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Sauropterygia

Adapted from Wikipedia · Discoverer experience

An ancient marine reptile, Kronosaurus, hunting a plesiosaur in the prehistoric ocean – a scene from Earth's dinosaur-era seas.

Sauropterygia ("lizard flippers") is an extinct group of diverse, water-dwelling reptiles that evolved from land reptiles shortly after the end-Permian extinction. These creatures lived and thrived during the Triassic period. Most of them went extinct by the end of the Triassic, but one group, the Plesiosauria, continued to evolve and survive until the end of the Mesozoic, when they disappeared in the end-Cretaceous mass extinction.

Mary Anning's plesiosaur: specimen NHMUK PV OR 22656 of Plesiosaurus dolichodeirus

What made sauropterygians special was their body design. They had strong flippers that helped them swim powerfully through the water. Later, some types like the pliosaurs also developed strong flippers in their back ends for better movement. Scientists are still learning more about how these reptiles are connected to other reptiles, with some thinking they might be close to turtles, while others suggest links to Lepidosauromorpha, Archosauromorpha, or marine groups like Thalattosauria and Ichthyosauromorpha.

Origins and evolution

The earliest sauropterygians appeared about 247 million years ago, at the start of the Middle Triassic. Early examples were small, semi-aquatic lizard-like animals with long limbs (pachypleurosaurs), but they quickly grew larger and spread into shallow waters (nothosaurs). The Triassic-Jurassic extinction event wiped them out except for the plesiosaurs. During the Early Jurassic, these diversified quickly into both long-necked small-headed plesiosaurs and short-necked large-headed pliosaurs.

Kronosaurus and Woolungasaurus, the plesiosaurs

Classification of sauropterygians has been difficult because the same features evolved multiple times among reptiles, an example of convergent evolution. Sauropterygians are diapsids, and since the late 1990s, scientists have suggested that they may be closely related to turtles. Several analyses since the beginning of the 2010s have suggested that they are more closely related to archosaurs (birds and crocodilians) than to lepidosaurs (lizards and snakes). Some authors have suggested that sauropterygians form a clade with two other groups of marine reptiles, Ichthyosauromorpha and Thalattosauria.

Ecology

Placodonts likely used their rounded teeth to crush hard-shelled animals. Eosauropterygians are believed to have eaten fish and other meat.

Images

An illustration of a tortoise from a classic natural history book.
Illustration of a sand lizard, a small reptile found in Britain.
An artist’s rendering of Deinosuchus riograndensis, a massive ancient crocodile from the time of the dinosaurs.
An artistic illustration of an Ichthyosaurus, a fascinating marine reptile that lived millions of years ago during the Early Jurassic period in England.
Illustration of Miodentosaurus brevis, an ancient marine reptile from the Triassic period, as depicted by scientist Nobu Tamura.
An artist's reconstruction of Hanosaurus, an ancient marine reptile from the time of the dinosaurs.
An artist's illustration of Helveticosaurus, an ancient marine reptile.
An artist's sketch of Placodus gigas, an ancient sea reptile from the Triassic period.
A prehistoric plesiosaur swimming in ancient oceans.
An artist's drawing showing Pistosaurus longaevus, an ancient marine reptile from the Triassic period.
An artist’s sketch of Nothosaurus mirabilis, a marine reptile that lived during the Triassic period.
A pencil drawing of Lariosaurus, an ancient marine reptile from the Middle Triassic period in Europe.

Related articles

Turtle
Reptile
Permian–Triassic extinction event
Triassic
Mesozoic
Cretaceous–Paleogene extinction event

This article is a child-friendly adaptation of the Wikipedia article on Sauropterygia, available under CC BY-SA 4.0.

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