Cretaceous Age Fossil Feathers Found in Alabama

More fossil feathers of Cretaceous Age have been found in the state of Alabama than in any other state. 14 fossil feathers, encased in shale, were found in a lens located in the Eutaw Formation, the site of an ancient shoreline. Shale is basically fossilized mud, and ocean currents rapidly buried the feathers in mud which eventually turned to shale. The fossilized feathers are impressions of the original objects. The Cretaceous Age lasted from 145 million years BP to 66 million years BP, and these feathers probably date to about 80 million years ago. Fossilized feathers have also been found in Kansas, New Jersey, New Mexico, and Alberta; but none of these states or provinces have yielded as many as Alabama.

Fossil feathers found in Alabama. The impressions were made in mud and later fossilized when the mud turned to shale. Photo from the below reference.

The feathers include 2 different sizes. Scientists believe the smaller ones come from extinct species of shorebirds. The larger feathers may be from the tails of either a species of hesperornthid or a dromaeosaur. Hesperornthids were an aquatic fish-eating dinosaur that occupied a niche similar to modern day penguins. They were related to the ancestors of birds, and they lived in lakes, rivers, and oceans. Dromaeosaurs include dozens of families of carnivorous dinosaurs ranging in size from 2 feet long to 20 feet long. Some species hunted in packs, though paleontologists are unsure whether they were organized hunters or disorganized mobs like modern Komodo dragons and crocodilians. Some species had a large retractable claw on their 2nd toe that could inflict devastating damage on their prey or each other. Carnivorous dinosaurs were cannibalistic, and the number of carnivorous predators in ratio to herbivorous prey was higher than in modern day ecosystems. For example today in a pristine environment there may be 1 large predator per 40 deer, but during the Cretaceous there may have been 1 predator per 5 large herbivores. Dromaeosaurids were related to the ancestors of birds, and some species may be directly ancestral to birds. Paleontologists don’t agree with each other about the exact evolutionary relationship between birds and dromaeosaurs. Nevertheless, I catalogued this blog entry under ornithology.

The larger feathers found in the Eutaw Formation may be from an extinct species of hesperornthid, an aquatic dinosaur. Image from Dinopedia.
Alternately, the larger feathers may be from a species of dromaeosaur. There were dozens of families of dromaeosaurs alive during the Cretaceous. Image from UCMP Berkeley.

Scientists looked at these fossil feathers under a microscope and found structures that look similar to the bacteria involved in feather decay. However, these structures also look like melanosomes responsible for the color in feathers. The feathers from the shorebirds were likely gray, brown, or black. Whether these structures are feather-consuming bacteria or melanosomes is yet another point of contention between paleontologists. Fossils are a vague clue compared to a live organism.

Reference:

Knight, T.; S. Bingham, R. Lewis, C. Saurda

“Feathers of the Ingersoll Shale, Eutaw Formation (Upper Cretaceous) Eastern Alabama: The Largest Collection of Feathers from the North American Mesozoic”

Palaios V. 28 N. 51 May/June 2011

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