Foliar cuticle of Ruflorinia orlandoi nov. sp. (Pteridospermophyta) from the Lower Cretaceous of Patagonia

Abstract

Foliar cuticle of a new species of Ruflorinia, R. orlandoi Carrizo et Del Fueyo, from the Lower Cretaceous Springhill Formation in Santa Cruz province, Argentina, is herein described with light and electronic (scanning and transmission) microscopy. The fronds of R. orlandoi nov. sp. are bipinnate and imparipinnate with a conspicuous main rachis bearing alternate to sub-opposite pinnae. Cuticular striations and hairs are present in both epidermises whereas stomata are only on the abaxial cuticle. Stomata have several papillate subsidiary cells and the guard cells are sunken. Ultrastructurally the adaxial and abaxial cuticles are composed of three and two cuticular layers, respectively. The cuticular characters here described are interpreted as a response to a possible adaptation to a wet climate as well as to the fluctuating environment produced by the gradual transition from fluvial to an estuarine and marine setting that characterizes the Springhill Formation. The discovery of this new species allows expanding the previous knowledge of the paleofloristic composition of the Springhill Formation with the addition of the first pteridospermous megafossil described for this formation. Moreover, the record of Ruflorinia orlandoi nov. sp. in the Springhill Formation highlights the importance of the Caytoniales during the Cretaceous in Patagonia.