Beneath the scales of Australia’s iconic monitor lizards (commonly known as goannas), scientists have discovered an unexpected secret: a hidden layer of bony skin structures known as osteoderms. These structures, which have been long overlooked, may hold the key to understanding how these ancient reptiles not only survived but thrived in one of the world’s harshest environments.
The findings, published on July 21 in the prestigious Zoological Journal of the Linnean Society, mark the first large-scale global study of osteoderms in lizards and snakes. The international collaboration brought together researchers from Australia, Europe and the United States, who used cutting-edge micro-CT scanning to examine nearly 2,000 reptile specimens from major museum collections including those held at Museums Victoria’s Research Institute.
‘We were astonished to find osteoderms in 29 Australo-Papuan monitor lizard species that had never been documented before,’ said Roy Ebel, lead author and researcher at Museums Victoria Research Institute and the Australian National University. ‘It’s a fivefold increase in known cases among goannas.’
Osteoderms are most commonly known from crocodiles, armadillos, and even some dinosaurs like Stegosaurus. But their function has remained something of an evolutionary mystery. While they may provide protection, scientists now suspect they may also support heat regulation, mobility and calcium storage during reproduction.
This new research reveals that osteoderms are far more widespread in lizards than previously thought, occurring in nearly half of all lizard species worldwide – an 85% increase on earlier estimates.
At the heart of this discovery lies the power of museum collections. Scientific institutions like Museums Victoria Research Institute play a critical role in preserving biodiversity through time, enabling researchers to study species long after they were collected. Many of the specimens used in this study were decades, and in some cases over 120 years old, but advances in imaging technology enabled scientists to uncover new insights without harming the original material. These collections are not just archives, they’re active tools for scientific discovery.
‘What’s so exciting about this finding is that it reshapes what we thought we knew about reptile evolution,’ said Dr Jane Melville, Museums Victoria Research Institute Senior Curator of Terrestrial Vertebrates. ‘It suggests that these skin bones may have evolved in response to environmental pressures as lizards adapted to Australia’s challenging landscapes.’
Until now, the presence of osteoderms in monitor lizards was considered rare and mostly confined to the famed Komodo dragon. But the discovery of their widespread presence across Australo-Papuan goannas opens up new questions about how these lizards adapted, survived and diversified across the continent.
This landmark study not only tells a new chapter in the story of Australia’s goannas, it provides a powerful new dataset for exploring how skin, structure, and survival have intertwined across millions of years of evolution.