Ancient Canadian tree amber preserved a history of feather evolution

16 Sep 2011

A treasure trove of fossilised prehistoric feathers -- preserved in amber tree resin and unearthed in western Canada -- has revealed a history of feather evolution from insulating dinosaur fuzz to barbed bird-like wings.

University of Alberta paleontology student Ryan McKellar took his microscope to nearly 4,000 thumbnail-sized scraps of amber.

They had been added to collections at the Royal Tyrrell Museum and private collection in Medicine Hat over the last decade. The three-week task left McKellar and colleagues with 11 examples of 80-million-year-old protofeathers that visibly chart the evolution of plumage, including increased complexity and different colours, throughout the Late Cretaceous era of dinosaurs.

Some amber blobs hold primitive single-filament protofeathers that are probably best described as "fuzz". Paleontologists believe that this insulating fluff belonged to non-flying dinosaurs like the tyrannosaurids. At the other end of the spectrum, the amber artifacts show how the filaments eventually coalesced to form central branches, and velcro-like barbs hook onto each other to create large surface areas for a sturdy flight surface. They're dead ringers for modern day bird feathers.

Other samples are adapted to better absorb water, like modern-day waterfowl. These birds use water-soaked feathers to counteract their buoyancy when they dive beneath the surface to catch prey.

Amber is essentially sticky tree resin that can encapsulate insects, feathers and other small objects, before hardening over and turning into a tough, translucent orange case. It's useful to paleontologists because it can fill in gaps left by the fossil record, including pigment. "I would describe the colours as typically ranging from brown to black," said McKellar. "The preservation of microscopic detail and pigmentation has provided a unique snapshot of feathers and their uses in the late Cretaceous forests of [Canada]."