Demersatheca Li et Edwards, gen. nov., a new genus of early land plants from the Lower Devonian, Yunnan Province, China

Abstract

Specimens from the Lower Devonian (possibly Pragian) Posongchong Formation of Wenshan, southeastern Yunnan Province, China, originally described as Zosterophyllum contiguum Li et Cai are reinterpreted and placed in the new combination Demersatheca contigua Li et Edwards, comb. nov. They consist of strobili in which sporangia, inserted decussately, form four vertical rows. The sporangia themselves have two valves, splitting around the convex margin, and are sunk into the strobilar axis such that only the abaxial valves, circular to elliptical in outline, are visible. Their contours are continuous with the surface of the strobilus producing a cylindrical structure. The strobili morphologically most closely resemble those of Zosterophyllum, but more detailed comparison is impossible because of the absence of anatomical information on the Chinese specimens.