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Muderongia patula
From Fensome et al., 2019:
Muderongia patula Duxbury, 2019, p.197, pl.23, figs.1–3,7; text-fig.4. Holotype: Duxbury, 2019, pl.23, fig.7. Age: late Barremian.
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Original description Duxbury, 2019:
Plate 23, Figures 1–3, 7; text-figure 4
Holotype: Plate 23, Figure 7.
Type Locality: Heslerton No. 2 at 27.05 m (core chip), late
Barremian age. Holotype: E.F. Y45.0.
Derivation of Name: From the Latin patulus, open, spread out, broad – in reference to the relative width of this species.
Diagnosis: A smooth, delicate, proximate and cornucavate cyst with two wall layers clearly represented. The two lateral horns are of approximately equal length and may be anteriorly rounded or have a distinct precingular projection and deep cingular notch; long postcingular projections occur on both lateral horns. Awell developed left antapical horn contrasts markedly with a rudimentary right antapical horn development or rounded right antapical area. There is no clear tabulation except for a narrow, faint cingulum. Rare denticles may occur towards horn extremities. The endocyst is well defined, having long lateral and left antapical projections but a rounded right antapex. Notching of the endocystal lateral projections can occur, reflecting the cingular notches in the pericyst. The archeopyle is apical, with the operculum usually lost.
Dimensions: Holotype: Length - 78 μm. Width - 104 μm.
Overall: Length - 91 (75) 63 μm; Width - 104 (90) 76 μm.
Specimens Measured: 5.
Remarks: Muderongia patula is a rare but very distinctive species very similar in outline to Vesperopsis longicornis (Batten and Lister 1988) Harding 1990, which differs in possessing an autophragm only (Harding 1990, p. 21, Lister and Batten 1988, p. 27). The possession of autophragm only or endophragm plus periphragm is currently considered generically significant, although perhaps paleosalinity differences might have played a role. Vesperopsis longicornis was described (Batten and Lister op. cit.) from the Vectis Formation (Wealden, fresh water to low salinity) of the Isle of Wight, and Harding (1990, p. 21) noted that it occurred in flood abundance in the highest part of the Weald Clay in theWarlingham borehole, Surrey. Wilpshaar and Leereveld (1994) noted that high abundances of their Muderongia Group (including Odontochitina and Phoberocysta) have been reported in sediments representing variable salinity conditions (e.g. Lister and Batten 1988).
Although the surface of M. patula n. sp. is smooth, small denticles can occur towards horn extremities (Plate 23, Figure 3 and text-fig. 4), a feature also reported for Muderongia australis Helby (1987, p. 300-303) and illustrated in his Figure 3C.
Muderongia patula Duxbury, 2019, p.197, pl.23, figs.1–3,7; text-fig.4. Holotype: Duxbury, 2019, pl.23, fig.7. Age: late Barremian.
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Original description Duxbury, 2019:
Plate 23, Figures 1–3, 7; text-figure 4
Holotype: Plate 23, Figure 7.
Type Locality: Heslerton No. 2 at 27.05 m (core chip), late
Barremian age. Holotype: E.F. Y45.0.
Derivation of Name: From the Latin patulus, open, spread out, broad – in reference to the relative width of this species.
Diagnosis: A smooth, delicate, proximate and cornucavate cyst with two wall layers clearly represented. The two lateral horns are of approximately equal length and may be anteriorly rounded or have a distinct precingular projection and deep cingular notch; long postcingular projections occur on both lateral horns. Awell developed left antapical horn contrasts markedly with a rudimentary right antapical horn development or rounded right antapical area. There is no clear tabulation except for a narrow, faint cingulum. Rare denticles may occur towards horn extremities. The endocyst is well defined, having long lateral and left antapical projections but a rounded right antapex. Notching of the endocystal lateral projections can occur, reflecting the cingular notches in the pericyst. The archeopyle is apical, with the operculum usually lost.
Dimensions: Holotype: Length - 78 μm. Width - 104 μm.
Overall: Length - 91 (75) 63 μm; Width - 104 (90) 76 μm.
Specimens Measured: 5.
Remarks: Muderongia patula is a rare but very distinctive species very similar in outline to Vesperopsis longicornis (Batten and Lister 1988) Harding 1990, which differs in possessing an autophragm only (Harding 1990, p. 21, Lister and Batten 1988, p. 27). The possession of autophragm only or endophragm plus periphragm is currently considered generically significant, although perhaps paleosalinity differences might have played a role. Vesperopsis longicornis was described (Batten and Lister op. cit.) from the Vectis Formation (Wealden, fresh water to low salinity) of the Isle of Wight, and Harding (1990, p. 21) noted that it occurred in flood abundance in the highest part of the Weald Clay in theWarlingham borehole, Surrey. Wilpshaar and Leereveld (1994) noted that high abundances of their Muderongia Group (including Odontochitina and Phoberocysta) have been reported in sediments representing variable salinity conditions (e.g. Lister and Batten 1988).
Although the surface of M. patula n. sp. is smooth, small denticles can occur towards horn extremities (Plate 23, Figure 3 and text-fig. 4), a feature also reported for Muderongia australis Helby (1987, p. 300-303) and illustrated in his Figure 3C.