Umkomasia uniramia Axsmith, Ed.L.Taylor, T.N.Taylor et Cúneo

Plant Fossil Names Registry Number: PFN000170


Authors: B. J. Axsmith, E. L. Taylor, T. N. Taylor & N. R. Cúneo

Rank: species

Reference: Axsmith, B. J., Taylor, E. L., Taylor, T. N. & Cúneo, N. R. (2000): New perspectives on the Mesozoic seed fern order Corystospermales based on attached organs from the Triassic of Antarctica. – American Journal of Botany 87(6): 757–768., link

Page of description: 758

Illustrations or figures: figs 3–17


Holotype T12–990a, T12–990b, Paleobotany Division of the Natural History Museum and Biodiversity Research Center, University of Kansas, Lawrence, Kansas, USA
Figures: figs 3, 4

Note: T12–990b is counterpart to T12–990a.

Paratypes—T12–1002 (figs 6, 8, 9), T12–1019a (fig. 10), T12–1028a (fig. 5), T12–1036a (fig. 11), T12–1049 (fig. 14), T12–1074 (fig. 7), T12–1076 (fig. 17), T12–1078 (fig. 12), T12–1080 (fig. 15), T12–1081 (fig. 13), T12–1082 (fig. 16).

Original diagnosis/description

Cupulate reproductive organs attached to vegetative branching systems of at least three orders, lower vegetative branch orders at least 2.3 cm wide, lateral short shoots alternately or distichously arranged, up to 6.5 cm long with closely spaced, slightly raised lenticular leaf bases with thickened lateral extensions, leaf attached to long shoots conforming to Dicroidium odontopteroides; cupulate reproductive structures in groups of at least three near apex of lateral short shoots, each organ consisting of a single axis and a subapical whorl of 4–8 cupules; cupulate organ axis up to 7.5 cm long × 4.0 mm wide, base slightly expanded, axis bearing an oppositely arranged pair of bracts in variable positions along upper quarter; bracts up to 5.0 mm long with broad bases and acute apices; cupules ovoid, up to 1.4 cm long × 1.3 cm wide, borne on recurved stalks up to 1.5 cm long, stalk expanding at point of attachment to cupule and partially extending over upper cupule surface as a midrib, dehisced cupules consisting of two flaps attached to midrib; cuticle of main axis and inner cupule surface smooth, outer cupule surface irregular.


The specific epithet uniramia refers to the unbranched architecture of the cupulate organ axis relative to other Umkomasia species that typically consist of two branch orders.


Late Middle to early Late Triassic.
Upper Fremouw or lower Falla Formation.


A ridge southeast of Schroeder Hill in the Shackleton Glacier region of Antarctica (~85° 23′ 717″ S, 174° 49′ 916″ W).

Plant fossil remain

macro- and meso-fossils-embryophytes except wood


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