A new transitional "libelluloid" family of odonates with Mesozoic affinities in the Eocene Green River Formation of Utah, USA

The new "libelluloid" family Cordulibellulidae is described to accommodate a new genus and species Cordulibellula inopinata from the Eocene Green River Formation, Utah, USA. Even if its affinities remain somewhat uncertain because of the lack of information on structures others than those of the hind wing, ts putative closest relatives are known from the Late Jurassic and Early Cretaceous. Therefore, this new fossil is interpreted as a "relict" taxon surviving until the Paleogene. This new addition to the odonatan paleoentomofauna of the Green River Formation confirms the high diversity of this clade during the Paleogene and in this formation. Key words: Insecta, Odonatoptera, Anisoptera, K/Pg boundary crisis, paleodiversity, Eocene, USA.