Scientists say the fossil of a small reptile related to dinosaurs and pterosaurs suggests some of the largest animals to live on Earth may have had extremely small ancestors.
A newly described species from Madagascar named Kongonaphon kely – “tiny bug slayer” – would have stood just 10 centimetres tall when it was around some 237 million years ago, they say, and may help explain the origins of flight in pterosaurs.
The fossil was discovered in Mid-to-Upper Triassic rocks in the southwest of the island off Africa’s east coast.
“There’s a general perception of dinosaurs as being giants but this new animal is very close to the divergence of dinosaurs and pterosaurs and it’s shockingly small,” says Christian Kammerer, lead author of a paper in Proceedings of the National Academy of Sciences.
The project involved input from the American Museum of Natural History, Madagascar’s University of Antananarivo, the University of California Santa Barbara and the Field Museum, US.
“This fossil site… from a poorly known time interval globally has produced some amazing fossils, and this tiny specimen was jumbled in among the hundreds we’ve collected from the site over the years,” says John Flynn, who led the team that found it in 1998.
“It took some time before we could focus on these bones, but once we did, it was clear we had something unique and worth a closer look.”
Dinosaurs and pterosaurs belong to the group Ornithodira but their origins are poorly known, Kammerer says, because few specimens from near the root of this lineage have been found. Most that have, have been considered “isolated exceptions to the rule”.
Scientific thought has been that body size remained similar among the first archosaurs – the larger reptile group that includes birds, crocodilians, non-avian dinosaurs and pterosaurs – and the earliest ornithodirans, before increasing in the dinosaur lineage.
However, recent discoveries have provided a better understanding of the early evolution of ornithodirans. “Analysing changes in body size throughout archosaur evolution, we found compelling evidence that it decreased sharply early in the history of the dinosaur-pterosaur lineage,” Kammerer says.
This “miniaturisation” event indicates that the dinosaur and pterosaur lineages originated from extremely small ancestors yielding important implications for their paleobiology. For instance, wear on the teeth of Kongonaphon suggests it ate insects.
A shift to insectivory, which is associated with small body size, may have helped early ornithodirans survive by occupying a niche different from their mostly meat-eating contemporaneous relatives, the researchers say.
The work also suggests that fuzzy skin coverings ranging from simple filaments to feathers, known on both the dinosaur and pterosaur sides of the ornithodiran tree, may have originated for thermoregulation in this small-bodied common ancestor.
Heat retention in small bodies is difficult, and the mid-late Triassic was a time of climatic extremes, inferred to have sharp shifts in temperature between hot days and cold nights.
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