Pseudofrenelopsis dinisii, a new species of the extinct conifer family Cheirolepidiaceae from the probable lower Hauterivian (Cretaceous) of western Portugal

Abstract

The Cheirolepidiaceae are an extinct family of conifers that was highly diverse during the Mesozoic, particularly at lower latitudes. Cheirolepidiaceous remains assigned to the genera Frenelopsis and Pseudofrenelopsis are very common in the Early Cretaceous floras of Portugal. A new species Pseudofrenelopsis dinisii is described from the Lower Cretaceous sediments (probably lower Hauterivian) of the Santa Susana Formation, at the Vale Cortiço site in the Lusitanian Basin of western Portugal. The new taxon is described based on morphology of the vegetative shoots and cuticular features. Pseudofrenelopsis dinisii consists of leafy shoots with spirally arranged leaves with an attenuate apex that enclose the stem, while leaves of the Brachyphyllum type occur on terminal shoots. The leaf margins bear well-developed trichomes; the stomatal apparatus is deeply sunken and strengthened by papillae, and the cuticle is moderately thick. Like other frenelopsids, P. dinisii displays these and other typically xeromorphic features, but although many other frenelopsids are associated with independent evidence for arid or saline conditions, the palynoflora from the bed with P. dinisii is rich in spores and shows no evidence of marine influence. Pseudofrenelopsis dinisii may represent the non-arid and non-saline end of the wide spectrum of environments occupied by Cheirolepidiaceae; its xeromorphic features may be adaptations to occasional periods of strong water stress. Comparisons with other sequences suggest a trend in the ecological preferences of both Pseudofrenelopsis and Frenelopsis from alluvial and upper deltaic environments before the Albian to saline coastal environments in the Albian and Cenomanian.