New species and new records of littoral and bathyal living Pectinoidea (Bivalvia: Propeamussiidae, Cyclochlamydidae, Pectinidae) from the western and southwestern Pacific
Author
Dijkstra, Henk H.
Naturalis Biodiversity Center, P. O. Box 9517, NL- 2300 RA Leiden (The Netherlands) henk. dijkstra @ naturalis. nl
dijkstra@naturalis.nl
Author
Maestrati, Philippe
ISYEB, UMR 7205 CNRS, MNHN, UPMC, EPHE, Muséum national d’Histoire naturelle, Sorbonne Universités, case postale 51, 57 rue Cuvier, F- 75231 Paris cedex 05 (France) philippe. maestrati @ mnhn. fr Published on 29 December 2017
maestrati@mnhn.fr
text
Zoosystema
2017
2017-12-31
39
4
473
485
http://dx.doi.org/10.5252/z2017n4a3
journal article
10.5252/z2017n4a3
1638-9387
4578634
urn:lsid:zoobank.org:pub:CE174614-6609-404A-9909-673B309820D5
Propeamussium regillum
n. sp.
(
Fig. 1
A-G)
TYPE MATERIAL. —
Papua New Guinea
. KAVIENG 2014, stn CP4441,
02°17’S
,
150°38’E
,
684-791 m
, alive,
holotype
spm (MNHN-IM-2013-58330). —
Same
data,
paratype
spm (MNHN-IM-2013-58329). — BIOPAPUA 2010, stn DW3680,
04°37’S
,
149°27’E
,
615-647 m
, alive,
paratype
spm (
MNHN-
IM-2013-57983). — PAPUA NIUGINI 2012, stn CP3981,
05°11’S
,
147°03’E
,
688 m
, alive,
paratype
spm (MNHN-IM-2000-33120). —
Stn CP
4014,
05°35’S
,
148°13’E
,
630-870 m
, alive,
2 paratypes
spms (MNHN-IM-2000-33119;
RMNH
.MOL.290821)
.
TYPE
LOCALITY. —
Papua New Guinea
,
New Ireland
,
02°17’S
,
150°38’E
,
684-791 m
(KAVIENG 2014, stn CP441).
DISTRIBUTION. — Bismarck Sea, live in
615-870 m
(maximum depth range),
647-688 m
(minimum depth range).
ETYMOLOGY. — Left valve with lamellose radials (Latin
regillus
, adjective meaning vertical rows of warp-threads).
FIG. 1. —
A -D
,
F
,
G
, holotype of
Propeamussium regillum
n. sp.
(MNHN-IM-2013-58330):
A
, exterior rv;
B
, interior rv;
C
, exterior lv;
D
, interior lv;
E
, paratype (MNHN-IM-2013-58329), prodissoconch and early ontogeny of lv shell disc;
F
, exterior detail lv;
G
, exterior detail rv;
H -N
, holotype of
Parvamussium minusculum
n. sp.
(MNHN-IM-2013-59427);
H
, exterior rv;
I
, interior rv;
J
, exterior lv;
K
, interior lv;
L
, prodissoconch and early ontogeny of lv shell disc;
M
, exterior detail lv;
N
, exterior detail rv. Abbreviations: see Material and methods. Scale bars: A-D, 10 mm; E, G, 200 µm; F, H-K, 1 mm; L, 50 µm; M, N, 100 µm.
DESCRIPTION
Shell
Up to
31.1 mm
high, fragile and transparent, almost circular, equilateral, inequivalve, slightly convex, left valve somewhat larger than right valve, auricles of left valve equal in shape and size, of right valve slightly unequal in shape, umbonal angle 100-110°.
Prodissoconch
240 µm
long, larval shell inflated and smooth.
Left valve
Smooth in early ontogeny to
c.
10 mm
below umbonal top, irregularly spaced radial ribbing commencing after that (
c.
10- 15 ribs), increasing by intermediate ribs in later growth stage to the periphery (
c.
50 ribs). Ribs with prominent lamellae; weak intercostal commarginal ridges on adults.
Auricles
With 3-4 delicate squamous radial riblets.
Right valve
Sculptured with fine, regularly spaced, close-set commarginal lamellae (5 per mm). Internal ribs 8 (2 central ribs weak or lacking), and 1-4 intercostal rudimentary riblets marginally. Marginal apron broad (
c.
6-8 mm
) and partly broken off. Hinge line straight. Resilifer triangular. No byssal fasciole or byssal notch, ctenolium lacking. Colour of left valve creamy, right valve whitish.
Dimension of
holotype
H
31.1 mm
, W
30 mm
, D
4.9 mm
.
REMARKS
The present species is morphologically closest to the superficially similar (shape, colour) congener
Propeamussium investigatoris
(E. A. Smith, 1906)
, known from the bathyal northern Indian Ocean and south-western Pacific (
Dijkstra & Kastoro 1997: 248
, figs 11-15;
Dijkstra & Maestrati 2008: 82
,
2012: 391
;
Dijkstra & Marshall 2008: 2
).
Both species differ in size (
P. regillum
n. sp.
up to
31 mm
,
P. investigatoris
up to
26 mm
but most specimens smaller, up to
20 mm
in height).
The sculpture of the left valve of both species is also different, viz. the early growth stage of
P. regillum
n. sp.
is smooth,
P. investigatoris
has a fine commarginal sculpture.
P. regillum
n. sp.
has finer and narrower radial ribs (
c.
30 in
adult growth stage) with prominent lamellae commencing
10 mm
below umbonal top, and
P. investigatoris
has many more small radial ribs (
c.
50 in
adult growth stage) with fine lamellae (
Dijkstra & Kastoro 1997
: fig. 15) commencing
1-2 mm
below the umbonal top.
The internal ribbing of
P. regillum
n. sp.
are more delicate with a broad marginal apron of the right valve (
c.
6-8 mm
wide), that of
P. investigatoris
are more solid and the apron is narrower (
c.
2-3 mm
wide).
Propeamussium jeffreysii
(E. A.
Smith, 1885
)
, known from the bathyal western Indian Ocean and western Pacific, is also similar in shape and colour, but differs from the present species by having an almost smooth shell disc of the left valve with delicate commarginal and radial sculpture in early ontogeny (smooth in
P. regillum
n. sp.
) and commarginal lamellae in the later growth stage (
P. regillum
n. sp.
with coarse, irregularly spaced radial ribs with prominent lamellae).