A new early angiosperm leaf from the Anfiteatro de Ticó Formation (Aptian), Santa Cruz Province, Argentina

Abstract

A new record of angiosperm from Aptian deposits of the Anfiteatro de Ticó Formation (basal unit of the Baqueró Group), in its type locality, north-center of Santa Cruz province, Argentina is reported. This record integrates the fossiliferous level Williamsonia-Zamites that contains abundant remains of bennettite leaves and was deposited in floodplain facies. The fossil consists of a single leaf imprint, with entire margin and festooned brochidodromous venation of low rank. It has features that define, in part, the nymphaeaphyll morphological type. This type occurs among the most early assemblages having angiosperms (northeastern Brazil, Portugal, South Australia, eastern North America), and is part of a physiognomic-foliar pool associated to taxa considered to be basal within the group. This foliar morphotype, is found in some members of extant angiosperms of usually herbaceous habit, and perhaps, by analogy, this may have been the original habit of our fossil species. The mega floristic record of eocretaceous angiosperms from Southern Hemisphere is scarce. In spite of them, angiosperm foliar remains from other location (Bajo Tigre) of the Anfiteatro de Ticó Formation are known. They are different to this new record. This incipient diversity suggests an even (pre-Aptian) presence of the angiosperms in the region.