Scientists discover hidden bones in skin of Australian monitor lizards— What they reveal is surprising

Rosenberg goanna (Varanus rosenbergi WAM R95408) showing osteoderms and internal skeleton on its left side. (Image: Roy Ebel)

In the dusty heart of Australia, a secret lies beneath the skin of goannas. While they roam dry lands and desert plains, these monitor lizards carry something unusual inside them—tiny bones hidden beneath their scales.

A global team of researchers has now found bony plates called osteoderms in 29 species of Australo-Papuan goannas. These tiny armour-like bones were not known to exist in most of these reptiles before. The discovery was made using micro-CT scans on nearly 2,000 reptile samples from museum collections across the world.

Bones That Were Always There, But Never Noticed

The study, led by Roy Ebel from Museums Victoria Research Institute, shows a fivefold increase in goannas known to have osteoderms. Scientists long believed these features were rare among lizards. Until now, only a few species—like the Komodo dragon—were thought to have them.

The research, published in the Zoological Journal of the Linnean Society, shows that these bony structures are present in almost half of all known lizard species. That’s an 85 percent jump from earlier estimates.

Osteoderms are not new to science. They are common in crocodiles, armadillos and even ancient dinosaurs like the Stegosaurus. But their true role in reptiles is still being studied. Scientists believe these bones may help with heat control, movement and even calcium supply during egg laying.

Museums Hold the Clues to the Past

Many of the lizards scanned for this study had been stored in museums for over a century. Thanks to new scanning technology, researchers could peer inside the specimens without harming them.

Dr. Jane Melville, senior curator at Museums Victoria, said the discovery changes how we understand lizard evolution. She said osteoderms may have helped goannas survive Australia’s tough environments.

These tiny bones may have been vital as the lizards spread across deserts and woodlands. They might even explain why goannas have been so successful in such extreme settings.

This research adds a new layer to the story of Australia’s reptiles. It shows how ancient skin, structure and survival are still linked today. Hidden in plain sight, these bones tell a quiet but powerful tale.