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The second genus of the extinct dragonfly family Urolibellulidae from the Eocene Green River Formation (Odonata, Anisoptera: Cavilabiata)

If the oldest record of the anisopteran ‘libelluloid’ group Anauriculida Bechly, 1996 goes to the Cretaceous (Fleck et al., 1999; Kohli et al., 2016), its extant families are scarce or even absent before the Eocene. Nevertheless, the Anauriculida were already rather diverse during Eocene with a Libellulidae in the earliest Eocene (Fleck et al., 2000), and the extinct monotypic family Urolibellulidae in the middle Eocene Green River Formation (Zeiri et al., 2015). Crown Libellulidae become more and more frequent and diverse during Oligocene, and even dominate the dragonfly fauna in some outcrops (Céreste, Rott, Aix-en-Provence, Bes-Konak) (Nel & Paicheler, 1993). Thus any discovery in the Paleocene–Eocene of a new fossil related to these families is welcome. Here we describe a complete hindwing of this kind from the Green River Formation in Colorado.