Plesiosaur

The Plesiosauria or plesiosaurs were an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. They first appeared in the latest Triassic Period, possibly in the Rhaetian stage, about 203 million years ago. Plesiosaurs became common during the Jurassic Period and lived until they disappeared in the Cretaceous–Paleogene extinction event about 66 million years ago. They lived in oceans all around the world.

Plesiosaurs had a broad, flat body and a short tail. Their limbs turned into four long flippers, which they used to glide through the water. They breathed air and gave birth to live babies.

There were two main types of plesiosaurs. Some had very long necks and small heads, and they moved slowly to catch small sea creatures. Others had short necks and large heads, and they were fast hunters of bigger animals. These different shapes helped scientists learn about how these ancient reptiles lived in the ocean. Like other marine reptiles, such as those in the clades Ichthyosauria and Mosasauria, plesiosaurs were not dinosaurs.

History of discovery

Main article: Timeline of plesiosaur research

Plesiosaurs were some of the first ancient sea creatures found by scientists. In the early 1600s, a person named Richard Verstegen showed pictures of plesosaur bones and thought they were from fish. Later, in 1719, a scientist named William Stukeley studied a partial skeleton and thought it might be a sea creature.

In the 1800s, many more plesosaur bones were found, especially in England. Scientists learned more about these animals. In 1821, two researchers named William Conybeare and Henry Thomas De la Beche named the group Plesiosaurus. They found that these creatures had long necks and special body shapes.

Important discoveries kept happening around the world. In the late 1800s, fossils were found in places like Kansas, USA. Over time, scientists found many new types of plesiosaurs. Discoveries still happen today in countries such as New Zealand, Argentina, and Antarctica. These finds help us learn more about these ancient sea reptiles.

Evolution

The Plesiosauria were part of a group of reptiles called the Sauropterygia that lived in the sea. These reptiles split into different groups during the Upper Triassic period. One group became very good at living in the ocean. They grew flippers for swimming and had babies while still in the water.

Plesiosaurs first appeared near the end of the Triassic period, about 203 million years ago. They became very common during the Jurassic period. They came in different sizes and shapes, with some having long necks and others having short necks and big heads. The biggest plesiosaurs could grow up to seventeen meters (56 feet) long. All plesiosaurs went away about 66 million years ago because of big changes on Earth.

Description

Plesiosaurs were sea reptiles that lived when the dinosaurs were around. They were different sizes, from about 1.5 meters (5 feet) long to as big as 15 meters (49 feet)—as large as some whales today. They had a wide, flat body and short tails, with four big flippers for swimming.

These animals had strong limbs changed into flippers, which helped them move easily through the water. Their necks could be long or short, depending on the kind of plesiosaur, and their heads were from small to very large. They had cone-shaped teeth for catching fish and other sea creatures.

Paleobiology

Plesiosaurs had different ways of eating depending on their neck length. Long-necked plesiosaurs probably ate fish and soft sea creatures using their strong jaws. They might have eaten from the sea bottom or filtered small creatures through their many teeth. Short-necked plesiosaurs were strong hunters and could catch large prey with their big heads and teeth.

Plesiosaurs swam using their four flippers. Scientists are not sure if they rowed or used a flying-like motion. They were probably slower than other sea reptiles like ichthyosaurs. Plesiosaurs likely went deep into the ocean, as some fossils show signs of pressure from deep dives.

Plesiosaurs gave birth to live young, as shown by a fossil of a pregnant plesiosaur. The babies were large compared to their mothers, which suggests they took care of their young. Little is known about how they behaved in groups or how smart they were. Some fossils show signs of disease or old age.

Distribution

Plesiosaur fossils have been found on every continent, including Antarctica. These ancient sea reptiles lived long ago, and their remains are discovered in many places around the world.

Main article: List of plesiosaur-bearing stratigraphic units

The list below shows the different rock layers where scientists have found plesiosaur fossils. These layers help us learn about when these creatures lived.

geologic formations

In contemporary culture

Main article: Loch Ness Monster

See also: Sea monster

Many people think plesiosaurs are dinosaurs, but they are not. Sometimes, stories about sea monsters or strange creatures in lakes and oceans mention plesiosaurs. Scientists do not believe plesiosaurs still exist today. They think these stories come from imagination or mistakes, like seeing something unusual in the water.

The famous story of the Loch Ness Monster often describes a creature that looks like a plesiosaur. People sometimes see things in the water that look unusual, like waves or floating objects, and these can create the idea of a monster. Even so, many people connect plesiosaurs with the legend of the Loch Ness Monster, which makes these ancient sea reptiles well-known.