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Palaeotetradinium maastrichtiense
Palaeotetradinium maastrichtiense Herngreen et al., 1986
Holotype: Herngreen et al., 1986, pl.12, figs.1-2
Locus typicus: Borehole Bunde 61F-312, Maastricht Region, the Netherlands
Stratum typicum: Maastrichtian (upper Cretaceous)
Age: Maastrichtian
Diagnosis: Herngreen et al. 1986, p. 57
A species of Palaeotetradinium with distinctly pointed endophragm and separated wall layers.
Description: Herngreen et al. 1986, p. 57
Proximate cyst with tetrahedral outline. The sides are slightly concave and the angles somewhat tapering and distally rounded. Cyst circumcavate; in optical section roundly triangular endophragm with distinctly pointed angles. Wall layers completely separated except probably for the middorsal or midventral area. No parasutural features observed. Peri- and endophragm smooth. In the holotype one of the tetrahedron points is wider and more angular in outline; it shows an opening (? archeopyle). Other specimens are damaged or distorted, thus preventing confirmation of this observation.
Affinities/Differential diagnosis:
Palaeotetradinium maastrichtiense sp. nov. differs from other species of this genus by the pointed endophragm and the circumcavate nature of the wall layers. In P. caudatum (Benson 1976) Stover and Evitt 1978 the endophragm completely fills the periphragm except for the elongated horns. The tetrahedron of P. silicorum as figured by Morgenroth (1968) has more pointed horns.
Inversidinium exilimurum McLean 1973 is similar to Palaeotetradinium maastrichtiense sp. nov. but it lacks the pointed endophragm. According to Stover and Evitt (1978) I. exilimurum, described from the Upper Paleocene of the Virginia--Maryland Coastal Plane, is a junior synonym of Palaeotetradinium minusculum (Alberti 1961) Stover and Evitt 1978. The present author doubts this synonymy because the inner body of the last species, which was originally described from the Lower Eocene of Germany, is rhombohedral and distinctly filling the epi- and hypocyst. In I. exilimurum the endophragm occupies the hypotractal portion of the pericyst. The details of the antapex are also different in both species. According to Alberti the antapical protrusions are separated by a longitudinal split, whereas in I. exilimurum the tip of the so-called truncated antapex is ruptured irregularly.
Dimensions: All measurements are in µm
holotype, and two other specimens
total length: 54, ? and 72
total breadth: 60, 57 and 76
length endophragm: 31, 27 and 36
breadth endophragm: 33, 36 and 40
distance wall layers: 3-4.5, 3 and ca 1.5
thickness of both wall layers: 0.75-1, 0.75-1 and 1
Holotype: Herngreen et al., 1986, pl.12, figs.1-2
Locus typicus: Borehole Bunde 61F-312, Maastricht Region, the Netherlands
Stratum typicum: Maastrichtian (upper Cretaceous)
Age: Maastrichtian
Diagnosis: Herngreen et al. 1986, p. 57
A species of Palaeotetradinium with distinctly pointed endophragm and separated wall layers.
Description: Herngreen et al. 1986, p. 57
Proximate cyst with tetrahedral outline. The sides are slightly concave and the angles somewhat tapering and distally rounded. Cyst circumcavate; in optical section roundly triangular endophragm with distinctly pointed angles. Wall layers completely separated except probably for the middorsal or midventral area. No parasutural features observed. Peri- and endophragm smooth. In the holotype one of the tetrahedron points is wider and more angular in outline; it shows an opening (? archeopyle). Other specimens are damaged or distorted, thus preventing confirmation of this observation.
Affinities/Differential diagnosis:
Palaeotetradinium maastrichtiense sp. nov. differs from other species of this genus by the pointed endophragm and the circumcavate nature of the wall layers. In P. caudatum (Benson 1976) Stover and Evitt 1978 the endophragm completely fills the periphragm except for the elongated horns. The tetrahedron of P. silicorum as figured by Morgenroth (1968) has more pointed horns.
Inversidinium exilimurum McLean 1973 is similar to Palaeotetradinium maastrichtiense sp. nov. but it lacks the pointed endophragm. According to Stover and Evitt (1978) I. exilimurum, described from the Upper Paleocene of the Virginia--Maryland Coastal Plane, is a junior synonym of Palaeotetradinium minusculum (Alberti 1961) Stover and Evitt 1978. The present author doubts this synonymy because the inner body of the last species, which was originally described from the Lower Eocene of Germany, is rhombohedral and distinctly filling the epi- and hypocyst. In I. exilimurum the endophragm occupies the hypotractal portion of the pericyst. The details of the antapex are also different in both species. According to Alberti the antapical protrusions are separated by a longitudinal split, whereas in I. exilimurum the tip of the so-called truncated antapex is ruptured irregularly.
Dimensions: All measurements are in µm
holotype, and two other specimens
total length: 54, ? and 72
total breadth: 60, 57 and 76
length endophragm: 31, 27 and 36
breadth endophragm: 33, 36 and 40
distance wall layers: 3-4.5, 3 and ca 1.5
thickness of both wall layers: 0.75-1, 0.75-1 and 1