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Wrevittia diutina ssp. contrabium
Plate 21, Figures 3, 4, 5, 8, 9, 16, 20
Holotype: Plate 21, Figure 5, 8, 9.
Paratype: Plate 21, Figures 3, 4.
Type Locality: Speeton Clay Formation, early Hauterivian, regale ammonite Zone. Holotype: Slide C11A(1), E.F. O43.1.
Paratype: Slide topC11B(2), E.F. J55.0.
Derivation of Name: From the Latin contrabium, a framework of beams - in reference to the complex periphragmal structure of this subspecies.
Diagnosis: A fairly thick-walled subspecies of intermediate size, smooth and with scattered intratabular baculae and/or coni. Ashort, blunt-ended apical horn is present, supported by a small “pericoel” which is highly perforate, the large perforations reducing it to a rigid framework. Tabulation, presumed to be of the formula 4', 6'', ?c, 6''', 1p, 1p.v., 1'''' is marked by denticulate crests which have large proximal perforations, particularly well-developed on the epicyst but which can also occur on the hypocyst. The archeopyle is single-plate precingular (3").
Dimensions: Holotype: Length - 66 μm. Width - 56 μm.
Paratype: Length - 56 μm. Width - 38 μm.
Complete specimens (2 recorded): 66 (61) 56 μm × 56 (47) 38 μm.
Remarks: This is a very rare subspecies, and only 2 specimens were recorded, restricted to Speeton Beds C11B(top) and C11A, early Hauterivian, lower regale ammonite Zone. The complete “skeletonisation” of the apical “pericoel” is a particularly striking feature.
Gonyaulacysta polythyris Davey 1979b possesses, “strongly developed, perforate parasutural crests” (Davey op. cit., p. 556), and its overall morphology is similar to Wrevittia diutina subsp. contrabium, as it, “belongs to the G. helicoidea lineage” (Davey, op. cit.). Although apparently cornucavate, G. polythyris displays no apical pericoel, and therefore no “skeletonisation” typical of W. diutina subsp. contrabium. Also, the sutural crests of G. polythyris are smooth whereas those of W. diutina subsp. contrabium are denticulate.
Holotype: Plate 21, Figure 5, 8, 9.
Paratype: Plate 21, Figures 3, 4.
Type Locality: Speeton Clay Formation, early Hauterivian, regale ammonite Zone. Holotype: Slide C11A(1), E.F. O43.1.
Paratype: Slide topC11B(2), E.F. J55.0.
Derivation of Name: From the Latin contrabium, a framework of beams - in reference to the complex periphragmal structure of this subspecies.
Diagnosis: A fairly thick-walled subspecies of intermediate size, smooth and with scattered intratabular baculae and/or coni. Ashort, blunt-ended apical horn is present, supported by a small “pericoel” which is highly perforate, the large perforations reducing it to a rigid framework. Tabulation, presumed to be of the formula 4', 6'', ?c, 6''', 1p, 1p.v., 1'''' is marked by denticulate crests which have large proximal perforations, particularly well-developed on the epicyst but which can also occur on the hypocyst. The archeopyle is single-plate precingular (3").
Dimensions: Holotype: Length - 66 μm. Width - 56 μm.
Paratype: Length - 56 μm. Width - 38 μm.
Complete specimens (2 recorded): 66 (61) 56 μm × 56 (47) 38 μm.
Remarks: This is a very rare subspecies, and only 2 specimens were recorded, restricted to Speeton Beds C11B(top) and C11A, early Hauterivian, lower regale ammonite Zone. The complete “skeletonisation” of the apical “pericoel” is a particularly striking feature.
Gonyaulacysta polythyris Davey 1979b possesses, “strongly developed, perforate parasutural crests” (Davey op. cit., p. 556), and its overall morphology is similar to Wrevittia diutina subsp. contrabium, as it, “belongs to the G. helicoidea lineage” (Davey, op. cit.). Although apparently cornucavate, G. polythyris displays no apical pericoel, and therefore no “skeletonisation” typical of W. diutina subsp. contrabium. Also, the sutural crests of G. polythyris are smooth whereas those of W. diutina subsp. contrabium are denticulate.