Menatanthus mosbruggeri gen. nov. et sp. nov. – A flower with in situ pollen tetrads from the Paleocene maar lake of Menat (Puy-de-Dôme, France)

The Paleocene Fossil-Lagerstatte Menat in France is well known for its wealth of outstandingly well preserved fossil insects and plants. Despite being known for more than a century, the palaeoflora, which is regarded as typical for the late Thanetian by some authors, has largely been neglected since the 1940s. New excavations and surveys yielded exceptionally well-preserved plant material, including a minute, heptamerous flower bearing in situ pollen tetrads, comparable to tetrads of the modern ericacean genus Kalmia L, in its anthers. The only known modern ericacean genus which is characterised by heptamerous flowers is Bejaria Mutis ex L., a basal relative of the tribe Phyllodoceae within Ericaceae, which also includes the genus Kalmia in a relatively basal position. However, heptamerous flowers also occur very rarely (mostly interpreted as teratologies) in a number of other modern Ericaceae, but also in various other modern angiosperm families. Due to the unique combination of a heptamerous flower with Kalmia-type pollen tetrads within the anthers, the new taxon Menatanthus mosbruggeri gen. nov. et sp. nov. is erected. The lack of morphological data from the flower itself and the fact that comparable pollen tetrads can be produced by a number of modern families, however, prevent an assignment of the new taxon to any known angiosperm family.