On Paleozoic plants from marine strata: Hexaloba finisensia new genus and species, a trigonocarpalean ovule from the Virgilian (Upper Pennsylvanian: Gzhelian) Finis Shale of Texas

Abstract

Twenty permineralized ovules were recovered from a mixed marine and terrestrial assemblage from the Finis Shale near Jacksboro, Texas, USA. The strata have been dated as Virgilian (upper Pennsylvanian: Gzhelian) based on ammonoid biostratigraphy, regionally correlated based on the marine assemblage, and globally correlated based on ammonoid, fusulinacean and conodont data. These morphotaxa conform to trigonocarpalean ovules based on their three angled symmetry and the presence of a stalked nucellus attached to the integument only at the base. The ovules share many features with the genus Pachytesta but represent a new genus based on their unique exterior shape, integumentary morphology, and vascular system. In addition, these specimens represent the youngest known occurrence of trigonocarpalean ovules, thereby extending their biostratigraphic range. The presence of these plant remains in a regionally and globally correlatable marine assemblage aids correlation of continental strata with established, biostratigraphically time equivalent, marine strata.