ABSTRACT
Cuticles of Mariopteris occidentalis are described from the Desmoinesian (Middle Pennsylvanian) of Oklahoma (USA). This species, like other mariopteroids, had a vine- to liana-like growth habit and climbed with specialized climber hooks. However, M. occidentalis is different from other mariopteroids in having small recurved hooks on the abaxial surfaces of the pinna axes. The diagnosis for M. occidentalis White 1899 is emended based on additional macroscopical observations and data on the epidermal anatomy; a lectotype is designated. M. occidentalis is compared with Pseudomariopteris cordato-ovata from the Stephanian and Autunian of Europe and North America, a taxon which is considered very similar and may be related. Although the two taxa indeed display similarities, significant evidence for a closer relationship could not be found. Finally, some features, e.g. marginal water pits and the stomatal structure, are considered with regard to their palaeoautecological significance where they are interpreted as adaptations to special physiological requirements of a vine- to liana-like life form.
ABSTRACT
Modern cladistic analyses support earlier suggestions that the Hymenophyllaceae (the "filmy ferns") are basal filicaleans. However, the fossil record of the family is ambiguous. A new fossil fern, Hopetedia praetermissa gen. et sp. nov., from the Upper Triassic Pekin Formation of North Carolina (USA), is described and interpreted as the oldest unequivocal representative of the Hymenophyllaceae based primarily on general frond morphology, indirect evidence for a filmy (membranaceous) habit, and soral position and morphology. Particularly compelling as evidence for the hymenophyllaceous affinity of H. praetermissa is the funneliform structure of the indusium (involucre), which is similar to that found primarilly in the extant Trichomanes (sensu lato) clade. However, the receptacle in H. praetermissa is relatively short and, thus, more like most representatives of the Hymenophyllum (sensu lato) clade. The Triassic age of this fossil is consistent with the basal or near basal position of the Hymenophyllaceae in all recent phylogenetic analyses of the filicalean ferns. Hopetedia preatermissa is evaluated in relationship to several previous reports of fossil Hymenophyllaceae.
ABSTRACT
A new Triassic corystosperm is described from the Shackleton Glacier region of Antarctica. The compression fossils include cupulate organs (Umkomasia uniramia) and leaves (Dicroidium odontopteroides) attached to short shoot-bearing branches. The cupulate organs occur in groups near the apices of the short shoots, and each consists of a single axis with a pair of bracts and a subapical whorl of five to eight ovoid cupules. This unique architecture indicates that the cupules are individual megasporophylls rather than leaflets of a compound megasporophyll. A branch bearing an attached D. odontopteroides leaf provides the first unequivocal evidence that Umkomasia cupulate organs and Dicroidium leaves were produced by the same plants. Although this had previously been assumed based on organ associations, the new specimens are important in demonstrating that a single species of corystosperm produced the unique cupulate organs described here and the geographically and stratigraphically widespread and common D. odontopteroides leaf. Therefore, biostratigraphic, paleoecological, and phylogenetic studies that treat Dicroidium leaf morphospecies as proxies for biological species of entire plants should be reconsidered. Phylogenetic analysis suggests that the corystosperm cupule is an unlikely homologue for the angiosperm carpel or outer integument.
