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A NEW JURASSIC ISOETITES (ISOETALES) FROM THE WALLOWA TERRANE IN HELLS CANYON, OREGON AND IDAHO
Author(s) -
Ash Sidney R.,
Pigg Kathleen B.
Publication year - 1991
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 - 10.1002/j.1537-2197.1991.tb14529.x
Subject(s) - sporangium , terrane , canyon , pennsylvanian , biology , paleontology , archaeology , botany , geology , structural basin , tectonics , spore , geography , geomorphology
A new species of the quillwort Isoetites, I. rolandii sp. nov. Ash and Pigg, is described from the Middle Jurassic Coon Hollow Formation in the Wallowa terrane in Hells Canyon, Oregon and Idaho. The new species is based on coalified impressions and mold‐casts of an isoetaceous corm with narrow, elongate leaves, and isolated masses of leaves that have been studied using light microscopy. Plants are about 10 cm in maximum height and consist of cormose plant bases from 1.5 to 2.5 cm wide and 0.6 cm high bearing incomplete microphyllous leaves up to 8.4 cm long and 3.0 mm wide, that taper to about 2.0 mm wide distally. Associated casts of sporophyll bases and sporangia contain spherical structures about 440 μ m in diameter that may represent megaspores. Based on the occurrence of complete plants, some specimens of I. rolandii are thought to have been preserved in situ. The new Isoetites provides the first floristic evidence for the occurrence of an aquatic or semiaquatic paleoenvironment in the Wallowa terrane. It is also the first documented occurrence of Isoetes‐ like plants in the Jurassic of western North America.