Finding osteoderms in a fast-breeding, easily maintained animal like a mouse could help unlock how and why the forces of evolution have continually produced underskin bone armor, Dr. Maden said. Now that they have narrowed down a list of genes that might be responsible for this trait, they can try to produce osteoderms in lab studies.

“I want to work out what genes are responsible for making osteoderms and then make a lab mouse with armor plating,” Dr. Maden said.

The building blocks for osteoderms might be in the heads of vertebrates, Dr. Stanley said. The vertebrate skeleton is largely formed of cartilage that grows bonier over time — but the skull bones form through hardening collagen, which the team suggests might have been repurposed from the armored heads in early lineages of fish.

“If you can grow a skull, you have the genetic architecture to grow bones in your skin,” Dr. Stanley said. The trick will be to use genomics to figure out whether the mice’s tail osteoderms form like their skulls. “That would lend credence to the idea that osteoderms went from armor, to skulls, back to armor.”

It’s also possible that osteoderms, which are generally tucked discreetly under fur and skin, may be considerably more common in mammals than generally thought: Nobody has actively gone looking for them, Dr. Stanley said. It took exploratory science like the openVertebrate Project to find them, he noted. Dr. Stanley hopes data from the project will lead to similar discoveries.

“Building that kind of accessibility to museum samples and the digital data pulled from them will have benefits for all kinds of fields,” Dr. Stanley said. “After all, we didn’t know what we were about to find.”