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Luehndea septata
Luehndea septata Riding and Helby, 2001a, p.5, figs.3A-P.
Holotype: Riding and Helby, 2001a, fig.3O
Age: Toarcian.
Original description (Riding and Helby, 2001a)
Description. A species of Luehndea which is subquadrangular to ellipsoidal in outline, and intermediate in size. Apparently two-layered, the periphragm is extended into solid, slender, distally-pointed gonal and intergonal processes which are normally connected by thin septa. The paracingular paraplates, however, appear to lack vertical parasutural septa. The absence of spines and septa in the broad paracingular region imparts a characteristic indented outline or waist. The processes are straight or slightly curved. Gonal spines are present at all major paraplate boundaries and may be separated by up to two, slightly shorter, intergonal spines. No intratabular processes, or other positive ornamentation, have been observed. The septa are smooth and the distal extremities are commonly concave. The autophragm is smooth or microscabrate. The autophragm is mooth or microscabrate. The archaeopyle is epicystal with the operculum typically attached ventrally.
Dimensions (µm, n=31): Min. (Mean) Max.
Overall length (incl. processes): 62 (80) 94
Length of cyst body (excl. processes): 40 (54) 67
Overall width (incl. processes): 55 (67) 77
Width of cyst body (excl. processes): 36 (44) 50
Length of processes: 7 (15) 27
The measured specimens are from sidewall core samples in Skua-5 (2646.00m), Skua-6 (2385.00m) and Skua-7a (2440.00m) wells.
Comments. This distinctive species of Luehndea is distinguished by its relatively large size compared to the other species within the genus and the prominent thin parasultural septa. These septa connect the gonal and intergonal processes, exept at the paracingulum. Each septum is concave and smooth distally. There are no vertical paracingular septa, therefore the equatorial area is devoid of ornamentation. The septa define the paratabulation pattern, which is consistent with that determined for the genus (Below, 1990, fig. 10; Bucefalo Palliani et al., 1997a). In a few samples the septa are suppressed; more commonly they may be reduced. The processes in Luehndea septata exhibit significant variety in length and those gonal spines associated with the two antapical paraplates are consistently the longest, often exceeding 20 µm in length. These relatively long antapical processes can be frequently be used as an orientational criterion. The processes close to the equatorial region are normally the smallest and these may be as short as 10 µm in length. Furthermore, the intergonal spines are normally shorter than the gonal spine.
Comparison. Luehndea septata is distinguished by the high parasutural septa between the processes (see Morgenroth, 1970, pl.9; Below, 1990, pl. 8) Luehnda cirilliae Bucefalo Palliani et al., 1997, L. spinosa Morgenroth 1970 and L. microreticulata Bucefalo Palliani et al., 1997a, fig. 3). Furthermore, Luehnda septata is about twice the average size of the European species (see Dimensions above). The latter have average lengths of 36-39 µm and avergae widths of 28-34 µm (Bucefalo Palliani et al. 1997a. fig. 3)
Derivation of name. From the Latin septum, meaning wall or partition.
Holotype and type locality. Fig. 3O, CPC 35116. Skua-7A well, sidewell core at 2440.00 m.
Stratigraphical distribution. See Appendix 1 and Fig. 12.
Holotype: Riding and Helby, 2001a, fig.3O
Age: Toarcian.
Original description (Riding and Helby, 2001a)
Description. A species of Luehndea which is subquadrangular to ellipsoidal in outline, and intermediate in size. Apparently two-layered, the periphragm is extended into solid, slender, distally-pointed gonal and intergonal processes which are normally connected by thin septa. The paracingular paraplates, however, appear to lack vertical parasutural septa. The absence of spines and septa in the broad paracingular region imparts a characteristic indented outline or waist. The processes are straight or slightly curved. Gonal spines are present at all major paraplate boundaries and may be separated by up to two, slightly shorter, intergonal spines. No intratabular processes, or other positive ornamentation, have been observed. The septa are smooth and the distal extremities are commonly concave. The autophragm is smooth or microscabrate. The autophragm is mooth or microscabrate. The archaeopyle is epicystal with the operculum typically attached ventrally.
Dimensions (µm, n=31): Min. (Mean) Max.
Overall length (incl. processes): 62 (80) 94
Length of cyst body (excl. processes): 40 (54) 67
Overall width (incl. processes): 55 (67) 77
Width of cyst body (excl. processes): 36 (44) 50
Length of processes: 7 (15) 27
The measured specimens are from sidewall core samples in Skua-5 (2646.00m), Skua-6 (2385.00m) and Skua-7a (2440.00m) wells.
Comments. This distinctive species of Luehndea is distinguished by its relatively large size compared to the other species within the genus and the prominent thin parasultural septa. These septa connect the gonal and intergonal processes, exept at the paracingulum. Each septum is concave and smooth distally. There are no vertical paracingular septa, therefore the equatorial area is devoid of ornamentation. The septa define the paratabulation pattern, which is consistent with that determined for the genus (Below, 1990, fig. 10; Bucefalo Palliani et al., 1997a). In a few samples the septa are suppressed; more commonly they may be reduced. The processes in Luehndea septata exhibit significant variety in length and those gonal spines associated with the two antapical paraplates are consistently the longest, often exceeding 20 µm in length. These relatively long antapical processes can be frequently be used as an orientational criterion. The processes close to the equatorial region are normally the smallest and these may be as short as 10 µm in length. Furthermore, the intergonal spines are normally shorter than the gonal spine.
Comparison. Luehndea septata is distinguished by the high parasutural septa between the processes (see Morgenroth, 1970, pl.9; Below, 1990, pl. 8) Luehnda cirilliae Bucefalo Palliani et al., 1997, L. spinosa Morgenroth 1970 and L. microreticulata Bucefalo Palliani et al., 1997a, fig. 3). Furthermore, Luehnda septata is about twice the average size of the European species (see Dimensions above). The latter have average lengths of 36-39 µm and avergae widths of 28-34 µm (Bucefalo Palliani et al. 1997a. fig. 3)
Derivation of name. From the Latin septum, meaning wall or partition.
Holotype and type locality. Fig. 3O, CPC 35116. Skua-7A well, sidewell core at 2440.00 m.
Stratigraphical distribution. See Appendix 1 and Fig. 12.