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Apteodinium unicornum
From Fensome et al., 2019:
Apteodinium unicornum (Kar, 1985, p.206, pl.49, fig.8) Jain and Garg, 1991, p.72. Emendation: Jain and Garg, 1991, p.72–73, as Apteodinium unicornum. Holotype: Kar, 1985, pl.49, fig.8. Originally Millioudinium, subsequently (and now)
Apteodinium. Age: Miocene.
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Original description: [Kar, 1985]:
Millioudodinium unicornum nov. sp.
Diagnosis - proximate cysts, subshperical to ellipsoidal, 51-72 x 48-70 μm, apical horn distinct. Wall conied, sometimes interspersed with grana, archaeopyle precingular, paracingulum generally indicated by parallel transverse equatorial ridges.
Comparison - Millioudodinium apionis (Cookson & Eisenack) Stover & Evitt (1978) resembles the present species in possessing a distinct apical horn but is separated by its smooth wall, a shell twice as long as broad and its bigger size (105 x 57 μm). M. tenuitabulatum (Gerlach) Stover & Evitt (1978) has a small apical horn and granulate wall.
Holotype - Pl. 49, fig. 8; size 60 x 59 μm; slide no. 8267/12.
Type Locality - Aida, Khari Nadi Formation, Miocene, Kachchh.
Occurrence - Aida, Khari Nadi Formation, Kachchh.
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Emended description by Jain and Garg, 1991:
Apteodinium unicornum (Kar) comb. nov. emend.
PI.2, figs 6, 7, 8; PI.3, fig.3; PI. 4, fig. 4
1985 Millioudodinium unicornum Kar, p. 206; pI. 49, fig. 8 (Holotype); Miocene; Palaeobotanist 34:1280 (Basionym).
Emended Diagnosis - Cyst proximate, acavate, subspherical to ellipsoidal in shape with a short, tapering, truncate apical horn. Cyst wall thin, apparently consists of autophragm only which is finely microgranulate. The wall appears to be differentiated with an inner microgranular layer and an outer discontinuous, very thin, smooth, faintly pitted to spongy, shagreenate layer.The latter is discernible only at a few places on the cyst specially at the apical horn, equatorial parasutural ridges along the paracingulum and/or antapical region; when present, this secondary layer is incipiently separated from the autophragm. However, it can also be interpreted as a thin loosely appressed periphragm (or ?ectophragm) but for its discontinuous and somewhat spongy nature which does not suggest distinct pericoel development. Parasutural features commonly expressed only by low but prominent, parallel equatorial ridges along the paracingulum; in some specimens additional faint parasutures are seen dividing the paracingulum into six paraplates, and a few are very faintly visible on the ventral side along the apical horn and parasulcal region. Paratabulation is typically indicated by archacopyle, paracingulum and narrow parasulus only; in few specimens the
paracingulum is divided indicating presence of six paraplates; the other faint parasutural ridges do not clearly express distinct paratabulation. Paracingulum is distinct, expressed by strongly helicoid, shallow, transverse equatorial depression. Parasulcus is distinctly marked by prominently offset ends of the paracingulum and a slight depression characterised by relatively faint ornamentation, in some specimens a faint
parasutural ridge forming a loop delimits the posterior parasulcal region. Archaeopyle is single plate precingular, type P (3"), usually broad with
rounded adapical margin, operculum free but often found in place.
Dimensions:
Holotype Range
Cyst size 66 x 66 μm 66-80 x 63-66 μm
Length of apical horn 03 μm 03-07 μm
Comparison - A. granulatum Eisenack emend. Lucas-Clarks 1987 has a much thicker and more differentiated wall and Ionger apical horn than A. unicornum. In wall structure it comes closer to A. maculatum Eisenack & Cookson 1960, but differs due to its differentiated wall having inner granular and outer shagreenate layers. A. maculatum has densely granulate to irregularly verrucate wall and almost spherical shape with a circular ambitus having a more prominent apical horn. The wall structure in this species conforms to the views of Lucas-Clark (1987). The prominently granular autophragm with a very thin, smooth to pitted (?spongy) outer layer, a short but prominent apical horn formed mainly by outer autophragm layer, limited paratabulation and parasutural features, distinguish it from the other known Apteodinium species.
Remarks - For the holotype of M. unicornum, Kar (1985, p. 206, 230) quoted two different slide nos. 8267/12 and 6634/12, the latter side no. refers to the holotype specimen.
Apteodinium unicornum (Kar, 1985, p.206, pl.49, fig.8) Jain and Garg, 1991, p.72. Emendation: Jain and Garg, 1991, p.72–73, as Apteodinium unicornum. Holotype: Kar, 1985, pl.49, fig.8. Originally Millioudinium, subsequently (and now)
Apteodinium. Age: Miocene.
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Original description: [Kar, 1985]:
Millioudodinium unicornum nov. sp.
Diagnosis - proximate cysts, subshperical to ellipsoidal, 51-72 x 48-70 μm, apical horn distinct. Wall conied, sometimes interspersed with grana, archaeopyle precingular, paracingulum generally indicated by parallel transverse equatorial ridges.
Comparison - Millioudodinium apionis (Cookson & Eisenack) Stover & Evitt (1978) resembles the present species in possessing a distinct apical horn but is separated by its smooth wall, a shell twice as long as broad and its bigger size (105 x 57 μm). M. tenuitabulatum (Gerlach) Stover & Evitt (1978) has a small apical horn and granulate wall.
Holotype - Pl. 49, fig. 8; size 60 x 59 μm; slide no. 8267/12.
Type Locality - Aida, Khari Nadi Formation, Miocene, Kachchh.
Occurrence - Aida, Khari Nadi Formation, Kachchh.
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Emended description by Jain and Garg, 1991:
Apteodinium unicornum (Kar) comb. nov. emend.
PI.2, figs 6, 7, 8; PI.3, fig.3; PI. 4, fig. 4
1985 Millioudodinium unicornum Kar, p. 206; pI. 49, fig. 8 (Holotype); Miocene; Palaeobotanist 34:1280 (Basionym).
Emended Diagnosis - Cyst proximate, acavate, subspherical to ellipsoidal in shape with a short, tapering, truncate apical horn. Cyst wall thin, apparently consists of autophragm only which is finely microgranulate. The wall appears to be differentiated with an inner microgranular layer and an outer discontinuous, very thin, smooth, faintly pitted to spongy, shagreenate layer.The latter is discernible only at a few places on the cyst specially at the apical horn, equatorial parasutural ridges along the paracingulum and/or antapical region; when present, this secondary layer is incipiently separated from the autophragm. However, it can also be interpreted as a thin loosely appressed periphragm (or ?ectophragm) but for its discontinuous and somewhat spongy nature which does not suggest distinct pericoel development. Parasutural features commonly expressed only by low but prominent, parallel equatorial ridges along the paracingulum; in some specimens additional faint parasutures are seen dividing the paracingulum into six paraplates, and a few are very faintly visible on the ventral side along the apical horn and parasulcal region. Paratabulation is typically indicated by archacopyle, paracingulum and narrow parasulus only; in few specimens the
paracingulum is divided indicating presence of six paraplates; the other faint parasutural ridges do not clearly express distinct paratabulation. Paracingulum is distinct, expressed by strongly helicoid, shallow, transverse equatorial depression. Parasulcus is distinctly marked by prominently offset ends of the paracingulum and a slight depression characterised by relatively faint ornamentation, in some specimens a faint
parasutural ridge forming a loop delimits the posterior parasulcal region. Archaeopyle is single plate precingular, type P (3"), usually broad with
rounded adapical margin, operculum free but often found in place.
Dimensions:
Holotype Range
Cyst size 66 x 66 μm 66-80 x 63-66 μm
Length of apical horn 03 μm 03-07 μm
Comparison - A. granulatum Eisenack emend. Lucas-Clarks 1987 has a much thicker and more differentiated wall and Ionger apical horn than A. unicornum. In wall structure it comes closer to A. maculatum Eisenack & Cookson 1960, but differs due to its differentiated wall having inner granular and outer shagreenate layers. A. maculatum has densely granulate to irregularly verrucate wall and almost spherical shape with a circular ambitus having a more prominent apical horn. The wall structure in this species conforms to the views of Lucas-Clark (1987). The prominently granular autophragm with a very thin, smooth to pitted (?spongy) outer layer, a short but prominent apical horn formed mainly by outer autophragm layer, limited paratabulation and parasutural features, distinguish it from the other known Apteodinium species.
Remarks - For the holotype of M. unicornum, Kar (1985, p. 206, 230) quoted two different slide nos. 8267/12 and 6634/12, the latter side no. refers to the holotype specimen.