Sometimes body armor just isn’t enough. A car-sized dinosaur covered in bony plates may have sported camo, too, a new study finds. That could mean this plant eater was a target for carnivores that relied more on sight than on smell to find their prey.
The dinosaur is named Borealopelta markmitchelli. It made headlines for being one of the best preserved armored dinosaurs ever unearthed. It had been entombed on its back some 110 million years ago. That was during the Cretaceous period. Soon, layers of fine marine sediments buried its bones. The conditions were ideal for turning this dino into a fossil, notes Caleb Brown. He is a paleontologist at the Royal Tyrrell Museum of Palaeontology in Drumheller, Canada.
He also was a coauthor of a new study that describes the dino’s looks. It appeared August 3 in Current Biology.
The fossil was found in western Canada in 2011. It was special because it showed large amounts of skin and soft tissue as well as the animal’s three-dimensional shape. “Most of the other armored dinosaurs are described based on the skeleton. In this case," Brown explains, "we can't see the skeleton because all the skin is still there."
That skin offered clues to what the dino looked like, including its coloring. “We’re just beginning to realize how important color is. And we’re beginning to have the methods to detect color” in fossils, says Martin Sander. He is a paleontologist at Bonn University in Germany. He was not part of this study.
Melanosomes are cellular structures that often preserve evidence of pigment — coloring — in fossils of animals. But despite ample tissue, the researchers didn’t find any of these. So Brown and his colleagues scouted for less direct evidence.
They looked for molecules that appear when pigments break down. The researchers found about a dozen types of these. They included large amounts of benzothiazole (BEN-zoh-THY-uh-zoal). This is a by-product of the reddish pigment pheomelanin (FEE-oh-MEL-uh-nin). Finding this chemical might mean the dinosaur had been reddish-brown.
Where those pigment by-products were found offers clues to the dinosaur’s appearance. This dino had a thin film of organic (carbon-based) chemicals on its back. They hint of there once having been a pigment there. That layer wasn’t on the belly. Such a pattern suggests countershading. This is when an animal is darker on its back than its underside, Brown explains. Countershading is a simple form of camouflage. It helps animals blend in with the ground when seen from above (or with the sky when seen from below).
This is not the first time countershading has been proposed for a dinosaur. But finding it on such a large plant eater is somewhat surprising, Brown says. Modern plant eaters that don similar camouflage tend to be smaller. And they’re usually at greater risk of becoming someone’s dinner. This dino’s skin patterning suggests that at least some top predators of its time might have relied more on eyesight than do today’s top carnivores. Modern meat eaters tend to favor smell when hunting, Brown says.
Some experts prefer stronger evidence for claims of coloration. Molecules like benzothiazole can come from melanin. However, they also can come from a number of other sources, such as oils, points out Johan Lindgren. He is a paleontologist at Lund University in Sweden. “What this paper nicely highlights is how little we actually know about the preservation of soft tissues in animal remains. There’s definitely something there. The question is, what are those [molecules], and where do they come from?”
Sander does accept the evidence for the reddish tint. However, it might not be the full story, he says. This dino could have displayed other colors that didn’t linger in the fossil record. But the countershading findings “point out the importance of vision” for dinosaurs, he says. In an era of sharp-eyed predators, camouflagewould have been an advantage for plant eaters — even ones built like tanks.
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biology The study of living things. The scientists who study them are known as biologists.
camouflage Hiding people or objects from an enemy by making them appear to be part of the natural surroundings. Animals can also use camouflage patterns on their skin, hide or fur to hide from predators.
carnivore An animal that either exclusively or primarily eats other animals.
coauthor One of a group (two or more people) who together had prepared a written work, such as a book, report or research paper. Not all coauthors may have contributed equally.
colleague Someone who works with another; a co-worker or team member.
countershading A pattern of protective colorings on some animals. Usually, parts of the animal that would normally fall in shadow are light and those facing the sky are dark. The reason: The animal will not stand out against the ground when viewed by predators from above, and may blend in with the sky if viewed from below.
Cretaceous A geologic time period that included the end of the Age of Dinosaurs. It ran from roughly 145.5 million years ago until 65.5 million years ago.
dinosaur A term that means terrible lizard. These ancient reptiles lived from about 250 million years ago to roughly 65 million years ago. All descended from egg-laying reptiles known as archosaurs. Their descendants eventually split into two lines. For many decades, they have been distinguished by their hips. The lizard-hipped line are believed to have led to the saurichians, such as two-footed theropods like T. rex and the lumbering four-footed Apatosaurus (once known as brontosaurus). A second line of so-called bird-hipped, or ornithischian dinosaurs, appears to have led to a widely differing group of animals that included the stegosaurs and duckbilled dinosaurs. But a new 2017 analysis now calls into question that characterization of relatedness based on hip shape.
fossil Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.”
marine Having to do with the ocean world or environment.
melanin A family of pigments found in all types of animals. They are responsible for the dark coloring in such things as feathers, hair, fur, skin and scales.
melanosome A structure within a cell that gives an organism color.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
organic (in chemistry) An adjective that indicates something is carbon-containing; a term that relates to the chemicals that make up living organisms.
paleontologist A scientist who specializes in studying fossils, the remains of ancient organisms.
pigment A material, like the natural colorings in skin, that alter the light reflected off of an object or transmitted through it. The overall color of a pigment typically depends on which wavelengths of visible light it absorbs and which ones it reflects. For example, a red pigment tends to reflect red wavelengths of light very well and typically absorbs other colors.
predator (adjective: predatory) A creature that preys on other animals for most or all of its food.
prey (n.) Animal species eaten by others. (v.) To attack and eat another species.
sediment Material (such as stones and sand) deposited by water, wind or glaciers.
tissue Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
Journal: C.M. Brown et al. An exceptionally preserved three-dimensional armored dinosaur reveals insights into coloration and Cretaceous predator-prey dynamics. Current Biology. Published online August 3, 2017. doi: 10.1016/j.cub.2017.06.071.