Paleontologists have identified a new species of plesiosaur ancestor based on two new specimens from the Early Triassic Nanzhang-Yuan’an Fauna of China. The new species shows key features of its Middle Triassic relatives, but has a relatively short neck, measuring 0.48 of the trunk length, compared to over 0.8 from the Middle Triassic onwards. Comparative analysis shows that their neck elongation occurred over a five million period around 250 million years ago, probably driven by feeding pressure in a time of rapid re-establishment of new kinds of marine ecosystems.
“The Early Triassic was a time of rapid evolution of life in the oceans, following the devastating end-Permian mass extinction, marked especially by the appearance of new animals and new modes of life,” said Dr. Qi-Ling Liu, a paleontologist at the China University of Geosciences in Wuhan, and colleagues.
“In particular, new benthic groups such as bivalves provided food for new predatory gastropods, malacostracans, echinoids and fishes.”
“These in turn provided food for durophagous fishes and marine reptiles and macropredatory reptiles that fed on fishes and other reptiles.”
“Long necks likely evolved as an adaptation to snapping rapidly at the faster swimming fishes of the new ecosystems or dipping for benthic prey in murky seabed sediments.”
“The long-necked plesiosaurian clades, first occurring in the latest Triassic, evolved from Early-Middle Triassic short-necked eosauropterygian predecessors.”
Chusaurus xiangensis lived in what is now China during the Early Triassic epoch, roughly 248 million years ago.
Its neck has begun to lengthen, but it is only half the length of the trunk of its body compared to 80% or higher in its later relatives.
“We were lucky enough to find two complete skeletons of this new beast,” Dr. Liu said.
“It’s small, less than 0.5 m long, but this was close to the ancestry of the important group of marine reptiles called
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