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Pterodinium fimbriatum
Plate 17, Figures 1, 4, 7, 10, 11
Holotype: Plate 17, Figures 1, 4
Type Locality: Speeton Bed LB6, early Barremian, variabilis ammonite Zone. Holotype: Slide LB6(1), E.F. J47.0.
Derivation of Name: From the Latin fimbriatus, fringed - in reference to the ornate sutural crests.
Diagnosis: A smooth, ovoidal, thin-walled species, without horns and bearing high, delicate sutural crests which are microperforate. These bear numerous, slender distal spines which bifurcate at right angles to the crestal margins. Zig-zag crests reflect six-sided cingular plates. Archeopyle formed by loss of a single mid-dorsal plate (3").
Dimensions: Holotype: Length - 58 μm. Width - 58 μm.
Overall - 61 (57) 51 μm × 58 (54) 51 μm
Specimens Measured: 5.
Remarks: The delicate nature of this species, particularly the distinctive high crests, usually results in some physical distortion and obscuring of the tabulation. No definitive plate formula has been resolved, although it appears to be typically gonyaulacoid.
The high crests vary in the degree and form of their microperforation, which is mainly dense and unaligned, but which can involve lines of larger perforations which are individually elongated at right angles to crest margins (Plate 17, Fig. 1). There is some variation in the length of distal spines between specimens and, as a rule, the longer the spines, the fewer there are per crest. In extreme cases, specimens with longer spines but still with very high crests (Plate 17, Fig. 11) are reminiscent of some species of Spiniferites Mantell 1850.
Pterodinium fimbriatum n. sp. is similar in some respects to Pterodinium aliferum Eisenack 1958, in having high, perforate crests which are distally divided to some extent and which clearly mark plate boundaries, including the cingular plates. It differs in being significantly smaller (P. aliferum range quoted in Sarjeant 1985, p. 74: overall length 80-90 μm, overall breadth 70-75 μm), in being less robust and in the more regular nature of its crestal spines. This species has a very restricted stratigraphic range, between Speeton Beds C2B and LB6 (early Barremian, variabilis Zone).
Holotype: Plate 17, Figures 1, 4
Type Locality: Speeton Bed LB6, early Barremian, variabilis ammonite Zone. Holotype: Slide LB6(1), E.F. J47.0.
Derivation of Name: From the Latin fimbriatus, fringed - in reference to the ornate sutural crests.
Diagnosis: A smooth, ovoidal, thin-walled species, without horns and bearing high, delicate sutural crests which are microperforate. These bear numerous, slender distal spines which bifurcate at right angles to the crestal margins. Zig-zag crests reflect six-sided cingular plates. Archeopyle formed by loss of a single mid-dorsal plate (3").
Dimensions: Holotype: Length - 58 μm. Width - 58 μm.
Overall - 61 (57) 51 μm × 58 (54) 51 μm
Specimens Measured: 5.
Remarks: The delicate nature of this species, particularly the distinctive high crests, usually results in some physical distortion and obscuring of the tabulation. No definitive plate formula has been resolved, although it appears to be typically gonyaulacoid.
The high crests vary in the degree and form of their microperforation, which is mainly dense and unaligned, but which can involve lines of larger perforations which are individually elongated at right angles to crest margins (Plate 17, Fig. 1). There is some variation in the length of distal spines between specimens and, as a rule, the longer the spines, the fewer there are per crest. In extreme cases, specimens with longer spines but still with very high crests (Plate 17, Fig. 11) are reminiscent of some species of Spiniferites Mantell 1850.
Pterodinium fimbriatum n. sp. is similar in some respects to Pterodinium aliferum Eisenack 1958, in having high, perforate crests which are distally divided to some extent and which clearly mark plate boundaries, including the cingular plates. It differs in being significantly smaller (P. aliferum range quoted in Sarjeant 1985, p. 74: overall length 80-90 μm, overall breadth 70-75 μm), in being less robust and in the more regular nature of its crestal spines. This species has a very restricted stratigraphic range, between Speeton Beds C2B and LB6 (early Barremian, variabilis Zone).