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Atlanticodinium striaticonulum
Atlanticodinium striaticonulum, Head and Mantilla-Duran, 2020 (p. 5-9)
Holotype: Plate 1, figs. 1–9. (Sample IODP U1313A-4H-3 W, 24–25 cm; Q44/1. Middle Pleistocene, central North Atlantic; ROMIP 65337.)
Stratigraphic range: confirmed range of Lower Pleistocene (866 ka) to present (possibly extends to at least upper Lower Pliocene (3.98 Ma))
Location: central North Atlantic Ocean
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Original description: [Head and Mantilla-Duran, 2020, p. 9]:
Diagnosis:
Central body spherical to ovoidal with relatively thick solid pedium and outer granulate layer. Processes short, numerous, nontabular, hollow, distally closed; round-tipped conical to verrucate or bacculate in profile. Process bases circular to subcircular, occasionally elongate. Processes internally striated, with striations converging towards tips. Granules on central body surface continue beneath process bases, where they are pronounced. Apex may be marked by a small protuberance. Archeopyle subtriangular in shape, precingular formed by loss of plate 3′′; margin with well defined angles; operculum free.
Description:
Cysts are pale yellow-brown to nearly colourless, and are proximate.
The central body is spherical to ovoidal, narrowing slightly towards the apex.
The wall is autophragmal with a relatively thick, solid pedium and outer granulate layer often of similar thickness.
Granules are of variable size from around 0.3 μm (or more depending on the specimen) up to about 1.0 μm in maximum diameter. Adjacent granules may coalesce to form a partial microrugulation / microreticulation. Processes are short, numerous, nontabular, with somewhat variable distance between adjacent processes. Processes are hollow, distally closed, and typically round-tipped, conical to baculate or verrucate in profile, with different shapes occurring on the same specimen; although most specimens have some round-tipped, conical processes, these being predominant on the holotype (Plate 1, fig. 7). Process bases are circular to subcircular, occasionally elongate, with a diameter of ~2.0 to 5.0 μm. Process shafts are internally striated, with striations extending lengthwise from the base converging towards the distal tips, which may lead to slight distal thickening on some, but not all, processes. Granules on the surface of the central body continue without interruption beneath the process bases where they appear coarser perhaps accentuated by the lensing effect of the distal thickening of some processes. Process striations appear to be extensions of the granulate layer. The outer surfaces of processes are smooth. Small coni, barely discernible under light microscopy, may occur between processes.
The apex may be marked by a barely discernible external protuberance and a more conspicuous thinning of the wall caused by a discrete bulge of the pedium (Plate 1, figs. 5, 11).
The archeopyle is precingular, subtriangular in shape (Plate 1, figs. 1–3; see also De Schepper et al., 2009, pl. 5, fig. 15), with angles well defined (e.g., Plate 2, fig. 8), but slight distortion of the archeopyle can give a somewhat rounded appearance to angles, as in the holotype (Plate 1, fig. 2). The archeopyle results from loss of plate 3′′. The operculum is free.
There is no other expression of tabulation.
Dimensions/Measurements:
Central body maximum diameter: holotype 43 μm; range 30 (mean 39.2) 49 μm, based on 24 measurements.
Maximum process length: holotype ~2.8 μm; range ~1.8 (mean 2.79) 4.8 μm, based on 28 measurements.
Average centre-to-centre distance between adjacent process bases: holotype ~5.5 μm; range 3.5 (mean 5.20) 6.5 μm, based on 25 measurements.
Wall thickness including granules: ~0.6 (mean 0.84) 1.0 μm, based on 17 measurements from broken/crumpled walls, not optical sections through inflated cysts. All measurements on specimens from IODP Hole U1313A.
Affinities/Comparison:
The processes on Atlanticodinium janduchenei lack striations, may be distally open, and lack coarse granulation on the central body surface below the process bases. The shape of the archeopyle is less triangular in Atlanticodinium janduchenei than in Atlanticodinium striaticonulum. Atlanticodinium sp. (below) has a 2P (or 3P?) archeopyle whereas Atlanticodinium striaticonulum has a 1P archeopyle.
Holotype: Plate 1, figs. 1–9. (Sample IODP U1313A-4H-3 W, 24–25 cm; Q44/1. Middle Pleistocene, central North Atlantic; ROMIP 65337.)
Stratigraphic range: confirmed range of Lower Pleistocene (866 ka) to present (possibly extends to at least upper Lower Pliocene (3.98 Ma))
Location: central North Atlantic Ocean
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Head and Mantilla-Duran, 2020, p. 9]:
Diagnosis:
Central body spherical to ovoidal with relatively thick solid pedium and outer granulate layer. Processes short, numerous, nontabular, hollow, distally closed; round-tipped conical to verrucate or bacculate in profile. Process bases circular to subcircular, occasionally elongate. Processes internally striated, with striations converging towards tips. Granules on central body surface continue beneath process bases, where they are pronounced. Apex may be marked by a small protuberance. Archeopyle subtriangular in shape, precingular formed by loss of plate 3′′; margin with well defined angles; operculum free.
Description:
Cysts are pale yellow-brown to nearly colourless, and are proximate.
The central body is spherical to ovoidal, narrowing slightly towards the apex.
The wall is autophragmal with a relatively thick, solid pedium and outer granulate layer often of similar thickness.
Granules are of variable size from around 0.3 μm (or more depending on the specimen) up to about 1.0 μm in maximum diameter. Adjacent granules may coalesce to form a partial microrugulation / microreticulation. Processes are short, numerous, nontabular, with somewhat variable distance between adjacent processes. Processes are hollow, distally closed, and typically round-tipped, conical to baculate or verrucate in profile, with different shapes occurring on the same specimen; although most specimens have some round-tipped, conical processes, these being predominant on the holotype (Plate 1, fig. 7). Process bases are circular to subcircular, occasionally elongate, with a diameter of ~2.0 to 5.0 μm. Process shafts are internally striated, with striations extending lengthwise from the base converging towards the distal tips, which may lead to slight distal thickening on some, but not all, processes. Granules on the surface of the central body continue without interruption beneath the process bases where they appear coarser perhaps accentuated by the lensing effect of the distal thickening of some processes. Process striations appear to be extensions of the granulate layer. The outer surfaces of processes are smooth. Small coni, barely discernible under light microscopy, may occur between processes.
The apex may be marked by a barely discernible external protuberance and a more conspicuous thinning of the wall caused by a discrete bulge of the pedium (Plate 1, figs. 5, 11).
The archeopyle is precingular, subtriangular in shape (Plate 1, figs. 1–3; see also De Schepper et al., 2009, pl. 5, fig. 15), with angles well defined (e.g., Plate 2, fig. 8), but slight distortion of the archeopyle can give a somewhat rounded appearance to angles, as in the holotype (Plate 1, fig. 2). The archeopyle results from loss of plate 3′′. The operculum is free.
There is no other expression of tabulation.
Dimensions/Measurements:
Central body maximum diameter: holotype 43 μm; range 30 (mean 39.2) 49 μm, based on 24 measurements.
Maximum process length: holotype ~2.8 μm; range ~1.8 (mean 2.79) 4.8 μm, based on 28 measurements.
Average centre-to-centre distance between adjacent process bases: holotype ~5.5 μm; range 3.5 (mean 5.20) 6.5 μm, based on 25 measurements.
Wall thickness including granules: ~0.6 (mean 0.84) 1.0 μm, based on 17 measurements from broken/crumpled walls, not optical sections through inflated cysts. All measurements on specimens from IODP Hole U1313A.
Affinities/Comparison:
The processes on Atlanticodinium janduchenei lack striations, may be distally open, and lack coarse granulation on the central body surface below the process bases. The shape of the archeopyle is less triangular in Atlanticodinium janduchenei than in Atlanticodinium striaticonulum. Atlanticodinium sp. (below) has a 2P (or 3P?) archeopyle whereas Atlanticodinium striaticonulum has a 1P archeopyle.