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Surculosphaeridium palmatum
From Fensome et al., 2019:
Surculosphaeridium palmatum
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Original Description Duxbury, 2019:
Plate 19, Figures 1, 2, 4, 5, 7, 8
Holotype: Plate 19, Figures 4, 7
Paratype: Plate 19, Figure 8
Type Locality: Heslerton No. 2 at 27.05 m (core chip), late Barremian age. Holotype: E.F. X28.0. Paratype Heslerton No. 2
at 22.00 m (core chip), E.F. F41.2.
Derivation of Name: From the Latin palmatus, shaped like the palm of the hand - in reference to the distal process terminations.
Diagnosis: A small, fairly thick-walled chorate cyst, smooth walled and bearing long, solid, simple, mesotabular processes, in length about half of the main body diameter. Processes taper and then expand into broad distal terminations. Rarely, individual cingular processes may bifurcate. Processes indicate a reflected tabulation pattern of 4', 6", 6c, 6''', 1p, 1''''. Distal terminations are palmate and in pre- and postcingular areas, the “heel” of each palm is adcingular. The archeopyle is tetratabular apical and the operculum is usually detached.
Dimensions: Holotype (operculum lost): Central body - 38 × 38 μm. Overall – 63 × 71 μm.
Paratype (complete): Central body – 43 × 35 μm. Overall -73 × 71 μm.
Complete specimens: Central body – 43 (43) 43 μm × 38 (37)
35 μm. Overall – 76 (75) 73 μm × 71 (71) 71 μm.
Specimens measured: 2.
Operculum lost: Central body – 41 (38) 33 μm × 41 (38) 33 μm.
Overall – 76 (63) 51 μm × 76 (71) 61 μm.
Specimens measured: 11.
Remarks: Surculosphaeridium palmatum is similar to Surculosphaeridium trunculum Davey 1979 and S. longifurcatum (Firtion 1952) Davey et al. 1966. It differs from S. trunculum in the simplicity of the processes, which are solid and without furcation, except for occasional bifurcation within the cingular series. In contrast, S. trunculum bears two process types, one bifurcating proximally and thinner processes, usually cingular, linked by medial bars. The palmate process terminations of S. palmatum contrast with those of S. trunculum, which “typically bifurcate or trifurcate and terminate with a small bifurcation or spinelets” (Davey 1979, p. 560). Surculosphaeridium longifurcatum typically bears distally branching processes with those marking the cingulum characteristically deeply-furcate. The irregular distal process terminations of this species again contrast markedly with those of S. palmatum. Davey (1979, p. 560) considered S. trunculum to be “probably ancestral” to S. longifurcatum, with the last species ranging no older than the Albian (after Davey and Verdier 1971). In the present study, S. palmatum ranges from 29.85 m to 16.00 m in Heslerton No. 2, upper Barremian, Zone LKP21 to the upper Barremian/lower Aptian, Zone LKP25.
Surculosphaeridium palmatum
---------------------------------------------------------------------------------------------------
Original Description Duxbury, 2019:
Plate 19, Figures 1, 2, 4, 5, 7, 8
Holotype: Plate 19, Figures 4, 7
Paratype: Plate 19, Figure 8
Type Locality: Heslerton No. 2 at 27.05 m (core chip), late Barremian age. Holotype: E.F. X28.0. Paratype Heslerton No. 2
at 22.00 m (core chip), E.F. F41.2.
Derivation of Name: From the Latin palmatus, shaped like the palm of the hand - in reference to the distal process terminations.
Diagnosis: A small, fairly thick-walled chorate cyst, smooth walled and bearing long, solid, simple, mesotabular processes, in length about half of the main body diameter. Processes taper and then expand into broad distal terminations. Rarely, individual cingular processes may bifurcate. Processes indicate a reflected tabulation pattern of 4', 6", 6c, 6''', 1p, 1''''. Distal terminations are palmate and in pre- and postcingular areas, the “heel” of each palm is adcingular. The archeopyle is tetratabular apical and the operculum is usually detached.
Dimensions: Holotype (operculum lost): Central body - 38 × 38 μm. Overall – 63 × 71 μm.
Paratype (complete): Central body – 43 × 35 μm. Overall -73 × 71 μm.
Complete specimens: Central body – 43 (43) 43 μm × 38 (37)
35 μm. Overall – 76 (75) 73 μm × 71 (71) 71 μm.
Specimens measured: 2.
Operculum lost: Central body – 41 (38) 33 μm × 41 (38) 33 μm.
Overall – 76 (63) 51 μm × 76 (71) 61 μm.
Specimens measured: 11.
Remarks: Surculosphaeridium palmatum is similar to Surculosphaeridium trunculum Davey 1979 and S. longifurcatum (Firtion 1952) Davey et al. 1966. It differs from S. trunculum in the simplicity of the processes, which are solid and without furcation, except for occasional bifurcation within the cingular series. In contrast, S. trunculum bears two process types, one bifurcating proximally and thinner processes, usually cingular, linked by medial bars. The palmate process terminations of S. palmatum contrast with those of S. trunculum, which “typically bifurcate or trifurcate and terminate with a small bifurcation or spinelets” (Davey 1979, p. 560). Surculosphaeridium longifurcatum typically bears distally branching processes with those marking the cingulum characteristically deeply-furcate. The irregular distal process terminations of this species again contrast markedly with those of S. palmatum. Davey (1979, p. 560) considered S. trunculum to be “probably ancestral” to S. longifurcatum, with the last species ranging no older than the Albian (after Davey and Verdier 1971). In the present study, S. palmatum ranges from 29.85 m to 16.00 m in Heslerton No. 2, upper Barremian, Zone LKP21 to the upper Barremian/lower Aptian, Zone LKP25.