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OSMUNDA (OSMUNDACEAE) FROM THE TRIASSIC OF Antarctica: an example of evolutionary stasis
Author(s) -
Phipps Carlie J.,
Taylor Thomas N.,
Taylor Edith L.,
Cúneo N. Rubén,
Boucher Lisa D.,
Yao Xuanli
Publication year - 1998
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.2307/2446424
Subject(s) - frond , sporangium , biology , fern , rhizome , annulus (botany) , botany , lamina , dehiscence , genus , spore
Compressed specimens of the fern Osmunda are described from the Triassic of the Allan Hills, Antarctica. The specimens consist of a once pinnate, deeply pinnatifid fertile frond as well as several sterile specimens. Six pinnae are present on the partial fertile rachis, with two sterile pinnae above four fertile pinnae. Both sterile and fertile specimens are virtually identical to the modern species Osmunda claytoniana . Entire fronds are fragmentary; the longest is 21 cm in length. Sterile pinnae are alternate and deeply pinnatifid, with slightly toothed pinnules and dichotomous venation. Fertile pinnae are 1–1.3 cm long, once pinnate, and lack vegetative lamina. Sporangia are clustered, each 300–375 µm in diameter, and possess a transverse annulus 6–8 cells long; dehiscence is by a vertical slit. Fronds arise from a rhizome 4 cm long by 1 cm wide; two croziers are present on the rhizome. Two frond segments up to 6 cm long and three deeply pinnatifid pinnae are present on the uppermost part of one rachis. Pinnules are ~4 mm long and 2–3 mm wide. The presence of this Osmunda species in the Triassic demonstrates stasis of frond morphology, both fertile and vegetative, for the genus.