Back
Exiguisphaera lasia
Plate 29, Figures 15, 19-22
Holotype: Plate 29, Figures 21, 22
Paratype: Plate 29, Figures 19, 20
Type Locality: Speeton Clay Formation, early Barremian, fissicostatum ammonite Zone. Holotype: Slide LB1(III), E.F. X37.3. Paratype: Slide LB1(III), E.F. U53.0.
Derivation of Name: From the Greek lasios, woolly - in reference to the surface ornament.
Diagnosis: A robust, small to intermediate, spheroidal dinoflagellate cyst with a sexiform gonyaulacacean tabulation pattern typical of the genus. The cyst is covered with a dense, low ornament consisting of granules, coni and very short spines which may be free or coalesce laterally to form an irregularly fibro-reticulate surface. Tabulation is usually vaguely expressed by alignment and linear increases in height of the ornament and sutural crests can range from low intermittent ridges to rare, complex features with short, solid spines ramifying and connected distally by a trabeculum. The archeopyle is precingular, type 2P, formed by the loss of plates 3'' and 4'', which can be separately retained within the cyst cavity.
Dimensions: Holotype: 48 × 51 μm.
Paratype: 53 × 53 μm. Overall: 61 (55) 48 μm × 63 (53) 48 μm
Specimens measured: 10
Remarks: Exiguisphaera lasia n. sp. is most similar to
Exiguisphaera asketa Duxbury 2018, but with low, particularly dense surface ornament and irregular sutural crests which can be obscured by the surface ornament. The tabulation of E. lasia is only poorly marked, the cingulum and ornament-free sulcal groove being particularly distinct. More complex, distally trabeculate crests are very rare.
Exiguisphaera lasia n. sp. was recorded only in Speeton Bed LB1 (uppermost fissicostatum Zone), where it was common, whereas E. asketa is restricted to a short interval across the Berriasian/Valanginian boundary (Duxbury 2018, p. 181).
Holotype: Plate 29, Figures 21, 22
Paratype: Plate 29, Figures 19, 20
Type Locality: Speeton Clay Formation, early Barremian, fissicostatum ammonite Zone. Holotype: Slide LB1(III), E.F. X37.3. Paratype: Slide LB1(III), E.F. U53.0.
Derivation of Name: From the Greek lasios, woolly - in reference to the surface ornament.
Diagnosis: A robust, small to intermediate, spheroidal dinoflagellate cyst with a sexiform gonyaulacacean tabulation pattern typical of the genus. The cyst is covered with a dense, low ornament consisting of granules, coni and very short spines which may be free or coalesce laterally to form an irregularly fibro-reticulate surface. Tabulation is usually vaguely expressed by alignment and linear increases in height of the ornament and sutural crests can range from low intermittent ridges to rare, complex features with short, solid spines ramifying and connected distally by a trabeculum. The archeopyle is precingular, type 2P, formed by the loss of plates 3'' and 4'', which can be separately retained within the cyst cavity.
Dimensions: Holotype: 48 × 51 μm.
Paratype: 53 × 53 μm. Overall: 61 (55) 48 μm × 63 (53) 48 μm
Specimens measured: 10
Remarks: Exiguisphaera lasia n. sp. is most similar to
Exiguisphaera asketa Duxbury 2018, but with low, particularly dense surface ornament and irregular sutural crests which can be obscured by the surface ornament. The tabulation of E. lasia is only poorly marked, the cingulum and ornament-free sulcal groove being particularly distinct. More complex, distally trabeculate crests are very rare.
Exiguisphaera lasia n. sp. was recorded only in Speeton Bed LB1 (uppermost fissicostatum Zone), where it was common, whereas E. asketa is restricted to a short interval across the Berriasian/Valanginian boundary (Duxbury 2018, p. 181).