科研之友
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摘要
Historically collected specimens of the Pennsylvanian pteridosperm Eremopteris artemisiaefolia have been reinvestigated to provide detailed information on its morphology and cuticular anatomy and to enable some of the external features of the plant to be reconstructed. The stem bore a distal crown of helically arranged compound leaves that show evidence they were actively abscissed from the plant. The blade consists of a main rachis that is straight or curved and may be undivided or show a single overtopped or occasionally dichotomous division. Secondary foliar segments are once or twice divided, with ultimate segments consisting of an elongate lanceolate blade, sometimes with one or two pairs of suboppositely arranged basal lobes or subsegments. Dense parallel veins run along the ultimate segments and only rarely fork. Stomata occur on both surfaces of the blade but more densely on the abaxial surface; papillae surrounded the abaxial stomata but not the adaxial ones. Remains of platyspermic bicornute ovules with a commissural rib in the minor plane are repeatedly associated with the leaves; these conform to the fossil genus Cornucarpus. Ovule cuicles include an inner integumentary cuticle, a nucellar cuticle that is attached only to the base of the inner integumentary cuticle, and a seed megaspore membrane. The nucellar apex comprises a small pollen chamber and extended nucellar beak consistent with cardiocarpalean ovules. Ovate structures on the main rachis and proximal parts of the secondary rachises are consistent in size with the ovule chalaza and are interpreted as the place of ovule attachment. Inclusion of our reconstruction of E. artemisiaefolia in a cladistic analysis of lignophytes suggests that it represents a distinct clade within a paraphyletic complex of basal pteridosperms and that it diverges after hydrasperman and medullosalean taxa and before the Callistophytales. The family Cornucarpaceae is redefined for this clade.
- 出版日期2009-6
