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Cauca rigida
Plate 8, Figures 3, 4, 7, 10
Holotype: Plate 8, Figure 7
Paratype: Plate 8, Figure 3
Type Locality: late Hauterivian, Speeton Clay Formation, Bed C6, speetonensis ammonite Zone. Holotype: Slide C6(1), E.F. H26.2. Paratype: Slide C6(1), E.F. K40.0.
Derivation of Name: From the Latin rigidus, stiff, hard, inflexible- in reference to the robust nature of this species.
Diagnosis: A relatively robust and thick-walled species, ellipsoidal to ovoidal with the epicyst shorter than the hypocyst. The epicyst is rounded triangular in outline, extending into a low apical prominence and the hypocyst is semicircular. The endophragm is smooth, scabrate or irregularly granular. The cyst bears well-defined sutural crests marking an apparently gonyaulacoid tabulation and a clear cingulum. Crests bear 30–40 long, broad, acuminate, bladelike processes. The archeopyle is epicystal, with the operculum usually attached.
Dimensions: Holotype (operculum attached): Central body: 41 × 38 μm Overall: 61 × 61 μm
Paratype (operculum detached): Central body: 28 × 41 μm Overall: 53 × 73 μm
Overall (complete specimens): Central body: 43 (41) 41 μm × 38 (37) 35 μm Overall: 61 (56) 51 μm × 61 (51) 43 μm
n.b. The paratype is the only specimen measured where the operculum was detached, and is therefore not included in the “Overall” measurements, above.
Specimens Measured: 4
Remarks: This species is relatively robust compared to other species of Cauca, and the main body is relatively large. In several respects, particularly its broad, acuminate processes aligned along well-defined crests, it resembles Hystrichodinium voigtii (Alberti 1961) Davey 1974, but differs in being smaller and less angular, and in possessing an epicystal archeopyle. Specimens often display physical breakage of processes at approximately half their original length.
In the present study, Cauca rigida was restricted to Speeton Bed C6, late Hauterivian, speetonensis Zone, although because of the large sampling gap above Bed C6 (Figs. 2, 5), the range of C. rigida may extend significantly higher in the late Hauterivian.
Holotype: Plate 8, Figure 7
Paratype: Plate 8, Figure 3
Type Locality: late Hauterivian, Speeton Clay Formation, Bed C6, speetonensis ammonite Zone. Holotype: Slide C6(1), E.F. H26.2. Paratype: Slide C6(1), E.F. K40.0.
Derivation of Name: From the Latin rigidus, stiff, hard, inflexible- in reference to the robust nature of this species.
Diagnosis: A relatively robust and thick-walled species, ellipsoidal to ovoidal with the epicyst shorter than the hypocyst. The epicyst is rounded triangular in outline, extending into a low apical prominence and the hypocyst is semicircular. The endophragm is smooth, scabrate or irregularly granular. The cyst bears well-defined sutural crests marking an apparently gonyaulacoid tabulation and a clear cingulum. Crests bear 30–40 long, broad, acuminate, bladelike processes. The archeopyle is epicystal, with the operculum usually attached.
Dimensions: Holotype (operculum attached): Central body: 41 × 38 μm Overall: 61 × 61 μm
Paratype (operculum detached): Central body: 28 × 41 μm Overall: 53 × 73 μm
Overall (complete specimens): Central body: 43 (41) 41 μm × 38 (37) 35 μm Overall: 61 (56) 51 μm × 61 (51) 43 μm
n.b. The paratype is the only specimen measured where the operculum was detached, and is therefore not included in the “Overall” measurements, above.
Specimens Measured: 4
Remarks: This species is relatively robust compared to other species of Cauca, and the main body is relatively large. In several respects, particularly its broad, acuminate processes aligned along well-defined crests, it resembles Hystrichodinium voigtii (Alberti 1961) Davey 1974, but differs in being smaller and less angular, and in possessing an epicystal archeopyle. Specimens often display physical breakage of processes at approximately half their original length.
In the present study, Cauca rigida was restricted to Speeton Bed C6, late Hauterivian, speetonensis Zone, although because of the large sampling gap above Bed C6 (Figs. 2, 5), the range of C. rigida may extend significantly higher in the late Hauterivian.