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Alterbia acutula
Alterbia acutula, (Wilson, 1967), Lentin and Williams, 1976
Originally Deflandrea, subsequently Alterbia (combination illegitimate), thirdly (and now) Alterbidinium.
Tax. sr. synonym of Albertia (subsequently Alterbia) recticornis (Vozzhennikova, 1967) Lentin and Williams, 1976, the original type species of the genus Alterbia, according to Whitney (1979, p.125). Alterbia acutula was thus the correct name for the type species of Alterbia, but the nomenclatural type of the genus was the holotype of Alterbia recticornis. Harker and Sarjeant in Harker et al. (1990, p.103-104) retained Alterbia (as Alterbidinium) recticornis as a separate species; however, Lentin anmd Williams, 1993, followed Lentin and Vozzhennikova (1990, p.31-32,194) and KhowajaAteequzzaman et al. (1991, p.42) in regarding Alterbidinium recticorne as a taxonomic junior synonym of Alterbia (as Alterbidinium) acutulum Wilson, 1967b.
Tax. sr. synonym of Alterbia curvicornis (Vozzhennikova, 1967) Lentin and Williams, 1976, according to Whitney (1979, p.125).
Khowaja-Ateequzzaman et al. (1991, p.41-42) emended the diagnosis of this species, as Alterbidinium acutulum.
Holotype: Wilson, 1967, fig.12
Locus typicus: Garden Cove Mudston at Head of Persevance Habour, Campbell Island, New Zealand
Stratum typicum: ?Teurian, Palaeocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Original description as Deflandrea acutula: [Wilson, 1967, p. 225-226]:
Description:
Test narrow, bi-layered, comprising smooth outer cyst tapering at poles, and smaller inner cyst. Right antapical horn long (l=14-36 µm), pointed. Left antapical horn absent, but position represented by minor angularity in margin of outer cyst.
Archaeopyle long, narrow, intercalary, situated on dorsal epitheca; operculum hinged to shell by posterior margin. Spiral transverse girdle represented by a folding of outer cyst.
Dimensions:
Holotype: l=83 µm, b=44 µm, inner cyst 44 µm x36 µm.
Two other measured specimens: SM 621: l=116 µm, b=47µm, inner cyst 47 µm x39 µm; SM 602: l=94 µm, b=50 µm, inner cyst=44 µm x41 µm
Affinities:
D. acutula shares certain features with several Antarctic species of Deflandrea described recently by the author (Wilson, 1967). In particular the archaeopyle resembles that of D. assymetrica and D. distincta, although it is much narrower. All three species possess a flat-tipped apical horn. D. acutula is distinguished from the two Antarctic species by its different shell outline, greater development of the right antapical horn, and the absence of a left antapical horn.
Originally Deflandrea, subsequently Alterbia (combination illegitimate), thirdly (and now) Alterbidinium.
Tax. sr. synonym of Albertia (subsequently Alterbia) recticornis (Vozzhennikova, 1967) Lentin and Williams, 1976, the original type species of the genus Alterbia, according to Whitney (1979, p.125). Alterbia acutula was thus the correct name for the type species of Alterbia, but the nomenclatural type of the genus was the holotype of Alterbia recticornis. Harker and Sarjeant in Harker et al. (1990, p.103-104) retained Alterbia (as Alterbidinium) recticornis as a separate species; however, Lentin anmd Williams, 1993, followed Lentin and Vozzhennikova (1990, p.31-32,194) and KhowajaAteequzzaman et al. (1991, p.42) in regarding Alterbidinium recticorne as a taxonomic junior synonym of Alterbia (as Alterbidinium) acutulum Wilson, 1967b.
Tax. sr. synonym of Alterbia curvicornis (Vozzhennikova, 1967) Lentin and Williams, 1976, according to Whitney (1979, p.125).
Khowaja-Ateequzzaman et al. (1991, p.41-42) emended the diagnosis of this species, as Alterbidinium acutulum.
Holotype: Wilson, 1967, fig.12
Locus typicus: Garden Cove Mudston at Head of Persevance Habour, Campbell Island, New Zealand
Stratum typicum: ?Teurian, Palaeocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Original description as Deflandrea acutula: [Wilson, 1967, p. 225-226]:
Description:
Test narrow, bi-layered, comprising smooth outer cyst tapering at poles, and smaller inner cyst. Right antapical horn long (l=14-36 µm), pointed. Left antapical horn absent, but position represented by minor angularity in margin of outer cyst.
Archaeopyle long, narrow, intercalary, situated on dorsal epitheca; operculum hinged to shell by posterior margin. Spiral transverse girdle represented by a folding of outer cyst.
Dimensions:
Holotype: l=83 µm, b=44 µm, inner cyst 44 µm x36 µm.
Two other measured specimens: SM 621: l=116 µm, b=47µm, inner cyst 47 µm x39 µm; SM 602: l=94 µm, b=50 µm, inner cyst=44 µm x41 µm
Affinities:
D. acutula shares certain features with several Antarctic species of Deflandrea described recently by the author (Wilson, 1967). In particular the archaeopyle resembles that of D. assymetrica and D. distincta, although it is much narrower. All three species possess a flat-tipped apical horn. D. acutula is distinguished from the two Antarctic species by its different shell outline, greater development of the right antapical horn, and the absence of a left antapical horn.