A three dimensional fossilised bird, representing the most complete avian specimen to-date from the Early Cretaceous of Gondwana (Northeast Brazil), is described online in Nature Communications. Roughly the size of a hummingbird, this fossil is the first of its kind to be found in South America.
Most feathered bird fossils from the Cretaceous have been recovered from Northeast China and these fossils comprise the majority of what we know about the early evolution of bird feathers. Ribbon-like feathers, which do not exist in living birds, have previously all been recovered from 2D slabs so little was known about their 3D shape.
Now Ismar Carvalho and colleagues describe a 3D bird fossil from Brazil with ribbon-like tail feathers, providing an unprecedented look at their structure and function. The feathers have an elliptical shaft and show a row of spots, which the authors interpret as the remnants of an ornamental colour pattern. The authors suggest that these tail feathers may be associated with sexual display, species recognition or visual communication, and not balance or flight, as this 3D fossil indicates that the tail feathers are not aerodynamically optimised. Documentation of ribbon-like tail feathers in South American bird ancestors broadens the distribution of ancient birds with this feather type, up to now only reported from China. Evidence from the bone development of the fossil also indicates that the bird is likely a juvenile.