Onychonycteris finneyi

Overview

Onychonycteris finneyi is an early bat with claws on every forelimb digit. It had short, broad wings and relatively long hindlimbs. This fossil raises questions about the order in which bats began flying and navigating by sound.^[1][2]

Key facts

Were flight and echolocation linked from the beginning? A 2008 study explained that the wing skeleton supports powered flight, while the ear's form suggests the possibility that echolocation was absent. The discovery allowed comparisons of the order in which the two abilities evolved.^[1]

Time and place

It is known from the Early Eocene of present-day Wyoming in the United States, about 52 million years ago. The fossils are studied as material from the Green River Formation. They offer a view of an ancient North American ecosystem inhabited by early bats.^[2][1]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

It had short, broad wings, short forearms and relatively long hindlimbs. Claws are known on every forelimb digit. A 2024 study reconstructed and compared wingspans of about 28–32 cm for two specimens.^[1][2][3]

Habitat and reproduction

The forelimbs formed wings while retaining claws on their digits. Researchers consider this limb arrangement together with the long hindlimbs to explore the relationship between flying and climbing. Ear shape offers another clue to how the animal used its body.^[1]

Fossil discovery

A 2008 paper introduced this Early Eocene bat from Wyoming and discussed the evolution of flight and ears. In 2024, reconstructed wings from the specimens were used in modelling ancient atmospheres and flight. The same fossil broadens questions from anatomy to physical function.^[1][3]

References

1. Simmons et al. (2008) — Early bats from Wyoming and the evolution of flight
2. Royal Ontario Museum — A new fossil in bat evolution
3. Palaeoatmosphere facilitates a gliding transition to powered flight in the Eocene bat, Onychonycteris finneyi
4. National Park Service — Exhibits and ecology of Fossil Lake
5. Royal Ontario Museum — A new fossil in bat evolution
6. Simmons et al. (2008) — Early bats from Wyoming and the evolution of flight
7. National Park Service — Fossil fishes of Fossil Butte

Research questions

What kinds of flight might short, broad wings have allowed? Researchers reconstruct the wings and compare limb proportions and ear structure together. Fossil observation and model calculations both help explore the lives of early bats.^[1][3]

Observation

Examine the elongated digits forming the wings and the claws at their tips together. Move your gaze from the forelimbs to the relatively long hindlimbs and tail membrane to see this early bat's different body configuration.^[1][2]