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Earliest Occurrence of Autorotating Seeds in Conifers: The Permian (Kungurian-Roadian) Manifera talaris gen. et sp. nov.
Cindy V. Looy and Robert A. Stevenson
International Journal of Plant Sciences
Vol. 175, No. 7 (September 2014), pp. 841-854
Published by: The University of Chicago Press
Stable URL: http://www.jstor.org/stable/10.1086/676973
Page Count: 14
You can always find the topics here!Topics: Conifers, Scars, Bracts, Taxa, Ovules, Fossils, Ellipses, Evolution, Plants, Frequency distribution
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We describe the conifer genus Manifera (Majonicaceae, voltzian Voltziales) from the Lower Pease River flora (Early Permian, north central Texas) on the basis of dispersed ovuliferous dwarf shoots and seeds and compare it with coeval and Late Permian taxa. Manifera talaris gen. et sp. nov. is exceptional for two reasons. First, it is the earliest known conifer with winged seeds adapted for autorotating wind dispersal; second, its seeds had variable wing configurations. The ovuliferous dwarf shoots of M. talaris were stalked and bilaterally symmetrical and were composed of five partially fused sporophylls and sterile scales. The sporophylls were in median and lateral positions, and the sterile scales were in intermediate positions. The seeds bore two integument-derived wings on the chalazal end of the seed, with the secondary wing ranging in size from rudimentary to a small stub to almost equal to that of the primary wing. Single-winged seeds are the most common morphology among extant anemochorous conifer seeds. When falling, such seeds autorotate about their center of mass, which significantly slows down their descent and increases the probability of longer-distance dispersal. The discovery of M. talaris seeds with these morphological traits shows that this mechanism of wind dispersal had already evolved in conifers by the Early Permian.
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