Meet Junornis: the tiny Cretaceous bird which reveals the earliest form of bounding flight

Newly-discovered Junornis huoi was the oldest bird capable of bounding flight – and represents an exciting update to what we know about complex flight

A 126-million-year-old fossil has demonstrated that birds were capable of a special form of flight much earlier than previously thought. The newly named Junornis huoi (which means “beautiful wing”) is known from a single incredibly preserved specimen with a superb skeleton and extensive preservation of feathers, including the wings and two long tail feathers which were likely used for display.

The fossil comes from the famous “Jehol” beds of China, which have produced numerous birds, dinosaurs, and other animals including predatory mammals and tadpoles of salamanders. The exceptional preservation of soft tissues such as feathers, claws, muscles and even gills has added considerably to our understanding of the evolution of various groups. The beds extend across northern China and even into North Korea, but Junornis is from the far western extent of these, coming from Inner Mongolia.

Junornis was a small bird, around 25-30 cm in wingspan. The whole animal is so well preserved it was possible for researchers to get very accurate measurements of the feathers and to calculate the shape of the wings and the likely weight of the animal when alive. These features very strongly constrain how birds fly – the shape of the wing (basically its length vs average width) and weight control how well birds can turn, how quickly they can take off, and if they can exploit winds to soar, or hover and so on. The great differences between the wings of vultures, albatross and wrens or crows underpin the ecology and behaviour of these animals.

Junornis it was about the same size, weight and wingshape as modern skylarks and therefore would fly in a similar way.
Another view of the fossil. Junornis it was about the same size, weight and wingshape as modern skylarks and therefore would fly in a similar way. Photograph: Liu et al.

In the case of Junornis it was about the same size, weight and wingshape as modern skylarks and therefore would fly in a similar way. Birds with this combination of wings and weight are animals that engage in “intermittent” or “bounding” flight where a burst of rapid flapping is followed by a phase where the wings are tucked against the body and the animal turns into a little missile before flapping again. Anyone who has seen a woodpecker or sparrow darting between gaps has probably seen this kind of locomotion and it’s really quite common among small birds. If you have the right wingshape it is actually a quite efficient way of getting around, and these wings also mean that Junornis would have been capable of taking off quickly, and would be highly manoeuvrable and able to perform tight turns in the air.

Slow motion video of a zebra finch engaging in bounding flight.

Few fossil birds are well preserved enough to demonstrate their likely flight patterns and the discovery of Junornis shows that birds were likely engaging in such behaviours considerably earlier than previously though. Dr Mike Habib of the University of Southern California who was involved in the research said “we did not expect to find evidence of such a complex flight pattern in such an early bird, so this find is very exciting.”

Junornis is a member of a group of birds called the Enantiornithes which lived in the Cretaceous Period and have been discovered on every continent except Antarctica. They went extinct with their non-avian dinosaur relatives at the end of the Cretaceous. The enantiornithines were rather diverse in form and size, so it is not clear if Junornis was typical or unusual but it does mean that this form of flight was one of a number being explored by early birds. As Dr Habib notes, “finding evidence for bounding flight in an early bird is exciting and updates our thinking about the origins of such sophisticated flight behaviours.” There is clearly still much more to come and in the future we are perhaps likely to find other birds who were capable of some unusual flight styles much earlier than thought.

References:

Liu D, Chiappe LM, Serrano F, Habib M, Zhang Y, Meng Q (2017) Flight aerodynamics in enantiornithines: Information from a new Chinese Early Cretaceous bird. PLoS ONE12(10): e0184637

Contributor

Dr Dave Hone

The GuardianTramp

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