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QUAESTORA AMPLECTA GEN. ET SP. N., A STRUCTURALLY SIMPLE MEDULLOSAN STEM FROM THE UPPER MISSISSIPPIAN OF ARKANSAS
Author(s) -
Mapes Gene,
Rothwell Gar W.
Publication year - 1980
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.1537-2197.1980.tb07694.x
Subject(s) - biology , petiole (insect anatomy) , xylem , botany , rosette (schizont appearance) , cambium , phloem , fern , anatomy , genus , immunology
A well preserved, permineralized seed fern stem is described from the Upper Mississippian Fayetteville Formation of north central Arkansas. Quaestora amplecta gen. et sp. n. is 41.6 cm long and exhibits six pairs of decussate, highly decurrent petiole bases. The stem has a cruciform, exarch protostele with prominent secondary xylem, vascular cambium and secondary phloem. Leaf traces are terete and occur as an outer ring with a small number of internal strands. The cauline vasculature, leaf‐trace production, petiolar anatomy and several other features indicate that this specimen represents the most structurally simple and geologically ancient medullosan stem presently recognized.