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Aprobolocysta alata
Aprobolacysta alata, Backhouse, 1987
Originally (and now) Aproboloeysta, subsequently Necrobroomea. Below, 1990, transferred this species to Necrobroomea Wiggins, 1975. Lentin and Williams, 1993, retained this species in Aprobolocysta.
Holotype: Backhouse, 1987, figs.9A-B
Locus typicus: Perth Basin, Australia
Stratum typicum: Middle Hauterivian-Early Barremian
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Original description: [Backhouse, 1987, p. 211-212]:
Description:
Cysts proximate ovoidal and elongated. Endophragm smooth or finely granular, about 0.5 µm thick, enveloped by a periphragm of similar thickness. Apex rounded, without an apical horn. Antapex with 2 antapical horns slightly developed in the endophragm, and more strongly developed in the periphragm. Periphragm raised in variably developed wavy folds or ridges mostly parasutural in position.
Highest fold along the posterior paracingular transverse parasuture. Parasutural features poorly developed along the anterior margin of the paracingulum. Raised, sometimes bulbous folds always clearly developed anterodorsally, between the precingular paraplates. Two small paraplates anterior to the 3"" paraplate probably anterior intercalary paraplates (Fig.5B). Apical series of at least 3 paraplates; possible fourth paraplate not evident on available material.
Paratabulation of the hypocyst poorly defined on most specimens. Holotype with 5 postcingular paraplates in the 2""" to 6""" positions. Paratype with a small 1""" paraplate faintly indicated to the left of the parasulcus (Fig.5D). Small antapical paraplate defined by low periphragmal ridges on the holotype (Fig.5B). Paratabulation formula ?4", ?2a, ?6"", 0c, 6""", 0p, 1"""".
Parasulcus indicated by the archeopyle suture, a gap in the posterior paracingular fold and on some specimens by periphragmal folds bordering the parasulcus between the paracingulum and the archeopyle suture.
Archeopyle apical, type [tA]; operculum usually missing. Archeopyle shape typical of Aprobolocysta and Batioladinium Brideaux 1975. Archeopyle suture with a deep sulcal notch and a short gabled 1"" paraplate.
Dimensions:
Length of holotype with operculum missing 66 µm, width measured across the perihypocyst 41 µm.
Range of length with operculum missing (19 specimens) 41(57)69 µm width 28(38)46 µm, total length of two specimens 64 and 70 µm.
Affinities:
Backhouse, 1987, p. 212: The full paratabulation of A. alata has not been satisfactorily determined because of the absence of the operculum from most specimens and poor development of paratabulation on the hypocyst, particularly in the parasulcal area. The holotype and several unillustrated specimens show 2 small paraplates above the 3"" paraplate. These have been provisionally interpreted as anterior intercalary paraplates, but confirmation must await a better determination of the apical paratabulation. Aprobolocysta alata is closest to A. eilema Duxbury 1977, from which it can be distinguished by the greater development of antapical horns and the presence of partial paratabulation.
Originally (and now) Aproboloeysta, subsequently Necrobroomea. Below, 1990, transferred this species to Necrobroomea Wiggins, 1975. Lentin and Williams, 1993, retained this species in Aprobolocysta.
Holotype: Backhouse, 1987, figs.9A-B
Locus typicus: Perth Basin, Australia
Stratum typicum: Middle Hauterivian-Early Barremian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Backhouse, 1987, p. 211-212]:
Description:
Cysts proximate ovoidal and elongated. Endophragm smooth or finely granular, about 0.5 µm thick, enveloped by a periphragm of similar thickness. Apex rounded, without an apical horn. Antapex with 2 antapical horns slightly developed in the endophragm, and more strongly developed in the periphragm. Periphragm raised in variably developed wavy folds or ridges mostly parasutural in position.
Highest fold along the posterior paracingular transverse parasuture. Parasutural features poorly developed along the anterior margin of the paracingulum. Raised, sometimes bulbous folds always clearly developed anterodorsally, between the precingular paraplates. Two small paraplates anterior to the 3"" paraplate probably anterior intercalary paraplates (Fig.5B). Apical series of at least 3 paraplates; possible fourth paraplate not evident on available material.
Paratabulation of the hypocyst poorly defined on most specimens. Holotype with 5 postcingular paraplates in the 2""" to 6""" positions. Paratype with a small 1""" paraplate faintly indicated to the left of the parasulcus (Fig.5D). Small antapical paraplate defined by low periphragmal ridges on the holotype (Fig.5B). Paratabulation formula ?4", ?2a, ?6"", 0c, 6""", 0p, 1"""".
Parasulcus indicated by the archeopyle suture, a gap in the posterior paracingular fold and on some specimens by periphragmal folds bordering the parasulcus between the paracingulum and the archeopyle suture.
Archeopyle apical, type [tA]; operculum usually missing. Archeopyle shape typical of Aprobolocysta and Batioladinium Brideaux 1975. Archeopyle suture with a deep sulcal notch and a short gabled 1"" paraplate.
Dimensions:
Length of holotype with operculum missing 66 µm, width measured across the perihypocyst 41 µm.
Range of length with operculum missing (19 specimens) 41(57)69 µm width 28(38)46 µm, total length of two specimens 64 and 70 µm.
Affinities:
Backhouse, 1987, p. 212: The full paratabulation of A. alata has not been satisfactorily determined because of the absence of the operculum from most specimens and poor development of paratabulation on the hypocyst, particularly in the parasulcal area. The holotype and several unillustrated specimens show 2 small paraplates above the 3"" paraplate. These have been provisionally interpreted as anterior intercalary paraplates, but confirmation must await a better determination of the apical paratabulation. Aprobolocysta alata is closest to A. eilema Duxbury 1977, from which it can be distinguished by the greater development of antapical horns and the presence of partial paratabulation.