Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic)
Author
Modzalevskaya, Tatiana L.
All-Russia Geological Research Institute (VSEGEI), Srednij pr. 74, St. Petersburg, 199106 (Russia) modz @ IB 2567. spb. edu.
text
Geodiversitas
2003
25
1
73
107
journal article
10.5281/zenodo.5375016
1638-9395
5375016
Sinochonetes wangi
Racheboeuf, 1987
(
Fig. 8
)
Sinochonetes wangi
Racheboeuf, 1987: 11
, pl. 3, figs 15-21.
MATERIAL EXAMINED. — Shells embedded in the coquina from loc. 21581, Krasnaya Bay, Komsomolets Island (
Männik
et al
. 2002
: fig. 1); Severnaya Zemlya or Pod”emnaya formations.
REMARKS
The dimensions of the shells vary from
6.5 to 9.6 mm
in length and from 10.0 to 14.0 mm in width; the average L/W ratio is 0.63. Anderidia diverges anteriorly and fuses with cardinalia posteriorly at 60°. Cardinal process is internally bilobed with additional, poorly developed lateral lobes, and is posteriorly closed by chilidium. The external and internal morphology of both valves are typical of the genus
Sinochonetes
, and our specimens are morphologically identical with
S
.
wangi
described from the lower Emsian(?) strata of Ellesmere Island (Canadian Arctic).
S
.
wangi
differs from the
type
species,
S
.
minutisulcatus
Hou & Xian, 1975
(Siegenian of South
China
,
Hou & Xian 1975: 25
, pl. 1, figs 3, 4), in having finer costellae (7-10 per
1 mm
), more numerous spines (five), and a poorly developed ventral sinus.
A B C
FIG. 8. —
Sinochonetes wangi
Racheboeuf, 1987
;
A -C
, interior view of pedicle valves (N 18/12991, 19/12991, 20/12991), loc. 21581, Severnaya Zemlya or Pod’’emnaya formations;
D
, ventral view of a complete valve (N 21/12991);
E
, external view of a shelly limestone with pedicle and brachial valves;
F
,
L
, complete valve (N 22/12991);
F
, dorsal view;
L
, posterior views with a pseudodeltidium and chilidium;
G
, dorsal valve, showing enlarged external surface with a fine striae (N 23/12991);
H
, posterior view of a pedicle valve, showing a delthyrium, covered by pseudodeltidium posteriorly (N 24/12991);
I
,
K
, dorsal valves with well preserved spines near cardinal margin (NN 25/12991, 26/12991);
J
, internal mould of a dorsal valve, showing a median septum and anderidia (N 27/12991). Scale bars: A-D, 2.5 mm; E, 5 mm; F-K, 2 mm; L, 1 mm.
FIG. 9. —
Dalejina
ex gr.
hybrida
(Sowerby
in
Murchison, 1839
), complete shell (N 2/12991), loc. 13, bed 89, Vodopad Formation;
A
, ventral view;
B
, dorsal view;
C
, lateral view;
D
, anterior view. Scale bar: 3 mm.
Class
RHYNCHONELLATA Williams, Carlson, Brunton, Holmer & Popov, 1996
Order
ORTHIDA Woodward, 1852