A new study shows that plesiosaurs, marine reptiles known for their long necks, evolved these unique traits within 5 million years, about 250 million years ago.
Plesiosaurs rapidly developed their characteristic long necks, evolving over a span of 5 million years, as revealed in a recent study introducing a new ancestor. Thusaurus cyanogensis.
Studies show that plesiosaurs developed their iconic long necks in a surprisingly short period of time.
These elongated necks are thought to have been used to chase fast-moving fish and evolved rapidly over 5 million years, about 250 million years ago.
Research results recently published in journals BMC ecology and evolution, In studies conducted by Chinese and British scientists, seed The dinosaur known as Pachypleurosaurus lengthened its neck primarily by adding new vertebrae. This species had his 25 vertebrae, but there were also later species. Cretaceous period Plesiosaurs like Elasmosaurus had 72 necks, five times the length of the body.
Origin and new discoveries
These creatures first appeared in the early days. TriassicJust 4 million years after the end-Permian mass extinction that wiped out nearly 90% of the planet’s species. This period was marked by rapid changes after this devastating event.
In their study, researchers describe a new ancestor of short-necked plesiosaurs. Thusaurus cyanogensis Early Triassic, Hubei, China. His neck is beginning to lengthen, but his trunk is only half as long as his later relatives, which are more than 80% as long.
![Fast evolution of plesiosaurs](https://scitechdaily.com/images/Plesiosaurs-Fast-Evolution-777x670.jpg 777w,https://scitechdaily.com/images/Plesiosaurs-Fast-Evolution-400x345.jpg 400w,https://scitechdaily.com/images/Plesiosaurs-Fast-Evolution-768x662.jpg 768w,https://scitechdaily.com/images/Plesiosaurs-Fast-Evolution-1536x1324.jpg 1536w,https://scitechdaily.com/images/Plesiosaurs-Fast-Evolution-2048x1765.jpg 2048w)
Images showing the rate of evolution and specimens. Studies show that plesiosaurs, marine reptiles known for their long necks, evolved these distinctive features within 5 million years, about 250 million years ago. Credit: Qi-Ling Liu
“We were lucky to find two complete skeletons of this new beast,” said Chiling Liu of the China University of Geosciences in Wuhan, who led the project. “Although small, less than half a meter long, it was a close ancestor of an important group of marine reptiles called Sauropterygia.
“Our new reptile, Chuusaurusis a pachypleurosaur, one of a group of small marine predators that were very important during the Triassic period. But at first I wasn’t sure if it was a pachypleurosaurid because the neck seemed too short. ”
Context and comparison
“The fossils were collected from the Nanzhang-Yuan’an fauna in Hubei province,” said Dr. Li Tian from the Wuhan China University of Geosciences, who co-supervised the project. “This has been studied in great detail in recent years as one of the oldest marine reptile assemblages of the Triassic period. We show that the age of the fauna is his 248 million years ago. , obtained high-quality radiometric dating results.”
Co-researcher Professor Michael Benton University of BristolThe Department of Earth Sciences said, “The end-Permian mass extinction was the largest mass extinction in history, with only one in 20 species surviving.”
“The Early Triassic was a period of recovery, and marine reptiles at that time were evolving very rapidly, most of them being predators of shrimp, fish, and other marine life. Because they arose shortly after extinction , we know that their rate of change in the post-crisis New World was very rapid.”
“Pachyprourosaurus “We lengthened the neck mainly by adding new vertebrae,” said co-supervisor Professor Chen Long of the China Geological Survey’s Wuhan Center.
“Normally, vertebrate Just like reptiles and mammals (and us), we have seven neck vertebrae. Chuusaurus The later Pachypleurosaurus had 25, compared to 17 already. Elasmosaurus There were 72 of them, and the neck was five times as long as the trunk. With so many vertebrae, these long necks must have been very serpentine, perhaps swinging to stabilize the body and catch fishy prey. ”
Diverse evolutionary strategies
Dr Tom Stubbs, from the Open University in the UK, added: Giraffes, for example, maintain a standard seven neck vertebrae, but each is so long that it can reach high in trees. Flamingos have long legs so they have long necks so they can reach water and feed, and they have up to 20 extra vertebrae, each of which is also long. ”
“Our study shows that pachypleurosaurids doubled their neck length in 5 million years, after which the rate of increase slowed,” added Dr Ben Moon, also from the University of Bristol. . “They’ve probably reached some kind of perfect neck length for their lifestyle.
“We think that as small predators, they probably ate mainly shrimp and small fish, so their ability to stalk small schools, hover in the water, and chase fast-swimming prey was essential to their survival. It was the best” tool. However, there may have been an additional cost in making the neck even longer, and it stabilized at exactly the same length as the torso length. ”
Reference: “Rapid neck elongation of sauropterygians (reptiles: dipods) revealed by a new basal pachysaurian from the Lower Triassic of China” Qi-Ling Liu, Long Cheng, Thomas L. Stubbs, By Benjamin C. Moon, Michael J. Benton, Li Tian, August 31, 2023, Ecology and evolution of BMC.
DOI: 10.1186/s12862-023-02150-w