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Parabohaidina operculata
Parabohaidina operculata He Chengquan, 1984b, p.155–156, pl.1, figs.19–20. Holotype: He Chengquan, 1984b, pl.1, fig.20. Age: Oligocene.
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Original description: [He Chengquan, 1984b] (translated from Chinese with Google):
Parabohaidina operculata (sp. nov.)
(Plate I, Figures 19, 20)
Description: The shell is flat, with a rounded or oblate rhombus outline, broadened or straight at the equatorial region. The shell wall is approximately 1 micron thick and divided into two layers of nearly equal thickness or indistinctly. The surface is a network of short wrinkles (or an incomplete fine network), often with a short wrinkle at the tail end, which is less evenly spaced and vermiform. Near the middle of the shell, a network of wrinkles develops (possibly as a result of interconnected wrinkles), with mesh sizes ranging from 1×2 to 2×3 microns. The ridges are low and slightly serrated along the outline. Sometimes, the shell wall thickens at a point corresponding to the apex. A girdle is absent, but one or two transverse folds are present in the equatorial region, perhaps reflecting a girdle. The palaeostoma is quite large, apical to subapical, with a width less than the shell width. The palaeostoma outline is straight dorsally, with V-shaped fissures at either end ventrally. The operculum is raised and usually connected.
The shell is 55-65 μm long and 60-68 μm wide; the holotype is greater than 60 μm long and 68 μm wide.
Discussion: The ornamentation of this new species is similar to that of Parabohaidina retirugosa Jiabo (1978, p. 44, plate 17, figs. 7-9), distinguished from the latter by its rather large palaeostoma and obscure body. This species has been tentatively assigned to Parabohaidina because of its rather large palaeostoma, possibly apiculate-subacute, larger than that of other species assigned to this genus.
Origin: Shangsi, Guangxi; the first and second sections of the Yongning Group.
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Original description: [He Chengquan, 1984b] (translated from Chinese with Google):
Parabohaidina operculata (sp. nov.)
(Plate I, Figures 19, 20)
Description: The shell is flat, with a rounded or oblate rhombus outline, broadened or straight at the equatorial region. The shell wall is approximately 1 micron thick and divided into two layers of nearly equal thickness or indistinctly. The surface is a network of short wrinkles (or an incomplete fine network), often with a short wrinkle at the tail end, which is less evenly spaced and vermiform. Near the middle of the shell, a network of wrinkles develops (possibly as a result of interconnected wrinkles), with mesh sizes ranging from 1×2 to 2×3 microns. The ridges are low and slightly serrated along the outline. Sometimes, the shell wall thickens at a point corresponding to the apex. A girdle is absent, but one or two transverse folds are present in the equatorial region, perhaps reflecting a girdle. The palaeostoma is quite large, apical to subapical, with a width less than the shell width. The palaeostoma outline is straight dorsally, with V-shaped fissures at either end ventrally. The operculum is raised and usually connected.
The shell is 55-65 μm long and 60-68 μm wide; the holotype is greater than 60 μm long and 68 μm wide.
Discussion: The ornamentation of this new species is similar to that of Parabohaidina retirugosa Jiabo (1978, p. 44, plate 17, figs. 7-9), distinguished from the latter by its rather large palaeostoma and obscure body. This species has been tentatively assigned to Parabohaidina because of its rather large palaeostoma, possibly apiculate-subacute, larger than that of other species assigned to this genus.
Origin: Shangsi, Guangxi; the first and second sections of the Yongning Group.