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Apectodinium paniculatum
Apectodinium paniculatum, (Costa and Downie, 1976), Lentin and Williams, 1977
Originally Wetzeliella, subsequently (and now) Apectodinium.
Holotype: Costa and Downie, 1976, pl.92, fig.1
Age: Early Eocene
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Original description as Wetzeliella (Apectodinium) paniculata: [Costa and Downie, 1977, p. 608-609]:
Diagnosis:
A species of Wetzeliella (Apectodinium) with a broadly rounded to subtriangular epitract and a subpolygonal hypotract. Apical horn absent or very much reduced; lateral horns broad and commonly long; well-developed antapical horns with a broad proximal part usually projecting into a long and complexly branched process.
Description:
The apical horn is absent or, if present, reduced to a short, blunt projection surmounted by a tuft of processes; the epitract is broadly rounded to subtriangular in outline. The lateral horns are variable in length and they may be reduced, but they are typically long, rather broad, sometimes bifurcating distally, and abundantly covered by processes. The antapical horns consist of a broad and usually short proximal part and a long, branched distal process; the proximal part of the antapical horns may be very short, the horns then being reduced to the long ramified process. Both antapical horns are of roughly the same length. The endophragm, which may be absent in some specimens, is frequently very thin and difficult to observe. The processes are long, intratabular, with sometimes tapering bases and long tubiform distal parts which may be simple, bifurcate or, at the antapical horns, complexly branched. The processes are commonly open distally, the distal margin bearing a variable number of very short aculei, but they may also be closed with simple or bifid distal endings. The archeopyle is of the type common to the subgenus, i.e. small, subquadrangular, with periphragm and endophragm in close contact at the margins.
Dimensions:
Holotype: over-all tract length 81 µm, breadth 92 µm; endoblast length 66 µm, breadth 74 µm; apical horn 3 µm; lateral horns 15 µm; antapical horn right 17 µm, left 15 µm; processes length 5-17 µm.
Observed range: over-all length 93-76 µm, breadth 95-76 µm; apical horn 0-4 µm; lateral horns 9-18 µm; antapical horns 11-20 µm; processes length 5-18 µm. Number of specimens measured: 10.
Affinities/Remarks:
The present species resembles W. (A.) homomorpha ssp. quinquelata, from which it differs by the long lateral horns; there are, however, numerous transitional forms between these taxa. W. (A.) paniculata differs from W. (A.) hyperacantha mainly in the absence of a well-developed apical horn and in the shape of the antapical horns; these in W. (A.) hyperacantha are shorter and do not bear a long ramified process distally.
Originally Wetzeliella, subsequently (and now) Apectodinium.
Holotype: Costa and Downie, 1976, pl.92, fig.1
Age: Early Eocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Wetzeliella (Apectodinium) paniculata: [Costa and Downie, 1977, p. 608-609]:
Diagnosis:
A species of Wetzeliella (Apectodinium) with a broadly rounded to subtriangular epitract and a subpolygonal hypotract. Apical horn absent or very much reduced; lateral horns broad and commonly long; well-developed antapical horns with a broad proximal part usually projecting into a long and complexly branched process.
Description:
The apical horn is absent or, if present, reduced to a short, blunt projection surmounted by a tuft of processes; the epitract is broadly rounded to subtriangular in outline. The lateral horns are variable in length and they may be reduced, but they are typically long, rather broad, sometimes bifurcating distally, and abundantly covered by processes. The antapical horns consist of a broad and usually short proximal part and a long, branched distal process; the proximal part of the antapical horns may be very short, the horns then being reduced to the long ramified process. Both antapical horns are of roughly the same length. The endophragm, which may be absent in some specimens, is frequently very thin and difficult to observe. The processes are long, intratabular, with sometimes tapering bases and long tubiform distal parts which may be simple, bifurcate or, at the antapical horns, complexly branched. The processes are commonly open distally, the distal margin bearing a variable number of very short aculei, but they may also be closed with simple or bifid distal endings. The archeopyle is of the type common to the subgenus, i.e. small, subquadrangular, with periphragm and endophragm in close contact at the margins.
Dimensions:
Holotype: over-all tract length 81 µm, breadth 92 µm; endoblast length 66 µm, breadth 74 µm; apical horn 3 µm; lateral horns 15 µm; antapical horn right 17 µm, left 15 µm; processes length 5-17 µm.
Observed range: over-all length 93-76 µm, breadth 95-76 µm; apical horn 0-4 µm; lateral horns 9-18 µm; antapical horns 11-20 µm; processes length 5-18 µm. Number of specimens measured: 10.
Affinities/Remarks:
The present species resembles W. (A.) homomorpha ssp. quinquelata, from which it differs by the long lateral horns; there are, however, numerous transitional forms between these taxa. W. (A.) paniculata differs from W. (A.) hyperacantha mainly in the absence of a well-developed apical horn and in the shape of the antapical horns; these in W. (A.) hyperacantha are shorter and do not bear a long ramified process distally.