Onychonycteris

Two specimens of Onychonycteris were found in the Green River Formation in 2003, and placed in a new family when the discovery was published in Nature, in February 2008. Onychonycteris means "clawed bat", in reference to the fact that this animal had claws on all five of its digits, whereas modern bats only have claws on the thumb (in most species) or thumb and index finger (in pteropodids). The specific epithet is a tribute to the fossil prospector and preparator who discovered it, Bonnie Finney. ==Description==

Onychonycteris was unique among bats in that it had claws on all five fingers, as opposed to two or three in all other known species. Its unique limb proportions represent an intermediate between bats and non-flying mammals, with longer hind-limbs and proportionally shorter wings. and this aerofoil likely contributed to an undulating flight style that alternated fluttering and gliding. This flight style may represent both a functional and evolutionary intermediate between gliding and powered flight. ==Paleobiology==

Flight vs. echolocation Onychonycteris finneyi was the strongest evidence so far in the debate on whether bats developed echolocation before or after they evolved the ability to fly. O. finneyi was, based on biomechanical analysis of its fossils, capable of both gliding and powered flight in both the hyperdense atmosphere of the Early Eocene as modelled based on geochemical proxies and an atmosphere characteristic of the present-day. O. finneyi had well-developed wings, and could clearly fly, but lacked the enlarged cochlea of all extant echolocating bats, closely resembling the old world fruit bats which do not echolocate. However, an independent evaluation of the Onychonycteris reference fossil in 2010 provided some evidence for other bone structures indicative of laryngeal echolocation, raising the possibility that Onychonycteris finneyi possessed the ability to echolocate after all. and Icaronycteris gunnelli. ==References==