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Eisenackia msounensis
Eisenackia msounensis Slimani et al., 2008, p.336,338, figs.7A–L,8A–B.
Holotype: Slimani et al., 2008, figs.7A–F,J, 8A–B.
Age: early Danian.
Original description (Slimani et al., 2008):
Eisenackia msounensis sp. nov. Figs. 7 and 8
Derivation of name. After the River Msoun which crosses the type locality.
Holotype. Sample OH 12, slide 1, EF V39/1 (Figs. 7AeF, J, and 8A, B).
Type locality and stratigraphic horizon. Ouled Haddou section, north of Taza, northern Morocco; clayey marls 35 cm above the K/T boundary, lower Danian.
Diagnosis. A species of Eisenackia with a finely granulate wall surface. Gonyaulacoid tabulation indicated by very low penitabular and intratabular (one per plate) ridges or thickenings. Archeopyle apical, type (tA). Operculum free.
Description. Proximate, subspherical to ovoid autocyst with intratabular (one per plate) low sinuous ridges (maximum height 1 µm). Phragm is massive, thick (up to 2 µm) and finely granular (Fig. 7J), but smooth and thinner (c. 1 µm) in sutural areas. Plates delimited by low ridges or thickenings (maximum height 1 µm), which are sometimes absent, especially on ventral surface of some specimens. Reflected tabulation is 4’ , 6’’, 6c, 6’’’, 1p, 1’’’’, 4s (Fig. 8A, B). Precingular plates are subpentagonal to nearly square. Cingular plates subrectangular (4-9 µm wide) and transversely elongate. 1’’’ is small and inconspicuous. 2’’’ is much smaller than the other postcingular plates. Antapical 1’’’’ plate is hexagonal and borders 3’’’, 4’’’, 5’’’, 6’’’, 1p and ps. Archeopyle apical, type (tA) with a zigzag margin and accessory sutures; operculum free.
Dimensions (in µm). Holotype and range for 10 specimens measured: length (without operculum) 46, 38(44)45; width 50, 38(48)52.
Discussion. The finely granulate autophragm and low penitabular and typical intratabular ridges serve to distinguish Eisenackia msounensis from other species of the genus. Eisenackia crassitabulata Deflandre and Cookson, 1955 differs in its reticulate wall without intratabular ornament. Eisenackia circumtabulata Drugg, 1967 has higher penitabular ridges and a smooth wall without intratabular ornament. Eisenachia margarita (Harland, 1979) Quattrocchio and Sarjeant, 2003, Eisenackia reticulata (Damassa, 1979a) Quattrocchio and Sarjeant, 2003, and E. chilensis Quattrocchio and Sarjeant, 2003 also have higher penitabular ridges and in addition, respectively, accessory ridges, reticulation and coni.
Stratigraphic occurrence. Samples OH 8e17, planktonic foraminiferal Guembelitria cretacea and Parvularugoglobigerina eugubina zones, lower Danian.
Holotype: Slimani et al., 2008, figs.7A–F,J, 8A–B.
Age: early Danian.
Original description (Slimani et al., 2008):
Eisenackia msounensis sp. nov. Figs. 7 and 8
Derivation of name. After the River Msoun which crosses the type locality.
Holotype. Sample OH 12, slide 1, EF V39/1 (Figs. 7AeF, J, and 8A, B).
Type locality and stratigraphic horizon. Ouled Haddou section, north of Taza, northern Morocco; clayey marls 35 cm above the K/T boundary, lower Danian.
Diagnosis. A species of Eisenackia with a finely granulate wall surface. Gonyaulacoid tabulation indicated by very low penitabular and intratabular (one per plate) ridges or thickenings. Archeopyle apical, type (tA). Operculum free.
Description. Proximate, subspherical to ovoid autocyst with intratabular (one per plate) low sinuous ridges (maximum height 1 µm). Phragm is massive, thick (up to 2 µm) and finely granular (Fig. 7J), but smooth and thinner (c. 1 µm) in sutural areas. Plates delimited by low ridges or thickenings (maximum height 1 µm), which are sometimes absent, especially on ventral surface of some specimens. Reflected tabulation is 4’ , 6’’, 6c, 6’’’, 1p, 1’’’’, 4s (Fig. 8A, B). Precingular plates are subpentagonal to nearly square. Cingular plates subrectangular (4-9 µm wide) and transversely elongate. 1’’’ is small and inconspicuous. 2’’’ is much smaller than the other postcingular plates. Antapical 1’’’’ plate is hexagonal and borders 3’’’, 4’’’, 5’’’, 6’’’, 1p and ps. Archeopyle apical, type (tA) with a zigzag margin and accessory sutures; operculum free.
Dimensions (in µm). Holotype and range for 10 specimens measured: length (without operculum) 46, 38(44)45; width 50, 38(48)52.
Discussion. The finely granulate autophragm and low penitabular and typical intratabular ridges serve to distinguish Eisenackia msounensis from other species of the genus. Eisenackia crassitabulata Deflandre and Cookson, 1955 differs in its reticulate wall without intratabular ornament. Eisenackia circumtabulata Drugg, 1967 has higher penitabular ridges and a smooth wall without intratabular ornament. Eisenachia margarita (Harland, 1979) Quattrocchio and Sarjeant, 2003, Eisenackia reticulata (Damassa, 1979a) Quattrocchio and Sarjeant, 2003, and E. chilensis Quattrocchio and Sarjeant, 2003 also have higher penitabular ridges and in addition, respectively, accessory ridges, reticulation and coni.
Stratigraphic occurrence. Samples OH 8e17, planktonic foraminiferal Guembelitria cretacea and Parvularugoglobigerina eugubina zones, lower Danian.