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Subtilisphaera terrula
Subilisphaera terrula (Davey, 1974) Lentin and Williams, 1976; emend. Harding, 1986
Originally Deflandrea, subsequently Subtilisphaera?, thirdly (and now) Subtilisphaera. At the time of the transfer, Lentin and Williams, 1976 questionably included this species in Subtilisphaera. Harding, 1986 included the species in Subtilisphaera without question.
Holotype: Davey, 1974, pl.8, fig.4
Locus typicus: Speeton Clay, England
Stratum typicum: middle Barremian
Original diagnosis: Davey, 1974, p. 65: Deflandrea terrula
The cyst is dorso-ventrally flattened and is composed of a subspherical inner body surrounded by a thinner outer wall. The inner body is in contact with the outer wall only in dorsal and ventral regions. The latter may have a rounded apex or may
be produced into a short horn; usually only a short left antapical horn is present. A well defined peridinoid tabulation is present marked by low thickenings of the outer wall; each suture is marked either by a single ridge or two adjacent parallel ridges. The cingulum is strongly defined by granular or spiny ridges. A wide sulcal depression is present with the cingulum displaced by its own width along it. Intratabular granules and sometimes spines are present. An archeopyle has never been observed. Dimensions: Range: cyst length: 53-88µ; cyst width: 37-68µ.
Original description: Davey, 1974, p. 65: Deflandrea terrula
The three anterior intercalary plates are usually visible and do not appear to be displaced and only occasionally is a breakage in the precingular or apical region observable.
Remark: D.terrula is characterised by a distinct tabulation, intratabular granules, a continuous cingulum and the absence of apical "shoulders" and an archaeopyle.
Emended Diagnosis: Harding, 1986, p. 101-104
Shape: ambitus ovoidal to sub-circular to peridinioid. Apex rounded or developed into a single short, broad apical horn. Antapex bears an eccentrically located horn on the left side, often poorly developed. Epipericyst and hypopericyst equidimensional. Moderate dorsoventral compression. Endocyst ovoidal to ellipsoidal, in contact with pericyst only in dorsal and ventral positions. Ambital
pericoel.
Phragma: periphragm 0.5µ thick. Ultra-structure (discernible on moor poorly preserved examples whose surface is slightly corroded) comprises interwoven fibrils of sporopollenin (Pl.2, fig.2). Surface sculpture units of granulae or low echinae appear to be swollen fibrillar endings. Sculpture is penitabular and
laevigate pandasutural zones are usually present. Endophragm 0.5µ thick, laevigate.
Paratabulation: excellent preservation has enabled a pericystal paratabulation formula of 4", 3a, 7"", 7c, 5""", 2"""", as, rs, ps, to be determined. Paraplate margins are crenellated on the margins overlapping adjacent plates (crenellations indicate
direction of plate imbrication). Endocystal paratabulation indeterminate. Archaeopyle: no clear archaeopyle seen (see Remarks).
Paracingulum: very prominent, generally 4µ wide shallow groove exhibiting transverse corrugations. Laevorotatory, displaced by its own width. Anterior and posterior margins of paracingulum often exhibit a raised "lip" ornamented with a single row of sharp echinae (up to 0.7µ tall). Parasulcus: broad (up to 10µ) and
extending well on to the epipericyst. Contains what appears to be a platelet bearing "flagellar markings" at the beginning of the paracingulum.
Dimensions: Range: length pericyst:40-60µ; breadth pericyst: 36-51µ; 110 specimens.
Remarks (shortened): On the basis of the light microscope the paratabulation is indeterminate. However, using the superior resolution of the electron microscope, a tabulation formula is presented herein. Amongst several hundred examples logged, not one clear archaeopyle structure has been observed in this species. Similar difficulties were experienced by Davey (1974, p.65, as Deflandrea) and by Jain and Millepied (1973, p.27) discussing S.senegalensis and by Duxbury (1983) discussing S.perlucida. Intercalary plates are always intact, the only breakage being apical fractures across paraplates (i.e. not along parasutures). The possibility suggested by Duxbury (1983) that the archaeopyle is formed by the loss of paraplate 3"" needs further investigation.
Originally Deflandrea, subsequently Subtilisphaera?, thirdly (and now) Subtilisphaera. At the time of the transfer, Lentin and Williams, 1976 questionably included this species in Subtilisphaera. Harding, 1986 included the species in Subtilisphaera without question.
Holotype: Davey, 1974, pl.8, fig.4
Locus typicus: Speeton Clay, England
Stratum typicum: middle Barremian
Original diagnosis: Davey, 1974, p. 65: Deflandrea terrula
The cyst is dorso-ventrally flattened and is composed of a subspherical inner body surrounded by a thinner outer wall. The inner body is in contact with the outer wall only in dorsal and ventral regions. The latter may have a rounded apex or may
be produced into a short horn; usually only a short left antapical horn is present. A well defined peridinoid tabulation is present marked by low thickenings of the outer wall; each suture is marked either by a single ridge or two adjacent parallel ridges. The cingulum is strongly defined by granular or spiny ridges. A wide sulcal depression is present with the cingulum displaced by its own width along it. Intratabular granules and sometimes spines are present. An archeopyle has never been observed. Dimensions: Range: cyst length: 53-88µ; cyst width: 37-68µ.
Original description: Davey, 1974, p. 65: Deflandrea terrula
The three anterior intercalary plates are usually visible and do not appear to be displaced and only occasionally is a breakage in the precingular or apical region observable.
Remark: D.terrula is characterised by a distinct tabulation, intratabular granules, a continuous cingulum and the absence of apical "shoulders" and an archaeopyle.
Emended Diagnosis: Harding, 1986, p. 101-104
Shape: ambitus ovoidal to sub-circular to peridinioid. Apex rounded or developed into a single short, broad apical horn. Antapex bears an eccentrically located horn on the left side, often poorly developed. Epipericyst and hypopericyst equidimensional. Moderate dorsoventral compression. Endocyst ovoidal to ellipsoidal, in contact with pericyst only in dorsal and ventral positions. Ambital
pericoel.
Phragma: periphragm 0.5µ thick. Ultra-structure (discernible on moor poorly preserved examples whose surface is slightly corroded) comprises interwoven fibrils of sporopollenin (Pl.2, fig.2). Surface sculpture units of granulae or low echinae appear to be swollen fibrillar endings. Sculpture is penitabular and
laevigate pandasutural zones are usually present. Endophragm 0.5µ thick, laevigate.
Paratabulation: excellent preservation has enabled a pericystal paratabulation formula of 4", 3a, 7"", 7c, 5""", 2"""", as, rs, ps, to be determined. Paraplate margins are crenellated on the margins overlapping adjacent plates (crenellations indicate
direction of plate imbrication). Endocystal paratabulation indeterminate. Archaeopyle: no clear archaeopyle seen (see Remarks).
Paracingulum: very prominent, generally 4µ wide shallow groove exhibiting transverse corrugations. Laevorotatory, displaced by its own width. Anterior and posterior margins of paracingulum often exhibit a raised "lip" ornamented with a single row of sharp echinae (up to 0.7µ tall). Parasulcus: broad (up to 10µ) and
extending well on to the epipericyst. Contains what appears to be a platelet bearing "flagellar markings" at the beginning of the paracingulum.
Dimensions: Range: length pericyst:40-60µ; breadth pericyst: 36-51µ; 110 specimens.
Remarks (shortened): On the basis of the light microscope the paratabulation is indeterminate. However, using the superior resolution of the electron microscope, a tabulation formula is presented herein. Amongst several hundred examples logged, not one clear archaeopyle structure has been observed in this species. Similar difficulties were experienced by Davey (1974, p.65, as Deflandrea) and by Jain and Millepied (1973, p.27) discussing S.senegalensis and by Duxbury (1983) discussing S.perlucida. Intercalary plates are always intact, the only breakage being apical fractures across paraplates (i.e. not along parasutures). The possibility suggested by Duxbury (1983) that the archaeopyle is formed by the loss of paraplate 3"" needs further investigation.