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Selenopemphix kepion
Selenopemphix kepion Harland and Pudsey, 2002, p.275–278, pl.3, figs.1–6; pl.5, figs.1–8; text-fig.4. Holotype: Harland and Pudsey, 2002, pl.5, figs.1–2. N.I.A. Age: late Miocene.
Original description (Harland & Pudsey, 2002)
Derivation of name: Greek, kepion, neuter, diminutive; meaning a small garden, orchard or plantation with reference to the small paratabulate fields that are evident on this species, especially conspicuous on the surface of the hypocyst.
Diagnosis: A brown intermediate-sized cyst, usually observed in polar compression. Cyst wall unstratified with a smooth surface that may bear scattered grana. Paratabulation, especially developed on hypocyst, outlined by a series of parasutures that are low, crenulated, sometimes striate, and denticulate, and may also be expressed as a series of elongate grana. In particular, they outline two rectangular antapical paraplates and five adjacent postcingular paraplates of typical protoperidiniacean tabulation pattern. Archaeopyle may be symmetrical to slightly offset to the left, monoplacoid and iso-deltaform. Operculum free.
Description: This intermediate-sized cyst is seen mostly in polar compression and has a reniform ambitus. The cyst wall is light to dark brown in colour, lacks observable stratification and is usually smooth but may carry many grana. These grana are randomly scattered over the surface of the cyst and are <1 μm in width and height. In the occasionally seen dorso-ventral compression the cyst is peridinioid in shape but with a broad apex, flat with slight thickening where the lateral parasuture meets parasutures on the ventral surface; the antapex is also broad with poorly developed antapical horns ( Plate V, 7–8). The paratabulation is outlined by a series of sutural membranes, ridges or positive elements; these membranes appear to be better developed on the hypocyst than the epicyst (Plate V, 1–4). The sutures on the hypocyst clearly reflect a peridiniacean tabulation pattern consisting of two large antapical paraplates each rectangular in nature and surrounded by five postcingular paraplates that are developed symmetrically. Although the paratabulation is conspicuous there is some suppression of minority features especially adjacent to the parasulcus where the sutures are not as well developed as elsewhere. On the epicyst the paratabulation is much less well developed but appears to reveal the lateral sutures between the intercalary paraplates series and the third apical plate on the dorsal surface and the apical and precingular paraplates series on the ventral surface. In addition, the sutures clearly outline the paracingulum, which is planar in character and shows little displacement (Plate V, 8). The sutures themselves are made up of narrow membranes that may be striate, crenulate to carrying a series of spinules with acicular to bifid and capitulate tips; the range of morphology is illustrated in Fig. 4. In some cases the parasutures are divided into a series of beads or grana along the course of the suture. The archaeopyle is formed by the loss of a single intercalary paraplate, the 2a. The operculum is usually lost but may remain in place in some specimens. The archaeopyle appears to be iso-deltaform in shape with an archaeopyle ratio of c. 1.0 and an archaeopyle signum of <1.0. The archaeopyle is, therefore, monoplacoid with a free operculum and situated either symmetrically or slightly offset to the left, relative to the dorso-ventral axis of the cyst. The shape of the archaeopyle is consistent with the cyst having a hexa peridiniacean paratabulation.
Nomenclatural types: The holotype is Specimen No. R.8001.22, Plate V, 1–2, slide RH308B, ODP 1095B-24X-3, 101–103, England Finder Q45/0 and is lodged in the collections of the British Antarctic Survey, Cambridge. Age: Late Miocene at 7.15 Ma.
The isotype is Specimen No. R.8001.25, Plate V, 7–8, slide RH308A, ODP 1095B-24X-3, 101–103, England Finder Q48/1 and is lodged in the collections of the British Antarctic Survey, Cambridge. Age: Late Miocene at 7.15 Ma.
Dimensions: Holotype, maximum dimension, between the lateral sides of the cyst and at right angles to the dorso-ventral axis, 59 μm; minimum dimension along the dorso-ventral axis, 43 μm.
Isotype, length of specimen from apex to antapex, 46 μm; width of specimen from left lateral side to right lateral side, 68 μm.
Range, maximum dimension (usually between the lateral sides of the cyst in polar compression) 41(52.1)68 μm, minimum dimension (usually between the dorsal and ventral surface in polar compression) 35(41.5)56 μm. Fifteen specimens measured.
Remarks: This conspicuous and easily identifiable new species differs from all others in having a defined paratabulation that is especially prominent on the hypocyst. The presence of specimens of this new species that occur in both polar and dorso-ventral compression belies the notion that the genus Selenopemphix only occurs as reniform cysts in polar compression. However cysts that are clearly broader and rounded at the apex and antapex will undoubtedly be preferentially preserved with polar compression. This characteristic may or may not be a useful criterion for further division of the modern genus Protoperidinium.
Occurrence: This new species was recovered in samples RH308, RH399 and RH310, Late Miocene and was included in the counts of Selenopemphix sp. A of Pudsey and Harland (2001). The cyst is present in sediments dated between 7.15 to 8.05 Ma.
Original description (Harland & Pudsey, 2002)
Derivation of name: Greek, kepion, neuter, diminutive; meaning a small garden, orchard or plantation with reference to the small paratabulate fields that are evident on this species, especially conspicuous on the surface of the hypocyst.
Diagnosis: A brown intermediate-sized cyst, usually observed in polar compression. Cyst wall unstratified with a smooth surface that may bear scattered grana. Paratabulation, especially developed on hypocyst, outlined by a series of parasutures that are low, crenulated, sometimes striate, and denticulate, and may also be expressed as a series of elongate grana. In particular, they outline two rectangular antapical paraplates and five adjacent postcingular paraplates of typical protoperidiniacean tabulation pattern. Archaeopyle may be symmetrical to slightly offset to the left, monoplacoid and iso-deltaform. Operculum free.
Description: This intermediate-sized cyst is seen mostly in polar compression and has a reniform ambitus. The cyst wall is light to dark brown in colour, lacks observable stratification and is usually smooth but may carry many grana. These grana are randomly scattered over the surface of the cyst and are <1 μm in width and height. In the occasionally seen dorso-ventral compression the cyst is peridinioid in shape but with a broad apex, flat with slight thickening where the lateral parasuture meets parasutures on the ventral surface; the antapex is also broad with poorly developed antapical horns ( Plate V, 7–8). The paratabulation is outlined by a series of sutural membranes, ridges or positive elements; these membranes appear to be better developed on the hypocyst than the epicyst (Plate V, 1–4). The sutures on the hypocyst clearly reflect a peridiniacean tabulation pattern consisting of two large antapical paraplates each rectangular in nature and surrounded by five postcingular paraplates that are developed symmetrically. Although the paratabulation is conspicuous there is some suppression of minority features especially adjacent to the parasulcus where the sutures are not as well developed as elsewhere. On the epicyst the paratabulation is much less well developed but appears to reveal the lateral sutures between the intercalary paraplates series and the third apical plate on the dorsal surface and the apical and precingular paraplates series on the ventral surface. In addition, the sutures clearly outline the paracingulum, which is planar in character and shows little displacement (Plate V, 8). The sutures themselves are made up of narrow membranes that may be striate, crenulate to carrying a series of spinules with acicular to bifid and capitulate tips; the range of morphology is illustrated in Fig. 4. In some cases the parasutures are divided into a series of beads or grana along the course of the suture. The archaeopyle is formed by the loss of a single intercalary paraplate, the 2a. The operculum is usually lost but may remain in place in some specimens. The archaeopyle appears to be iso-deltaform in shape with an archaeopyle ratio of c. 1.0 and an archaeopyle signum of <1.0. The archaeopyle is, therefore, monoplacoid with a free operculum and situated either symmetrically or slightly offset to the left, relative to the dorso-ventral axis of the cyst. The shape of the archaeopyle is consistent with the cyst having a hexa peridiniacean paratabulation.
Nomenclatural types: The holotype is Specimen No. R.8001.22, Plate V, 1–2, slide RH308B, ODP 1095B-24X-3, 101–103, England Finder Q45/0 and is lodged in the collections of the British Antarctic Survey, Cambridge. Age: Late Miocene at 7.15 Ma.
The isotype is Specimen No. R.8001.25, Plate V, 7–8, slide RH308A, ODP 1095B-24X-3, 101–103, England Finder Q48/1 and is lodged in the collections of the British Antarctic Survey, Cambridge. Age: Late Miocene at 7.15 Ma.
Dimensions: Holotype, maximum dimension, between the lateral sides of the cyst and at right angles to the dorso-ventral axis, 59 μm; minimum dimension along the dorso-ventral axis, 43 μm.
Isotype, length of specimen from apex to antapex, 46 μm; width of specimen from left lateral side to right lateral side, 68 μm.
Range, maximum dimension (usually between the lateral sides of the cyst in polar compression) 41(52.1)68 μm, minimum dimension (usually between the dorsal and ventral surface in polar compression) 35(41.5)56 μm. Fifteen specimens measured.
Remarks: This conspicuous and easily identifiable new species differs from all others in having a defined paratabulation that is especially prominent on the hypocyst. The presence of specimens of this new species that occur in both polar and dorso-ventral compression belies the notion that the genus Selenopemphix only occurs as reniform cysts in polar compression. However cysts that are clearly broader and rounded at the apex and antapex will undoubtedly be preferentially preserved with polar compression. This characteristic may or may not be a useful criterion for further division of the modern genus Protoperidinium.
Occurrence: This new species was recovered in samples RH308, RH399 and RH310, Late Miocene and was included in the counts of Selenopemphix sp. A of Pudsey and Harland (2001). The cyst is present in sediments dated between 7.15 to 8.05 Ma.