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Schematophora amabilis
Schematophora amabilis Stevens, 1987
Holotype: Stevens, 1987, fig.3I-K
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Berriasian
Original description: Stevens, 1987, p. 193
Cysts proximochorate and subspherical in shape. Autophragm scabrate and up to 1 µm thick. Archeopyle apical, type [tA], with a zigzag principal suture, and accessory sutures which may extend the whole length of the precingular paraplates. Operculum rounded, and free, but generally adherent at the sulcal notch, though it may have been broken away due to compression of the cyst. Paratabulation consisting of striate mostly complete penitabular ridges (1.5-3.5 µm high and less than 1 µm wide) with uneven crests. Penitabular ridges defining all paraplate boundaries with the exception of the cingular paraplates delineated only by parasutural ridges between adjacent cingular paraplates. Parasulcus and posterior intercalary paraplate bounded in part by discontinuous, apparently aligned, features which may be penitabularly distributed. Paratabulation gonyaulacacean with a formula: 4", 6", 6c, 5""", 1p, 1"""", Xs (Fig.8). Five postcingular paraplates interpreted as 2""" to 6""". The Ip paraplate is interpreted as filling the broad space between the 2""" and the ps paraplates and is partially delimited by a few irregular processes and a short ridge. Paracingulum dividing the cyst equally, 4 to 5.5 µm wide, offset by one half to a full paracingulum width. Parasulcus expressed by a relatively broad area, unsubdivided on the epicyst, bordered by aligned, irregularly shaped, rounded processes (up to 1 µm in height and diameter), which may be remnants of penitabular ridges. Parasulcus extending posteriorly from the sulcal notch to close to the antapex, extremely large ps paraplate making up most of its hypocystal portion. Measurements. Cyst length (dehisced) 28(36.5)44 µm, cyst width 32(42)50 µm (27 specimens).
Variability. Cyst shape and size fairly constant. The penitabular nature of the ridges often difficult to discern because of the close juxtaposition of the ridges to the paraplate boundaries (Fig.3K). The aligned processes bordering the parasulcus and the processes and short ridge defining the 1p paraplate, may be remnants of discontinuous penitabular ridges (Fig.31). Operculum generally adherent and upright (Fig.3H,L) or collapsed into the autocoel (Fig.31-K); it may also be broken away on compressed cysts.
Affinities:
Stevens, 1987, p. 193: Generic assignment is based on the definition of penitabular ridges, except at the paracingulum. Schematophora speciosa Deflandre & Cookson 1955 differs from S. amabilis in having penitabular ridges substantially towards the centre of each paraplate, no delineation of cingular paraplates and subdivision of up to 3 paraplates in the parasulcus. Schematophora amabilis differs from Meiourogonyaulax Sarjeant 1966 in having penitabular rather than parasutural ridges. Schematophora amabilis differs from species of Alisocysta Stover & Evitt 1978 in lacking penitabular ridges in the paracingular area. S. amabilis superficially resembles Cernicysta helbyi (Morgan) Stover & Helby 1987 in its shape and size, however the 2-layered nature of the latter is evident in the separation of the wall layers at the parasutural ridges.
Holotype: Stevens, 1987, fig.3I-K
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Berriasian
Original description: Stevens, 1987, p. 193
Cysts proximochorate and subspherical in shape. Autophragm scabrate and up to 1 µm thick. Archeopyle apical, type [tA], with a zigzag principal suture, and accessory sutures which may extend the whole length of the precingular paraplates. Operculum rounded, and free, but generally adherent at the sulcal notch, though it may have been broken away due to compression of the cyst. Paratabulation consisting of striate mostly complete penitabular ridges (1.5-3.5 µm high and less than 1 µm wide) with uneven crests. Penitabular ridges defining all paraplate boundaries with the exception of the cingular paraplates delineated only by parasutural ridges between adjacent cingular paraplates. Parasulcus and posterior intercalary paraplate bounded in part by discontinuous, apparently aligned, features which may be penitabularly distributed. Paratabulation gonyaulacacean with a formula: 4", 6", 6c, 5""", 1p, 1"""", Xs (Fig.8). Five postcingular paraplates interpreted as 2""" to 6""". The Ip paraplate is interpreted as filling the broad space between the 2""" and the ps paraplates and is partially delimited by a few irregular processes and a short ridge. Paracingulum dividing the cyst equally, 4 to 5.5 µm wide, offset by one half to a full paracingulum width. Parasulcus expressed by a relatively broad area, unsubdivided on the epicyst, bordered by aligned, irregularly shaped, rounded processes (up to 1 µm in height and diameter), which may be remnants of penitabular ridges. Parasulcus extending posteriorly from the sulcal notch to close to the antapex, extremely large ps paraplate making up most of its hypocystal portion. Measurements. Cyst length (dehisced) 28(36.5)44 µm, cyst width 32(42)50 µm (27 specimens).
Variability. Cyst shape and size fairly constant. The penitabular nature of the ridges often difficult to discern because of the close juxtaposition of the ridges to the paraplate boundaries (Fig.3K). The aligned processes bordering the parasulcus and the processes and short ridge defining the 1p paraplate, may be remnants of discontinuous penitabular ridges (Fig.31). Operculum generally adherent and upright (Fig.3H,L) or collapsed into the autocoel (Fig.31-K); it may also be broken away on compressed cysts.
Affinities:
Stevens, 1987, p. 193: Generic assignment is based on the definition of penitabular ridges, except at the paracingulum. Schematophora speciosa Deflandre & Cookson 1955 differs from S. amabilis in having penitabular ridges substantially towards the centre of each paraplate, no delineation of cingular paraplates and subdivision of up to 3 paraplates in the parasulcus. Schematophora amabilis differs from Meiourogonyaulax Sarjeant 1966 in having penitabular rather than parasutural ridges. Schematophora amabilis differs from species of Alisocysta Stover & Evitt 1978 in lacking penitabular ridges in the paracingular area. S. amabilis superficially resembles Cernicysta helbyi (Morgan) Stover & Helby 1987 in its shape and size, however the 2-layered nature of the latter is evident in the separation of the wall layers at the parasutural ridges.