Dinosaurs may have descended from four-inch-tall ancestors

A new study from the American Museum of Natural History suggests that some of the biggest animals that ever lived had ancestors that were tiny. Researchers have discovered an ancient relative of dinosaurs and pterosaurs that was only four inches tall.

The fossil reptile, Kongonaphon kely, existed around 237 million years ago. The new species is also referred to as the “tiny bug slayer” because it appears to have survived on a diet of insects.

“There’s a general perception of dinosaurs as being giants,” said study co-author Christian Kammerer. “But this new animal is very close to the divergence of dinosaurs and pterosaurs, and it’s shockingly small.”

Due to a lack of fossil evidence, the origins of Ornithodira groups such as dinosaurs and pterosaurs are not very well understood. The fossils of Kongonaphon were discovered in 1998 in Madagascar by a team of researchers led by paleontologist John Flynn.

“This fossil site in southwestern Madagascar 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,” said Flynn. 

“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. This is a great case for why field discoveries – combined with modern technology to analyze the fossils recovered – is still so important.”

Kammerer explained that Kongonaphon is not the first small animal known near the root of the Ornithodira family tree, but such specimens were previously considered “isolated exceptions to the rule.” It was assumed that body size remained similar among the first archosaurs and the earliest ornithodirans, before some creatures became gigantic.

“Recent discoveries like Kongonaphon have given us a much better understanding of the early evolution of ornithodirans. Analyzing changes in body size throughout archosaur evolution, we found compelling evidence that it decreased sharply early in the history of the dinosaur-pterosaur lineage,” said Kammerer.

The “miniaturization event” may have served as a survival strategy for early ornithodirans. For example, teeth marks found on Kongonaphon show that the tiny creature preyed on insects. This diet eliminated the need for the creatures to compete with their relatives for meat.

The research also suggests that feathers and other fuzzy skin coverings found on dinosaurs and pterosaurs may have originated to protect their small-bodied ancestors from the climate extremes of the mid-late Triassic period.

“Discovery of this tiny relative of dinosaurs and pterosaurs emphasizes the importance of Madagascar’s fossil record for improving knowledge of vertebrate history during times that are poorly known in other places,” said study co-author Professor Lovasoa Ranivoharimanana. 

“Over two decades, our collaborative Madagascar-U.S. teams have trained many Malagasy students in paleontological sciences, and discoveries like this helps people in Madagascar and around the world better appreciate the exceptional record of ancient life preserved in the rocks of our country.”

The study is published in the journal Proceedings of the National Academy of Sciences.

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By Chrissy Sexton, Earth.com Staff Writer