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Hapsidaulax margarethae
Hapsidaulax margarethae Sarjeant, 1975b, p.144–147, pl.1, figs.a–d, pl.2, figs.a–d; text-figs.1A–D,2A–D,3A–D. Emendation: Stancliffe and Sarjeant, 1990, p.203.
Holotype: Sarjeant, 1975, pls.1c-d; Stancliffe and Sarjeant, 1990, text.-fig.4, nos.1-3
Paratypes: Sarjeant, 1975
Locus typicus: Lower Ostrea Beds (Great Estuarine Series), foreshore exposure, Duntulm, Isle of Skye, Inverness-shire, Scotland
Stratum typicum: Bathonian (pre-Discus Zone)
Original diagnosis: Sarjeant, 1975, p. 144
A specics of Hapsidalllax having an ellipsoidal to spheroidal or broadly ovoidal ccntral body. Phragma thin, with a surface ornamentation of granulcs or without such ornamentation. Tabulation pattern as depicted in Figs. 1-3 and described below. Trabeculae closest to the surface of the central body at thc apical pole, farthest from its surface towards the antapical pole, though compression or distortion may make this less apparent. Trabeculae of very variable thickness, sometimes broadening greatly at positions of junction; they are frequently penetrated by coarse or fine perforations but may entirely lack such perforations. Trabeculae supported by sutural processes and may be further linked to the sutures by extremely tenuous crests, entire or fenestrate and occasionally faintly striate; but some specimens, especially those with coarse trabeculae, may entirely lack such crests.
Original description: Sarjeant, 1975, p. 145-148
There is considerable variation in shape of the central body--from elongate ellipsoidal to spheroidal or even broadly ovoidal, in relation to the longitudinal axis of thc cyst; this may result in part from its extreme thinness and consequent ready deformability during diagenesis. For the same reason, a shift in position of the enclosing mesh of trabeculae, with relation to thc central body, may occur; in paratype I, for example, the central body is closely appressed to the apical trabeculae. Individual cysts thus exhibit a variety of appearances, their diversity further enhanced by variations in the relative thickness and degree of perforation of the trabeculae and, for the palynologist, by the different orientations in which they are found. Thc apex may exhibit a small protuberance, too meagre to be callcd an apical horn, formcd apparently by a slight outward deflection of the trabeculae of a small preapical plate-area. Plate-area 1" of the apical series is large and elongate in shape, occupying the anterior prolongation of the sulcus; the other four apical plates are polygonal and of much smaller size. An anterior intercalary plate (ra) separates the apical series from precingular plate-area 7" which is, in consequence, of reduced size; a second, smaller intcrcalary plate (za) is situated between apical plate-areas 2" and 3" and precingular platc 2". Altogether, seven plate-areas compose the precingular series, the first and seventh of these being the smallest and platcs 3" to 5" of almost equal size. Archaeopyle formation appears to occur by loss of plate-area 3", but the thinness of the central body and the observational problems presented by the crests and trabeculae made this difficult to confirm.
Six postcingular plate-areas are developed, the first (1""") being reduced to accommodate a large posterior intercalary plate-area (1p) and the others (2" to 6") being of relatively constant size. The sulcal area consists of at least two divisions, possibly more; it extends approximately from mid-point on the epitract to mid-point on the hypotract and is separated from the antapex by a posterior ventral plate-area (1pv). The single antapical plate (1"""") is only of moderate size.
The thickness of the trabeculae varies greatly, not only between individuals but even in each individual cyst. The trabeculae may be unmodified but are very often perforate, sometimes having a beaded appearance resulting from the alignment of large perforations. (Paratype I shows both these features well; see Fig. 2.) The processes linking them to the surface are few and are not readily seen; they appear to be consistently gonal in position, but some sutural processes may also be developed. Crest development is also very variable, not only between individuals but also on each individual; the crests are tenuous and hard to perceive, sometimes striated, very frequently fenestrate or torn. The three type specimens were selected with a view to exhibiting the range in morphology. The holotype, a specimen in polar orientation, was selected because it shows thc apical tabulation particularly well. It is also of average morphology, with trabeculae well developed, sometimes perforate but not especially coarse, and with crests present but not prominent. Paratype I, which is in lateral view, shows the plates of the pre- and postcingular scries espccially well and thus effectively completcs the picture of the tabulation; it shows the characteristic "beaded" trabeculae well and almost totally lacks crests. Paratype II, in contrast, has well developcd crests, the trabeculae being much less noticeable and only to a small degree perforate.
Dimensions. Holotype (in apical view); overall diameters 41x46 Ám, diameters of central body 30x27 Ám. Paratype I; overall length 45 Ám, overall breadth 44 Ám, length of central body 20 Ám, breadth 25 Ám. Paratype II (in slightly oblique apical view), overall diameters 38x43 Ám, diameters of central body 34,5x22 Ám. Range of dimcnsions; overall Iength 30-51 Ám, overall breadth 32-46 Ám, length of central body 23,5-34,5 Ám, breadth 20-37 Ám.
Emended description: Stancliffe and Sarjeant, 1990, p. 203
Central body spherical to subspherical; phragma thin, with or without granular omament. Paratabulation formula 5", 2a, 7", 0c, 6""", 1p, 1pv, 1"""", Is. Trabeculae of very variable thickness, sometimes broadening at their junctions; frequently they have intemal vacuoles of variable size. The trabeculae are supported by parasutural processes and may be linked to the parasutures by tenuous crests, entire or fenestrate, occaslonally faintly striate; however some cysts, especially those with coarse trabeculae, entirely lack crests. Cingulum not developed, so that the precingular paraplates contact the pootcingular paraplates. Only one elongate sulcal paraplate is discernible.
Remark: The general process morphology is very variable, with gradation from processes joined only distally by trabeculae to processes joined by high crests rising from the body. In cross-section these crests swell distally, being supponed by a much thinner proximal portion. This could be a precursor to the development of a fully separate trabecula or it could indicate Ihat the wall had grown outward and fused with the trabecula. When separately developed, the trabeculae frequently are perforate.
Holotype: Sarjeant, 1975, pls.1c-d; Stancliffe and Sarjeant, 1990, text.-fig.4, nos.1-3
Paratypes: Sarjeant, 1975
Locus typicus: Lower Ostrea Beds (Great Estuarine Series), foreshore exposure, Duntulm, Isle of Skye, Inverness-shire, Scotland
Stratum typicum: Bathonian (pre-Discus Zone)
Original diagnosis: Sarjeant, 1975, p. 144
A specics of Hapsidalllax having an ellipsoidal to spheroidal or broadly ovoidal ccntral body. Phragma thin, with a surface ornamentation of granulcs or without such ornamentation. Tabulation pattern as depicted in Figs. 1-3 and described below. Trabeculae closest to the surface of the central body at thc apical pole, farthest from its surface towards the antapical pole, though compression or distortion may make this less apparent. Trabeculae of very variable thickness, sometimes broadening greatly at positions of junction; they are frequently penetrated by coarse or fine perforations but may entirely lack such perforations. Trabeculae supported by sutural processes and may be further linked to the sutures by extremely tenuous crests, entire or fenestrate and occasionally faintly striate; but some specimens, especially those with coarse trabeculae, may entirely lack such crests.
Original description: Sarjeant, 1975, p. 145-148
There is considerable variation in shape of the central body--from elongate ellipsoidal to spheroidal or even broadly ovoidal, in relation to the longitudinal axis of thc cyst; this may result in part from its extreme thinness and consequent ready deformability during diagenesis. For the same reason, a shift in position of the enclosing mesh of trabeculae, with relation to thc central body, may occur; in paratype I, for example, the central body is closely appressed to the apical trabeculae. Individual cysts thus exhibit a variety of appearances, their diversity further enhanced by variations in the relative thickness and degree of perforation of the trabeculae and, for the palynologist, by the different orientations in which they are found. Thc apex may exhibit a small protuberance, too meagre to be callcd an apical horn, formcd apparently by a slight outward deflection of the trabeculae of a small preapical plate-area. Plate-area 1" of the apical series is large and elongate in shape, occupying the anterior prolongation of the sulcus; the other four apical plates are polygonal and of much smaller size. An anterior intercalary plate (ra) separates the apical series from precingular plate-area 7" which is, in consequence, of reduced size; a second, smaller intcrcalary plate (za) is situated between apical plate-areas 2" and 3" and precingular platc 2". Altogether, seven plate-areas compose the precingular series, the first and seventh of these being the smallest and platcs 3" to 5" of almost equal size. Archaeopyle formation appears to occur by loss of plate-area 3", but the thinness of the central body and the observational problems presented by the crests and trabeculae made this difficult to confirm.
Six postcingular plate-areas are developed, the first (1""") being reduced to accommodate a large posterior intercalary plate-area (1p) and the others (2" to 6") being of relatively constant size. The sulcal area consists of at least two divisions, possibly more; it extends approximately from mid-point on the epitract to mid-point on the hypotract and is separated from the antapex by a posterior ventral plate-area (1pv). The single antapical plate (1"""") is only of moderate size.
The thickness of the trabeculae varies greatly, not only between individuals but even in each individual cyst. The trabeculae may be unmodified but are very often perforate, sometimes having a beaded appearance resulting from the alignment of large perforations. (Paratype I shows both these features well; see Fig. 2.) The processes linking them to the surface are few and are not readily seen; they appear to be consistently gonal in position, but some sutural processes may also be developed. Crest development is also very variable, not only between individuals but also on each individual; the crests are tenuous and hard to perceive, sometimes striated, very frequently fenestrate or torn. The three type specimens were selected with a view to exhibiting the range in morphology. The holotype, a specimen in polar orientation, was selected because it shows thc apical tabulation particularly well. It is also of average morphology, with trabeculae well developed, sometimes perforate but not especially coarse, and with crests present but not prominent. Paratype I, which is in lateral view, shows the plates of the pre- and postcingular scries espccially well and thus effectively completcs the picture of the tabulation; it shows the characteristic "beaded" trabeculae well and almost totally lacks crests. Paratype II, in contrast, has well developcd crests, the trabeculae being much less noticeable and only to a small degree perforate.
Dimensions. Holotype (in apical view); overall diameters 41x46 Ám, diameters of central body 30x27 Ám. Paratype I; overall length 45 Ám, overall breadth 44 Ám, length of central body 20 Ám, breadth 25 Ám. Paratype II (in slightly oblique apical view), overall diameters 38x43 Ám, diameters of central body 34,5x22 Ám. Range of dimcnsions; overall Iength 30-51 Ám, overall breadth 32-46 Ám, length of central body 23,5-34,5 Ám, breadth 20-37 Ám.
Emended description: Stancliffe and Sarjeant, 1990, p. 203
Central body spherical to subspherical; phragma thin, with or without granular omament. Paratabulation formula 5", 2a, 7", 0c, 6""", 1p, 1pv, 1"""", Is. Trabeculae of very variable thickness, sometimes broadening at their junctions; frequently they have intemal vacuoles of variable size. The trabeculae are supported by parasutural processes and may be linked to the parasutures by tenuous crests, entire or fenestrate, occaslonally faintly striate; however some cysts, especially those with coarse trabeculae, entirely lack crests. Cingulum not developed, so that the precingular paraplates contact the pootcingular paraplates. Only one elongate sulcal paraplate is discernible.
Remark: The general process morphology is very variable, with gradation from processes joined only distally by trabeculae to processes joined by high crests rising from the body. In cross-section these crests swell distally, being supponed by a much thinner proximal portion. This could be a precursor to the development of a fully separate trabecula or it could indicate Ihat the wall had grown outward and fused with the trabecula. When separately developed, the trabeculae frequently are perforate.