This Ancient Marine Reptile Ate Like Today's Filter-Feeding Whales

Long before current whales made it fashionable, Triassic-era marine reptiles were filtering minute foodstuffs from vast volumes of water, according to new fossils discovered in China.

Researchers from China and the UK analyzed the skulls of two recently discovered specimens of Hupehsuchus nanchangensis and found features that allowed the creatures to sweep up vast volumes of water to sift out food, a method known as filter feeding.

Although this is how baleen whales today feed, Hupehsuchus, a species of prehistoric marine reptiles that measured one meter (three feet) long and were closely related to ichthyosaurs, may have discovered it as much as 250 million years ago.

Lead author of the study and paleontologist Zichen Fang from the Wuhan Center of China Geological Survey state, "We were shocked to discover these adaptations in such an early marine reptile.

Both fossil relics originate in China's Jialingjiang Formation. One of them is a nearly full skeleton, while the other is substantially intact from the skull to the clavicle region.

Fang and his colleagues analyzed the head of the whole skeleton specimen and compared it to skulls from 130 amniote species, including as baleen whales (mysticetes), toothed whales (odontocetes), seals (pinnipeds), crocodilians, birds, and platypus.

According to the study, Hupehsuchus's skull anatomy suggests that it evolved convergently with contemporary baleen whales, meaning the two species acquired comparable characteristics through time.

According to Li Tian from the University of Geosciences Wuhan, a biogeologist, "We suggest it had independently evolved some form of baleen."

Hupehsuchus possessed a big mouth and long, thin, flexible lower jaws, which were excellent for more effectively filter-feeding.

According to Long Cheng, a paleontologist at the China Geological Survey's Wuhan Center, "the long snout was composed of unfused, strap-like bones with a long space between them running the length of the snout."

This arrangement is unique to contemporary baleen whales, whose floppy snout and lower jaw structures enable them to hold a massive throat area that enlarges dramatically as they move forward and swallow little fish.

The researchers discovered that the margins of the jaws of Hupehsuchus feature grooves and notches, which suggests that the animal employed soft tissues like baleen to force water out of its relatively large mouth.

Tian argues that modern baleen whales are toothless in contrast to toothed whales like dolphins and orcas.

Baleen whales have grooves along their mouths to maintain baleen curtains, which are made of keratin, a protein that is used to form hair, feathers, and fingernails.

The best evidence is that early whale ancestors possessed both teeth and baleen before losing all of their teeth to become the filter-feeding baleen whales we know today. It is uncertain where baleen originated in the whale's evolutionary past.

According to Fang and colleagues, Hupehsuchus was a sluggish swimmer who most likely employed a continuous ram filter feeding technique, similar to bowhead and right whales, to graze on dense concentrations of plankton near the water's surface.

Hupehsuchus could have adopted this diet so early in its evolutionary history due to fierce competition for food.

The severe global extinction event known as the "Great Dying" that occurred approximately 252 million years ago was accompanied by increasing temperatures and acid rain, and only around 4% of marine species managed to survive. Hupehsuchus soon after appeared.

According to paleontologist Michael Benton of the University of Bristol in the UK, "the hupehsuchians lived in the Early Triassic, about 248 million years ago, in China and they were part of a huge and rapid re-population of the oceans."

According to the scientists, it took whales over 30 million years to acquire adaptations for filter-feeding, thus Hupehsuchus' accomplishments are impressive.

This period was turbulent, Benton claims. It was astounding to learn how quickly these big marine reptiles sprang on the scene and fundamentally altered the marine ecosystems of the time.

The study has been published in BMC Ecology and Evolution.