The Early Cretaceous Aroid, Spixiarum kipea gen. et sp nov., and implications on early dispersal and ecology of basal monocots

Morphology and anatomy of a fossil monocotyledon from the late Early Cretaceous and extant monocots are compared. Anatomy was examined based on publications, while leaf morphology, especially the venation, required new observations on fresh and herbarium material. Spixiarum kipea gen. et sp. nov. belongs most likely to Araceae, and may be sister to Orontioideae or is even part of this tribe. Consequently, proto-Araceae were most likely present during the Early Cretaceous in South America. The occurrence of Spixiarum in South America indicates a north Gondwana origin for Orontioideae and and thus may indicate a Gondwanan origin for proto-Araceae. Sedimentological and taphonomic context indicate that Spixiarum had probably a helophytic ecology similar to living Orontioideae and formed possibly the aquatic vegetation of the Crato Lake in association with the Nymphaeales Pluricarpellatia peltata and Jaguariba wiersemana. Early Cretaceous monocotyledon remains have been rarely recorded. It is debatable if their scarceness is a sign of low diversity or may be due to taphonomic/ecologic reasons.