An international team of palaeontologists, including researchers from the University of New England (UNE), examined how scale size and shape changed from juveniles to adults in dinosaurs and modern reptiles such as Australian crocodiles, lizards and snakes. Their findings, published this week in the Journal of Anatomy, show that most scales maintain the same shape and relative size into adulthood, indicating that they continue to serve a protective role rather than being used for visual signals like courtship displays.
The study also examined the enlarged ‘feature scales’ of the horned dinosaur Chasmosaurus, which stand out from the surrounding smaller scales. Despite their prominence, these feature scales do not significantly increase in size as the animal matures.
Lead researcher and UNE PhD student Nathan Enriquez said the findings provide new insights into reptilian and dinosaurian skin development.
“We can now say with confidence that both dinosaurs and modern reptiles generally don’t change the shape or relative size of their scales as they grow. This tells us that once they emerge as babies, those scales remain largely the same throughout life,” Mr Enriquez said.
“This also suggests that different adult behaviours, such as mating interactions, probably don’t involve enlarged scales.”
However, in some cases, scale size does increase relative to body proportions.
“This happens when certain body regions change in size as the animal grows. For example, the scales on the tails of blue-tongued lizards become proportionately larger as their tails lengthen, and the scales on crocodile torsos widen as they become stockier,” Mr Enriquez said.
The study also raises new questions about the function of dinosaur feature scales, which were present across all major dinosaur groups but are rare among modern reptiles.
“We only had two fossil specimens of Chasmosaurus to study, so our conclusions are limited by sample size. But it was clear that in adult Chasmosaurus, these feature scales—some reaching nearly six centimetres in diameter—were too small and flat to be effective visual signals for an animal weighing three tonnes,” Mr Enriquez said.
“The young Chasmosaurus we studied had feature scales in the same areas of the pelvis, and they were roughly the same size in proportion to its body as those in adults. This suggests that the scales were not increasing in size as the animals matured and were unlikely to be used for courtship displays.”
So what purpose did these feature scales serve?
“We don’t know for sure. The evidence suggests they might just be trivial developmental features of skin growth, with no specific function. But then why do they appear in so many dinosaur groups yet are so rare in modern reptiles in comparison? That’s a question we still need to explore,” Mr Enriquez said.
Link to publication: https://onlinelibrary.wiley.com/doi/10.1111/joa.14247
Contact: Nathan J. Enriquez – nenrique@myune.edu.au; 0423925607
