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Netrelytron stegastum
Netrelytron stegasta (Sarjeant, 1961a, p.114–115, pl.15, fig.15; text-fig.14) Wiggins, 1975, p.110. Holotype: Sarjeant, 1961a, pl.15, fig.15; text-fig.14 (left figure); Sarjeant et al., 1987, pl.1, fig.6. Originally Netrelytron, subsequently (and now) Kalyptea, thirdly Pareodinia. Poulsen (1996, p.61) retained this species in Kalyptea. Taxonomic junior synonyms: Netrelytron par and Netrelytron trinetrum, both according to Poulsen (1996, p.61); Kalyptea jurassica, according to Wiggins (1975, p.110) and Kunz (1990 [January], p.12) — however, Below (1990 [October], p.65) considered Kalyptea jurassica to be a taxonomic junior synonym of Kalyptea (as Pareodinia) diceras. Age: early Oxfordian.
Original description: Sarjeant, 1961, p. 114-115
Diagnosis: A species of Netrelytron having an outer membrane of almost spherical shape, with conical horns arising from it at two opposed extremities. These horns have rounded tips and tend to be inclined rather than vertical in their relation to the surface of the ovoidal centre to whose long axis their position corresponds.
Description: All specimens found are invested almost completely in a mass of formless organic matter; this follows the rough outline of the outer membrane and may represent a protective envelope formed around itself by the living organism. Outer membrane thin, devoid of ornamentation. In two specimens seen it is perforated by a roughly oval aperture on one flank, a corresponding gap in the cloak of extraneous meterial being noted. Character of the ovoidal inner shell difficult to determine; it appears of moderate thickness and devoid of ornamentation save possibly for a very faint granulation. Both inner shell and outer membrane frequently folded in some degree. The type specimen and a paratype are both stained with safranin; however, the two other specimens seen are unstained, having a yellowish-brown hue, the inner shell more strongly coloured than the outer membrane.
Remarks (Sarjeant, 1961): The perforation in the outer membrane may be interpreted as a pylome, in which case this surface would be termed dorsal (cf. Eisenack 1958). If this interpretaion were correct, a relationship to the Order Dinoflagellata would be suggested; however, no aperture was observable in the two other specimens seen, and its constancy cannot be affirmed. Similarly, since only four specmens of this distinctive microfossil have been seen, the constancy of the envelope of organic matter cannot be vouched for. All specimens found derived from the 100-foot Oxford horizon, the material from which was very well oxidized; other microfossils from this horizon rarely show any degree of investment in extraneous material, and it is impropable that all specimens of a relatively smooth form such as this should have become fortuitously enwrapped when hystrichospheres bearing complex spines, such as the two species of Cannosphaeropsis present, remain free.
Supplemental description: Gitmez, 1970, p.315
This cavate cyst is spindle-shaped, with apical and antapical horns. There is an endoblast of ovoidal shape. The surface is granular. It was consistently observed with a mass of organic matter surrounding the shell. Neither tabulation nor an archaeopyle was observed.
Dimensions: Range of the English specimens (5 specimens measured): length 89-90 µm, breadth 40-58 µm, horn length 12-16 µm. Range of the French specimens (4 specimens measured): length 80-88 µm, breadth 57-62 µm, horn length 13-15 µm. Holotype dimensions, as mentioned by Sarjeant (length 125 µm, breadth 55 µm), are larger than the Kimmeridge specimens.
Original description: Sarjeant, 1961, p. 114-115
Diagnosis: A species of Netrelytron having an outer membrane of almost spherical shape, with conical horns arising from it at two opposed extremities. These horns have rounded tips and tend to be inclined rather than vertical in their relation to the surface of the ovoidal centre to whose long axis their position corresponds.
Description: All specimens found are invested almost completely in a mass of formless organic matter; this follows the rough outline of the outer membrane and may represent a protective envelope formed around itself by the living organism. Outer membrane thin, devoid of ornamentation. In two specimens seen it is perforated by a roughly oval aperture on one flank, a corresponding gap in the cloak of extraneous meterial being noted. Character of the ovoidal inner shell difficult to determine; it appears of moderate thickness and devoid of ornamentation save possibly for a very faint granulation. Both inner shell and outer membrane frequently folded in some degree. The type specimen and a paratype are both stained with safranin; however, the two other specimens seen are unstained, having a yellowish-brown hue, the inner shell more strongly coloured than the outer membrane.
Remarks (Sarjeant, 1961): The perforation in the outer membrane may be interpreted as a pylome, in which case this surface would be termed dorsal (cf. Eisenack 1958). If this interpretaion were correct, a relationship to the Order Dinoflagellata would be suggested; however, no aperture was observable in the two other specimens seen, and its constancy cannot be affirmed. Similarly, since only four specmens of this distinctive microfossil have been seen, the constancy of the envelope of organic matter cannot be vouched for. All specimens found derived from the 100-foot Oxford horizon, the material from which was very well oxidized; other microfossils from this horizon rarely show any degree of investment in extraneous material, and it is impropable that all specimens of a relatively smooth form such as this should have become fortuitously enwrapped when hystrichospheres bearing complex spines, such as the two species of Cannosphaeropsis present, remain free.
Supplemental description: Gitmez, 1970, p.315
This cavate cyst is spindle-shaped, with apical and antapical horns. There is an endoblast of ovoidal shape. The surface is granular. It was consistently observed with a mass of organic matter surrounding the shell. Neither tabulation nor an archaeopyle was observed.
Dimensions: Range of the English specimens (5 specimens measured): length 89-90 µm, breadth 40-58 µm, horn length 12-16 µm. Range of the French specimens (4 specimens measured): length 80-88 µm, breadth 57-62 µm, horn length 13-15 µm. Holotype dimensions, as mentioned by Sarjeant (length 125 µm, breadth 55 µm), are larger than the Kimmeridge specimens.