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Paraevansia mammillata
Paraevansia mammillata Quattrocchio and Sarjeant, 1992, p.83–84 (al. 2–235 — 2–236), pl.4, figs.5–9; pl.5, figs.5–10. Holotype: Quattrocchio and Sarjeant, 1992, pl.4, fig.5. Age: middle-late Tithonian.
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Original description: [Quattrocchio and Sarjeant, 1992]:
Paraevansia mammillata sp. nov.
(Plate 4, Figs 5-9; Plate 5, figs. 5-10)
Derivatio nominis. L., mammillatus, breast-shaped.
Diagnosis. Cysts proximate, cryptotabulate, acavate. Ambitus subspheroidal to ovoidal, with a short mamelon-like apical horn. The horn is broad-based and distally well-rounded, without any apicular structure in specimens seen. The autophragm is densely ornamented by micro-
granules (scabrae) or verrucae (height less than 0.5 μm). Paracingulum broad, indicated by a shallow indentation of the phragma or not at all, other elements of the paratabulation being feebly or not indicated. Archae opyle typically intercalary (3I), but may also involve apical paraplates 2' and 3'. Operculum attached marginally or detached.
Illustrated specimens. Holotype: 2967/4: 5,9/145,6 (Plate 4, Fig. 5); paratype: 2968/1: 20,8/135,7 (Plate 4, Fig. 7). Other figured specimens: 2968/1: 5,9/139,9 (Plate 4, Fig. 6): 2968/1: 16,9/136,3 (Plate 4, Fig. 8); 2968/1: 20,1/140,5 (Plate 4, Fig. 9); 296712: 15,5/103,2 (Plate 5, Fig. 5); 2967/1: 18,6/104,2 (Plate 5, Fig. 10).
Dimensions. Holotype: overall length 55 μm, maximum breadth 48 μm, length of horn 5 μm, breadth of horn 6 μm. Paratype: overall length
45 μm, maximum breadth 30 μm, length of horn 2 μm, breadth of horn 4 μm. Range: overall length 46-55 μm, maximum breadth 30-48 μm,
length of horn 3-5 μm, breadth of horn 4-5 μm (25 specimens measured).
Remarks. This species corresponds in paratabulation with P. brachythelis (Fensome, 1979) emend. Below 1990, but the apical horn is of dissimilar shape, the phragma is less thick and not clearly divisible into endophragm and periphragm, and the ornamentation is less coarse.
P. mammillata was only found in the Upper Tithonian (2968 level; 12,5% of total microplankton; see Text-fig. 11).
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Original description: [Quattrocchio and Sarjeant, 1992]:
Paraevansia mammillata sp. nov.
(Plate 4, Figs 5-9; Plate 5, figs. 5-10)
Derivatio nominis. L., mammillatus, breast-shaped.
Diagnosis. Cysts proximate, cryptotabulate, acavate. Ambitus subspheroidal to ovoidal, with a short mamelon-like apical horn. The horn is broad-based and distally well-rounded, without any apicular structure in specimens seen. The autophragm is densely ornamented by micro-
granules (scabrae) or verrucae (height less than 0.5 μm). Paracingulum broad, indicated by a shallow indentation of the phragma or not at all, other elements of the paratabulation being feebly or not indicated. Archae opyle typically intercalary (3I), but may also involve apical paraplates 2' and 3'. Operculum attached marginally or detached.
Illustrated specimens. Holotype: 2967/4: 5,9/145,6 (Plate 4, Fig. 5); paratype: 2968/1: 20,8/135,7 (Plate 4, Fig. 7). Other figured specimens: 2968/1: 5,9/139,9 (Plate 4, Fig. 6): 2968/1: 16,9/136,3 (Plate 4, Fig. 8); 2968/1: 20,1/140,5 (Plate 4, Fig. 9); 296712: 15,5/103,2 (Plate 5, Fig. 5); 2967/1: 18,6/104,2 (Plate 5, Fig. 10).
Dimensions. Holotype: overall length 55 μm, maximum breadth 48 μm, length of horn 5 μm, breadth of horn 6 μm. Paratype: overall length
45 μm, maximum breadth 30 μm, length of horn 2 μm, breadth of horn 4 μm. Range: overall length 46-55 μm, maximum breadth 30-48 μm,
length of horn 3-5 μm, breadth of horn 4-5 μm (25 specimens measured).
Remarks. This species corresponds in paratabulation with P. brachythelis (Fensome, 1979) emend. Below 1990, but the apical horn is of dissimilar shape, the phragma is less thick and not clearly divisible into endophragm and periphragm, and the ornamentation is less coarse.
P. mammillata was only found in the Upper Tithonian (2968 level; 12,5% of total microplankton; see Text-fig. 11).