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Epelidosphaeridia turrita
From Fensome et al., 2019:
Brideaux, 1977, p.13, pl.4, figs.1–9. Holotype: Brideaux, 1977, pl.4, figs.1–3; Fensome et al., 2019a, figs.20M–O. NOW Epelidosphaeridia? Originally Canningia?, subsequently Ovoidinium, thirdly (and now) Epelidosphaeridia?. Questionable assignment: Brideaux (1977, p.13). Sangiorgi et al. (2009, p.252) speculated that this species may belong to Arcticacysta. Age: Barremian.
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Holotype: Brideaux, 1977, pl.4, figs.1-3
Locus typicus: Richardson Mountains, Mackenzie District, Canada
Stratum typicum: Barremian
Original description: Brideaux, 1977, p. 13: Canningia turrita
Shape: Pericyst apex not observed; antapex rounded or with left antapical prominence developed. Endocyst as above, the two layers closely appressed and without pericoel development; dorso-ventral compression.
Phragma: Periphragm thin, less than 1.0 µm thick; the surface scabrate, or with scattered grana or coni less than 1.0 µm high. Endophragm thin, less than 0.5 µm thick and smooth.
Paratabulation Paratabulation of 4?', ?!1-3)a, 7'', 0c, ?''', ?'''', ?p, denoted by the shape of the archeopyle and accessory parasutures in the precingular paraplate series; other evidence for paratabulation lacking. Endophragm showing no evidence of paratabulation.
Archeopyle/operculum: Archeopyle interpreted as being formed by the loss of at least three apical paraplates (probably 2'-4') and one or three intercalary paraplates (1a or 1a-3a). Operculum free, never observed; the two layers probably separating as a unit.
Pericingulum/perisulcus: Surface expression of pericingulum not observed on periphragm; some specimens possessing slight invaginations of the profile at mid-latitudes interpreted as representing the position of the pericingulum; no surface expression of perisulcus on periphragm.
Dimensions - Overall length, complete specimens not observed, 37-55 µm; overall width, 34-55 µm.
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Comments Fensome et al., 2019a:
In his original description for this species, Brideaux (1977, p. 13) noted that “the two [wall] layers [are] closely appressed … without pericoel development ….” It seems that Brideaux (1977) assumed that two layers were present based on comparison with similar species, but probably saw no actual evidence for separate layers. On proposing a new genus, Arcticacysta, from the Miocene of the Arctic, Sangiorgi et al. (2009, p. 252) stated: "The only other dinosporin cyst having a 3A(?)3I archeopyle is ‘Canningia’ turrita Brideaux 1977 …. The assignment to the genus ‘Canningia’ by Brideaux (1977) was … provisional, since the archeopyle of Canningia sensu stricto is formed by the loss of four apical plates only. The description of ‘Canningia’ turrita seems to closely resemble that of Arcticacysta, except for the mentioning of a pericyst and an endocyst, which have never been observed in Arcticacysta."
Sangiorgi et al. (2009) did not consider Epelidosphaeridia for their new material, probably because Epelidosphaeridia has never been formally emended. As mentioned above, Arcticacysta might be a taxonomic junior synonym of Epelidosphaeridia, although the age difference mitigates against a close relationship. One of several putatively (non-marine?) ovoidinioidean genera from the Palaeogene of China might also prove senior to Arcticacysta (see Fensome et al. 1993, p. 136), but further investigation of this possibility is beyond the scope of the present work. Here we agree with Below (1981) that this species appears more like an ovoidinioidean than an areoligeracean, but provisionally assign it to the acavate genus Epelidosphaeridia rather than follow him in including it in the cavate genus Ovoidinium.
Stratigraphical occurrence. Brideaux (1977) recorded Epelidosphaeridia? (as Canningia) turrita from a sidewall core in the Barremian of the Northwest Territories, former District of Mackenzie, Canada.
Brideaux, 1977, p.13, pl.4, figs.1–9. Holotype: Brideaux, 1977, pl.4, figs.1–3; Fensome et al., 2019a, figs.20M–O. NOW Epelidosphaeridia? Originally Canningia?, subsequently Ovoidinium, thirdly (and now) Epelidosphaeridia?. Questionable assignment: Brideaux (1977, p.13). Sangiorgi et al. (2009, p.252) speculated that this species may belong to Arcticacysta. Age: Barremian.
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Holotype: Brideaux, 1977, pl.4, figs.1-3
Locus typicus: Richardson Mountains, Mackenzie District, Canada
Stratum typicum: Barremian
Original description: Brideaux, 1977, p. 13: Canningia turrita
Shape: Pericyst apex not observed; antapex rounded or with left antapical prominence developed. Endocyst as above, the two layers closely appressed and without pericoel development; dorso-ventral compression.
Phragma: Periphragm thin, less than 1.0 µm thick; the surface scabrate, or with scattered grana or coni less than 1.0 µm high. Endophragm thin, less than 0.5 µm thick and smooth.
Paratabulation Paratabulation of 4?', ?!1-3)a, 7'', 0c, ?''', ?'''', ?p, denoted by the shape of the archeopyle and accessory parasutures in the precingular paraplate series; other evidence for paratabulation lacking. Endophragm showing no evidence of paratabulation.
Archeopyle/operculum: Archeopyle interpreted as being formed by the loss of at least three apical paraplates (probably 2'-4') and one or three intercalary paraplates (1a or 1a-3a). Operculum free, never observed; the two layers probably separating as a unit.
Pericingulum/perisulcus: Surface expression of pericingulum not observed on periphragm; some specimens possessing slight invaginations of the profile at mid-latitudes interpreted as representing the position of the pericingulum; no surface expression of perisulcus on periphragm.
Dimensions - Overall length, complete specimens not observed, 37-55 µm; overall width, 34-55 µm.
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Comments Fensome et al., 2019a:
In his original description for this species, Brideaux (1977, p. 13) noted that “the two [wall] layers [are] closely appressed … without pericoel development ….” It seems that Brideaux (1977) assumed that two layers were present based on comparison with similar species, but probably saw no actual evidence for separate layers. On proposing a new genus, Arcticacysta, from the Miocene of the Arctic, Sangiorgi et al. (2009, p. 252) stated: "The only other dinosporin cyst having a 3A(?)3I archeopyle is ‘Canningia’ turrita Brideaux 1977 …. The assignment to the genus ‘Canningia’ by Brideaux (1977) was … provisional, since the archeopyle of Canningia sensu stricto is formed by the loss of four apical plates only. The description of ‘Canningia’ turrita seems to closely resemble that of Arcticacysta, except for the mentioning of a pericyst and an endocyst, which have never been observed in Arcticacysta."
Sangiorgi et al. (2009) did not consider Epelidosphaeridia for their new material, probably because Epelidosphaeridia has never been formally emended. As mentioned above, Arcticacysta might be a taxonomic junior synonym of Epelidosphaeridia, although the age difference mitigates against a close relationship. One of several putatively (non-marine?) ovoidinioidean genera from the Palaeogene of China might also prove senior to Arcticacysta (see Fensome et al. 1993, p. 136), but further investigation of this possibility is beyond the scope of the present work. Here we agree with Below (1981) that this species appears more like an ovoidinioidean than an areoligeracean, but provisionally assign it to the acavate genus Epelidosphaeridia rather than follow him in including it in the cavate genus Ovoidinium.
Stratigraphical occurrence. Brideaux (1977) recorded Epelidosphaeridia? (as Canningia) turrita from a sidewall core in the Barremian of the Northwest Territories, former District of Mackenzie, Canada.