A new Pachytesta ovule from Iowa

Abstract

A new species of the medullosan seed fern genus, Pachytesta, is described from specimens discovered in coal balls from Iowa. The specimens used in this study were located in coal balls, which are concretions of ancient permineralized peat. Anatomical study of the new species was made possible through the use of mounted cellulose acetate peels and photomicroscopy. The ovule is approximately 5.0-5.5 cm long and 2.4 -2.8 cm wide at its mid point. The integument contains a sarcotesta with 12 vascular bundles, a sclerotesta of radiating fibers and variable thickness, and an endotesta consisting of a thin cuticle. The primary ribs of the ovule are commissured. Based on the anatomical features studied, Pachytesta sp. A. is most similar to Taylor’s (1965) P. olivaeformis, P. composita, P. illinoensis group and is potentially a member of this group.