Stenoscisma gjelis Lazarev, 1975
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This small to medium sized brachiopod has a distinctive triangular
shape with many well developed radial plications and a deep wide fold
and sulcus that is sharply offset from the other portions of the
shell margin. S. gjelis has about 15 plications across the width of
the shell at maturity, including 4 plications present on the fold and
a matching 5 plications present on the sulcus. The maximum shell
width is near the anterior margin, that has a nearly straight edge
when seen from dorsal or ventral views. The beaks overhang the
hingeline. It has a thick-walled shell. Stenoscisma is a distinctive
rhynchonellid that is easily recognize because of its sharply offset
fold and sulcus and nearly straight anterior margin.
The specimen shown here is a topotype specimen, obtained from the
type locality for the species at the Gzhel quarries (cied as "Gzhel'
Station": Lazarev, 1975).
Stenoscisma is a common brachiopod in Russian Early Permian
(Cisuralian) biotas, occurring widely in shallow shelf environments
and in reef deposits. The Early Permian species Stenoscisma mutabilis
is similar to the Gzhelian species Stenoscisma gjelis in having a
shell with a thick layer of secondary prismatic calcite. The presence
of a thick secondary shell layer suggests a high level of food
resource and warm, clear water conditions.
Lazarev, S.S., 1975, Middle and Late Carboniferous Stenoscismatacea
(Brachiopoda) of the Moscow Syneclise; Paleontological Journal, v. 9,
no. 2, p.213-220, pl. 8, fig. 5-9.
["Sredne - posdnekamennougolnie brachiopody Stenoscimatacea
Phylum Brachiopoda (brachiopods)
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