Sprecher
Beschreibung
Leguminosae is a monophyletic family composed of ca. 19,000 species distributed worldwide and growing from deserts to wet tropical forests. The Leguminosae fossil record is relatively abundant and diverse, comprising leaflets, wood, fruits, flowers, and pollen. Nevertheless, this diversity – in particular when based on the leaf fossil record – should be interpreted with caution because distantly related extant Leguminosae species commonly show similar leaflet morphology resulting from convergent evolution. Here, we revise Oligocene leaflets from Southwest Europe (France and Spain) previously attributed to Mimosa and Mimosites and compare them with other Cenozoic European records to clarify their taxonomy. Several fossil-species were synonymized, and three new taxonomic combinations were established under the fossil-genus Parvileguminophyllum. Morphological comparison with extant legumes reveals affinities with Mimosa and Senegalia species thriving in seasonally dry tropical climates (Aw/As Köppen types). However, palaeoclimatic data from the localities in which the here studied Parvileguminophyllum species occurred indicate that the fossil-species grew in humid subtropical conditions (Cfa/Cwa). The results indicate that the Parvileguminophyllum fossil-species became extinct during the Miocene, a period marked by increasing global aridity. Our analyses suggest that cooler temperatures and more frequent frost events were the primary drivers of this extinction. This interpretation challenges the long-standing assumption that Paleogene leguminous fossil-species from South Europe reflected xeric environments and radiated during intervals of increasing aridity, a view that may stem from their morphological resemblance to extant taxa growing in arid environments.