The Anatomy of Rotoxylon dawsonii comb. nov. (Cladoxylon dawsonii) from the Upper Devonian of New York State

Abstract

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Denglongia hubeiensis gen. et sp. nov., a New Plant Attributed to Cladoxylopsida from the Upper Devonian (Frasnian) of South China

“…Moniliformopses, the sphenopsid-fern clade, is characterized by the presence of ''peripheral permanent protoxylem,'' and Radiatopses is united in part by the presence of ''radiate protoxylem'' (Beck and Stein 1993). The Iridopteridales and Cladoxylopsida are two basal groups of Moniliformopses attracting much more recent attention (Berry and Stein 2000;Cordi and Stein 2005;MeyerBerthaud et al 2007;Stein et al 2007;Wang 2007;Wang and Lin 2007;Wang 2008) and are significant for investigations of the origin, early diversification, and evolution of ferns or sphenopsids (Stewart and Rothwell 1993;Taylor and Taylor 1993).…”

“…The Iridopteridales are characterized by primary-xylem ribs connected centrally (protostele), peripheral permanent protoxylem strands, iterative branch system, and the presence of both branches and ultimate appendages in whorls (Berry and Stein 2000). Other potential synapormorphies include the asymmetric pattern of vascular trace departure, placement of traces in regular offset orthostichies, and large metaxylem tracheids located along the midplane of the primary-xylem ribs (Cordi and Stein 2005). Iridopteridales so far include four genera known anatomically (Arachnoxylon Read, Asteropteris Dawson, Iridopteris Arnold, and Rotoxylon Cordi and Stein), the genus Anapaulia Berry and Edwards known only in morphology, and two genera known both anatomically and morphologically (Ibyka Skog and Banks, Compsocradus Berry and Stein;Stein 1981Stein , 1982Berry and Stein 2000).…”

“…Iridopteridales so far include four genera known anatomically (Arachnoxylon Read, Asteropteris Dawson, Iridopteris Arnold, and Rotoxylon Cordi and Stein), the genus Anapaulia Berry and Edwards known only in morphology, and two genera known both anatomically and morphologically (Ibyka Skog and Banks, Compsocradus Berry and Stein;Stein 1981Stein , 1982Berry and Stein 2000). Metacladophyton Wang and Geng was considered an iridopteridalean by Berry and Stein (2000) and Wang and Lin (2007) but was assigned to the Pseudosporochnales by Cordi and Stein (2005). The ordinal level was left incertae sedis within the Cladoxylopsida by Wang and Geng (1997) and Xue and Hao (2007a).…”

“…Pseudosporochnus, Wattieza, Calamophyton, and Lorophyton constitute the order Pseudosporochnales (Leclercq and Banks 1962;Schweitzer 1973;Fairon-Demaret and Li 1993;Berry 2000), which are characterized by a digitate branching pattern, irregularly inserted lateral branching systems, and dissection of primary xylem (Leclercq and Banks 1962;Schweitzer 1973;Stein and Hueber 1989;Fairon-Demaret and Li 1993;Berry 2000;Cordi and Stein 2005). The digitate branching pattern and irregular insertion of lateral branches in the Pseudosporochnales differ from the whorled insertion of lateral branches in Denglongia.…”

“…On the basis of studies of Metacladophyton ziguinum, Wang and Lin (2007) suggested that the presence of a dissected stele might be another potential synapomorphy of the Cladoxylopsida sensu lato. Cordi and Stein (2005) followed the proposal of Berry and Stein (2000), adding some new anatomical characters (e.g., distribution of metaxylem tracheids and symmetry of vascular trace departure). Subsequently, Metacladophyton and Polypetalophyton were excluded by Xue and Hao (2007a) from the Iridopteridales or Psuedosporochnales on the basis of the presence of secondary xylem (or radially aligned metaxylem) and planation of ultimate appendages.…”