Article: Fossil down feather from the Lower Cretaceous of Brazil
An Early Cretaceous (Aptian) fossil feather has been discovered in the Araripe Basin, northeast Brazil. Its features, including an overall fluffy aspect, indicate that it is a definitive down feather. This new material provides empirical evidence that birds had already developed an effective thermoregulatory insulation cover, with down feathers, by the Early Cretaceous. Furthermore, in the absence of skeletal remains, the fossil feathers are the only reliable evidence of Mesozoic birds in Brazil.