Changxingia longifolia gen. et sp. nov., a new lycopsid from the Late Devonian of Zhejiang Province, South China

• Changxingia is the fourth monosporangiate-strobilus lycopsid from the Devonian.
• It contributes to know the reproductive biology of early heterosporous lycopsids.
• Diversifications of megaspore dispersal mechanisms occurred in the Late Devonian.
• Megasporophyll–sporangium complexes act as megaspore dispersal units.

Changxingia longifolia gen. et sp. nov. is described from the Upper Devonian Wutong Formation, Changxing County, northern Zhejiang Province, China. It possesses dichotomous axes, linear and smooth sterile leaves, rhomboidal leaf cushions with ligule pits and oval–oblanceolate leaf scars, and terminal sterile shoots or probable megasporangiate strobili. Leaves may have been persistent or not. Leaf cushions or bases bearing a ridge are helically arranged in parastichies on wide axes. Smooth megasporophylls with vertically expanded base borne in helices include a pedicel, a heel and an upturned linear lamina. The pedicel consists of a distinct keel and horizontal alations and the lamina has the distal part reflexed abaxially. A single ellipsoidal and sessile megasporangium occurs on the adaxial side of the pedicel and produces Lagenicula-type megaspores with delicate spines. Changxingia may be assigned to the Dichostrobiles of the Isoёtales sensu lato and is compared with related taxa of the Late Palaeozoic. Fertile units (megasporophyll–sporangium complexes) are interpreted to have functioned as spore dispersal units. Heterosporous lycopsids with monosporangiate strobili are scarce in the Devonian, and Changxingia thus contributes to understanding of their early evolutionary history and megaspore dispersal mechanisms.