Taxonomy Online - Carboniferous spores part I - Species details


Species name
Umbonatisporites variabilis Hibbert & Lacey, 1969

Description
Radial, trilete, acamerate miospores. Amb circular to subcircular. Trilete mark frequently indistinct or torn; sutures when seen are short, simple and straight, extending up to one-sixth of spore radius. Exine 1–2 µm thick, ornamented on distal surface and equatorial portion of the proximal surface with variable squat biform baculate or pilate projections arranged randomly over the surface. Elements variable in shape and size on any one specimen; individual elements up to 4.5 µm high and 1.0–1.5 µm in basal diameter, widening towards the apex. At the terminus of each element are one to three rounded heads, each surmounted by a single thin tapering spina. Between the larger biform elements, slender tapering spinae 2–4 µm long and up to 1 µm wide may occur.

Other descriptions
Hibbert & Lacey, 1969, pp. 423–424, pl. 78, figs. 12–13, pl. 79, figs. 1–3

Size
Overall equatorial diameter excluding projecting ornament 95(106)134 µm

Remarks
Distinguished from Umbonatisporites distinctus Clayton 1971 by the multiple character of the spinose terminations surmounting the expanded baculate projections.

Range
Mississippian; Visean to Serpukhovian [early Arnsbergian] (Hibbert and Lacey, 1969, and unpublished information)

Images

MPK 7429 MPK 7429 Figure 63a
Greengate Well Limestone, Tipalt Burn, Northumberland, England; Serpukhovian [Pendleian], NC Biozone, Sample MPA 31137, Specimen MPK 7430. Densely ornamented specimen. Elements consist of slender-based processes which expand significantly to flat or rounded topped termini which bear one to three small, sharply pointed spinose projections. Specimen maximum dimension 101 µm.


MPK 7430 MPK 7430 Figure 63b
Shales below Holme Wood Marine Band, Mousegill Beck, Stainmore, Cumbria, England; Serpukhovian [Arnsbergian], TK Biozone, Sample M21, Specimen MPK 7429. Specimen showing bulbous based processes with tapering shafts surmounted by small spinose projections. Exine relatively thick. Few elements appear to be located in the equatorial region. Specimen maximum dimension 119 µm.