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Contribution to the knowledge of the family Caecidae: 16.
Revision of the Caecidae of Easter Island (Chile)
(Caenogastropoda: Rissooidea Gray J. E., 1847)
Contribución al conocimiento de la familia Caecidae: 16. Revisión
de los Caecidae de la Isla de Pascua (Chile) (Caenogastropoda:
Rissooidea J. E. Gray, 1847)
Bret RAINES* and Mauro PIZZINI**
Recibido el 26-X-2004. Aceptado el 11-II-2005
ABSTRACT
With the exception of two species, members of the family Caecidae from Easter Island have
been previously neglected. Based on type and additional material, a revision of the species
known to date from Easter Is. is herein proposed, with the description of 5 new species:
Caecum rehderi spec. nov., C. heterochromum spec. nov., C. pascuanum spec. nov., C.
rapanuiense spec. nov., C. campanulatum spec. nov.
RESUMEN
Con la excepción de dos especies, los miembros de la familia Caecidae de la Isla de
Pascua han sido previamente desatendido. Basado en el tipo y en el material adicional, se
propone aquí dentro, una revisión de las especies conocidas hasta la fecha de la Isla de
Pascua, y incluye la descripción de 5 nuevas especies: C. rehderi esp. n., C. heterochro-
mum esp. n., C. pascuanum esp. n., C. rapanuiense esp. n., C. campanulatum esp. n.
KEY WORDS: Mollusca, Caenogastropoda, Rissooidea, Caecidae, taxonomy, new species, Easter Island,
Western Pacific.
PALABRAS CLAVE: Mollusca, Caenogastropoda, Rissooidea, Caecidae, taxonomia, nuevas especies, Isla de
Pascua, Pacífico Occidental.
INTRODUCTION
Easter Island (Fig. 1) is found in a to-
tally isolated position approximately
3,500 Km from the coast of Chile. From a
zoogeographical point of view, Easter Is.
is in a very peculiar area within the east-
ern Indo-Pacific region, and to the point
that, in 1965, Schilder proposed the Ra-
panuian province as a separate biogeo-
graphical province from the Polynesian
province. The submarine seascape fea-
tures widely scattered corals affixed to
the rugged volcanic substrate. The de-
pauperate benthic community employs a
variety of adaptive strategies for survival
in an environment stressed by waves,
currents and the absence of mineral nu-
* Research Associate, Natural History Museum of Los Angeles County , P.O. Box 612 Victorville, CA 92393
USA. e-mail: rainesbk@yahoo.com
** Largo della Caffarelletta, 6, 00179 ROME (Italy). e-mail: ma.pizzini@libero.it
© Sociedad Española de Malacología Iberus, 23 (1): 49-65, 2005
49
trients. Most of the corals and other bot-
tom invertebrates are typical of the Indo-
Pacific reefs, but reefs have not formed.
The circulation pattern, and espe-
cially the marked upwelling between
the South Pacific and Mentor currents,
contributes to the isolation of the area.
In terms of marine ecosystems, this in-
sularity has also produced a high degree
of radiation in many groups, and partic-
ularly in the caenogastropods. Thus the
fauna can essentially be described as
typical Pacific fauna with a relatively
high number of endemic species. The is-
land’s marine benthic fauna is generally
characterised by a high degree of
species diversity and a low abundance,
and this is true for both hard and soft
bottoms. The meiobenthic family Caeci-
dae also follows this pattern.
The Caecidae of the Easter Island
have been scarcely studied in the past,
with the exception of the work of
R
EHDER
(1980). Past surveys have
reported endemicity rates within the
molluscan fauna ranging from 37% to
42% (R
EHDER
,1980, D
I
S
ALVO
, R
ANDALL
AND
C
EA
,1988, R
AINES
, 2002). Rehder
also indicates that some species appear
to have a dual relationship with certain
species from Hawaii, as well as species
from the Kermadec Islands. In prepara-
tion for his 1980 publication, Rehder
reviewed all previous studies and expe-
ditions. In addition to examining all the
Easter Is. material in US museums, he
also examined the full store of material
housed in the Museo National de Histo-
ria Natural in Santiago, Chile. In all,
Rehder examined over 7,000 specimens,
of which 3480 were collected during his
trip to the island in 1974.
In the mid 1980’s, DiSalvo and his
team conducted a comprehensive survey
of Easter Island’s sublittoral marine
environment. The authors of the present
work had the good fortune of having
access to examples of all the molluscan
material collected during DiSalvo’s
investigation. Other than the few publi-
cations that we have been working on
(O
LIVER
, 1915, S
CHILDER
, 1965, R
EHDER
,
1980, D
I
S
ALVO ET AL
., 1988, R
AINES
, 2002)
no other serious work on molluscs has
been completed during the last ten
years. With regard to Caecidae, during
the three trips to Easter Island, the
authors of the present work collected
more than 350 specimens of this family.
Rehder mentions only two species:
Caecum cf. solitarium Oliver, 1915, and C.
amydroglyptum Rehder, 1980. In all other
publications, which we have reviewed,
Caecidae are listed simply as ‘Caecum
species’. No other descriptions or illus-
trations were provided.
So we present herein a revision of
the species known to date from Easter
Is., based on type and additional mater-
ial, with the description of five new
species.
Abbreviations used:
AMS: Australian Museum Sydney,
Sydney (Australia)
CM: Canterbury Museum, Christchurch
(New Zealand)
LACM: Natural History Museum of Los
Angeles County, Los Angeles (U.S.A.)
MNHN: Museum National d’Histoire
Naturelle, Paris (France)
MPR: Mauro Pizzini collection.
NHML: Natural History Museum,
London (U.K.)
NMNZ: Museum of New Zealand Te
Papa Tongarewa, Wellington (New
Zealand)
NSMT: National Science Museum,
Tokyo (Japan)
USNM: National Museum of Natural
History, Washington D.C. (U.S.A.)
WAM: Western Australian Museum,
Perth (Australia)
Terminology:
Abapical: towards the apices (of the
septum)
Adapical: opposite to the apices direc-
tion (of the septum)
Aperture, apertural end: the round ante-
rior opening of the shell.
Apex, apical end: the smaller, narrower,
closed posterior end of the tube.
Cutting plane: the plane individuated
by the edge of the shell at the apex
(excluding septum and mucro).
Iberus, 23 (1), 2005
50
Interspace: area between rings, with /
without microsculpture.
Meiobenthic: referred to all interstitial
molluscs living in sediment of
varying granule size.
Microsculpture: usually visible at very
high magnification or under SEM can
be transverse, longitudinal or both.
Mucro: small to large prong projecting
from the septum.
Rings, annular sculpture: transverse,
raised sculpture (equivalent to the
axial sculpture of the normally
coiled gastropods).
Septum: closure of the shell at the apex,
as it sheds earlier stages.
Shell(s): the shell, beached without gas-
tropod.
Spm(s): live collected specimen(s), with
soft parts and/or operculum(a).
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
51
Figure 1. Biogeographical provinces within the tropical eastern Indo-Pacific as proposed by
S
CHILDER
(1965), and as illustrated by R
EHDER
(1980): Micronesian: M; Hawaiian: H; Fijian: F;
Polynesian: P; Rapanuian: R; Kermadec Islands: K (added by the authors).
Figura 1. Las provincias biogeographicas dentro del Indo-Pacífico oriental tropical propuestas por
S
CHILDER
(1965) e ilustradas por R
EHDER
(1980): Micronesian:M; Hawaiano:H; Fijian:F; Poline-
sio:P; Rapanuian:R; Kermadec Islands:K(añadida por los autores).
RESULTS
Superfamily R
ISSOOIDEA
Gray J. E., 1847
Family C
AECIDAE
Gray J. E., 1850
Genus Caecum Fleming, 1813
Diagnosis (B
ANDEL
, 1996): “The shell of the teleoconch is a small, slightly curved tube orna-
mented only with growth lines, numerous ring-like collabral lirae ad/or axial ribs. The poste-
rior end of the tube is closed by a conical septum. The protoconch is trochospirally or planispi-
rally coiled. Uncoiling of the shell begins after metamorphosis”.
Type species (B
ANDEL
, 1996): Dentalium imperforatum Kanmaker, 1798 (= trachea Montagu, 1803)
from Europe, Mediterranean Sea and Atlantic to southern England.
Caecum rehderi spec. nov. (Fig. 2)
Caecum cf. solitarium; Rehder, 1980: 31-32, pl. 5, fig. 11.
Type material: Holotype, LACM 3019; 1 paratype, LACM 3020; 1 paratype, USNM 756269; 1
paratype, MNHN.
Material examined: 1 specimen, Onetea, Hotuiti (length: 2.42 mm, USNM 756269) (Oct. 1974, leg.
H. Rehder); 4 specimens, Punta Rosalia, east of Anakena (Apr. 1998, leg. B. Raines),
Type locality: In sand collected along the base of cliffs at 10-20m, off Punta Rosalia, east of
Anakena, Easter Is., Chile. 27° 04’ 18” S, 109° 19’ 45” W.
Description: Shell small (holotype
measures, length: 2.08 mm; width: 0.42
mm), tube-like, slender, gently arched,
semi-translucent to opaque white. Tube
seemingly smooth almost glassy, sub-
cylindrical, with posterior end only
slightly smaller than anterior end.
Microsculpture nearly obsolete, with
only fine annular growth lines sometimes
present under magnification. Anterior
end somewhat flared just above aperture
Iberus, 23 (1), 2005
52
Figure 2. Caecum rehderi spec. nov. A: holotype LACM 3019, gold coated, length 2.08 mm; B:
detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 2. Caecum rehderi spec. nov.A:holotipo LACM 3019, metalizado en oro, longitud 2,08 mm;
B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
with incised annular rings. Aperture cir-
cular, but slightly constricted. Posterior
end with tapered rim. Septum not
retracted, subquadrate lateral outline
inclined with elevated edge slightly right
of center when viewed frontally. Opercu-
lum and soft parts unknown.
Original description of C. cf. solitar-
ium Rehder, 1980: “Diagnosis. Shell
small, 2.4 to 2.7 mm in length, glassy,
grayish-white to whitish, slender, gently
A
B
D
C
500 µm
20 µm
100 µm
100 µm
curved, diameter at posterior end only
slightly smaller than at anterior end,
where the aperture is slightly con-
stricted and somewhat opaque above
the aperture; the sculpture consists of
fine, rather crowded, subobscure
(worn?) annular riblets that gradually
and slightly increase in strength toward
the aperture; septum exserted, sub-
quadrate with a slightly convex surface
inclined from an elevated edge at the
right dorsal sector to the edge of the
posterior rim of the shell at the left
ventral sector.
Range. Kermadec Islands (and
Easter Island ?).
Material. 1 specimen from sta E-27A,
USNM 756269.
Measurements (mm). USNM 756269:
length, 2.42; diameter at anterior end, 0.4“.
Discussion: Rehder reported a caecid
from Easter Island, which he tentatively
identified as Caecum cf. solitarium Oliver,
1915. However, it seems that Rehder un-
fortunately overlooked several key char-
acteristics within Oliver’s description.
The first being the septum of C. solitar-
ium, which O
LIVER
(1915) described as
“…hemispherical, making an abrupt
shoulder at the junction of the shell”;
even the septum of Rehder’s specimen
(Fig. 3) could be associated to a tale ty-
pology. Oliver also mentions, that the
sculpture of C. solitarium consists of sim-
ple growth lines, while Rehder refers to
the sculpture as consisting of suboscure
(worn?) annular riblets that gradually
and slightly increase in strength toward
the aperture. Other main difference be-
tween C. solitarium Oliver, 1915 and C.
solitarium sensu Rehder is that the first
has a nearly uniform diameter, while the
second shows the diameter at posterior
end only slightly smaller than at ante-
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
53
Figure 3. Caecum cf. solitarium Rehder (1980). A: USNM 756269, uncoated, length 2.42 mm; B:
detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 3. Caecum cf. solitarium Rehder (1980). A: USNM 756269, no metalizado, longitud 2,42 mm;
B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
1 mm
20 µm
200 µm
300 µm
A
B
D
C
rior end. Furthermore, it appears Re-
hder did not examine Oliver’s type ma-
terial, because if he would have done,
he would have noted that the two speci-
mens have significantly different ante-
rior ends (Figs. 3D, 4B), and that the
holotype of C. solitarium is badly broken
and lacks the entire posterior end (Fig.
4). The damage to the holotype is old
and worn, and possibly occurred in situ
suggesting that Oliver may have chosen
an imperfect specimen as the type and
actually described another in his de-
scription. (Scofield, 2002, pers. commu-
nication). Rehder’s specimen is, how-
ever, consistent with C. rehderi, and
therefore, has been designated as the
paratype. Although Rehder broke the
anterior end of his specimen while mea-
suring it, all the pieces were available
for examination. The specimens which
we found, actually showed a series of
small rings along the entire tube; and
apart from the relativity of the term’s
significance, we hold that the difference
between our specimens and those de-
scribed by the two authors falls within
the species’ range of variability, in light,
above all else, of the high degree of
adaptation of the local molluscs to the
island’s distinguishing geo-climatic con-
ditions. It is known that a number of
species of Caecidae (i.e. C. lightfootae
Pizzini, Nofroni and Oliverio, 1994),
though they have the same general
shape (septum, tube and aperture),
could show a very wide range of vari-
ability in terms of the type of sculpture.
Remarks: Caecum rehderi seems to be
an unusually fragile species. Of the five
known specimens, Rehder chipped the
aperture of his specimen (USNM
756269) while measuring it, the holotype
has a small longitudinal crack toward
Iberus, 23 (1), 2005
54
Figure 4. Caecum solitarium Oliver, 1915. A: Holotype CM M2867, uncoated, length 1.68 mm;
B: detail of aperture; C: microsculpture; D: detail of posterior. SEM imaging by N. Andrews.
Figura 4. Caecum solitarium Oliver, 1915. A: Holotipo CM M2867, no metalizado, longitud 1,68 mm;
B: detalle de la abertura; C: microescultura; D: detalle trasero. Imágenes al MEB por N. Andrews.
300 µm
20 µm
200 µm
100 µm
A
BD
C
the aperture end, the other paratype has
a chip in the aperture, and the junior
author completely crushed another
specimen while examining it.
Geographical distribution: Oliver
described Caecum solitarium only from
the Kermadec Islands, while Rehder
tentatively indicated the species as
being from Easter Is. In our opinion,
according to the present knowledge, C.
solitarium is restricted to the Kermadec
Is.
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
55
Figure 5. Caecum amydroglyptum Rehder, 1980. A: holotype USNM 757977, uncoated, length 1.67
mm; B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 5. Caecum amydroglyptum Rehder, 1980. A: holotipo USNM 757977, no metalizado, longitud
1,67 mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
Caecum amydroglyptum Rehder, 1980 (Figs. 5, 6)
Caecum amydroglyptum; Rehder, 1980: 32, pl. 5, fig. 12.
Type material: Holotype, USNM 757977; 1 paratype, USNM 757978
Material examined: Original types. Holotype, USNM 757977; paratype, USNM 757978, (Oct. 1974,
leg. H. Rehder). 132 specimens in sand collected along the base of cliffs at 10-20m, off Punta Rosalia,
east of Anakena, 27° 04’ 18” S, 109° 19’ 45” W (Apr. 1998, leg. B. Raines).
Voucher material: 4 specimens were deposited in each of the following institutions: LACM; USNM
1018792; MNHN; NHML; NMNZ M.273207; NSMT Mo 73562; AMS C.205278; WAM S13783, and
6 specimens (3 adults/3 juveniles), MPR. 13 shells, beach of Anakena Bay, on the northern coast of
Easter Is., picked up among the rocky bottom on the west side of the bay at low tide, among com-
munities of Dictyotales, with Galaxaura obtusata. (12-1-1995, leg. E. Rolán), MPR.
Type locality: Station E-27A, Onetea, Hotuiti: in patch of sand above high tide level.
A
B
D
C
200 µm
500 µm
20 µm
300 µm
Original description: “Shell small,
from 1.3 to 1.7 mm in length, curved,
rather evenly cylindrical with the ante-
rior end in fully grown specimens
slightly swollen above the aperture;
glassy grayish white to light orange
yellow in color; sculpture consists of
rather strong, somewhat distantly
spaced annular ribs that become more
or less obscure in the middle part of the
shell, with microscopic, longitudinal
wavy striae that are obscure at the ante-
rior and posterior ends; septum, low,
dome-shaped. “
Additional description: Shell small
(mean length: 1.7 mm; width: min. 0.3
mm, max 0.4 mm), curved, colour
grayish white. The tube is perfectly
cylindrical, except near the aperture,
and its sculpture consists of about 36-40
rings, with some in the middle part of
the shell being less raised and changing
their shape, until they resemble very
fine growth lines. Microsculpture
formed by longitudinal worm-like striae
visible at enlargement of at least 180x.
Septum dome-shaped, slightly raised
over the cutting plane. Aperture consist-
ing of a large protuberance crossed by
slightly raised rings. Operculum and
soft parts unknown.
Remarks: We agree totally with
Rehder’s conclusions; because we have
“…been unable to identify this species with
any published taxon” from either the
Indo-Pacific Provinces, the Panamic
Prov. or the Chilean Prov. We have
found only one species that resembles C.
amydroglyptum, which is C. vertebrale
Hedley, 1899, from Funafuti Is. It is
quite similar to amydroglyptum in terms
of the sculpture of the tube, longitudinal
Iberus, 23 (1), 2005
56
Figure 6. Caecum amydroglyptum Rehder, 1980. A: Voucher specimen LACM, gold coated, length
1.53 mm; B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D.
Geiger.
Figura 6. Caecum amydroglyptum Rehder, 1980. A: El espécimen del vale LACM, metalizado en oro,
longitud 1,53 mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB
por D. Geiger.
A
B
D
C20 µm
500 µm
100 µm
100 µm
microsculpture and septum, but
Rehder’s species shows a much greater
swelling of the tube above the apertural
end, which is crossed by small sculp-
tured rings, while the adapical part of
vertebrale has almost the same diameter
of the tube. In addition, C. amydroglyp-
tum presents, along the entire length of
the tube, a very strong microsculpture
consisting of worm-like, longitudinal
striae, covering also the top of the rings,
while that of vertebrale is an indistinct
microsculpture not surely comparable to
a real striation (pers. observ.).
Geographical distribution: This species
would appear to be limited to Easter Is.
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
57
Figure 7. Caecum heterochromum spec. nov. A: holotype LACM 3021, gold coated, length 1.42
mm; B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 7. Caecum heterochromum spec. nov. A: holotipo LACM 3021, metalizado en oro, longitud 1,42
mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
Caecum heterochromum spec. nov. (Figs. 7, 8)
Type material: Holotype, LACM 3021; 6 paratypes, LACM 3022; 6 Paratypes, USNM 1018789; 6
Paratypes, MNHN; 6 Paratypes, NHML; 6 Paratypes, NMNZ M.273205; 6 Paratypes, NSMT Mo
73560; 6 Paratypes, AMS C.205275; 6 Paratypes, WAM S13780; 9 Paratypes, MPR.
Material examined: 168 specimens: off Hanga Nui; and 8 specimens off the western coastline
near Tahai (Dec. 2000, leg. B. Raines). 39 shells, beach of Anakena Bay, on the northern coast of
Easter Is., picked up among the rocky bottom on the west side of the bay at low tide, among
communities of Dictyotales, with Galaxaura obtusata. (12-1-1995, leg. E. Rolán) MPR.
Voucher material: 39 shells, beach of Anakena Bay, on the northern coast of Easter Is., picked up
among the rocky bottom on the west side of the bay at low tide, among communities of Dicty-
otales, with Galaxaura obtusata. (12-1-1995, leg. E. Rolán) MPR.
A
B
D
C
200 µm
20 µm
100 µm
100 µm
Type locality: In sand collected along the base of cliffs at 20m off Hanga Nui, Easter Is., Chile.
27° 07’ 46” S, 109° 16’ 35” W.
Derivation of the name: From the greek ετερος: other and χρωµα: colour.
sponding breadth and depth, particu-
larly in the upper portion of the tube
and near the aperture, to others that lack
any type of sculpture; these two extreme
represent the limits of the species’ range
of variability, given that they were
found in intermediate specimens whose
rings are barely visible. The microsculp-
ture also presents a wide range of vari-
ability, with some specimens not
showing any trace of microsculpture,
while the surface of other specimens, at
an enlargement of 30x, presents a
microsculpture consisting of a large
number of very fine, worm-like striae
Iberus, 23 (1), 2005
58
Figure 8. Caecum heterochromum spec. nov. A: paratype from lot LACM 3022, gold coated, length
1.53 mm; B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 8. Caecum heterochromum spec. nov. A: paratipo de la porción LACM 3022, metalizado en oro,
longitud 1,53 mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB
por D. Geiger.
Description: Shell small (mean
length: 1.6 mm; mean width: 0.4 mm)
with the tube subcylindrical in shape in
the abapical part and cylindrical up to
the vicinity of the aperture (Fig. 8),
where there is a slight swelling, fol-
lowed by a narrowing of the tube; the
aperture is perfectly circular, simple and
rimmed by a very slight flaring towards
the outside. The septum is dome-shaped
and slightly raised over the cutting
plane. Its sculpture is extremely vari-
able, ranging from specimens with
approximately 50 small raised rings that
are separated by interstices of corre-
A
BD
C
100 µm
100 µm
20 µm
200 µm
that follow its axial direction, while
others have a rough surface. C. hete-
rochromum has an extremely variable
colouring and pattern; white, cream-
coloured shell with a pattern consisting
of brown, zigzagging lines running
almost parallel in a horizontal direction
(axial). There are also some specimens
showing a brown irregular stripe in the
middle portion of the shell. The colour-
ing is again a creamy white, with an
irregular vertical design consisting of
unequal spots. Operculum corneous,
light brown; its external side consists of
a smooth central nucleus and 5-6 con-
centric rings that run from this nucleus
up to the external border. Soft parts
unknown.
Remarks: Caecum heterochromum,
despite the limited nature of the name,
it is, in absolute terms, the most variable
of the species to be found on Easter Is.
In fact, its range of variability involves
not only its colouring and patterns, but
also major morphological characteris-
tics, such as microsculpture and sculp-
ture. Nevertheless, the silhouette, the
form of the septum and that of the tube,
as well as the apertural end, which,
when taken as a whole, constitute the
general form, are a constant that we
consider to be a distinguishing charac-
teristics of this species.
Geographical distribution: The species
is currently noted only in relation to
Easter Is.
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
59
Figure 9. Caecum pascuanum spec. nov. A: holotype LACM 3023, gold coated, length 1.64 mm;
B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 9. Caecum pascuanum spec. nov. A: holotipo LACM 3023, metalizado en oro, longitud 1,64
mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
A
B
D
C20 µm
100 µm
100 µm
500 µm
Caecum pascuanum spec. nov. (Fig. 9)
Type material: Holotype, LACM 3023; 2 paratypes, LACM 3024; 1 paratype, USNM 1018790; 1
paratype, MNHN; 1 paratype, NHML; 1 paratype, AMS C.205276; 1 paratype, WAM S13781; 1
paratype, MPR.
Material examined: 9 specimens, Hanga-Teo on the northern coastline (Dec. 2000, leg. B. Raines).
Type locality: In silty mud collected at 15m in cave off Hanga-Teo on the northern coast, Easter Is.,
Chile, 27° 03’ 37” S, 109° 21’ 58” W.
Derivation of the name: The name of this new species comes from a latinized adjective formed
from the Spanish name of the island, “Isla de Pascua”.
Description: Shell small (holotype
measures, length: 1.96 mm; width: 0.36
mm), gently curved. The tube, evenly
cylindrical for almost its entire length,
presents a slightly smaller diameter only
in the abapical part. Towards the adapical
part, the tube widens visibly in a large
varix crossed by 5-6 rings that are sizable
but raised to various degrees, being sepa-
rated by interspaces that also vary in
terms of their depth and width. The
Iberus, 23 (1), 2005
60
Figure 10. Caecum rapanuiense spec. nov. A: holotype LACM 3025, gold coated, length 1.58 mm;
B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 10. Caecum rapanuiense spec. nov. A: holotipo LACM 3025, metalizado en oro, longitud 1,58
mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
septum protrudes to a significant extent
over the cutting plane with an unguiform
mucro, visible to a greater or lesser extent
and oriented towards the dorsal side of
the tube. Frequently visible on the cutting
plane are residues of what may be a tem-
porary septum (P
IZZINI
, N
OFRONI AND
O
LIVERIO
, 1998). Even under intensive
enlargement, no microsculptures are
visible. Circular aperture. Operculum
and soft parts unknown.
A
B
D
C20 µm
100 µm
100 µm
500 µm
Remarks: Caecum pascuanum presents
numerous morphological analogies with
C. rehderi, including the shape of the
tube and the septum, though it is set
apart by a large varix crossed by rings,
which is completely absent in the other.
In fact, this varix, though it can be
accentuated to a greater or lesser extent
- for that matter, consistently within the
range of variability - is always present
and would appear to represent the dis-
tinguishing morphological characteris-
tics of this species.
Geographical distribution: The species
is currently known only in its typical
location.
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
61
Figure 11. Caecum crystallinum Folin, 1879. A: holotype NHML 1887.2.9.2363; B: detail of aper-
ture. SEM imaging by K. Way.
Figura 11. Caecum crystallinum Folin, 1879. A: holotipo NHML 1887.2.9.2363; B: detalle de la
abertura. Imágenes al MEB por K. Way.
Caecum rapanuiense spec. nov. (Fig. 10)
Type material: Holotype, LACM 3025; 2 paratypes, LACM 3026; 1 paratype, USNM 1018791; 1
paratype, MNHN; 1 paratype, NHML; 1 paratype, NMNZ M.273206; 1 paratype, NSMT Mo 73561;
1 paratype, AMS C.205277; 1 paratype, WAM S13782; 1 paratype, MPR.
Material examined: 12 specimens, off the western coastline near Tahai (Dec. 2000, leg. B. Raines).
Type locality: Dredged at 30m in fine sand off the western coastline near Tahai, Easter Is., Chile,
27° 07’ 20” S, 109° 26’ 30” W.
Derivation of the name: This species take its title from the ancient name for Easter Is., which was
Rapa Nui.
Description: Shell small (dimensions
of the spm no. 3 from Easter Is., length:
1.5 mm; width: 0.35 mm), slightly
curved. Tube completely smooth
showing only a microsculpture consist-
ing of very weakly defined growth lines.
Septum dome-shaped, with the mucro
reduced to a small pedunculum, resem-
bling a squashed ball, found on the exte-
rior and oriented to the right. Aperture
simple, with no varix and only slight
swelling: further on the swelling tends
to contract, with a slightly reflected lip.
Growth stage and soft parts unknown.
Remarks: Following an initial exam-
ination, we tentatively classified this
species as C. crystallinum Folin, 1879,
despite the absence of the mucro in the
original type (Fig. 11), but it is
straighter, and the texture of the shell
is different, exhibiting under the
microscope fine longitudinal striations
(Fig. 11B), while C. rapanuiense shows
only very fine growth lines (Fig. 10C).
It also resembles C. glabriforme
Carpenter, 1857, but this species has
fairly strong microsculpture and a
large well developed septum. In terms
AB
185 µm
52.6 µm
of the general shape of the tube and
septum, it resembles C. neocaledonicum
Folin, 1868, but the latter shows some
raised rings in the abapical part of the
tube near the aperture (P
IZZINI
, 1998),
while our species is completely
smooth.
Geographical distribution: Caecum
rapanuiense is actually known only from
Easter Is., the type locality.
Iberus, 23 (1), 2005
62
Figure 12. Caecum campanulatum spec. nov. A: holotype LACM 3027, gold coated, length 1.96
mm; B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 12. Caecum campanulatum spec. nov. A: holotipo LACM 3027, metalizado en oro, longitud 1,96
mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
Caecum campanulatum spec. nov. (Fig. 12)
Type material: Holotype, LACM 3027; 1 paratype, LACM 3028; 1 paratype, USNM 1019067.
Material examined: 6 specimens, off Hanga Nui (Dec. 2000, leg. B. Raines); 2 specimens, Punta
Rosalia, east of Anakena (Apr. 1998, leg. B. Raines).
Type locality: In sand collected along the base of cliffs at 20m, off Hanga Nui, Easter Is., Chile,
27° 07’ 46” S, 109° 16’ 35” W.
Derivation of the name: The name of the new species comes from the latinized adjective campan-
ulatus, which refers to the bell-shaped form of the apertural end.
Description: Shell small (holotype’s
dimensions, length: 1.64 mm; width:
0.31 mm). Tube slightly arched, slender,
with it’s abapical part only slightly
smaller then adapical. The tube widens
slightly near the apertural end, with a
silhouette that closely resembles that of
a bell, quickly narrowing itself once
again and ending in a sharp edge. The
microsculpture is quite obsolete and
A
BD
C
500 µm
20 µm
100 µm
100 µm
scarcely visible, even under intensive
optical enlargement, while the sculpture
would appear to consist of rings, which
are also barely observable, though they
are more visible near the aperture. The
septum is dome-shaped and scarcely
raised over the cutting plane. The aper-
ture is circular. Colour translucent, with
faint axial brown wavy lines. Opercu-
lum and soft parts unknown.
Remarks: Caecum campanulatum
shows some similarities with Caecum
amydroglyptum about the general shape
of the tube and the mucro, but the latter
has a longitudinal microsculpture cover-
ing all the tube, while the first one pre-
sents only a microsculpture consisting
of a scarcely visible growth striation.
Besides the species closely resembles
another new sp. currently being studied
(P
IZZINI AND
N
OFRONI
,submitted).
Endemic to the Fiji Is., it is also present
in other Indian-Pacific zones.
Geographical distribution: Caecum cam-
panulatum is currently known only on
Easter Is., its typical location.
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
63
Figure 13. Strebloceras subannulatum Folin, 1879. A: syntype NHML 1887.2.9.2308-2310, length
3.0 mm; B: detail of septum. SEM imaging by K. Way.
Figura 13. Strebloceras subannulatum Folin, 1879. A: sintipo NHML 1887.2.9.2308-2310, longi-
tud 3,0 mm; B: detalle del septo. Imágenes al MEB por K. Way.
Superfamily R
ISSOOIDEA
Gray J. E., 1847
Family C
AECIDAE
Gray J. E., 1850
Genus Strebloceras Carpenter, 1859 [1858]
Diagnosis (B
ANDEL
, 1996): “The protoconch is trochospirally coiled, and the teleoconch is
uncoiled forming a slightly curving tube with slowly increasing diameter. Protoconch and
teleoconch remain together during the whole life-time”.
Type species (B
ANDEL
, 1996): According to C
OSSMANN
(1896) Caecum edwarsii Deshayes, 1864 [Oligocene
of France]; according to G
OUGEROT AND
L
E
R
ENARD
(1981), Strebloceras lituus Deshayes, 1861.
Strebloceras subannulatum Folin, 1879 [not Caecum (Brochina) subannulatum
Folin, 1870 (Mediterranean Sea)] (Figs. 13, 14)
Type material: 2 syntypes, NHML 1887.2.9.2308-2310.
Material examined: Original types, 2 syntypes NHML 1887.2.9.2308-2310; 23 specimens, Punta
Rosalia, east of Anakena (Apr. 1998, leg. B. Raines).
Voucher material: 2 specimens were deposited in each of the following institutions: LACM;
USNM 1018793; MNHN; NHML; NMNZ M.273208; NSMT Mo 73563; AMS C.205279; WAM
A
B
100 µm
333 µm
S13784; and MPR. 4 shells, beach of Anakena Bay, N. of Easter Is.: almost exposed coast, picked
up among rocky bottom on the west side of the bay, among communities of Dictyotales, with
Galaxaura obtusata. (12-1-1995, leg. E. Rolán) MPR.
Type locality: Reefs of Honolulu, 40 fms (73m).
Original description: “Minute, double-
curved head, vitreous, diaphanous and
clear; oblique nucleus of spirals; an-
fractibus duobus: postea testa tubularia,
latitudine acrescens, curvam duplicem
sequens, transversim subannulata, an-
nulis latis, minutissime expressis, suba-
cutis, late separatis: oblique aperture.
Long.: 3 mm; lat.: 0 mm 5“ (F
OLIN
, 1879).
Additional description: Shell small
(average length: 3.5 mm; min. diam. 0.18
mm, max diam. 0.7 mm), whitish; larval
shell (diam. of the last whorl about 0.23
mm) is slightly trochospiral, consisting
of roughly 2 and a half whorls. The tube
is separated from the protoconch by an
incision which, when seen in side-view,
Iberus, 23 (1), 2005
64
Figure 14. Strebloceras subannulatum Folin, 1879. A: Voucher specimen LACM, gold coated, length
3.3 mm; B: detail of septum; C: microsculpture; D: detail of aperture. SEM imaging by D. Geiger.
Figura 14. Strebloceras subannulatum Folin, 1879. A: voucher espécimen LACM, metalizado en oro, lon-
gitud 3,3 mm; B: detalle del septo; C: microescultura; D: detalle de la abertura. Imágenes al MEB por D. Geiger.
is horseshoe shaped (Fig. 14B); the tube
has a double curve that forms itself on
two different levels and is crossed by a
microsculpture whose abapical portion
consists of fine, sinuous growth stria-
tions that gradually transform them-
selves, as they grow, into fairly clear-cut,
visible rings on the adapical portion of
the tube. The aperture is perfectly circu-
lar, with an almost sharp, oblique edge.
The operculum and the soft parts are
unknown.
Geographical distribution: Described
from Honolulu, its distribution has now
extended to the Easter Is. as well.
Remarks: The specimens found on Easter
Is. are wholly identical to the specimens of
A
BD
C
200 µm
100 µm
20 µm
500 µm
the typical series (Figs. 13, 14) and to the
specimens from Hawaii (MPR), despite the
fact that the tube of the former is slightly
wider than that of the latter; the length is
also greater, but this is due to the fact that the
specimens in question are adult.
R
AINES AND
P
IZZINI
: Revision of the Caecidae of Easter Island (Chile)
65
CONCLUSIONS
As a result of the present comprehen-
sive review and revision of Easter Is. Cae-
cidae, we discovered an unusual
anomaly regarding the family’s endemic-
ity rate. Unlike other regions, where the
rate is fairly low among this family, over
71% of the known caecid species are
endemic to the island. This is the highest
rate ever observed within any region.
ACKNOWLEDGEMENTS
We would like to thank Luis DiSalvo
(Coquimbo, Chile) for providing material
collected during his survey of the island’s
marine environment; Jerry Harasewych
(National Museum of Natural History)
for his support and loan of Rehder’s type
and voucher material; Paul Scofield and
Neil Andrews (Canterbury Museum) for
their comments and support in providing
SEM images of Oliver’s type material;
Kathie Way (British Museum of Natural
History) for providing SEM images of the
Folin type material; Daniel Geiger (Santa
Barbara Museum of Natural History) for
his time and effort on the remaining SEM
work; Lindsey Groves (Natural History
Museum of Los Angeles County) and
Michel Garcia (Sociedad de Explotación y
Exploración Marítima Orca, Ltda.) for
their continued support; Emilio Rolán
(Spain) for sending some specimens. We
also wish to thank both Ms. Caterina Ciu-
ferri and Ms. Mary Taylor, who helped us
with captions in Spanish, and Ms.
Viviana Meyohas for her linguistic assis-
tance in English, which proved necessary,
on occasion, in the exchange of corre-
spondence between the first and the sec-
ond author.
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ANDEL
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OSSMANN
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