Stellula meridionalis gen. et sp. nov., the oldest fossil flower from the Early Cretaceous of Argentina

Abstract

In this contribution, we describe a novel angiosperm floral axis, Stellula meridionalis gen. et sp. nov., consisting of a botryoid inflorescence, from the upper Aptian La Cantera Formation, San Luis Basin, central-western Argentina. Flowers are small, sessile and arranged distally on the inflorescences. Some specimens were found organically associated with leaves of “LC-Microphyll trifoliate”, a previously described and published fossil taxon. The leaves are nanophyllous, petiolate, with pinnately lobed or toothed margins, and the apex isn't preserved. Morphological features, such as pinnately lobed or toothed leaves with glandular margins, small trimerous actinomorphic flowers with floral organs in whorls, suggest an affinity with an early lineage of eudicots, likely within the Ranunculales. However, the absence of in situ pollen prevents definitive systematic assignment of the new taxon. Pollen analyses of dispersed taxa recovered from the same stratigraphic interval have revealed diverse angiosperm families, underscoring the complexity and increasing diversity of angiosperms in the mid-latitudes of South America during the Early Cretaceous.