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Michouxdinium proserpinum
Michouxdinium proserpinum (van Mourik et al., 2001, p.239,241, figs.7a–e) Williams et al., 2015, p.307.
Originally Charlesdowniea, subsequently (and now) Michouxdinium.
Holotype: van Mourik et al., 2001, figs.7b–c.
Age: late Eocene.
Original description (van Mourik et al., 2001):
Etymology: Named for Proserpina, wife of the god Pluto in Greek mythology.
Holotype: Slide I, 1053A-8H-5, 35-38 (D45), Fig. 7b and c.
Diagnosis: Rhomboidal to pentagonal pericyst with short unequal antapical horns, soleiform archeopyle and reduced process complexes, which we term paraplate-centred process complexes, that are located towards the centre of the paraplates and are distally united by perforate membrane or trabeculae. Some of the processes are distally free.
Description: Shape Pericyst. Ambitus rhomboidal to pentagonal (peridinioid), strongly compressed dorsoventrally, with either a short or no apical horn, short broad cingular horns or no cingular horns and unequal antapical horns, the left always the longer. Endocyst. Ambitus rhomboidal, may be appressed to pericyst other than in vicinity of horns. Pericoels. Cornucavate with a maximum of one apical, two cingular and one or two antapical pericoels. Alternatively, there is a single ambital pericoel uniting the pericoel areas beneath the horns. Phragma. Periphragm of uniform thickness, about l ! am, with very broad pandasutural zones devoid of ornamentation and paraplatecentred process complexes, although on individual paraplates these can migrate towards the apex on the epicyst and the antapex on the hypocyst. Processes of individual complex united distally by perforate membrane or trabeculae. Six to eight processes in most complexes. Some processes are free. Endophragrn. Less than 1 µm thick, smooth. Paratabulation. Tabulation on pericyst expressed by process complexes and is as for genus. Paraplate complex 1' rhomboidal and largest of the apicals. 2' and 4' represented by linear process complexes with processes often free. Process complex on paraplate 3' of similar shape to 1' but smaller. All three anterior intercalaries with small paraplate-centred process complexes and with 2a being quadrate. Of the precingulars, process complexes of 1" and 7" are same elongate triangular outline, 2" and 6" are linear complexes aligned longitudinally with processes commonly free. Paraplates 3", 4" and 5" have linear process complexes aligned latitudinally. The five postcingulars include identical triangular, latitudinally elongate complexes on 1'" and 5'", identical longitudinally elongate complexes on 2" and 4" and a latitudinally elongate 3'" complex. There are two, more or less equal antapical complexes, representing 1 .... and 2''. Paracingulum. On the pericyst, cingulars marked by single row of processes, sometimes connected distally, sometimes free; slightly helicoidal. Parasulcus. On the pericyst extending longitudinally from below 1' to the antapical horn(s). Four process complexes, the largest, the posterior sulcal, sometimes being separated into two complexes and located in part on the antapical horns. Archeopyle. Periarcheopyle: quadra, intercalary, soleiform, operculum remaining attached along anterior parasuture QI. Sometimes there can be tearing along this parasuture to give the illusion of a detached operculum. Endoarcheopyle: appears to be same as periarcheopyle.
Dimensions: Pericyst. Length 113-116 μm, breadth 85- 107 μm (n = 6). Endocyst. Length 72-92 μm, breadth 74-89 μm. Horns. Apical, 7-8 μm, antapical, 8-15 μm; process length, 4-12 μm.
Type locality ODP Site 1053A, 31.25 mbsf, 40.74 mbsf, 43.74 mbsf, and 59.95 msbf, Blake Nose, offshore from Florida. Other localities JOIDES Hole 1537' (16368 mbsf), Blake Plateau.
Stratigraphic range Upper Eocene sequence.
Comparison There is only one described species of Charlesdowniea, C. limitata (Stover & Hardenbol 1994) with a soleiform archeopyle. In C. limitata, the processes just in from the paraplate boundaries are united by distal trabeculae, so that they form simulate or penitabulate complexes, whose borders run parallel to the outline of the paraplates. A species from the middle Eocene succession of England that superficially resembles C. proserpina is Charlesdowniea variabilis. However, the archeopyle of Charlesdowniea variabilis (Bujak, in Bujak et al. 1980) Lentin & Vozzhennikova (1989) has a free operculum and the process complexes fill most of the paraplate.
Originally Charlesdowniea, subsequently (and now) Michouxdinium.
Holotype: van Mourik et al., 2001, figs.7b–c.
Age: late Eocene.
Original description (van Mourik et al., 2001):
Etymology: Named for Proserpina, wife of the god Pluto in Greek mythology.
Holotype: Slide I, 1053A-8H-5, 35-38 (D45), Fig. 7b and c.
Diagnosis: Rhomboidal to pentagonal pericyst with short unequal antapical horns, soleiform archeopyle and reduced process complexes, which we term paraplate-centred process complexes, that are located towards the centre of the paraplates and are distally united by perforate membrane or trabeculae. Some of the processes are distally free.
Description: Shape Pericyst. Ambitus rhomboidal to pentagonal (peridinioid), strongly compressed dorsoventrally, with either a short or no apical horn, short broad cingular horns or no cingular horns and unequal antapical horns, the left always the longer. Endocyst. Ambitus rhomboidal, may be appressed to pericyst other than in vicinity of horns. Pericoels. Cornucavate with a maximum of one apical, two cingular and one or two antapical pericoels. Alternatively, there is a single ambital pericoel uniting the pericoel areas beneath the horns. Phragma. Periphragm of uniform thickness, about l ! am, with very broad pandasutural zones devoid of ornamentation and paraplatecentred process complexes, although on individual paraplates these can migrate towards the apex on the epicyst and the antapex on the hypocyst. Processes of individual complex united distally by perforate membrane or trabeculae. Six to eight processes in most complexes. Some processes are free. Endophragrn. Less than 1 µm thick, smooth. Paratabulation. Tabulation on pericyst expressed by process complexes and is as for genus. Paraplate complex 1' rhomboidal and largest of the apicals. 2' and 4' represented by linear process complexes with processes often free. Process complex on paraplate 3' of similar shape to 1' but smaller. All three anterior intercalaries with small paraplate-centred process complexes and with 2a being quadrate. Of the precingulars, process complexes of 1" and 7" are same elongate triangular outline, 2" and 6" are linear complexes aligned longitudinally with processes commonly free. Paraplates 3", 4" and 5" have linear process complexes aligned latitudinally. The five postcingulars include identical triangular, latitudinally elongate complexes on 1'" and 5'", identical longitudinally elongate complexes on 2" and 4" and a latitudinally elongate 3'" complex. There are two, more or less equal antapical complexes, representing 1 .... and 2''. Paracingulum. On the pericyst, cingulars marked by single row of processes, sometimes connected distally, sometimes free; slightly helicoidal. Parasulcus. On the pericyst extending longitudinally from below 1' to the antapical horn(s). Four process complexes, the largest, the posterior sulcal, sometimes being separated into two complexes and located in part on the antapical horns. Archeopyle. Periarcheopyle: quadra, intercalary, soleiform, operculum remaining attached along anterior parasuture QI. Sometimes there can be tearing along this parasuture to give the illusion of a detached operculum. Endoarcheopyle: appears to be same as periarcheopyle.
Dimensions: Pericyst. Length 113-116 μm, breadth 85- 107 μm (n = 6). Endocyst. Length 72-92 μm, breadth 74-89 μm. Horns. Apical, 7-8 μm, antapical, 8-15 μm; process length, 4-12 μm.
Type locality ODP Site 1053A, 31.25 mbsf, 40.74 mbsf, 43.74 mbsf, and 59.95 msbf, Blake Nose, offshore from Florida. Other localities JOIDES Hole 1537' (16368 mbsf), Blake Plateau.
Stratigraphic range Upper Eocene sequence.
Comparison There is only one described species of Charlesdowniea, C. limitata (Stover & Hardenbol 1994) with a soleiform archeopyle. In C. limitata, the processes just in from the paraplate boundaries are united by distal trabeculae, so that they form simulate or penitabulate complexes, whose borders run parallel to the outline of the paraplates. A species from the middle Eocene succession of England that superficially resembles C. proserpina is Charlesdowniea variabilis. However, the archeopyle of Charlesdowniea variabilis (Bujak, in Bujak et al. 1980) Lentin & Vozzhennikova (1989) has a free operculum and the process complexes fill most of the paraplate.