Back
Herendeenia alaskaensis
Herenddenia alaskaensis (Stover and Evitt, 1978) Stover and Helby, 1987
Originally Omatia, subsequently (and now) Herendeenia. Stover and Helby (1987b, p.155–156) provided a revised description for this species.
Holotype: Wiggins, 1969, pl.1, figs.1-3 (as Herendeenia pisciformis).
Originally Omatia, subsequently (and now) Herendeenia.
Age: Neocomian, probably Late Hauterivian-Barremian
Revised description: Stover and Helby, 1987, p. 155-156
Cysts proximate, elongate ellipsoidal with a relatively slender, pointed apical projection formed by the periphragm, and a narrow, truncated antapical end (Fig 12A D). WalI about 1 Ám or less in thickness, with an outer sculptured part and an inner, slightly thicker unsculptured part. Boundary between them not sharply delineated except in the polar areas where parasutural ridges are formed. Ornamentation of circular, elliptical and irregularly shaped, low, closely spaced and uniformly distributed granules (Fig. 12C,D). Epicystal parasutural ridges generally outline 3 apical paraplates and anterior parts of 5 precingular paraplates (Fig.llA,B). On most specimens parasutural ridges rise to eight gonal peaks: one at the apex, 2 on the ventral surface near the base of the apical projection, 1 on each lateral surface and 1 at each anterior angle of the middorsal paraplate. Hypocystal parasutural ridges generally delineating the posterior parts of 4 postcingular paraplates, the posterior intercalary and the antapical paraplates. The transverse ridge defining the anterior limit of paraplate 1"""" usually straight or nearly so. Parasutural ridges at the lateral margins of the precingular and postcingular paraplates decrease in height away from the poles and terminate at approximately one half the distance to the equator. Indications of paratabulation in the area between the ends of the ridges may be lacking, or may consist of faint parasutural lines and parasutures. Together, the parasutural features and parasutures may reveal a paratabulation of 3", 6", 6c, 5""", 1p, 1""""; however, on the majority of specimens paratabulation of only 3", 5", Xc, 4""", 1"""" is discernible.
Paracingulum and parasulcus generally not expressed, occasional specimens showing indications of the former, usually on the dorsal surface. Six cingular paraplates outlined on the holotype, ends of the paracingulum markedly offset. Archeoyple precingular, type P, and formed by the release of paraplate 3"; operculum commonly free. Measurements and calculations based on 50 complete specimens: length 100(124)150 µm; width 30(37)45 µm; length to width ratio 2.8(3.3)4.1.
Affinities:
Stover and Helby, 1987, p.156: Herendeenia alaskaensis differs from H. pisciformis in being smaller, relatively narrower, and thinner walled. In addition, H. alaskaensis has a single, ventral apical paraplate that is small in comparison with the two, relatively large, ventral, apical paraplates on H. pisciformis. Paratabulation beyond the broad circumcentral area is usually clearer on H. pisciformis than on H. alaskaensis, especially on the hypocyst. However, the paratabulation on the former is confined almost exclusively to that expressed by the parasutural ridges, whereas on H. alaskaensis it may be expressed by parasutures and linear markings as well as by parasutural ridges. Lastly, the prominent epicystal gonal "peaks", so characteristic of the apex of H. alaskaensis, do not occur on H. pisciformis.
Originally Omatia, subsequently (and now) Herendeenia. Stover and Helby (1987b, p.155–156) provided a revised description for this species.
Holotype: Wiggins, 1969, pl.1, figs.1-3 (as Herendeenia pisciformis).
Originally Omatia, subsequently (and now) Herendeenia.
Age: Neocomian, probably Late Hauterivian-Barremian
Revised description: Stover and Helby, 1987, p. 155-156
Cysts proximate, elongate ellipsoidal with a relatively slender, pointed apical projection formed by the periphragm, and a narrow, truncated antapical end (Fig 12A D). WalI about 1 Ám or less in thickness, with an outer sculptured part and an inner, slightly thicker unsculptured part. Boundary between them not sharply delineated except in the polar areas where parasutural ridges are formed. Ornamentation of circular, elliptical and irregularly shaped, low, closely spaced and uniformly distributed granules (Fig. 12C,D). Epicystal parasutural ridges generally outline 3 apical paraplates and anterior parts of 5 precingular paraplates (Fig.llA,B). On most specimens parasutural ridges rise to eight gonal peaks: one at the apex, 2 on the ventral surface near the base of the apical projection, 1 on each lateral surface and 1 at each anterior angle of the middorsal paraplate. Hypocystal parasutural ridges generally delineating the posterior parts of 4 postcingular paraplates, the posterior intercalary and the antapical paraplates. The transverse ridge defining the anterior limit of paraplate 1"""" usually straight or nearly so. Parasutural ridges at the lateral margins of the precingular and postcingular paraplates decrease in height away from the poles and terminate at approximately one half the distance to the equator. Indications of paratabulation in the area between the ends of the ridges may be lacking, or may consist of faint parasutural lines and parasutures. Together, the parasutural features and parasutures may reveal a paratabulation of 3", 6", 6c, 5""", 1p, 1""""; however, on the majority of specimens paratabulation of only 3", 5", Xc, 4""", 1"""" is discernible.
Paracingulum and parasulcus generally not expressed, occasional specimens showing indications of the former, usually on the dorsal surface. Six cingular paraplates outlined on the holotype, ends of the paracingulum markedly offset. Archeoyple precingular, type P, and formed by the release of paraplate 3"; operculum commonly free. Measurements and calculations based on 50 complete specimens: length 100(124)150 µm; width 30(37)45 µm; length to width ratio 2.8(3.3)4.1.
Affinities:
Stover and Helby, 1987, p.156: Herendeenia alaskaensis differs from H. pisciformis in being smaller, relatively narrower, and thinner walled. In addition, H. alaskaensis has a single, ventral apical paraplate that is small in comparison with the two, relatively large, ventral, apical paraplates on H. pisciformis. Paratabulation beyond the broad circumcentral area is usually clearer on H. pisciformis than on H. alaskaensis, especially on the hypocyst. However, the paratabulation on the former is confined almost exclusively to that expressed by the parasutural ridges, whereas on H. alaskaensis it may be expressed by parasutures and linear markings as well as by parasutural ridges. Lastly, the prominent epicystal gonal "peaks", so characteristic of the apex of H. alaskaensis, do not occur on H. pisciformis.