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Spiniferites fibrosus
Plate 26, Figures 13, 16, 17, 18-21
Holotype: Plate 26, Figures 13, 17, 21.
Type Locality: Speeton Clay Formation, Bed C11A, early Hauterivian, regale ammonite Zone. Holotype: Slide C11A(2), E.F. N42.0
Derivation of Name: From the Latin fibrosus, fibrous - in reference to the periphragm texture.
Diagnosis: A species with a spheroidal endocyst, covered by a dense, finely granular ornament, and a closely attached, fibrous pericyst. The periphragm forms short gonal and sutural processes, one quarter to one half of the endocyst diameter in height, proximally connected by low curved crests. Aprominentcingulum with zig-zag margins is clearly seen, and this has a ventral offset of approximally one cingulum width. Process terminations are usually bifurcate (sutural) and trifurcate (gonal), although both can be irregular in their furcation. An apical structure is present, of equal height to the processes, and this characteristically bears a relatively large lateral hole. The archeopyle is single plate precingular (3").
Dimensions: Holotype: Central body - 38 × 41 μm; Overall - 56 × 56 μm.
All measured specimens: Central body - 48 (42) 35 μm × 51 (39) 33 μm. Overall: 63 (60) 56 μm × 68 (56) 51 μm.
Specimens Measured: 14.
Remarks: Spiniferites fibrosus n. sp. differs from other species of the genus in its combination of a densely but finely granular endocyst, a fibrous pericyst and process terminations which tend to be somewhat irregular. The latter are reminiscent of, but with shorter terminations than, those of Avellodinium falsificum Duxbury 1977 and Avellodinium lepidum Backhouse 1988 (see Plate 11, Figs. 2, 4, 10 and Plate 11, Fig. 3), and the periphragm texture is similar to that of Avellodinium variabilis Duxbury n. sp., but Avellodinium has an epicystal archeopyle. This species was restricted to Bed C11A at Speeton (early Hauterivian, lower regale ammonite Zone), where it was common.
Holotype: Plate 26, Figures 13, 17, 21.
Type Locality: Speeton Clay Formation, Bed C11A, early Hauterivian, regale ammonite Zone. Holotype: Slide C11A(2), E.F. N42.0
Derivation of Name: From the Latin fibrosus, fibrous - in reference to the periphragm texture.
Diagnosis: A species with a spheroidal endocyst, covered by a dense, finely granular ornament, and a closely attached, fibrous pericyst. The periphragm forms short gonal and sutural processes, one quarter to one half of the endocyst diameter in height, proximally connected by low curved crests. Aprominentcingulum with zig-zag margins is clearly seen, and this has a ventral offset of approximally one cingulum width. Process terminations are usually bifurcate (sutural) and trifurcate (gonal), although both can be irregular in their furcation. An apical structure is present, of equal height to the processes, and this characteristically bears a relatively large lateral hole. The archeopyle is single plate precingular (3").
Dimensions: Holotype: Central body - 38 × 41 μm; Overall - 56 × 56 μm.
All measured specimens: Central body - 48 (42) 35 μm × 51 (39) 33 μm. Overall: 63 (60) 56 μm × 68 (56) 51 μm.
Specimens Measured: 14.
Remarks: Spiniferites fibrosus n. sp. differs from other species of the genus in its combination of a densely but finely granular endocyst, a fibrous pericyst and process terminations which tend to be somewhat irregular. The latter are reminiscent of, but with shorter terminations than, those of Avellodinium falsificum Duxbury 1977 and Avellodinium lepidum Backhouse 1988 (see Plate 11, Figs. 2, 4, 10 and Plate 11, Fig. 3), and the periphragm texture is similar to that of Avellodinium variabilis Duxbury n. sp., but Avellodinium has an epicystal archeopyle. This species was restricted to Bed C11A at Speeton (early Hauterivian, lower regale ammonite Zone), where it was common.