Bivalves from the latest Jurassic-earliest Cretaceous hydrocarbon seep carbonates from central Spitsbergen, Svalbard
Author
Hryniewicz, Krzysztof
krzysztof.hryniewicz@nhm.uio.no
Author
Little, Crispin T. S.
earctsl@leeds.ac.uk
Author
Nakrem, Hans Arne
krzysztof.hryniewicz@nhm.uio.no
text
Zootaxa
2014
2014-09-02
3859
1
1
66
journal article
4900
10.11646/zootaxa.3859.1.1
d866af6f-cbcd-47f4-a4f3-1499c1789ae3
1175-5326
4930112
24FCAAE1-AB7C-4FAD-8698-D0C9F12400EC
Camptochlamys
(
Camptochlamys
)
clathratus
(
Roemer, 1836
)
(
Figure 10 L–O
)
1836
Pecten clathratus
sp. nov.
—Roemer, p. 212, pl. 13, fig. 9.
1984
Camptonectes
(
Camptochlamys
)
clathratus
(Roemer)
—Johnson, p. 143, pl. 4, figs. 23, 26, 27, pl. 5, figs. 1–3, 6, text-figs. 131–136 and references therein.
1984
Camptonectes
(
Camptochlamys
)
intertextus
(Roemer)
—Kelly, p. 75, pl. 6, figs. 16–18.
Material examined.
Two poorly preserved specimens. In addition, a single disarticulated specimen from the Dorsoplanites bed (
PMO
226.603). See Appendix 1 for the list of specimens.
Dimensions.
15.8–23.8 mm
in length,
15.8–23.2 mm
in height. See Appendix 2H for details.
Description.
Shell small to medium, thin. Both valves suborbicular, left valve moderately inflated, with anterior and posterior auricles subequal and not prominent. Umbonal angle
ca.
100°; hinge line straight, umbones orthogyrate and not projecting. Curvature of right valve unknown. Anterodorsal margin straight to very weakly convex, posterodorsal margin straight. Anterior and posterior margins subequal, with anterior margin slightly more rounded. Ventral margin evenly rounded. Ornament composed of series of dense commarginal lamellae intersected by fine primary ribs and secondary radial riblets. Intersection of radial and commarginal ornament forms a cancellate pattern. Specimen measuring
23.2 mm
in height has three growth lines per millimeter. Musculature and dentition unknown.
Remarks.
Our specimens have an external ornament and shell morphology within the range of
Camptonectes
(
Camptochlamys
)
clathratus
(
Roemer, 1836
)
. Similarly shaped and ornamented specimens have been recorded by
Kelly (1984)
as
C
.
(
Cc
.)
intertextus
(
Roemer, 1839
)
, which is the younger synonym of
C
.
(
Cc
.)
clathratus
according to
Johnson (1984)
.
Occurrence
. The species is known from Bajocian to Kimmeridgian of Western and Central Europe (
Johnson 1984
), and the Middle Volgian of
Greenland
(
Fürsich 1982
). It has been recorded previously from the Jurassic of
Svalbard
as
Pecten
(
Chlamys
)
pertextus
var.
densiradiatus
var. nov.
by
Sokolov & Bodylevsky (1931
, p. 54, pl. 3, figs. 6a–b). Seep 8 (Upper Volgian), Slottsmøya Member (
Tab. 1
); also Dorsoplanites bed (Middle Volgian),
Svalbard
.
Palaeoecology.
Camptonectes
(
Camptochlamys
)
clathratus
was a byssally attached filter feeder (
Johnson 1984
) and in the
Svalbard
seeps it probably attached onto exposed carbonate substrates. The umbonal angle increase during ontogenesis (
Johnson 1984
) suggests that juveniles may have been attached to a firm substrate with a byssus, which was then lost in adults so they became recliners (e.g.
Stanley 1970
). In the Mid- to early Late Jurassic
C
.
(
Cc
.)
clathratus
is often associated with shallow water corals, upon which juveniles were supposed to attach byssally, and oolitic facies, in which the adult forms reclined (
Johnson 1984
). The
Svalbard
specimens (
Sokolov & Bodylevsky 1931
; this study) represent both the youngest occurrence and the most offshore occurrence of the species, which suggests that it either had a broader ecological tolerance than previously suspected, or
C
.
(
Cc
.)
clathratus
shifted its preference to more offshore environments around the latest Jurassic.