Skin bones are more common in lizards than we thought
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Skin bones are more common in lizards than we thought
Osteoderms are bony deposits embedded in the skin. During the ‘Age of Dinosaurs’ they gave rise to the plate- and spine-shaped elements of the iconic armoured ankylosaurs and stegosaurs. Now, the first large-scale global study of squamate osteoderms has revealed they also lurk beneath the scales of Australia’s iconic monitor lizards – also known as goannas. It suggests that these skin bones may have evolved in response to environmental pressures as lizards adapted to Australia’s challenging landscapes. Researchers say their new data lays important groundwork for future large- scale and systematic approaches to studying osteoderm function, which may shed light on the enigmatic evolutionary past of these structures.
Osteoderms are bony deposits embedded in the skin. During the “Age of Dinosaurs”, they gave rise to the plate- and spine-shaped elements of the iconic armoured ankylosaurs and stegosaurs.
Today, osteoderms are still found widely, albeit inconsistently, in limbed animals (tetrapods) including armadillos, turtles, crocodilians and some amphibians.
But modern squamate reptiles – lizards and snakes – boast the biggest diversity in osteoderm shape, distribution and expression.
Now, the first large-scale global study of squamate osteoderms has revealed they also lurk beneath the scales of Australia’s iconic monitor lizards – also known as goannas.
“We were astonished to find osteoderms in 29 Australo-Papuan monitor lizard species that had never been documented before,” says Roy Ebel, a researcher at the Australian National University and the Museums Victoria Research Institute.
“It’s a fivefold increase in known cases among goannas.”
Examples of newly discovered osteoderms (magenta) in Australo-Papuan monitor lizards. Credit: Roy Ebel
Ebel and collaborators from Australia, Europe and the US have now compile the first comprehensive catalogue of osteoderms in squamate reptiles.
They collated more than 580 mentions of osteoderms in the existing literature and used micro-computed tomography (micro-CT) to examine more than 1,300 reptile specimens in major museum collections around the world.
The findings revealed that osteoderms can be found in nearly half of all lizards (46%) and are significantly more common than previous research had suggested.
“What’s so exciting about this finding is that it reshapes what we thought we knew about reptile evolution,’ adds Dr Jane Melville, senior curator of terrestrial vertebrates at Museums Victoria Research Institute.
“It suggests that these skin bones may have evolved in response to environmental pressures as lizards adapted to Australia’s challenging landscapes.”
Osteoderms (cyan) in tokay gecko (Gekko gecko). Credit: Roy Ebel
Scientists hypothesise that osteoderms provide a variety of functions, including protection, heat regulation, mobility and calcium storage during reproduction. But many of these ideas have not been studied systematically.
The researchers say their new data lays important groundwork for future large-scale and systematic approaches to studying osteoderm function, which may shed light on the enigmatic evolutionary past of these structures.
“Specifically, this concerns the possibility of their repeated acquisition throughout the squamate tree of life and the underlying selective pressures that could have led to this,” they write.
“A better understanding of these aspects might inspire biomimetics and provide new insight into evolutionary trajectories and constraints that shaped present-day biodiversity.”
The research has been published in the Zoological Journal of the Linnean Society.
Source: https://cosmosmagazine.com/nature/animals/osteoderm-skin-bones-lizards/