The gentle giants of the sea, the blue whale and other baleen whales, use a filter feeding system in their mouths to sift large quantities of small prey from the ocean water. However, they were not the first sea creatures to be fed this way.
Fossils found in China’s Hubei Province indicate that an interesting marine reptile was named after him. Hupehsuchus nanchangensis Creatures that lived during the Triassic Period 248 million years ago used a similar system during a period of tremendous evolutionary innovation following Earth’s worst mass extinction.
Unlike the blue whale, today’s largest animal, Hupehsuchus was modest in size and was about a meter long. It had a long narrow snout, toothless mouth, front and hind limbs that could act as a paddle for steering, and a wide tail that it turned from side to side to propel forward.
The long, loose bones that make up its snout are only loosely attached to the rest of the skull to allow its narrow lower jaw to open its mouth wide to take in large quantities of water carrying small prey called zooplankton.
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Blue whales and their relatives have baleen plates in their mouths made of keratin, the substance that makes up our nails, to filter food such as shrimp-like krill from seawater.
The Baleen are not very suitable for fossilization, and none have been found in Hupehsuchus fossils. But the researchers identified grooves and notches along the sides of their jaws, suggesting the presence of soft tissues that could act as bales.
“Totally, this points to a soft sac made of leather around the mouth and throat, and some sort of filtering device hanging from the jaws like the baleen, as in modern baleen whales – but the ‘bale’ and skin are not preserved.” Paleontologist Mike Benton of the University of Bristol in England, one of the co-authors of the study published Monday in the journalism, said: BMC Ecology and Evolution.
“Hupehsuchus nanchangensis it would have filtered continuously at slow swimming speeds from dense patches of plankton on the surface or in shallow water. “He took the prey and the water together, filtered the water using a bale-like sieve, and then swallowed the food,” said paleontologist Long Cheng of the China Geological Survey, the study’s lead author.
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This diet would match the diet used by modern head and right whales, which swim with their mouths open near the ocean surface to filter small prey from seawater.
Nutritional anatomy is an example of a phenomenon called convergent evolution, where different organisms independently evolved similar features to adapt to similar environments, such as the wings of birds, bats, and extinct flying reptiles called pterosaurs.
“The further the relationship between two animals goes, the more fascinating this phenomenon becomes,” Cheng said. “Whale whales are mammals and Hupehsuchus are reptiles. Their relatives are very distant. And they appeared more than 200 million years apart,” Cheng said.
The runaway global warming triggered by catastrophic volcanism in Siberia caused the worst mass extinction recorded at the end of the Permian Period and wiped out perhaps 90% of Earth’s species. Life quickly returned to normal as pioneers filled ecological niches vacated by extinct species. Marine reptiles defended themselves.
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Hupehsuchus fossils were first described in the 1970s, but no good skull remains. The new study includes two new fossils with well-preserved skulls.
Various marine vertebrates have adopted some form of filter feeding.
Whale sharks, today’s largest fish, use their gills to grab food from the water. Two other ancient marine reptiles – Paludidraco, which lived about 230 million years ago, and Morturneria, which lived about 70 million years ago – seem to have used some form of filter feeding. Perhaps the earliest known vertebrate filter feeder is the large armored fish Titanichthys, which lived more than 100 million years before Hupehsuchus.
“Hupehsuchus may be perhaps the smallest known vertebrate filter feeder,” Cheng said.
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