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Gonyaulacysta centriconnata
Gonyaulacysta centriconnata Riding, 1983
Holotype: Riding, 1983, pl.1, fig.1-3; Jan du Chene et al., 1986, pl.40, fig.10-11
Locus typicus: Nettleton Bottom Borehole, Lincolnshire, England
Stratum typicum: Middle Callovian-Early Oxfordian
Original description: Riding, 1983, p. 198
Diagnosis: proximate dinoflagellate cyst, suturocavate (Benedek et al., 1982), with subcircular to ovoid contact areas of periphragm and endophragm developed in the centers of paraplate areas 1", 1-2"", ?3"", 4-6"", ?1""", 2-6""", 1p and ?1"""". A pronounced epipericoel is developed. Paratabulation standard gonyaulacoid (4", 6"", 6c, ?s, 6""", 1p, 1""""), expressed on the thin, tenuous periphragm by denticulate perasutural crests. Archaeopyle precingular, formed by the loss of paraplate 3"".
Endocyst ovoid to subcircular in shape.
(annotated) Additional description: Outline often slightly elongate. Apical horn poorly developed or prominent, frequently capitate, often attaining 1/10 of the cyst length. Endocyst wall 1.5 Ám thick, smooth to very finely granulate. Endocyst may be badly ruptured on compression. Parasutural crests tend to be more strongly denticulate towards the antapex. Paraplate 1""" typically very narrow. Paracingulum usually relatively broad, laevorotatory. Parasulcus largely confined to the hypocyst, normally fairly straight. Parasulcal paratabulation at best vaguely indicated. Epicystal paratabulation accords much closer to the epithecal tabulation of Gonyaulax polyedra Stein 1883 than to that of Gonyaulax spinifera (Claparede and Lachmann) Diesing 1866 (see Eaton 1980, p.861).
Affinities:
Riding, 1983, p. 199-200
G. centriconnata is particularly similar to G. jurassica and G. pectinigera, in that the latter two species appear to be occasionally suturocavate, but only in one or two paraplates. G. centriconnata is consistently suturocavate.
Parasutural crests of G. jurassica and G. pectinigera are generally much more denticulate. Parasutural crest denticles of G. centriconnata are sharply pointed distally, those of the other two species are much longer and very variable in distal character.
In G. centriconnata the hypocyst and epicyst are equal in size. In G. jurassica the length of the epicyst is up to 2x that of the hypocyst. G. centriconnata does not possess the prominent elongate apical horn, surmounted by two preapical paraplates characteristic of G. jurassica. G. pectinigera has a small apical horn, but, unlike G. centriconnata a prominent epipericoel is never present.
The genus Pentadinium is also suturocavate, but differs from G. centriconnata in that it is spherical (no epipericoel), a prominent pericoel is developed in the paracingular region and may possess a highly sculptured endophragm.
Holotype: Riding, 1983, pl.1, fig.1-3; Jan du Chene et al., 1986, pl.40, fig.10-11
Locus typicus: Nettleton Bottom Borehole, Lincolnshire, England
Stratum typicum: Middle Callovian-Early Oxfordian
Original description: Riding, 1983, p. 198
Diagnosis: proximate dinoflagellate cyst, suturocavate (Benedek et al., 1982), with subcircular to ovoid contact areas of periphragm and endophragm developed in the centers of paraplate areas 1", 1-2"", ?3"", 4-6"", ?1""", 2-6""", 1p and ?1"""". A pronounced epipericoel is developed. Paratabulation standard gonyaulacoid (4", 6"", 6c, ?s, 6""", 1p, 1""""), expressed on the thin, tenuous periphragm by denticulate perasutural crests. Archaeopyle precingular, formed by the loss of paraplate 3"".
Endocyst ovoid to subcircular in shape.
(annotated) Additional description: Outline often slightly elongate. Apical horn poorly developed or prominent, frequently capitate, often attaining 1/10 of the cyst length. Endocyst wall 1.5 Ám thick, smooth to very finely granulate. Endocyst may be badly ruptured on compression. Parasutural crests tend to be more strongly denticulate towards the antapex. Paraplate 1""" typically very narrow. Paracingulum usually relatively broad, laevorotatory. Parasulcus largely confined to the hypocyst, normally fairly straight. Parasulcal paratabulation at best vaguely indicated. Epicystal paratabulation accords much closer to the epithecal tabulation of Gonyaulax polyedra Stein 1883 than to that of Gonyaulax spinifera (Claparede and Lachmann) Diesing 1866 (see Eaton 1980, p.861).
Affinities:
Riding, 1983, p. 199-200
G. centriconnata is particularly similar to G. jurassica and G. pectinigera, in that the latter two species appear to be occasionally suturocavate, but only in one or two paraplates. G. centriconnata is consistently suturocavate.
Parasutural crests of G. jurassica and G. pectinigera are generally much more denticulate. Parasutural crest denticles of G. centriconnata are sharply pointed distally, those of the other two species are much longer and very variable in distal character.
In G. centriconnata the hypocyst and epicyst are equal in size. In G. jurassica the length of the epicyst is up to 2x that of the hypocyst. G. centriconnata does not possess the prominent elongate apical horn, surmounted by two preapical paraplates characteristic of G. jurassica. G. pectinigera has a small apical horn, but, unlike G. centriconnata a prominent epipericoel is never present.
The genus Pentadinium is also suturocavate, but differs from G. centriconnata in that it is spherical (no epipericoel), a prominent pericoel is developed in the paracingular region and may possess a highly sculptured endophragm.