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Thalassiphora fenestrata
Thalassiphora fenestrata Liengjarern et al., 1980
Holotype: Liengjarern et al., 1980, pl.54, fig.1
Locus typicus: Whitecliff Bay, Isle of Wight, England
Stratum typicum: Oligocene
Original diagnosis: Liengjarern et al., 1980, p.489
Thalassiphora with partial fenestration of the periphragm. The fenestration is restricted to the lateral and ventral areas of the periphragm. The extent of the fenestrated area is variable, but it never extends over the whole dorsal region. The perforations are large, more or less circular, and may be closely packed forming an irregular reticulum. The ventral flange of the pericyst is narrow and is fenestrated throughout.
Original description: Liengjarern et al., 1980, p.489
This species is similar to T. pelagica in shape and in wall structure but the extension of the periphragm on the ventral side appears to be more reduced than is common in T. pelagica that is, the ventral lacuna is larger. Perforations develop in the periphragm in ventral and lateral areas and disappear towards the mid-dorsal area. Between these perforations, the fibres are more loosely packed. A large number of smaller perforations occur between the larger fenestrations, the latter are of variable diameter tending to be larger closer to the ambitus. Ventrally, the pericyst occurs as a relatively narrow flange which is strongly fenestrate throughout. The antapical keel may often be reduced or, sometimes, absent.
Measurements. Holotype, endocyst 81x67 Ám, pericyst diameter 150 Ám.
Range. Endocyst 73(77)89 x 59(67)77 Ám, pericyst diameter 126(154)182 Ám. Specimens measured 10.
Comments: This species, which is apparently restricted in distribution to the latest Eocene and ?early Oligocene, seems to be an intermediate form between T. reticulata Morgenroth 1966, which is characteristic of younger Oligocene deposits and whose pericoel is fenestrate virtually all over, and T. pelagica
Holotype: Liengjarern et al., 1980, pl.54, fig.1
Locus typicus: Whitecliff Bay, Isle of Wight, England
Stratum typicum: Oligocene
Original diagnosis: Liengjarern et al., 1980, p.489
Thalassiphora with partial fenestration of the periphragm. The fenestration is restricted to the lateral and ventral areas of the periphragm. The extent of the fenestrated area is variable, but it never extends over the whole dorsal region. The perforations are large, more or less circular, and may be closely packed forming an irregular reticulum. The ventral flange of the pericyst is narrow and is fenestrated throughout.
Original description: Liengjarern et al., 1980, p.489
This species is similar to T. pelagica in shape and in wall structure but the extension of the periphragm on the ventral side appears to be more reduced than is common in T. pelagica that is, the ventral lacuna is larger. Perforations develop in the periphragm in ventral and lateral areas and disappear towards the mid-dorsal area. Between these perforations, the fibres are more loosely packed. A large number of smaller perforations occur between the larger fenestrations, the latter are of variable diameter tending to be larger closer to the ambitus. Ventrally, the pericyst occurs as a relatively narrow flange which is strongly fenestrate throughout. The antapical keel may often be reduced or, sometimes, absent.
Measurements. Holotype, endocyst 81x67 Ám, pericyst diameter 150 Ám.
Range. Endocyst 73(77)89 x 59(67)77 Ám, pericyst diameter 126(154)182 Ám. Specimens measured 10.
Comments: This species, which is apparently restricted in distribution to the latest Eocene and ?early Oligocene, seems to be an intermediate form between T. reticulata Morgenroth 1966, which is characteristic of younger Oligocene deposits and whose pericoel is fenestrate virtually all over, and T. pelagica