Microreticulatisporites concavus M.A.Butterworth et R.W.Williams

Plant Fossil Names Registry Number: PFN003300

Act LSID: urn:lsid:plantfossilnames.org:act:3300

Authors: M. A. Butterworth & R. W. Williams

Rank: species

Reference: Butterworth, M. A. & Williams, R. W. (1958): The small spore floras of coals in the Limestone Coal Group and Upper Limestone Group of the Lower Carboniferous of Scotland. – Transactions of the Royal Society of Edinburgh 63(2): 353–392.

Page of description: 367

Illustrations or figures: pl. 1, figs 55, 56

Other combinations

Maiaspora concava (M.A.Butterworth et R.W.Williams) D.A.Mamontov et D.McLean in Mamontov, McLean & Gavrilova 2024


Holotype NHMUK PM FM1196 (slide T.45/1), Natural History Museum, London, United Kingdom
Figures: fig. 10 (A–B)
Previously published illustration or figures: fig. 10 (A–B) in Mamontov, D. A., McLean, D. & Gavrilova, O. A. (2024): Maiaspora: the hallmark of gleichenioid ferns (Gleicheniales) from the early Carboniferous. – Pap. Palaeontol. 10(3): e1561 (1–42).

Original diagnosis/description

Size approximately 30-55 μm, outline triangular, apices broadly rounded, inter-radial margins concave; ornamentation finely microreticulate, distinct and regular. Rays extending for two-thirds radius.

Description. Spore coat thin, colour yellow. Inter-radial margins concave. Size of thirty-six measured specimens ranged from 32 to 52 μm; mean 40 μm; holotype 44 μm. Regular microreticulate ornament, lacunae approximately 2 μm in diameter, muri up to 3 μm wide, slightly arched, giving rise to a regularly notched margin. Rays straight, simple frequently torn.

Emended diagnosis

Spores radial, trilete, acavate, azonate, with triangular-concave amb; apices broadly rounded. Laesurae straight, simple, extending for two-thirds to fourth-fifths of radius. Exospore thick, covered with metareticuloid sculpture having coarse secondary ornament of verrucae, coni and tuberculae on the muri tips. Mean height of apiculate elements is >1 μm. Lumina are polygonal; scrobicula placed in the center of each lumen.


Carboniferous, Mississippian, Serpukhovian
Limestone Coal Formation, early Pendleian, Serpukhovian, Upper Mississippian


United Kingdom
Seam at 1872 ft 7 in Righead borehole, West Fife Coalfield, Scotland,

Plant fossil remain

pollen and spores


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