Conostoma williamsoniin. sp., a lagenostomalean ovule from the Pennsylvanian of the Illinois Basin

摘要

Ellipsoid lagenostomalean ovules previously regarded asConostoma oblongumare recognized as a distinct species based on shape, number of vascular bundles, and histological features of the integument.Conostoma williamsoniin. sp. is shorter and broader thanC.oblongumand possesses a larger number (eight or nine) of vascular bundles. Features of the integument are similar to those ofC.oblongumandC.chappellicumand include a smooth outer margin and a two-zoned sclerotesta.Conostoma williamsoniiincreases our understanding of the diversity of lagenostomalean ovules during the Middle Pennsylvanian and calls to question the occurrence ofC.oblongumin currently known North American coal-ball floras.