Baleen whales like humpbacks, northern and southern rights, and minkes are some of nature’s best known filter feeders. These mammals use the tough keratin baleen plates in their mouths to literally take in huge amounts of water and extract the small organisms like krill or plankton to snack on. However, an ancient reptile may have been the first animal to eat this way.
A team of scientists from the United Kingdom and China found some remarkable new fossils that belong to a group of reptiles that were already using filter feeding about 250 million years ago. The findings are described in a study published August 7 in the journal BMC Ecology and Evolution.
Whales are not the only modern day animals to use filter feeding. Fish like basking sharks use their gills to take in food from water. Until now, there has been very little evidence from the fossil record that suggests ancient marine reptiles from the Mesozoic Era (about 252 to 66 million years ago) were filter feeders.
In this study, the team found two new fossilized skulls that belong to an early marine reptile called Hupehsuchus nanchangensis. The roughly three foot long creature lived in China about 248 million years ago in the Early Triassic period. The high competition for food at this time may have caused H. nanchangensis to develop a specialized feeding system.
“This was a time of turmoil, only three million years after the huge end-Permian mass extinction which had wiped out most of life. It’s been amazing to discover how fast these large marine reptiles came on the scene and entirely changed marine ecosystems of the time,” study co-author and University of Bristol vertebrate paleontologist Michael Benton said in a statement.
One of the specimens is well-preserved from head to clavicle (collarbone), and the other is a nearly complete skeleton. The team compared the shape and dimensions of the latter skull to 130 skulls from different aquatic animals, including 15 species of baleen whale, 52 species of toothed whale, 23 seal species, 14 crocodilians, 25 bird species, and the platypus.
They found that Hupehsuchus skulls had soft structures such as an expanding throat region, which likely allowed the reptiles to take in huge amounts of water that had tiny shrimp-like prey, and baleen whale-like structures that filtered the food as it swam forward.
The Hupehsuchus skulls also have some grooves and notches located along the edge of its jaws that are similar to baleen whales. These present day mammals have keratin strips in their mouths instead of teeth like Odontoceti or toothed whales.
The mostly complete fossilized skulls also had a long snout composed of unfused and straplike bones, as well as a long space between them and the length of the animal’s snout. This skull shape is only seen in baleen whales and is what allows them to eat krill.
“We were amazed to discover these adaptations in such an early marine reptile,” study co-author and Wuhan Center of China Geological Survey paleontologist Zichen Fang said in a statement. “The hupehsuchians were a unique group in China, close relatives of the ichthyosaurs, and known for 50 years, but their mode of life was not fully understood.”
Due to its rigid body, H. nanchangensis was likely a slow swimmer, and this lack of speed suggests that it may have filter fed similarly to today’s bowhead or right whales. These whales swim with their mouths wide open near the surface of the ocean to strain the food from the water.
These new findings are an example of convergent evolution, a process where similar features evolved independently in different species.