Diaphorodendron, gen. nov., a Segregate from Lepidodendron (Pennsylvanian Age)

Abstract

Diaphorodendron is described as a new genus on the basis of anatomically preserved specimens previously included in Lepidodendron. Species include D. vasculare (type species), D. scleroticum, D. dicentricum, and D. phillipsii. Circumscription of this new genus leaves Lepidodendron as a monophyletic, morphologically cohesive taxon. Traditionally Lepidodendron has been recog- nized by its higher-than-wide leaf cushions, a character that appears to be the ancestral (plesio- morphic) state in the Lepidodendrales. The consequence of relying on this single trait has been inclusion of forms distinct in most aspects of basic morphology within Lepidodendron, masking rather extensive diversification in the Lepidodendrales. While sharing basic leaf-cushion shape, Diaphorodendron and Lepidodendron differ in many anatomical features and details of leaf-cushion morphology (especially relative thickness of leaf cushions and presence or absence of infrafoliar parichnos). By correlating anatomy and leaf-cushion morphology, characteristics can be recognized by which Diaphorodendron and Lepidodendron can be distinguished in compression preservation. The purpose of this report is to establish a new generic name for a distinctive, structural- ly-preserved group of Pennsylvanian-age lep- idodendrid lycopods previously included in the genus Lepidodendron Sternberg. The species that form the nucleus of this segregate genus are Lepidodendron vasculare Binney, L. scleroticum Pannell, L. phillipsii DiMichele, and L. dicentri- cum Felix (=L. schizostelicum Arnold) (see