Equisitites

Equisetites is a genus of fossil plants allied with, if not identical to, modern Equisetum, which is the only extant genus of the ancient lineage Sphenopsida. This class-level group of lower vascular plants is characterized by whorled vegetative and reproductive appendages, distinctive nodal and internodal morphologies, and unique "sporangiophores", specialized reproductive organs of uncertain homology on which the sporangia are borne. Described, heretofore, from rocks ranging in age from Middle Permian through Pleistocene, Equisetites is primarily a genus of the post-Paleozoic. Fossils similar to isolated leaf sheaths of this genus have been found in a single deposit of Early Permian age from north-central Texas. Five specimens are known, each composed of up to 10 basally fused and apically free leaves (see figure) that are straight-sided but taper sharply to an acute tip. Leaves have a single midvein. Attribution to Equisetites must remain tentative in the absence of any other organs of the plant, including stems. However, it is common in some species of extant Equisetum for leaf sheaths to fall away from the main stem as they die and dry, so such isolation is not entirely unexpected.

DiMichele, W.A., Van Konijnenburg-Van Cittert, J.H.A., Looy, C.V. and Chaney, D.S. Equisetites from the Early Permian of North-Central Texas. In: Lucas, S.G., Zeigler, K.E. (eds.), New Mexico Museum of Natural History and Science Bulletin 30, 56-59.