Back
Alterbia obscura
Alterbia obscura, (Drugg, 1967), Lentin and Williams, 1976
Combination illegitimate: the generic name Alterbia is illegitimate.
Holotype: Drugg, 1967, pl.2, fig.8
Locus typicus: Escarpado Canyon, California
Stratum typicum: Maastrichtian-Danian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Deflandrea obscura: [Drugg, 1967, p. 17]:
Diagnosis:
Test ovoid in outline, bearing one short apical horn and two short unequally developed antapical horns. Test membrane closely adherent to the cyst which completely fills the test cavity except for the horns. Cyst wall thin and smooth, questionably punctate at times. Test wall smooth, occasionally bearing scattered grana. Girdle circular to slightly spiral, marked by low flanges which are sometimes denticulate. Longitudinal furrow delineated by folds on the hypotheca, barely extending onto the epitheca on some specimens.
A six-sided archeopyle usually visible on the dorsal epitheca as is faint tabulation. The presence of this tabulation can be detected most easily by using phase contrast microscopy. The dorsal tabulation consists of 3 precingular plates, 3 intercalary plates (the center one functions as an operculum), and 1 apical plate. Sometimes 3 postcingular plates are also suggested as being present.
Dimensions:
The size ranges from 40 to 54 µm wide and from 45 to 60 µm long.
Affinities:
By possessing rudimentary tabulation this species resembles those described by Manum (1963), such as Deflandrea scheii, but differs considerably in gross detail. It differs from D. minor Alberti 1959 in possessing tabulation, reduced horns, and a cyst more closely appressed to the test. Other similar species are D. ventriosa Alberti 1959 and D. microgranulata Stanley 1965. The non-granular cyst of D. obscura serves to separate it from these two species.
Combination illegitimate: the generic name Alterbia is illegitimate.
Holotype: Drugg, 1967, pl.2, fig.8
Locus typicus: Escarpado Canyon, California
Stratum typicum: Maastrichtian-Danian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Deflandrea obscura: [Drugg, 1967, p. 17]:
Diagnosis:
Test ovoid in outline, bearing one short apical horn and two short unequally developed antapical horns. Test membrane closely adherent to the cyst which completely fills the test cavity except for the horns. Cyst wall thin and smooth, questionably punctate at times. Test wall smooth, occasionally bearing scattered grana. Girdle circular to slightly spiral, marked by low flanges which are sometimes denticulate. Longitudinal furrow delineated by folds on the hypotheca, barely extending onto the epitheca on some specimens.
A six-sided archeopyle usually visible on the dorsal epitheca as is faint tabulation. The presence of this tabulation can be detected most easily by using phase contrast microscopy. The dorsal tabulation consists of 3 precingular plates, 3 intercalary plates (the center one functions as an operculum), and 1 apical plate. Sometimes 3 postcingular plates are also suggested as being present.
Dimensions:
The size ranges from 40 to 54 µm wide and from 45 to 60 µm long.
Affinities:
By possessing rudimentary tabulation this species resembles those described by Manum (1963), such as Deflandrea scheii, but differs considerably in gross detail. It differs from D. minor Alberti 1959 in possessing tabulation, reduced horns, and a cyst more closely appressed to the test. Other similar species are D. ventriosa Alberti 1959 and D. microgranulata Stanley 1965. The non-granular cyst of D. obscura serves to separate it from these two species.