Dinosaur Dandies

Movies portray dinosaurs as gray monsters covered in scales, but scientists have long known that, in reality, many had bold patterns and bright, flashy feathers.

In contrast, the mammals that coexisted with them all had dark brown or gray fur, a color that could have played a role in their survival, according to a new study.

“Mammals were living in the shadow of the dinosaurs, quite literally,” said Jasmina Wiemann, a molecular paleobiologist at Johns Hopkins University who was not involved in the study. They probably lived as nocturnal beings to avoid the giant dinosaurs active during the day, she added.

To study the color of mammals from the Mesozoic era – also known as the Age of Dinosaurs – and which lasted from 250 to 66 million years ago, scientists analyzed fossils that preserve melanosomes, “the intracellular structures in living animals’ skin, feathers, and fur that contain the pigment melanin,” explained Science Magazine.

Searching for color in the fossil record can explain how ancient creatures camouflaged themselves, competed for social status, or sent cues to potential mates.

Researchers created a database of the fur color and melanosomes of 116 modern mammals such as monkeys, bats, and cats.

They then developed a model that predicted fur color from the shape of a melanosome and found a recurring correspondence between one melanosome’s shape and one fur color across all species. Red and orange fur had spherical melanosomes, while dark fur had more elongated melanosomes.

Researchers then studied the fossil of a newly discovered ancient mammal that lived about 160 million years ago in what is now northeastern China. The fossil showed hair impressions all around its body, even between limbs, indicating the mammal had fur-covered membranes, like a modern flying squirrel.

This medium-sized creature, weighing about as much as a billiard ball, was interpreted as a glider. Researchers named it Arboroharamiya fuscus – fuscus meaning “dark” or “dusky” in Latin.

They then looked at the melanosomes from A. fuscus and five other mammal fossils under an electron microscope and put the measurements in their model made of living animals’ melanosomes. The fossil mammals’ melanosomes looked oval-shaped, so their model predicted that all early mammals likely had dark brown fur.

Through fluorescence imaging, the study found that fossils had high concentrations of copper – associated with the melanin type that produces black and brown fur – and lacked zinc, which is associated with the melanin responsible for lighter colors of fur such as beige, yellow, and red.

Researchers also think that dark fur helped them regulate their body temperature, as dark colors absorb more light and retain heat to stay warm during the night.

“Once the dinosaurs were gone, then (mammals) were free to take on numerous colors,” said lead study author Matthew Shawkey.