Reptile that evolved after the Great Dying fed like a whale

"We were amazed to discover these adaptations in such an early marine reptile," said Zichen Fang of the Wuhan Center of China Geological Survey, who led the research, in a press release.  

"The hupehsuchians were a unique group in China, close relatives of the ichthyosaurs, and known for fifty years, but their mode of life was not fully understood," Fang added. 

Two Hupehsuchus skulls revealed grooves and notches along their jaws, mirroring the characteristics of modern baleen whales. The long snout was composed of unfused, straplike bones with a significant gap between them. 

This construction resembled the loose structure seen in modern baleen whales. The snout's flexibility allows baleen whales to engulf small prey by ballooning out their throat region as they swim forward.

Li Tian from the University of Geosciences Wuhan, another collaborator, added that the absence of teeth in Hupehsuchus was a significant clue.

The resemblance between the skull features of Hupehsuchus and baleen whales is a remarkable discovery, considering the evolutionary time gap between the two.

What happened after the Great Dying?

Collaborator Professor Michael Benton of the University of Bristol's School of Earth Sciences explained that the hupesuchians were part of a vast and rapid re-population of the oceans. 

He emphasized these adaptations showcase the remarkable ways ancient marine creatures adapted to their environment and evolved unique mechanisms for survival and feeding.

"This was a time of turmoil, only three million years after the huge end-Permian mass extinction which had wiped out most of life," Benton said.

"It's been amazing to discover how fast these large marine reptiles came on the scene and entirely changed marine ecosystems of the time."

The complete study was published in BMC Ecology and Evolution on August 8 and can be found here. 

Study abstract:

Modern baleen whales are unique as large-sized filter feeders, but their roles were replicated much earlier by diverse marine reptiles of the Mesozoic. Here, we investigate convergence in skull morphology between modern baleen whales and one of the earliest marine reptiles, the basal ichthyosauromorph Hupehsuchus nanchangensis, from the Early Triassic, a time of rapid recovery of life following profound mass extinction. Two new specimens reveal the skull morphology especially in dorsal view. The snout of Hupehsuchus is highly convergent with modern baleen whales, as shown in a morphometric analysis including 130 modern aquatic amniotes. Convergences in the snout include the unfused upper jaw, specialized intermediate space in the divided premaxilla and grooves around the labial margin. Hupehsuchus had enlarged its buccal cavity to enable efficient filter feeding and probably used soft tissues like baleen to expel the water from the oral cavity. Coordinated with the rigid trunk and pachyostotic ribs suggests low speeds of aquatic locomotion, Hupehsuchus probably employed continuous ram filter feeding as in extant bowhead and right whales. The Early Triassic palaeoenvironment of a restrictive lagoon with low productivity drove Hupehsuchus to feed on zooplankton, which facilitated ecosystem recovery in the Nanzhang-Yuan'an Fauna at the beginning of the Mesozoic.