre is the Australia–New Zealand region, with a
total of 13 species (belonging to Volutomitra,Peculator and
Microvoluta) and maximum diversity off the southern and
eastern coasts of Australia (nine species) and off the North
Island of New Zealand (seven species). Another major centre
is central eastern America, in fact essentially the Caribbean,
where nine species (belonging to Volutomitra, Conomitra and
Microvoluta) have been recorded so far. The Antarctic is char-
acterized by its own radiation in the genus Paradmete (five
species), with two species penetrating the Magellanic province
(Fig. 25). Four species are known from South Africa (assuming
that Magdalemitra does belong to Volutomitridae), but several
species remain to be described (Kilburn, pers. comm.). The
fauna of middle and high latitudes in the northern hemisphere
is poor, with no more than two species sympatric at a global
scale. The scarcity, or even complete absence, of volutomitrids
in most parts of the Indo-Pacific is remarkable: a single spe-
cies is known from the Philippines and Hawaii, two in Japan,
and none at all from e.g. Indonesia. The fauna of Japan is
well inventoried and the paucity of volutomitrids there can-
not be explained by undercollecting. Thus placed in perspect-
ive, the discovery of 14 species of Volutomitridae in the New
Caledonia region places this part of the world as a major
centre of diversity for the family. It brings the total number of
Recent Volutomitridae known worldwide to 50 named (and
two still unnamed) species or, in other words, the New Cale-
donia region is home to 25% of the world volutomitrid
fauna.
The New Caledonia region as a centre of
volutomitrid diversity
The material studied in the present paper totals 178 lots and
1472 specimens, of which 149 lots and 1268 specimens are
from the New Caledonia region alone. Admittedly, this reflects
in part the intensity of the collecting effort there, compared
with other parts of the Indo-Pacific, but we believe that it does
reflect also the reality of a centre of volutomitrid diversity
in that part of the South-West Pacific. The 29 samples and
204 specimens collected outside the New Caledonia region
(SW Indian Ocean, Fiji, Wallis and Futuna, Tonga) amount
to respectively 16% and 14% of the total, but these repres-
ent a single species, Microvoluta joloensis,or7.1%ofthe
total number of species. Furthermore, the fact that four species
(Microvoluta engonia,M. mitrella,M. sp., and Peculator sp.)
are all still known from single lots suggests that more spe-
cies may be awaiting to be discovered in the New Caledonia
region.
Bathymetrically, the highest species diversity in New
Caledonia is essentially confined to the 250–750 m depth range
and, in that respect, differs from the Caribbean and Australia–
New Zealand regions, in which the highest richness starts in
the shallow offshore. Three of the New Caledonia species have
records deeper than 750 m (at 1980 m, a record of M. joloensis
which could be the deepest record for the family), but these
refer to empty shells and may have little or no biological sig-
nificance.
The high number of species in the New Caledonia
region appears to result from four factors: regional spatial
heterogeneity; frequency of hard substrates; syntopy; and a
historical heritage shared with Australia and New Zealand.
(a) Regional spatial heterogeneity. Not only are all but
one (Microvoluta joloensis) of the species of Volutomitridae
present in the New Caledonia region endemic to that region,
but also species are often restricted to one area within the
region (Table 2): the distribution of as many as 10 out of 14
species is restricted in this way; the Coral Sea plateaus and the
Loyalty Ridge (same latitude, but 900 km longitude apart)

496 Philippe Bouchet & Yuri I. Kantor
Figure 25 Geographic representation of the diversity of Volutomitridae in Pacific and Antarctic regions. The intensity of the tones of grey is
proportional to the number of species: respectively 1–2, 4–5, 6–7 and 14 species.
share only one of their cumulated six species; the areas just
north and south of New Caledonia (750 km apart) have to-
gether 10 species, but only three species are shared. Such re-
stricted distributions do not appear to be the result of sampling
artefact, and even species represented by many lots may
have surprisingly narrow ranges. Thus Volutomitra ziczac is
found in an area of 35 km of maximal extension north of
New Caledonia, and this restricted distribution is confirmed
by dredgings on the boat Tui II operatedbyM.Creyssac.
North of New Caledonia, V. glabella was recorded in 30 sta-
tions, clustering in an area of 80 km of maximal extension,
while in the south of New Caledonia it is confined to an area
less than 15 km in maximal extension (Bouchet & Kantor,
2000b).
(b) One environmental parameter that segregates the
deep-sea substrates of the New Caledonia area apart from
those of many western Pacific archipelagoes and continental
areas is the frequency of hard substrates. In fact, most sub-
strates of the Coral Sea plateaus, of the slopes north (Grand
Passage) and south (Norfolk Ridge) of New Caledonia, and
of the Loyalty Ridge are hard substrates. The only exceptions
are off the coasts of New Caledonia itself, where there is a
succession of soft substrates on the sediment cone at the out-
let of the barrier reef passes. A single sample of Microvoluta
joloensis (BATHUS 1, sta. CP651) and the type lot of M. en-
gonia, n. sp. appear to originate from such soft substrates. This
suggests that, at least in that part of the tropical Indo-Pacific,
volutomitrids prefer hard substrates, which in turn explains
their local relative abundance.
(c) Syntopy. Contrasting with the regional spatial het-
erogeneity discussed above, the present material also doc-
uments several instances of co-occurrence in the same sta-
tion (=syntopy; as opposed to sympatry =co-occurrence
of species in the same geographical area, but not necessar-
ily with the same ecological/bathymetric co-occurrence) of
two or more species of Volutomitridae. The three species of

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 497
Species Coral Sea North of New New Caledonia South of New Loyalty Ridge
Caledonia proper Caledonia/Norfolk
Ridge
Volutomitra glabella ++
V. vaubani ++
V. ziczac,n.sp. +
Microvoluta amphissa,n.sp. +
M. cryptomitra,n.sp. + + +
M. cythara,n.sp. +
M. dolichura,n.sp. +
M. echinata,n.sp. +
M. engonia,n.sp. +
M. joloensis +++
M. mitrella,n.sp. +
M. respergens,n.sp. +
M.sp. +
Peculator sp. +
Total number of species 3 5 1 8 3
Table 2 Regional distribution of the species of Volutomitridae in the New Caledonia area.
Volutomitra (V. glabella, V. ziczac and V. vaubani)may,
although exceptionally, co-occur in the north of New
Caledonia, and instances of co-occurrence of two of them
are not rare. There are also instances of co-occurrence of
Microvoluta joloensis with M. cryptomitra (three cases),
M. amphissa,M. respergens and M. mitrella, and of
M. amphissa with M. mitrella (one case each) on the Nor-
folk and Loyalty Ridges, but we have no evidence of more
than two species of Microvoluta co-occurring.
(d) Historical heritage. Although now situated in trop-
ical latitudes, New Caledonia has shared a long tectonic his-
tory with New Zealand, stretching back to the Mesozoic, and
this is reflected in numerous, well documented, cases of vi-
cariance in the terrestrial biota of the two land masses. The
geologically instant dispersal of invertebrate larvae over large
distances tends to obscure this historical heritage when shal-
low water biotas are compared, but this heritage remains ap-
parent when cold, deep-water taxa are considered. For in-
stance, the occurrence in New Caledonia of bathyal species
of, e.g. Alcithoe (Gastropoda Volutidae; Bouchet & Poppe,
1988) or Ataxocerithium (Gastropoda Cerithiopsidae; unpub-
lished observations), is best explained by the historically con-
tinuous distribution of these taxa on Norfolk Ridge connect-
ing the North Island of New Zealand and New Caledonia. In
other words, the New Caledonia volutomitrid richness deserves
separate recognition because it is situated at tropical latitudes,
but is otherwise essentially part of the Australia–New Zealand
radiation, with which it shares the same genera but not the
same species.
Applicability of paucispiral protoconch
morphometry to volutomitrid taxonomy
All known Recent species of Volutomitridae have paucis-
piral protoconchs indicating non-planktotrophic larval devel-
opment, and all are smooth, without any sculpture. However,
it would be erroneous to conclude that the protoconch is use-
less in volutomitrid taxonomy. In fact, even rather similar
paucispiral protoconchs of closely allied species, when ac-
curately measured, provide important information, allowing
species discrimination.
The number of protoconch whorls depends greatly on
the method of counting; in the present study, we have ap-
plied the method described under “Material and Methods” and
illustrated in Fig. 1. Cernohorsky (1970b, p. 93, figs. 190–
212) illustrated rather variable protoconch morphologies for a
number of Recent and fossil species of Volutomitridae. Unfor-
tunately, the protoconchs were not drawn in standard positions
and therefore their comparison is hardly possible, and the same
is true for several SEM photographs of protoconchs of Parad-
mete illustrated by Numanami (1996).
When placed in a similar, standard position, the pro-
toconchs of all species of Volutomitra and Microvoluta
studied by us seem to be very similar to each other in shape,
and differ essentially in size (Fig. 10 – all protoconchs at
the same scale). Thus, the average protoconch diameter (D2)
ranges 1100–1440 µm in species of Volutomitra, and 630–
820 µm in most species of Microvoluta (Table 3). How-
ever, the protoconch of Microvoluta mitrella,n.sp.isex-
ceptionally large for the genus, and is comparable in size
with those of species of Volutomitra. (Nevertheless, the gen-
eral shell shape suggest a placement in Microvoluta rather
than Volutomitra, though this remains to be confirmed ana-
tomically.) Number of protoconch whorls ranges 1.75–2.5 in
Volutomitra and 1.5–2.1 in Microvoluta.Atafinerresolu-
tion, when protoconch dimensions are plotted against each
other, or against other shell parameters, on a scatter plot, the
different forms of Microvoluta joloensis are not separable,
while M. cythara, n. sp. stands clearly apart from M. joloensis
(Fig. 18).

498 Philippe Bouchet & Yuri I. Kantor
Species D2, range D2, average σPRE, range PRE, σNumber of
(µm) (µm) (µm) average specimens
(µm)
Volutomitra glabella 1350–1650 1440 10 na 1240 80 8
V. vaubani 1030–1210 1100 40 630–1030 820 90 37
V. ziczac, n. sp. 1010–1300 1210 70 720–900 820 70 15
Microvoluta amphissa, n. sp. 710–790 770 20 480–580 540 20 12
M. cryptomitra, n. sp. 800–840 750–780 2
M. cythara, n. sp. 800–840 820 20 520–640 580 50 7
M. dolichura, n. sp. 700–750 730 20 670–780 720 50 5
M. echinata, n. sp. 670–730 700 20 520–570 540 20 5
M. engonia, n. sp. 610–670 630 30 440–480 460 20 3
M. mitrella, n. sp. 1246–1277 880–940 2
M. respergens, n. sp. 770–900 820 50 620–720 670 40 7
Table 3 Some standard protoconch measurements for studied species of Volutomitridae. D2 =diameter of protoconch and first 1/4
teleoconch whorl; PRE =exposed height of protoconch (see Fig. 1).
Anatomy
The anatomy of Peculator hedleyi and Microvoluta marginata
has been examined by Ponder (1972); of Paradmete fragil-
lima and P. c u r t a by Arnaud & van Mol (1979); of Vo-
lutomitra groenlandica alaskana by Kantor & Harasewych
(1992); and of V. glabella by Bouchet & Kantor (2000b).
The present paper describes the gross anatomy of Volutomitra
ziczac,n.sp.,andMicrovoluta cythara, n. sp., and provides
more superficial information on M. amphissa,n.sp.and
M. joloensis.
The morphology of the digestive system of the species
studied herein is rather uniform, and minor differences concern
the relative length of different parts of the oesophagus, as well
as the degree of fusion of the salivary glands. Conversely, we
found significant differences in the morphology of the jaw.
The volutomitrid jaw was first isolated and illustrated by
Kantor & Harasewych (1992) in Volutomitra groenlandica
alaskana, although Ponder (1972) and Arnaud & van Mol
(1979) had already reported a strong cuticular lining of the
buccal cavity. The jaw of species of Volutomitra forms a thin
Taxon Median cusp/total tooth length Reference
Volutomitra erebus 0.50 Bayer, 1971
V. glabella 0.37 Bouchet and Kantor, 2002b
V. groenlandica groenlandica 0.52 Sars, 1878
V. groenlandica alaskana 0.32 Kantor and Harasewych, 1992
V. persephone 0.43 Bayer, 1971
V. ziczac, n. sp. 0.42 this study
Microvoluta amphissa, n. sp. 0.57–0.63 this paper
M. cythara, n. sp. 0.47 this paper
M. joloensis 0.56–0.62 this paper
Paradmete arnaudi 0.72 Numanami, 1996
P. brevidensis 0.67 Numanami, 1996
P. curta 0.49 Numanami, 1996
P. fragillima 0.72 Numanami, 1996
Peculator hedleyi 0.70 Ponder, 1972
Table 4 Comparison of the shape of central radular tooth in different species of Volutomitridae.
cuticular shield, folded lengthwise to form an enclosed (V.
groenlandica alaskana) or semi-enclosed funnel (V. glabella,
V. z i c z a c , n. sp.), the narrow end of which protrudes through the
mouth opening. The jaw of the three species of Microvoluta
forms a thin horse-shoe-shaped plate, with long and narrow
lateral flaps; the ventral edge of its anterior part is sharp and
probably acts as a cutting edge. Kantor & Harasewych (1992)
speculated on the possible use of the jaw and radula in Vo-
lutomitra, and hypothesized that Volutomitra feeds on fluids,
the jaw being used to ‘seal’ minor incisions made by the radula
in the prey’s integuments. If correct, this hypothesis cannot be
extended to Microvoluta, since the jaw is not closed ventrally
and cannot be operating in the same way. The diet of Micro-
voluta is not known; Ponder (1972) had recorded fine mineral
particles, diatom cases and spicule-like fragments in the faecal
material of M. marginata.
Radular morphology is basically similar in all taxa
examined, and generic and specific differences are small. In
Volutomitra, the lateral teeth are very small and thin, while
in Microvoluta they are relatively much larger and more stout

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 499
(Fig. 11 – lt); they are also strongly developed in three of
four species of Paradmete (Numanami, 1996). The central
tooth generally has a long median cusp with a transversely
concave anterior surface, and the base of the tooth has a pair
of anteriorly bent, long, plates, the lower portion of which
are curved laterally. Further details of its morphology depend
significantly on the angle of observation, but strictly dorsal
views allow comparison of the relative length of the median
cusp; the ratio between cusp length and total tooth length dif-
fers significantly between species (Table 4). Although there is
overlap between genera, species of Volutomitra tend to have
the shortest cusp, those of Paradmete and Peculator the longest
one, with Microvoluta having a cusp of intermediate relative
length.
Acknowledgements
We would like to express our thanks to Richard Kilburn and
Richard Salisbury for their assistance in compiling the list of
Recent Volutomitridae, as well as for other valuable comments.
We thank Alan Beu for linguistic polishing, Pierre Lozouet and
Alan Beu for comments of the fossil record, Winston Ponder
and an anonymous referee for comments on an earlier version
of this paper.
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Appendix
Taxa Maximum Depth range Distribution Reference
size
Volutomitra
V. groenlandica alaskana 47 mm 73–1504 m N Pacific north of 32◦N Cernohorsky, 1970b
Dall, 1902
V. banksi (Dall, 1951) 43 mm 146–586 m New Zealand from Cernohorsky, 1970b
Banks Peninsula to
Chatham Islands
V. erebus Bayer, 1971 36 mm 567–597 m Colombia Bayer, 1971
V. bayeri Okutani, 1982126 mm 334–379 m Surinam Okutani, 1982
V. glabella Bouchet & 25 mm (190) 258–525 New Caledonia Bouchet & Kantor, 2000b
Kantor, 2000 (613) m
V. groenlandica (Beck in 30 mm 7–770 m N Atlantic north of 40◦N Cernohorsky, 1970b
M¨
oller, 1842) Bouchet & War´
en, 1985
V. hottentotta (Thiele, 1925) 8 mm 155 m S Africa Cernohorsky, 1970b; 1983
V. obscura (Hutton, 1873) 22 mm 9–64 m Southern Australia, Cernohorsky, 1970b
Tasmania, North
Island of New
Zealand
V. pailoloana ( J. Cate, 1963) 30 mm 468–518 m Hawaiian Islands Cernohorsky, 1970b
V. persephone Bayer, 1971 41 mm 664–1574 m Panama [Atlantic] Bayer, 1971
?V. tenella Golikov & 6.6 mm 1320 m Central Kurile Islands Golikov & Sirenko, 1998
Sirenko, 1998
V. vaubani Cernohorsky, 18 mm (255) 310–570 New Caledonia this paper
1982 (600) m
V. ziczac, n. sp. 16 mm (190) 300–450 New Caledonia this paper
(550) m
Appendix Checklist of the Recent species of Volutomitridae, with their geographical and bathymetrical distribution. Depth ranges in New
Caledonia refer to live-taken samples or, in parentheses, to empty shells. The status of depth records elsewhere in the world is
generally not known and may refer to empty shells.

New Caledonia: the major centre of biodiversity for volutomitrid molluscs 501
Taxa Maximum Depth range Distribution Reference
size
Paradmete Strebel, 1908
P. arnaudi Numanami, 1996 10.5 mm 300 m Antarctic Numanami, 1996
P. breidensis Numanami, 1996 7 mm 337–441 m Antarctic Numanami, 1996
P. cryptomara (Rochebrune 22 mm 55–220 m Magellanic Cernohorsky, 1970b
& Mabille, 1885)
P. curta Strebel, 1908 25 mm 95–650 m Kerguelen Is, Antarctic Cernohorsky, 1970b;
shelf Numanami, 1996
P. fragillima (Watson, 1882) 24 mm 30–603 m Falkland Islands to Cernohorsky, 1970b;
Antarctic continental Numanami, 1996
shelf
P. percarinata Powell, 1951 17 mm 300–810 m Antarctic Cernohorsky, 1970b
Peculator Iredale, 1924
P. baccatus Cernohorsky, 1980 6.5 mm 75–158 m Southern Australia Cernohorsky, 1980
P. hedleyi (Murdoch, 1905) 9.5 mm 5–64 m North Island of New Cernohorsky, 1970b
Zealand
P. obconicus (Powell, 1952) 7 mm 55–260 m North Island of New Cernohorsky, 1970b
Zealand
P. verconis Iredale, 1924 12 mm 18–46 m New South Wales, Wilson, 1994
Australia
P. porphyria (Verco, 1896) 11 mm 27–95 m Southern Australia, Cernohorsky, 1970b
North Island of New
Zealand
Microvoluta Angas, 1877
M. amphissa, n. sp. 7.5 mm 470–680 (850) m New Caledonia the present paper
M. australis Angas, 1877 11 mm 9–183 m Australia, New South Wales Cernohorsky, 1970b
M. blakeana (Dall, 1889) 10 mm 146–1171 m Caribbean Cernohorsky, 1970b
M. cryptomitra, n. sp. 9.5 mm (600–1320) m New Caledonia this paper
M. cythara, n. sp. 10.5 mm (355) 400–410 m New Caledonia this paper
M. dolichura, n. sp. 10 mm (500) m New Caledonia this paper
M. echinata, n. sp. 5.9 mm (500–577) m New Caledonia this paper
M. engonia, n. sp. 3.8 mm (320–344) m New Caledonia this paper
M. euzonata (Sowerby, 1900)29 mm sublittoral S. Africa Kaicher, 1976, Turner, 2001;
Kilburn, pers. comm.
M. garrardi Cernohorsky, 7 mm 100–120 m Australia, south Cernohorsky, 1975; Wilson,
1975 Queensland 1994
M. hondoana (Yokoyama, 10.5 mm 50–200 m Central Honshu, Kuroda et al. 1971;
1922) Japan Higo et al., 1999
M. intermedia Dall, 1890 15 mm 750–908 m Caribbean Cernohorsky, 1970b
M. joloensis Cernohorsky, 14.5 mm 250–578 SW Indian Ocean, the present paper
1970 (1980) m Philippines, New
Caledonia, Fiji, Tonga,
Wallis and Futuna
M. marginata (Hutton, 1885) 8 mm 20–260 m North Island of New Cernohorsky, 1970b
Zealand
M. miranda (E.A. Smith, 1891) 11 mm 120–750 m Australia, New South Cernohorsky, 1983
[=Microvoluta ponderi Wales
Cernohorsky, 1975]
M. mitrella, n. sp. 10.5 mm (775) m New Caledonia this paper
M. respergens, n. sp. 9.5 mm (715) 751 m New Caledonia this paper
M. royana Iredale, 1924 11 mm 27–402 m Eastern Australia, Cernohorsky, 1970b; 1978
Kermadec Is.
Appendix continued.

502 Philippe Bouchet & Yuri I. Kantor
Taxa Maximum Depth range Distribution Reference
size
M. stadialis (Hedley, 1911) 6 mm 90 m Southern Australia Cernohorsky, 1975; Wilson,
1994
M. superstes Bouchet & 5.6 mm 208–330 m NE Atlantic Bouchet & War´
en, 1985
War´
en, 1985
M. teretiuscula (Thiele, 1925) 8 mm 155 m S. Africa Cernohorsky, 1970b
?M. veldhoveni de Jong & 9 mm ? Curacao, Aruba de Jong & Coomans, 1988
Coomans, 1988
Conomitra Conrad, 1865
C. carribeana Weisbord, 1929 14 mm 91 m Colombia Petuch, 1987; MALACOLOG
C. leonardhilli Petuch, 1987 18 mm 35 m Venezuela Petuch, 1987
C. lindae Petuch, 1987 10 mm 35 m Colombia Petuch, 1987
Magdalemitra Kilburn, 1974
M. gilesorum Kilburn, 1974 20 mm sublittoral South Africa Kilburn, 1974
1Volutomitra bayeri Okutani, 1982 is hardly distinguishable from V. erebus Bayer, 1971, but a revision of the Atlantic species is beyond the scope of
this paper, and we treat these two nominal species as valid.
2Microvoluta euzonata is attributed to Volutomitridae with doubts, as it shares conchological characters of both Costellariidae and Volutomitridae;
the radula has never been examined. The only adequate illustration is provided by Kaicher (1976).
Appendix continued.