Pilosisporites notensis Cookson and Dettmann, 1958

Seegets-Villiers, Doris E., 2016, Morphological variation of stratigraphically important species in the genus Pilosisporites Delcourt & Sprumont, 1955 in the Gippsland Basin, southeastern Australia, Memoirs of Museum Victoria 74, pp. 81-91 : 86-88

Pilosisporites notensis Cookson and Dettmann, 1958 emend.

Figure 3 A–J

Synonymy: 1958 Pilosisporites notensis Cookson and Dettmann , p. 102, pl. 15, figs 1, 3

1963 Pilosisporites notensis Cookson and Dettmann ; Dettmann, p. 37–38, pl. 4, figs 1–5; p. 33 fig 4D

1964 Pilosisporites notensis Cookson and Dettmann ; Balme, p.74, pl. VII, fig. 10

1969 Pilosisporites notensis Cookson and Dettmann ; Dettmann and Playford, pl. 11, fig. 2

1973 Pilosisporites notensis Cookson and Dettmann ; Burger, pl. 2, fig. 1

1974 Pilosisporites notensis Cookson and Dettmann ; Burger, pl. 13 fig 11

1976 Pilosisporites notensis Cookson and Dettmann ; Norvick and Burger, pl. 18, fig 17

non 1978 Pilosisporites notensis Cookson and Dettmann ; Backhouse, p.18, Pl. 2, fig. 1

1980 Pilosisporites notensis Cookson and Dettmann ; Burger, p. 52, pl. 6, fig. 5

1986 Pilosisporites notensis Cookson and Dettmann ; Dettmann, fig. 6M

1987 Pilosisporites notensis Cookson and Dettmann ; Helby et al., fig. 20N

1988 Pilosisporites notensis Cookson and Dettmann ; Backhouse, pl.15 fig. 2

2012 Pilosisporites notensis Cookson and Dettmann ; Wagstaff et al., pl.II fig. 2

Emended diagnosis: Trilete spores, with strongly convex distal and almost flat proximal surface. Amb triangular with concave to nearly straight sides and broadly rounded apices. Laesurae straight, length 2 / 3 to ¾ of spore radius, with raised, membraneous lips. Exine 1.5–3.5 µm thick, ornamented by straight-sided or curved cones and/or spines (sensu Punt et al., 1994) of 0.5–3.5 µm basal diameter and 1–6.5 µm height. This sculpture co-occurs with rare other sculpture types including baculae, clavae, pilae, tuberculae and verrucae (fig. 4). Sculptural elements consistently arranged along laesurae margins and either covering the entire spore surface or restricted to the apical areas. Sculpture elements of equal size and distribution on proximal and distal surface.

Size: Equatorial diameter 52 (80) 125 µm (136 specimens), polar diameter 52 (71) 91 µm (14 specimens).

Remarks and comparison: Specimens generally conform to the original descriptions ( Cookson and Dettmann, 1958; Dettmann, 1963). However, observations on a large number of specimens in this study have revealed differences regarding the distribution and type of sculptural elements (figs. 3, 4). The most common morphological extreme of P. notensis exhibits short sculptural elements (up to 3 µm high) and base diameters of between 0.5–3 µm. This group shows sculpture distributed either over the entire spore surface as illustrated by Backhouse (1988) or mainly restricted to apical areas where they are closely packed (fig. 3G). The second morphological extreme, shows elongate sculptural elements (up to 6.5 µm), with a narrow basal diameter of as little as 1 µm. Sculptural elements are either distributed over the entire distal and proximal surface (figs. 3E, F, H) or primarily restricted to and closely packed together in the apical areas of the spore (fig. 3B) as in the original description of P. notensis by Cookson and Dettmann (1958) and as occurs in the holotype (fig. 3A).

The specimens of P. notensis with long apically distributed spines, superficially resemble P. ingramii Backhouse (1988) in that they possess long spines, and in some instances, a single row of small spines on the laesurae. However, the grain size in general exceeds that of P. ingramii and sculptural elements are in general shorter. Between each morphological end member there is a continual spectrum of distribution of sculptural elements on the amb of the spores ranging from primarily the apex with rare inter-apical occurrences, to increasing frequency of elements inter-apically to spores in which the sculpture extends over the entire surface of the amb. Sculptural element size and distribution is independent of the overall size of the grain.

Two other species of Pilosisporites bear a resemblance to P. notensis . Pilosisporites trichopapillosus (Thiergart) Delcourt and Sprumont, 1955 is recorded as also having sculpture variation in which the long spines were restricted to apical areas or covering the entire surface of the grain ( Couper, 1958). However, there is no suggestion that there are any sculptural elements other than spines on this species (e.g. Couper, 1958; Singh, 1964; Archangelsky and Llorens, 2005). Pilosisporites verus (Delcourt and Sprumont) emend. Archangelsky and Llorens, 2005 has sculptural elements that include spines with broad bases and acute apices that are sometimes curved, with lesser numbers of cones, bacula, granules and mameliform processes. The sculptural elements are often concentrated at the apical areas ( Singh, 1964) but the spines in P. verus are longer, i.e. 5.5–11 μm ( Archangelsky and Llorens, 2005), than those that occur in P. notensis . The equatorial diameter of both these species is also within the lower end of the size of P. notensis .

Distribution (this study): Base of the Foraminisporis wonthaggiensis Zone to within the lower part of the P. grandis subzone of the C. paradoxa Zone. This study found that both end members co-occur in the older part of the succession with their First Appearance Datum (FAD) at the base of the F. wonthaggiensis Zone. However , in the uppermost part of the range of P.notensis , i.e. in the C. striatus and C. paradoxa zones, only the shorter spined forms occur (figs. 3C, D). P. notensis is never abundant or common in the upper part of its range.