As part of an ongoing study of Late Paleozoic terrestrial plants preserved in marine environments, a number of specimens of permineralized ovules of medullosan seedferns have been discovered in the Virgilian (Gzhelian), Finis Shale near Jacksboro, Texas. Age assessment of the strata is based on ammonoid biostratigraphy. Twenty of these specimens are exceptionally well preserved by limonite and pyrite permineralization. These specimens have been analyzed from wafers and cellulose acetate peels, to provide detailed information about external form, as well as internal cellular anatomy. Analysis of the ovules suggests that they represent a new species of Pachytesta. The specimens conform to Pachytesta in the presence of three angled symmetry of the integument with three secondary ribs, and a stalked nucellus free from the integument except at the base; a single vascular strand enters the base of the ovule, and subsequently branches into discrete bundles in the nucellus. As in all species of Pachytesta, this species has a three layered integument consisting of an innermost endotesta, a middle sclerotesta, and an outermost sarcotesta. Unlike previous reports of Pachytesta, in this species, the sarcotesta forms six approximately isomorphic exterior longitudinal lobes that usually extend from the micropylar end to the chalaza. Cells of the sarcotesta are homogenous, elongated, radially aligned, and form a single layer. Unexpectedly, the integument is apparently un-vascularized. This new species expands the range of variation within Pachytesta. In addition, these specimens from strata dated by marine biostratigraphy, represent the youngest known occurrence of this genus and thereby extend the known biostratigraphic range of Pachytesta.

Key words: Gzhelian, medullosan, Pachytesta, seedfern ovule, trigonocarp