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Fostericysta
From Fensome et al., 2019:
Fostericysta, Riding, 2005b, p.1091.
Substitute name for Fosteria Riding and Helby, 2001e (an illegitimate name).
Type: Riding and Helby, 2001e, fig.3I as Fosteria eclipsiana.
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Original description: [Riding and Helby, 2001e]:
Diagnosis:
Small, proximate to proximochorate, acavate cysts, rounded subquadrate to subpolygonal in dorsoventral outline, with a prominent, incised paracingular region. Autophragm smooth or with low relief ornamentation. A gonyaulacalean paratabulation formula of ?4', 6", ?6c, 6"', 1p, 1"", Xs and may be surmounted by relatively short ornamentational elements. Paracingulum indicated by both the incised equatorial region and by ridges/crests bordering the precingular, postcingular paraplate series and occasional, inconsistent intraparacingular plate boundaries. Parasulcus delimited by parasulcal ridges or crests, not obviously subdivided. Archaeopyle apical, assumed to be type 4A; operculum free, simple. Accumulation bodies may be present.
Remarks:
This distinctive new gonyaulacalean genus normally exhibits a full paratabulation, however the paracingulum and parasulcus are not obviously subdivided. This genus ostensibly appears to be of cladopyxiacean affinity in terms of its size, shape and general appearance. However, the 1p/1"" parasuture is considerably off centre (Figs. 2, 3), which suggests it is not standard partiform sensu Evitt (1985, p. 112-116), although it has features in common with partiform species Glyphanodinium facetum Drugg 1964 (see Evitt, 1985, fig. 5.18. A). Detail of the central parasulcal region in Fosteria is unclear (Figs. 2, 3).
Affinities:
Fosteria is similar in morphology, size, shape and wall relationships to the Jurassic Reutlingia Drugg 1978 emend. Below 1987 and its relatives, for example Parvocysta Bjaerke 1980 and Susadinium Dörhörfer & Davies 1980 (see Riding, 1984). However members of this Parvocysa suite (Riding 1984) all have intercalary archaeopyles and paratabulation patterns differing from Fosteria (see Below, 1987a). Mikrocysta Bjaerke 1980 emend. Below 1987 differs from Fosteria in having a type 2A apical archaeopyle and is essentially partiform, with a strong mid antapical 1""/2"" parasuture and an inverted omegaform ps paraplate (Below, 1987b pl. 2,3). The schematic paratabulation diagram of the hypocyst of Mikrocysta bjaerkei of Below (1987b, fig. 3b) closely resembles paratabulation on the hypocyst of F. eclipsiana. We note that the shape of the ps paraplate and the location of the 1"'/2"" parasutural boundary in the latter diagram does not accord with the specimens of M. bjaerkei illustrated by Below (1987b, pl. 2, 3). Mikrocysta bjaerkei is distinguished from Fosteria in losing only two, rather than four, apical paraplates during excystment, in addition to having an unequivocally partiform paratabulation pattern. Fosteria is also morphologically similar to Horologinella Cookson & Eisenack 1962 emend. Blackhouse 1988 and Dollidinium Helby & Stover 1987. These are both distinguished from Fosteria by their paratabulation patterns, their apical type 2A (3'/4') archeopyles. Horologinella may have an enlarged type A (4') archeopyle which can impinge on paraplates 3' and 5' (Blackhouse, 1988 p. 90, fig 26). Dollidinium, Horologinella and Mikrocysta also lack denticulate crests. Dollidinium is further distinguished by the occurrence of apical and antapical lobes.
Fostericysta, Riding, 2005b, p.1091.
Substitute name for Fosteria Riding and Helby, 2001e (an illegitimate name).
Type: Riding and Helby, 2001e, fig.3I as Fosteria eclipsiana.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Riding and Helby, 2001e]:
Diagnosis:
Small, proximate to proximochorate, acavate cysts, rounded subquadrate to subpolygonal in dorsoventral outline, with a prominent, incised paracingular region. Autophragm smooth or with low relief ornamentation. A gonyaulacalean paratabulation formula of ?4', 6", ?6c, 6"', 1p, 1"", Xs and may be surmounted by relatively short ornamentational elements. Paracingulum indicated by both the incised equatorial region and by ridges/crests bordering the precingular, postcingular paraplate series and occasional, inconsistent intraparacingular plate boundaries. Parasulcus delimited by parasulcal ridges or crests, not obviously subdivided. Archaeopyle apical, assumed to be type 4A; operculum free, simple. Accumulation bodies may be present.
Remarks:
This distinctive new gonyaulacalean genus normally exhibits a full paratabulation, however the paracingulum and parasulcus are not obviously subdivided. This genus ostensibly appears to be of cladopyxiacean affinity in terms of its size, shape and general appearance. However, the 1p/1"" parasuture is considerably off centre (Figs. 2, 3), which suggests it is not standard partiform sensu Evitt (1985, p. 112-116), although it has features in common with partiform species Glyphanodinium facetum Drugg 1964 (see Evitt, 1985, fig. 5.18. A). Detail of the central parasulcal region in Fosteria is unclear (Figs. 2, 3).
Affinities:
Fosteria is similar in morphology, size, shape and wall relationships to the Jurassic Reutlingia Drugg 1978 emend. Below 1987 and its relatives, for example Parvocysta Bjaerke 1980 and Susadinium Dörhörfer & Davies 1980 (see Riding, 1984). However members of this Parvocysa suite (Riding 1984) all have intercalary archaeopyles and paratabulation patterns differing from Fosteria (see Below, 1987a). Mikrocysta Bjaerke 1980 emend. Below 1987 differs from Fosteria in having a type 2A apical archaeopyle and is essentially partiform, with a strong mid antapical 1""/2"" parasuture and an inverted omegaform ps paraplate (Below, 1987b pl. 2,3). The schematic paratabulation diagram of the hypocyst of Mikrocysta bjaerkei of Below (1987b, fig. 3b) closely resembles paratabulation on the hypocyst of F. eclipsiana. We note that the shape of the ps paraplate and the location of the 1"'/2"" parasutural boundary in the latter diagram does not accord with the specimens of M. bjaerkei illustrated by Below (1987b, pl. 2, 3). Mikrocysta bjaerkei is distinguished from Fosteria in losing only two, rather than four, apical paraplates during excystment, in addition to having an unequivocally partiform paratabulation pattern. Fosteria is also morphologically similar to Horologinella Cookson & Eisenack 1962 emend. Blackhouse 1988 and Dollidinium Helby & Stover 1987. These are both distinguished from Fosteria by their paratabulation patterns, their apical type 2A (3'/4') archeopyles. Horologinella may have an enlarged type A (4') archeopyle which can impinge on paraplates 3' and 5' (Blackhouse, 1988 p. 90, fig 26). Dollidinium, Horologinella and Mikrocysta also lack denticulate crests. Dollidinium is further distinguished by the occurrence of apical and antapical lobes.