Back
Umbodinium crustov
Umbodinium crustov Bint, 1983, p.175-176,178, pl.1, figs.1-12; text-figs.2A-B,3F,4A-D
Holotype: Bint, 1983, pl.1, figs.1-3; text-fig.4A; Fensome et al., 1993a, figs.1-3,7 - p.1083.
Age: Late Albian
Paratypes: Bint, 1983
Locus typicus: Kansas, USA
Stratum typicum: Late Albian
Original description: Bint, 1983, p. 175
Small to intermediate-sized, single-walled, subspherical cyst (but invariably flattened in these samples), epicyst modified by combination apical and intercalary archeopyle. Paratabulation not expressed, except by principal and accessory archeopyle sutures which define three apical paraplates (and imply a fourth), two intercalaries, and seven precingulars. Ventral paratabulation style is ortho. First apical paraplate is not outlined; 2' and 4' are approximately symmetrical, but 4' is slightly larger and its contact with 7'' is slightly more posterior than that of 2' with 1"; 3' is mid-dorsal and four-sided with two consistently convex sides along which it contacts the intercalary paraplates. Two symmetrically disposed intercalaries are hexagonal and transversely elongate with longest, parallel sides abutting 3" and 5" below and 3' above. Dorsal precingulars 3", 4", and 5" are respectively planate, camerate, and planate. Paracingulum and parasulcus not delimited; neither are any hypocystal paratabular features present.
Combination archeopyle has a compound operculum with apical series adnate ventrally and both intercalary paraplates free, Type (tA)a2I. Principal archeopyle suture follows the course of the anterior margin of the precingular series, but terminates ventrally without extending along any side of 1'. Thus the locus of adnation is across the width of the first apical paraplate. Accessory archeopyle sutures subdivide the compound operculum into an adnate apical piece and two free intercalary opercular pieces. Accessory sutures also occur between precingular paraplates, ranging from short knicks to sutures which reach almost to the equator of the cyst. Under light microscopy, the autophragm appears scabrate. Scanning electron microscopy revealed a uniformly textured surface consisting of minute (less than 0.3 µm), closely spaced pits and bumps, with occasional discrete granules (about 0.5 µm). Wall thickness is about 0.8 µm.
Size: All specimens of Umbodinium crustov encountered in this study have an open archeopyle and are flattened to some extent because they occur in shales. Consequently, the accessory sutures between the precingular paraplates tend to be enlarged, and it is rare to see a specimen in which original subspherical diameter can be determined. The following measurements, which are thought to approximate original subspherical diameter, were obtained from 15 specimens: 41(47)55 µm. Flattened specimens measure up to 67 µm wide in lateral view.
Holotype: Bint, 1983, pl.1, figs.1-3; text-fig.4A; Fensome et al., 1993a, figs.1-3,7 - p.1083.
Age: Late Albian
Paratypes: Bint, 1983
Locus typicus: Kansas, USA
Stratum typicum: Late Albian
Original description: Bint, 1983, p. 175
Small to intermediate-sized, single-walled, subspherical cyst (but invariably flattened in these samples), epicyst modified by combination apical and intercalary archeopyle. Paratabulation not expressed, except by principal and accessory archeopyle sutures which define three apical paraplates (and imply a fourth), two intercalaries, and seven precingulars. Ventral paratabulation style is ortho. First apical paraplate is not outlined; 2' and 4' are approximately symmetrical, but 4' is slightly larger and its contact with 7'' is slightly more posterior than that of 2' with 1"; 3' is mid-dorsal and four-sided with two consistently convex sides along which it contacts the intercalary paraplates. Two symmetrically disposed intercalaries are hexagonal and transversely elongate with longest, parallel sides abutting 3" and 5" below and 3' above. Dorsal precingulars 3", 4", and 5" are respectively planate, camerate, and planate. Paracingulum and parasulcus not delimited; neither are any hypocystal paratabular features present.
Combination archeopyle has a compound operculum with apical series adnate ventrally and both intercalary paraplates free, Type (tA)a2I. Principal archeopyle suture follows the course of the anterior margin of the precingular series, but terminates ventrally without extending along any side of 1'. Thus the locus of adnation is across the width of the first apical paraplate. Accessory archeopyle sutures subdivide the compound operculum into an adnate apical piece and two free intercalary opercular pieces. Accessory sutures also occur between precingular paraplates, ranging from short knicks to sutures which reach almost to the equator of the cyst. Under light microscopy, the autophragm appears scabrate. Scanning electron microscopy revealed a uniformly textured surface consisting of minute (less than 0.3 µm), closely spaced pits and bumps, with occasional discrete granules (about 0.5 µm). Wall thickness is about 0.8 µm.
Size: All specimens of Umbodinium crustov encountered in this study have an open archeopyle and are flattened to some extent because they occur in shales. Consequently, the accessory sutures between the precingular paraplates tend to be enlarged, and it is rare to see a specimen in which original subspherical diameter can be determined. The following measurements, which are thought to approximate original subspherical diameter, were obtained from 15 specimens: 41(47)55 µm. Flattened specimens measure up to 67 µm wide in lateral view.