Taxonomy Online - Carboniferous spores part I - Species details


Species name
Convolutispora circumvallata Clayton, 1971

Description
Radial trilete acamerate miospores. Amb circular–subcircular. Trilete mark distinct or obscured by ornamentation, sutures simple or accompanied by wide labra, extending more than three-quarters of spore radius. Ornament on entire distal surface and equatorial portion of proximal surface consists of rounded anastomosing ridges, some of which may be fused together to form an imperfect reticulum. Ridges variable in width along length and often have expanded tops particularly where ridges join. The channels and irregular lumina between the ridges are normally equal to or wider than the mean width of the ridges. Ridges 3–12 µm high and 5–15 µm wide. Exine up to 5 µm thick.

Other descriptions
Clayton, 1971, p. 582, pl. 1, figs. 5–7. Higgs, Clayton and Keegan, 1988, p. 63, pl. 6, fig. 12

Size
Overall equatorial diameter 64(90)112 μm

Remarks
The range of morphological variability displayed by this species is wide but few specimens display a sufficiently well developed reticulation to justify inclusion within the genus Dictyotriletes. Reticulatisporites ancoralis Balme & Hassell 1962 is superficially similar but has a better developed reticulum and a thinner exine.

Range
Mississippian; Tournaisian to Visean; CM to Pu biozones (Clayton et al., 1977)

Images

MPK 7421 MPK 7421 Figure 9a
Pinskey Gill Beds, Wygarth Gill Borehole, Ravenstonedale, Cumbria, England; Mississippian, Tournaisian, CM Biozone, Sample MPA 302, Specimen MPK 7421. Distal focus. Subcircular miospore, trilete mark obscured by heavy convolute ornament. Distal surface and equatorial portion of proximal surface of exine ornamented with dense network of wide, round-topped ridges, which coalesce to form incomplete reticulate pattern. Specimen maximum dimension 101 μm.


MPK 7422 MPK 7422 Figure 9b
Pinskey Gill Beds, Wygarth Gill Borehole, Ravenstonedale, Cumbria, England; Mississippian, Tournaisian, CM Biozone, Sample MPA 302, Specimen MPK 7422. Heavy convolute round-topped ridges form irregular pattern. Trilete mark distinct, sutures extend at least three quarters of spore radius and accompanied by low broad labra. Specimen maximum dimension 94 μm.