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Apectodinium parvum
Apectodinium parvum, (Alberti, 1961), Lentin and Williams, 1977; Emend. Harland, 1979
Originally Wetzeliella, subsequently Wetzeliella subgen. Apectodinium, thirdly (and now) Apectodinium.
Costa and Downie, 1976, transferred this species to Wetzeliella subgen. Apectodinium.
Holotype: Alberti, 1961, pl.1, fig.14
Locus typicus: Hildesheim, Germany
Stratum typicum: Early Eocene
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Original description as Wetzeliella (Wetzeliella) parva: [Alberti, 1961, p. 8]: (Translation: LPP)
Diagnosis:
Shell flattened, outline pentagonal, sometimes slightly rounded. Lateral horns rarely indicated. Apical horn short, usually outstanding. Two +/- long antapical horns. No transverse furrow. A to the outer margin of the shell closely appressed delicate inner body usually present. Shell densly covered by +/- long spines. Epitheca acute to retangular. Hypotheca wide with two antapical horns of unequal length. These horns, which are equivalent to the apical horns can diverge or converge.
On several studied forms misses the inner body or is because of the dense cover of spines not visible. The spines can by fused at their bases.
Affinities:
W. parva differs from H. geometricum in the elongated pentagonal outline and the small, more or less outstanding horn.
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Emended description:
Harland 1979c, p. 66:
Diagnosis:
Pentagonal cyst having closely adpressed thin wall layers. Horn development limited to the apical and more especially the antapical regions; lateral horns are absent. Processes are intratabular or sutural, the latter may exhibit low membranes in the cingular region, short, erect to sinuous, slender with blunt or bifid distal terminations.
Archeopyle I2a/I2a ?reduced.
Description:
Wall layers are smooth to micro-granulate or microrecticulate. The horn development, prominent at the antapex, is variously developed with relation to the apical horn which may or may not be present. Although the lateral horns are absent some specimens do show slight swelling of the periphragm in the lateral position. All the horns bear processes. The processes are usually 1/6-1/5 the cyst diameter in length and may be branched; those that are obviously sutural and linked by membranes often outline the planar, non-indented cingulum.
Variation:
Intraspecific variation in W. (A.) parva is confined to the apical horn and to some extent in the development of lateral "swellings". Specimens have been seen which link this species to W. (A. ) quinquelata. Some variation is also seen in process morphology, especially with regard to the development of sutural lists in the cingular area.
Dimensions:
The present material has a range of length of endoblast exclusive of processes 46.25 (53.39) 65.00 µm, and a breadth 42.50 (51.34) 58.75 µm. Fourteen specimens measured.
Occurrence:
W. (A.) parva has been recorded from the Upper Palaeocene and lower Eocene of Germany (Alberti, 1961), from the Palaeocene or lower Eocene of New Zealand (Wilson, 1968), from the Landenian and Ypresian of Belgium (De Coninck, 1968), from the I,ower Eocene I of Germany (Gocht, 1969), and the Sparnacian of the Paris Basin (Gruas-Cavagnetto, 1968). Chateauneuf and Gruas-Cavagnetto (1968) recorded it from the Thanetian to Sparnacian in the Paris Basin. Costa and Downie (1976) recorded it from the Palaeocene and Lower Eocene I of Germany, Woolwich Beds of England and Landenian of Belgium. Harker and Sarjeant (1975) gave its range as Upper Palaeocene to Lower Eocene j n Europe; and Lower Oligocene in the rest of the world. This last range is at variance with the available data.
The present specimens come from the lower London Clay of the IGS Stanford-le Hope Borehole and the Upper Palaeocene of the North Sea Basin, wells 53/4-4 and 44/24-1. Its range is considered to be ?NP 8--?NP 10.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Apectodinium parvum (Alberti, 1961) Lentin and Williams, 1977b, emend. Harland, 1979c. According to Harland (1979), has a pentagonal pericyst with closely appressed endocyst. Horn development is limited to the apical and more especially the antapical regions. Lateral horns are absent. Processes are intratabular or sutural, the latter may have low membranes in the cingular region. Processes short, erect to sinuous, slender with blunt or bifid distal terminations.
Size: length 60-99 µm, width 39-68 µm.
Originally Wetzeliella, subsequently Wetzeliella subgen. Apectodinium, thirdly (and now) Apectodinium.
Costa and Downie, 1976, transferred this species to Wetzeliella subgen. Apectodinium.
Holotype: Alberti, 1961, pl.1, fig.14
Locus typicus: Hildesheim, Germany
Stratum typicum: Early Eocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Wetzeliella (Wetzeliella) parva: [Alberti, 1961, p. 8]: (Translation: LPP)
Diagnosis:
Shell flattened, outline pentagonal, sometimes slightly rounded. Lateral horns rarely indicated. Apical horn short, usually outstanding. Two +/- long antapical horns. No transverse furrow. A to the outer margin of the shell closely appressed delicate inner body usually present. Shell densly covered by +/- long spines. Epitheca acute to retangular. Hypotheca wide with two antapical horns of unequal length. These horns, which are equivalent to the apical horns can diverge or converge.
On several studied forms misses the inner body or is because of the dense cover of spines not visible. The spines can by fused at their bases.
Affinities:
W. parva differs from H. geometricum in the elongated pentagonal outline and the small, more or less outstanding horn.
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Emended description:
Harland 1979c, p. 66:
Diagnosis:
Pentagonal cyst having closely adpressed thin wall layers. Horn development limited to the apical and more especially the antapical regions; lateral horns are absent. Processes are intratabular or sutural, the latter may exhibit low membranes in the cingular region, short, erect to sinuous, slender with blunt or bifid distal terminations.
Archeopyle I2a/I2a ?reduced.
Description:
Wall layers are smooth to micro-granulate or microrecticulate. The horn development, prominent at the antapex, is variously developed with relation to the apical horn which may or may not be present. Although the lateral horns are absent some specimens do show slight swelling of the periphragm in the lateral position. All the horns bear processes. The processes are usually 1/6-1/5 the cyst diameter in length and may be branched; those that are obviously sutural and linked by membranes often outline the planar, non-indented cingulum.
Variation:
Intraspecific variation in W. (A.) parva is confined to the apical horn and to some extent in the development of lateral "swellings". Specimens have been seen which link this species to W. (A. ) quinquelata. Some variation is also seen in process morphology, especially with regard to the development of sutural lists in the cingular area.
Dimensions:
The present material has a range of length of endoblast exclusive of processes 46.25 (53.39) 65.00 µm, and a breadth 42.50 (51.34) 58.75 µm. Fourteen specimens measured.
Occurrence:
W. (A.) parva has been recorded from the Upper Palaeocene and lower Eocene of Germany (Alberti, 1961), from the Palaeocene or lower Eocene of New Zealand (Wilson, 1968), from the Landenian and Ypresian of Belgium (De Coninck, 1968), from the I,ower Eocene I of Germany (Gocht, 1969), and the Sparnacian of the Paris Basin (Gruas-Cavagnetto, 1968). Chateauneuf and Gruas-Cavagnetto (1968) recorded it from the Thanetian to Sparnacian in the Paris Basin. Costa and Downie (1976) recorded it from the Palaeocene and Lower Eocene I of Germany, Woolwich Beds of England and Landenian of Belgium. Harker and Sarjeant (1975) gave its range as Upper Palaeocene to Lower Eocene j n Europe; and Lower Oligocene in the rest of the world. This last range is at variance with the available data.
The present specimens come from the lower London Clay of the IGS Stanford-le Hope Borehole and the Upper Palaeocene of the North Sea Basin, wells 53/4-4 and 44/24-1. Its range is considered to be ?NP 8--?NP 10.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Apectodinium parvum (Alberti, 1961) Lentin and Williams, 1977b, emend. Harland, 1979c. According to Harland (1979), has a pentagonal pericyst with closely appressed endocyst. Horn development is limited to the apical and more especially the antapical regions. Lateral horns are absent. Processes are intratabular or sutural, the latter may have low membranes in the cingular region. Processes short, erect to sinuous, slender with blunt or bifid distal terminations.
Size: length 60-99 µm, width 39-68 µm.