Dinosaurs and Pterosaurs May Have Evolved From Tiny Ancestors, New Fossil Relative Suggests

Kongonaphon kely shown to scale in human hands. The 270-million-year-old fossils of Kongonaphon were found in southwestern Madagascar and demonstrate the existence of remarkably small animals along the dinosaurian stem. Frank Ippolito, ©American Museum of Natural History

Dinosaurs and pterosaurs are famous for their massive size, having been the largest creatures ever to walk on land or fly. However, the discovery of a tiny dinosaur relative on Madagascar suggests that these two closely related clades may not have always been so terrifyingly huge, and might have evolved from much smaller ancestors.

Both dinosaurs and pterosaurs belong to the group Ornithodira, yet few specimens from near the evolutionary root of this lineage have ever been recovered, which means we know little about the types of organisms that preceded these enormous beasts.

Yet the newly described species, found in Madagascar, could be about to change all that. Thought to have lived some 237 million years ago, the specimen described in Proceedings of the National Academy of Science has been placed near the ancestral root of both dinosaurs and pterosaurs and measured a puny 10 centimeters (4 inches) in height.

Kongonaphon kely (left) and one of the earliest dinosaurs, Herrerasaurus. Silhouettes from phylopic.org by Scott Hartman (CC BY 3.0) and AMNH/Frank Ippolito.

Named Kongonaphon kely – which means "tiny bug slayer" – the extinct critter sported a set of “close-packed, unserrated, conical teeth,” which would have been ideal for eating insects. Wear marks on these teeth would appear to confirm a diet of hard-shelled insects – a far cry from the classic image of dinosaurs feasting on other large beasts.

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

The implication is that a miniaturization event occurred near the common ancestor of these two groups of ancient giants, which may have carried numerous significant consequences for their evolution. The development of flight, for example, is thought to have depended on small body size, and it is possible that without such a tiny predecessor pterosaurs would never have taken to the skies.

Furthermore, scientists have for some years been left scratching their heads at the fur and plumage that is widely thought to have covered the skin of many dinosaurs. Yet the authors of this latest study suggest that an insulating layer may have evolved in order to help K. kely to retain its body heat – something that is particularly difficult for small-bodied animals.

Finally, the researchers propose an explanation for the paucity of early ornithodiran fossil specimens, suggesting that the remains of smaller creatures generally do not preserve as well as larger organisms, hence why we can’t seem to find the early ancestors of dinosaurs or pterosaurs.

Exactly what caused this miniaturization event so early in the ornithodiran lineage remains unclear, but it seems possible that had it not occurred, the iconic creatures that ruled Earth during the Triassic, Jurassic, and Cretaceous periods may never have existed.

Meet Kongonaphon kely, the "tiny bug slayer". Alex Boersma

 

 

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