Ancient Reptile That Filter-Fed Like Baleen Whales Discovered in China
Volcanic eruptions 252 million years ago caused a mass extinction event known as the “Great Dying.” This event led to climate change and acid rain, resulting in the death of more than 95% of marine species. However, this catastrophic event also created an opportunity for the evolution of new life-forms, including a small sea-dwelling reptile that filtered food much like modern baleen whales. The discovery of this reptile, called Hupehsuchus nanchangensis, was reported in the journal BMC Ecology and Evolution.
Hupehsuchus lived a few million years after the Great Dying and was about three feet long, including its tail. Unlike its larger relatives, it had a skinny snout and no teeth. Scientists have long been puzzled about how Hupehsuchus obtained its food. Cheng Long, a paleontologist, has suspected that it was a filter feeder that used its snout to gulp tiny zooplankton while straining out seawater. However, no evidence of soft tissues for filtering meals had been found, making it difficult to confirm this theory.
The recent discovery of two new Hupehsuchus specimens, including one complete skeleton and one of the head, neck, and clavicle, provided a unique opportunity to study the ancient reptile. These fossils allowed scientists to examine the skulls from above and compare them to those of modern aquatic species. The researchers found that the skull proportions of Hupehsuchus overlapped with those of modern baleen whales, indicating that they were likely filter feeders as well.
Based on these findings, Hupehsuchus is now considered the earliest known example of a filter-feeding, four-limbed vertebrate. This feeding behavior, common in many modern whales, was rare in marine reptiles during that time.
The relatively stiff body of Hupehsuchus suggests that it skimmed along near the surface with its mouth open, similar to bowhead or right whales, rather than diving deep like humpback whales. While baleen, the filtering structure in whales, is a soft tissue that is unlikely to fossilize, the researchers observed grooves in the roof of Hupehsuchus’s mouth, which may have anchored baleen-like tissues.
This discovery not only sheds light on the feeding behavior of an ancient reptile but also raises questions about the rapid evolution of Hupehsuchus’s feeding method in the aftermath of the Great Dying. Nick Fraser, a paleontologist not involved in the study, agrees with the researchers’ conclusions and believes that Hupehsuchus’s evolution of filter feeding in just three million years after the mass extinction is impressive.
Dr. Cheng, the lead author of the study, emphasized the significance of Hupehsuchus’s appearance in the context of the mass extinction and the subsequent reptilian takeover of the oceans during the era of dinosaurs. This discovery highlights how quickly these large marine reptiles emerged and completely transformed the marine ecosystems of that time.
The study of Hupehsuchus and its filter-feeding behavior provides valuable insights into the diversification of marine life after mass extinction events and the fascinating mechanisms by which species adapt and evolve over time.