A new cycad stem from the Cretaceous in Argentina and its phylogenetic relationships with other Cycadales

MARTÍNEZ, L.C.A.; ARTABE, A.E.; BODNAE, J.

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012 vol. 170 p. 436 - 458

0024-4074

The cycads are an old group of seed plants. Fossil stems assigned to theCycadales are rare, however, few descriptions of them are known. In this paper, a newgenus of cycad stem, called Wintucycas, is described on the basis of specimens found inthe Allen Formation (Upper Cretaceous) at the Salitral Ojo de Agua locality, Río NegroProvince, Argentina. The most remarkable features of Wintucyas are: a columnar stemwith persistent leaf bases, abscence of cataphylls, a wide pith, medullary vascularbundles, mucilage canals and idioblasts; a polyxylic vascular cylinder, inverted xylem,and manoxylic wood. The new genus was included in a phylogenetic analysis and itsrelationships with fossil and extant genera of the Cycadales were examined. In theresulting phylogenetic hypothesis, Wintucycas is circumscribed to theEncephalartoideae subfamily, which supports the existence of a greater diversity of thisgroup in South America during the Cretaceous.