Article: A new genus of early land plants with novel strobilar construction from the Lower Devonian Posongchong Formation, Yunnan Province, China
Li Cheng-Sen and Dianne Edwards
Adoketophyton subverticillatum (Li and Cai) comb. nov. is described from the Siegenian of southern Yunnan, China. It consists of dichotomously branching axes, with terminal compact strobili in which lateral units are inserted oppositely and decussately so that they form four vertical rows. Each unit comprises a stalked, fan-shaped, bract-like appendage bearing an adaxial sporangium with dehiscence into two equal valves. Although such reproductive characteristics parallel those of lycophytes, the shape of bract and absence of microphylls indicate that this plant presents a new combination of characters, presumably within the tracheophytes. It is perhaps closest to the Barinophytales, another group of vascular plants of uncertain affinity. Anatomical information, particularly on the cauline xylem and on the vascularization of the bract (if any) is required before assignment to a higher taxon. These Lower Devonian assemblages from Yunnan include cosmopolitan genera such as Zosterophyllum and Drepanophycus, but they also contain a high proportion of endemic taxa many of which exhibit novel combinations of characters not yet known elsewhere. Their distinctive nature may thus be evidence for provincialism in early land vegetation.