Tiny Ancestor of Dinosaurs and Pterosaurs Stood Just 4 Inches Tall

Researchers have described a new reptile species that lived 237 million years ago during the Triassic period in what is now Madagascar. The finding suggests that dinosaurs and pterosaurs, a group of ancient flying reptiles, may have originated from surprisingly tiny ancestors.

A team of scientists has described the species, dubbed Kongonaphon kely—meaning "tiny bug slayer"—in a study published in the journal Proceedings of the National Academy of Sciences.

The reptile, which would have measured only around four inches in height, is an early member of the animal group Ornithodira to which both dinosaurs and pterosaurs—among the largest ever land-dwelling and flying animals—belong.

"There's a general perception of dinosaurs as being giants," Christian Kammerer, a paleontologist at the North Carolina Museum of Natural Sciences and author of the study, said in a statement. "But this new animal is very close to the divergence of dinosaurs and pterosaurs, and it's shockingly small."

The origins of Ornithodira are poorly understood because researchers have discovered very few specimens representing early members of the group. Thus, the discovery of Kongonaphon kely could have important implications for our understanding of pterosaur and dinosaur evolution.

Researchers discovered the fossilized bones of the K. kely specimen in Madagascar in 1998. However, the authors of the latest study did not begin investigating the bones straight away.

"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," John Flynn, another author of the study from the American Museum of Natural History, said in the statement.

While the skeleton was incomplete, the authors were able to estimate Kongonaphon kely's size based on related animals, while also suggesting that it would have been a light-bodied, long-legged predator.

Furthermore, the shape of the teeth and microscopic analysis of wear patterns on them indicated that the reptile fed primarily on small invertebrates like insects.

While researchers have previously found other small animals that were early members of Ornithodira, these were often considered isolated exceptions in a wider group of reptiles known as archosaurs. Most scientists have thought that the earliest members of this group, which includes dinosaurs, pterosaurs ornithodirans, were animals whose body size remained relatively similar, before increasingly larger dinosaurs and pterosaurs appeared.

Kongonaphon kely
Artist's illustration of Kongonaphon kely in what would have been its natural environment. Alex Boersma

However, the latest study—along with other findings—supports the idea that the early members of the dinosaur-pterosaur lineage went through a period of miniaturization.

"This discovery is significant because it represents a very rarely-observed size class in this group of reptiles. Dinosaurs are generally large-bodied animals, and their evolution is characterized by multiple independent trends towards gigantism. Pterosaurs were smaller overall—as it is difficult to be able to fly at large sizes—but also show trends towards gigantism," Kammerer told Newsweek.

"Given how pervasive the trend towards larger body sizes is in these groups, it is interesting that we found their common ancestors would have been remarkably small. Kongonaphon is an exceptionally tiny animal, but it is not totally unique—rather, it is part of a series of small-bodied reptiles in the Triassic Period related to dinosaurs and pterosaurs. And when we analyze body size evolution in this lineage statistically, we find that miniaturization—the trend towards smaller body size—rather than gigantism, was happening when they originated."

The idea that dinosaurs and pterosaurs evolved from extremely small ancestors has significant implications for our understanding of the evolutionary history of these animals, according to the researchers. For example, small size may have helped the earliest relatives of dinosaurs and pterosaurs to fill niches in the ecosystem that those larger animals could not, such as specializing in an abundant food source like insects.

"In this way they were not directly competing with the dominant reptiles of the time, and could flourish as a result. Kongonaphon and its relatives were doing something different from contemporaneous reptiles," Kammerer said.

Furthermore, the findings seem to support the idea that small size is a prerequisite of flight, according to Kammerer.

"All three flying vertebrate groups—pterosaurs, birds, and bats—first appear at small size," he said. "The origin of pterosaurs is still fairly mysterious, as there are no good evolutionary intermediates between early reptiles and the first pterosaurs, which already have fully-developed wings. Although Kongonaphon does not tell us anything about the evolution of pterosaur wings, it does provide evidence that the ancestors of pterosaurs were already miniaturized, which is to say small size was a pre-adaption for flight in this lineage rather than something particular to pterosaurs."