Back
Palynodinium minus
Palynodinium minus Willumsen, 2006, p.957–959, figs.3A–K.
Holotype: Willumsen, 2006, figs.3A–B,D–E.
Age: latest Maastrichtian–earliest Danian.
Original description (Willumsen, 2006)
Derivation of name. After the relatively few, reduced, morphological characters compared with other species in the
genus.
Types. Holotype, FRF M34/f558, L18704, 1-4, 16 mm, England Finder reference G41,4, Fig. 3A, B, D, E. Paratypes, FRF M34/f195, L18330, 1-1, 6 mm, S32, Fig. 3C, F, I.; FRF M34/f195, L18330, 1-1, 6 mm, D38,2, Fig. 3G, H, J, K. Type locality and stratum. Mid-Waipara River, between Doctors Gorge and Canterbury Plains, North Canterbury, New Zealand; uppermost part of Conway Formation, within non-calcareous glauconitic bioturbated sandstone.
Diagnosis:
Small species of Palynodinium with relatively long processes and relatively reduced, ventrally located pericoels. The two pericoels reduced compared with other species in genus and cavity between endo- and periphragm is only partly developed on lower part of epicyst (Fig. 3AeK). Surface of cyst microreticulate; paratabulation indicated only by hexagonal archeopyle margin.
Description:
Small, skolochorate, moderately dorsoventrally compressed gonyaulacoid cyst with a lenticular shape. Endo- and periphragm thin (max. 1 µm), and two pericoels are developed on ventral side of lower part of epicyst and hypocyst (Fig. 3A, B, D, E). Size of pericoels is about one-third that of endocyst and cavity between periphragm and endophragm is only partly developed on lower part of epicyst. Cavity between two wall layers is better developed on hypocyst. A smaller cavity between wall-layers is developed on antapical tip of cyst; this feature is only visible on specimens with attached operculum; elsewhere, endo- and periphragm are appressed. Surface of
cyst microreticulate and covered by processes ca. 13-22 µm long. Process tips may be bifurcate, bifid or capitate. Archeopyle is type tA. Apical outline is asymmetrical and compression of cyst is moderate in polar view. A few specimens with attached operculum were observed. Indications of paratabulation, apart from archeopyle margin, not observed.
Dimensions: Holotype Range Specimens measured in µm
Total cyst length excl. processes 73 64(79)101 12
Length of endocyst excl. pericoels 40 44(50)63 10
Width of endocyst excl. pericoels 48 29(40)50 10
Width of pericoel excl. processes 15 10(21)26 9
Maximum length of processes 18 13(16)22 12
Stratigraphic occurrence. The first sporadic occurrence of P. minus is directly below the K/P boundary within the uppermost part of the Manumiella druggii Interval Zone (Helby et al., 1987; Wilson, 1987, 1988; Wilson et al., 1989). The last occurrence is in the lowermost part of the Danian Trithyrodinium evittii Interval Zone of Wilson (1987, 1988) and Wilson et al. (1989) (Fig. 2). In the mid-Waipara River section P. minus occurs in an interval from 3 cm below to 52.5 cm above the K/P boundary (Fig. 2; Table 1). The last occurrence is at 47.5 cm above the boundary (M34/f203). In the Grey River section P. minus occurs in an interval from 1 cm below to 70 cm above the K/P boundary (Fig. 2, Table 2). The last record is 30 cm above the boundary (sample M34/f278).
Comparison:
Palynodinium minus differs from the type species of the genus, P. grallator, in having two reduced, ventrally placed pericoels. The cavities between the two wall layers are not fully developed in P. minus and they are located on the lower part of the epicyst. Palynodinium grallator has well-developed cavities between the peri- and endophragm and these pericoels extend from the epicyst to hypocyst (Gocht, 1970, figs. 2, 4, 5). Furthermore, P. minus has no indication of tabulation in the cingular and dorsal areas of the cyst whereas P. grallator has both sutures and processes indicating the paratabulation in the cingular and antapical parts (see Fig. 3LeO). Palynodinium biculleum (Kirsch, 1991) differs from P. minus in having a smooth surface and an indication of the cingulum in the dorsal region of the cyst. Palynodinium minus differs from all other known members of the genus in having two much reduced ventral pericoels, a microreticulate cyst surface and a paratabulation that is only indicated by a hexagonal archeopyle margin.
Holotype: Willumsen, 2006, figs.3A–B,D–E.
Age: latest Maastrichtian–earliest Danian.
Original description (Willumsen, 2006)
Derivation of name. After the relatively few, reduced, morphological characters compared with other species in the
genus.
Types. Holotype, FRF M34/f558, L18704, 1-4, 16 mm, England Finder reference G41,4, Fig. 3A, B, D, E. Paratypes, FRF M34/f195, L18330, 1-1, 6 mm, S32, Fig. 3C, F, I.; FRF M34/f195, L18330, 1-1, 6 mm, D38,2, Fig. 3G, H, J, K. Type locality and stratum. Mid-Waipara River, between Doctors Gorge and Canterbury Plains, North Canterbury, New Zealand; uppermost part of Conway Formation, within non-calcareous glauconitic bioturbated sandstone.
Diagnosis:
Small species of Palynodinium with relatively long processes and relatively reduced, ventrally located pericoels. The two pericoels reduced compared with other species in genus and cavity between endo- and periphragm is only partly developed on lower part of epicyst (Fig. 3AeK). Surface of cyst microreticulate; paratabulation indicated only by hexagonal archeopyle margin.
Description:
Small, skolochorate, moderately dorsoventrally compressed gonyaulacoid cyst with a lenticular shape. Endo- and periphragm thin (max. 1 µm), and two pericoels are developed on ventral side of lower part of epicyst and hypocyst (Fig. 3A, B, D, E). Size of pericoels is about one-third that of endocyst and cavity between periphragm and endophragm is only partly developed on lower part of epicyst. Cavity between two wall layers is better developed on hypocyst. A smaller cavity between wall-layers is developed on antapical tip of cyst; this feature is only visible on specimens with attached operculum; elsewhere, endo- and periphragm are appressed. Surface of
cyst microreticulate and covered by processes ca. 13-22 µm long. Process tips may be bifurcate, bifid or capitate. Archeopyle is type tA. Apical outline is asymmetrical and compression of cyst is moderate in polar view. A few specimens with attached operculum were observed. Indications of paratabulation, apart from archeopyle margin, not observed.
Dimensions: Holotype Range Specimens measured in µm
Total cyst length excl. processes 73 64(79)101 12
Length of endocyst excl. pericoels 40 44(50)63 10
Width of endocyst excl. pericoels 48 29(40)50 10
Width of pericoel excl. processes 15 10(21)26 9
Maximum length of processes 18 13(16)22 12
Stratigraphic occurrence. The first sporadic occurrence of P. minus is directly below the K/P boundary within the uppermost part of the Manumiella druggii Interval Zone (Helby et al., 1987; Wilson, 1987, 1988; Wilson et al., 1989). The last occurrence is in the lowermost part of the Danian Trithyrodinium evittii Interval Zone of Wilson (1987, 1988) and Wilson et al. (1989) (Fig. 2). In the mid-Waipara River section P. minus occurs in an interval from 3 cm below to 52.5 cm above the K/P boundary (Fig. 2; Table 1). The last occurrence is at 47.5 cm above the boundary (M34/f203). In the Grey River section P. minus occurs in an interval from 1 cm below to 70 cm above the K/P boundary (Fig. 2, Table 2). The last record is 30 cm above the boundary (sample M34/f278).
Comparison:
Palynodinium minus differs from the type species of the genus, P. grallator, in having two reduced, ventrally placed pericoels. The cavities between the two wall layers are not fully developed in P. minus and they are located on the lower part of the epicyst. Palynodinium grallator has well-developed cavities between the peri- and endophragm and these pericoels extend from the epicyst to hypocyst (Gocht, 1970, figs. 2, 4, 5). Furthermore, P. minus has no indication of tabulation in the cingular and dorsal areas of the cyst whereas P. grallator has both sutures and processes indicating the paratabulation in the cingular and antapical parts (see Fig. 3LeO). Palynodinium biculleum (Kirsch, 1991) differs from P. minus in having a smooth surface and an indication of the cingulum in the dorsal region of the cyst. Palynodinium minus differs from all other known members of the genus in having two much reduced ventral pericoels, a microreticulate cyst surface and a paratabulation that is only indicated by a hexagonal archeopyle margin.