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Achomosphaera psilata
Achomosphaera psilata sp.nov.
Fig. 7A-B,(See Plate 2 and 4).
Type species: Achomosphaera ramulifera (Deflandre, 1937) Evitt, 1963.
Derivation of the name: Psilata, from the smooth surface, without ornamentation.
Diagnosis: The presence of a precingular archeopyle and gonal processes without sutural septae permits assigning this morphotype to Achomosphaera (Stover and Evitt, 1978).
Description: Acavate, spherical, chorate dinoflagellate cyst, with precingular archeopyle type P (3″). The cyst surface is completely smooth. Processes are gonal, tubular in shape, hollow, within a cylindrical to subcylindrical base, and the surface and distal termination are also psilata. The distal tips of the processes reflect the trifurcate nature of gonal processes, showing a flat platform with a triangular outline with undulated margins. Most of the bases of processes are not connected. However, the cingular processes are joined in pairs, as seen in plate 13, fig. 1,2,3.
Dimensions: Diameter of central body: 58 μm; length of processes: 28–30 μm. Observed Range: Diameter of the central body: 58–70 μm; length of processes: 27–35 μm; Thickness of processes:5–8.5 μm Number of specimens measured: 6.
Differentiation: A. psilata is easily distinguishable from other species in this genera due to the absence of ornamentation on the cyst surface and the broad processes. Another difference is the lack of distal 1937) Evitt, 1963, A. alcicornu (Eisenack, 1954) Davey and Williams, 1966and A. andalousiensis (Jan du Chˆene, 1977) Jan du Chˆene and Londeix, 1988. Additionally, A. psilata has no reticulate surface, unlike A. crassipellis (Deflandre and Cookson, 1955) Stover and Evitt, 1978; and A. sagena Davey and Williams, 1966. It also lacks quadrifurcate terminations on tips of processes, which is present in A. quadrata Antolinez- Delgado and Oboh-Ikuenobe, 2007. Lastly, A. psilata does not have randomly distributed grana or granules on the cyst surface, a feature in A. eggadania Vieira et al., 2018, and A. progranulata Vieira et al., 2018.
Type locality: Southern Gulf of Mexico, Campeche escarpment, offshore Yucatan peninsula, Site 94 DSDP-Leg 10.
Type level: Late Oligocene,
Range: Occurrence in samples of the Late Oligocene (371.5–370.5 mbsf,).
Occurrence: FAD of this species corresponds within the early/late Oligocene transition (28.1 MY).
Fig. 7A-B,(See Plate 2 and 4).
Type species: Achomosphaera ramulifera (Deflandre, 1937) Evitt, 1963.
Derivation of the name: Psilata, from the smooth surface, without ornamentation.
Diagnosis: The presence of a precingular archeopyle and gonal processes without sutural septae permits assigning this morphotype to Achomosphaera (Stover and Evitt, 1978).
Description: Acavate, spherical, chorate dinoflagellate cyst, with precingular archeopyle type P (3″). The cyst surface is completely smooth. Processes are gonal, tubular in shape, hollow, within a cylindrical to subcylindrical base, and the surface and distal termination are also psilata. The distal tips of the processes reflect the trifurcate nature of gonal processes, showing a flat platform with a triangular outline with undulated margins. Most of the bases of processes are not connected. However, the cingular processes are joined in pairs, as seen in plate 13, fig. 1,2,3.
Dimensions: Diameter of central body: 58 μm; length of processes: 28–30 μm. Observed Range: Diameter of the central body: 58–70 μm; length of processes: 27–35 μm; Thickness of processes:5–8.5 μm Number of specimens measured: 6.
Differentiation: A. psilata is easily distinguishable from other species in this genera due to the absence of ornamentation on the cyst surface and the broad processes. Another difference is the lack of distal 1937) Evitt, 1963, A. alcicornu (Eisenack, 1954) Davey and Williams, 1966and A. andalousiensis (Jan du Chˆene, 1977) Jan du Chˆene and Londeix, 1988. Additionally, A. psilata has no reticulate surface, unlike A. crassipellis (Deflandre and Cookson, 1955) Stover and Evitt, 1978; and A. sagena Davey and Williams, 1966. It also lacks quadrifurcate terminations on tips of processes, which is present in A. quadrata Antolinez- Delgado and Oboh-Ikuenobe, 2007. Lastly, A. psilata does not have randomly distributed grana or granules on the cyst surface, a feature in A. eggadania Vieira et al., 2018, and A. progranulata Vieira et al., 2018.
Type locality: Southern Gulf of Mexico, Campeche escarpment, offshore Yucatan peninsula, Site 94 DSDP-Leg 10.
Type level: Late Oligocene,
Range: Occurrence in samples of the Late Oligocene (371.5–370.5 mbsf,).
Occurrence: FAD of this species corresponds within the early/late Oligocene transition (28.1 MY).