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Michouxdinium aculeatum
Michouxdinium aculeatum (Michoux, 1988, p.24,26, pl.1, figs.1,4,7–8; pl.2, figs.1–2, text-figs.5A–B,6A–B) Williams et al., 2015, p.307.
Originally Kisselevia, subsequently Charlesdowniea, thirdly (and now) Michouxdinium.
Holotype: Michoux, 1988, pl.1, figs.1,4,7; text-figs.5A–B.
Age: early Eocene.
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Original description (Michoux, 1988)
Original diagnosis: Michoux, 1988, p. 24: Kisselovia aculeata
Circumcavate to cornucavate peridiniod cyst with penitabular arrangement of furcate
processes, linked by their tips. Paraquadra paratabulation pattern. 2a archeopyle soleiform; peri- and endopercula adnate.
Original description: Michoux, 1988, p.24, 26: Kisselovia aculeata
Pentagonal peridinioid cyst, with strong dorso-ventral compression. One apical, two
lateral and two antapical horns, the right of which is slightly shorter. The sides are straight to slightly convex, except between the antapical horns where a faint concavity may be observed. The endophragm is ellipsoidal to pentagonal, sometimes protruding into the horns. Extreme reduction of the narrow pericoel may lead to cornucavation in some of the horns. Periphragm smooth, endophragm slightly granular. The processes are slender, usually simple, distally polyfurcate, and arranged in penitabular complexes. Adjacent processes are linked by the tip of their distal aculei within each complex; linkage is often interrupted. Apical paraplates 2" and 4" bear arcuate complexes. Precingular paraplates 2" and 6", along with the paracingulum, bear linear complexes. First apical 1" bears a wide, five-sided complex. Paraplate pairs 2"/2" and 4"/6" are located on the lateral sides of the ventral epicyst. The 2"/2" and 4"/6" boundaries abut against the lateral sides of 1" (see Plate 1, figs. 4, 7, and Text-Figure 5) revealing a para ventral paratabulation pattern for the epicyst (in an ortho pattern, the development of 1" and 7" would preclude the 1"/2" and 1"/6" contacts). The dorsal epicystal surface clearly shows a quadra paratabulation pattern, with 2a narrower than subjacent 4". Isolated intratabular processes may be present in the center of some paraplates (see for example paraplate 2a, Plate 1, fig. 8 and Plate 2, fig. 5). The archeopyle is standard soleiform, with both opercula seemingly adnate adapically (even under high magnification in light microscopy, no trace of development of the archeopyle suture along the 3"/ 2a boundary was detected on the endophragm). Paratabulation. 4", 3a, 7", Xc, 5""", 2"""", as, ps.
Dimensions: Pericyst. Length: 97 (112) 128 Ám. Width: 95 (109) 128 Ám. Holotype: 124x 121 Ám. Archeopyle. Length: 18 (23) 28 Ám. Width: 19 (24) 28 Ám. Holotype: 18x 19 Ám. Processes: up to 7 Ám.
Affinities:
Michoux, 1988, p.26: Kisselovia aculeata
With its aculei interconnecting adjacent processes along the perimeter of the penitabular complexes, Kisselovia aculeata n. sp. bears close similarity to Kisselovia stellata Damassa. The latter species, however, is more elongated, with a strongly reduced right antapical horn, higher processes (up to
20 Ám in length) and a trapezoidal archeopyle. Kisselovia tenuivirgula (Williams & Downie) Lentin & Williams has trabeculae extending across the paraplates.
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Originally Kisselevia, subsequently Charlesdowniea, thirdly (and now) Michouxdinium.
Holotype: Michoux, 1988, pl.1, figs.1,4,7; text-figs.5A–B.
Age: early Eocene.
------------------------------------------
Original description (Michoux, 1988)
Original diagnosis: Michoux, 1988, p. 24: Kisselovia aculeata
Circumcavate to cornucavate peridiniod cyst with penitabular arrangement of furcate
processes, linked by their tips. Paraquadra paratabulation pattern. 2a archeopyle soleiform; peri- and endopercula adnate.
Original description: Michoux, 1988, p.24, 26: Kisselovia aculeata
Pentagonal peridinioid cyst, with strong dorso-ventral compression. One apical, two
lateral and two antapical horns, the right of which is slightly shorter. The sides are straight to slightly convex, except between the antapical horns where a faint concavity may be observed. The endophragm is ellipsoidal to pentagonal, sometimes protruding into the horns. Extreme reduction of the narrow pericoel may lead to cornucavation in some of the horns. Periphragm smooth, endophragm slightly granular. The processes are slender, usually simple, distally polyfurcate, and arranged in penitabular complexes. Adjacent processes are linked by the tip of their distal aculei within each complex; linkage is often interrupted. Apical paraplates 2" and 4" bear arcuate complexes. Precingular paraplates 2" and 6", along with the paracingulum, bear linear complexes. First apical 1" bears a wide, five-sided complex. Paraplate pairs 2"/2" and 4"/6" are located on the lateral sides of the ventral epicyst. The 2"/2" and 4"/6" boundaries abut against the lateral sides of 1" (see Plate 1, figs. 4, 7, and Text-Figure 5) revealing a para ventral paratabulation pattern for the epicyst (in an ortho pattern, the development of 1" and 7" would preclude the 1"/2" and 1"/6" contacts). The dorsal epicystal surface clearly shows a quadra paratabulation pattern, with 2a narrower than subjacent 4". Isolated intratabular processes may be present in the center of some paraplates (see for example paraplate 2a, Plate 1, fig. 8 and Plate 2, fig. 5). The archeopyle is standard soleiform, with both opercula seemingly adnate adapically (even under high magnification in light microscopy, no trace of development of the archeopyle suture along the 3"/ 2a boundary was detected on the endophragm). Paratabulation. 4", 3a, 7", Xc, 5""", 2"""", as, ps.
Dimensions: Pericyst. Length: 97 (112) 128 Ám. Width: 95 (109) 128 Ám. Holotype: 124x 121 Ám. Archeopyle. Length: 18 (23) 28 Ám. Width: 19 (24) 28 Ám. Holotype: 18x 19 Ám. Processes: up to 7 Ám.
Affinities:
Michoux, 1988, p.26: Kisselovia aculeata
With its aculei interconnecting adjacent processes along the perimeter of the penitabular complexes, Kisselovia aculeata n. sp. bears close similarity to Kisselovia stellata Damassa. The latter species, however, is more elongated, with a strongly reduced right antapical horn, higher processes (up to
20 Ám in length) and a trapezoidal archeopyle. Kisselovia tenuivirgula (Williams & Downie) Lentin & Williams has trabeculae extending across the paraplates.
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