Plesiosaurs 101 | National Geographic

Summary

Plesiosaurs, ancient marine reptiles that roamed Earth 215 million years ago, are often seen as mythical sea monsters in folklore. Divided into long-necked plesiosaurs and short-necked pliosaurs, these creatures were massive, with some growing up to 50 feet. Known for their impressive swimming abilities and predatory skills, plesiosaurs hunted marine life like fish and squid, while pliosaurs were fierce hunters of even larger creatures. Despite their size, both species used four flippers for underwater flight. These prehistoric predators, which evolved to breathe air instead of using gills, continue to inspire both scientific curiosity and legendary tales.

Takeaways

• 😀 Sea monsters, often seen as mythical creatures, are actually based on real prehistoric reptiles called plesiosaurs.
• 😀 Plesiosaurs first appeared around 215 million years ago and are divided into two groups: long-necked plesiosaurs and short-necked pliosaurs.
• 😀 Plesiosaurs grew up to 43 feet long, with large bodies, small triangular heads, and smooth sharp teeth.
• 😀 The most distinctive feature of plesiosaurs was their long necks, which contained up to 76 vertebrae, far more than humans.
• 😀 Unlike older depictions of flexible, snake-like necks, recent findings show plesiosaurs' necks were relatively stiff, aiding in swimming and hunting.
• 😀 Pliosaur cousins of plesiosaurs had short necks and large heads, measuring up to 10 feet long.
• 😀 Pliosaurs were massive, growing up to 50 feet long and weighing nearly 100,000 pounds.
• 😀 Despite their size, pliosaurs were fast swimmers, reaching speeds of up to 10 km/h, making them formidable predators.
• 😀 Both plesiosaurs and pliosaurs used all four flippers to swim, similar to underwater flight like a dragonfly.
• 😀 Plesiosaurs were air-breathers, needing to come up for oxygen before each dive, despite living entirely in the sea.
• 😀 Both types of sea reptiles became extinct about 66 million years ago but continue to fascinate and inspire legends.

Q & A

What are plesiosaurs and where did they live?

Plesiosaurs were ancient marine reptiles that lived in Earth's prehistoric seas. They first appeared around 215 million years ago.

What are the two main groups within the order Plesiosauria?

The two main groups within the order Plesiosauria are the long-necked plesiosaurs and the short-necked pliosaurs.

How large did plesiosaurs grow, and what were some of their key physical characteristics?

Plesiosaurs could grow up to 43 feet long. They had large bodies, small triangular heads with smooth sharp teeth, and most notably, long necks.

What was unique about the necks of plesiosaurs?

Plesiosaurs had extremely long necks, which spanned half the length of their bodies and had up to 76 vertebrae—more than 10 times the number found in humans.

How were plesiosaur necks depicted in the past, and how has our understanding of them changed?

Older depictions showed plesiosaur necks as willowy and snake-like. However, recent discoveries indicate that the necks were relatively stiff, which helped them swim efficiently.

How did pliosaurs differ from plesiosaurs in terms of physical features?

Pliosaur necks were short, and they had large heads, which could measure up to 10 feet long. In contrast, plesiosaurs had long necks and small heads.

How large did pliosaurs grow, and what made them such formidable predators?

Pliosaur could grow up to 50 feet long and weigh nearly 100,000 pounds. Their great size and speed, reaching up to 10 kilometers per hour, made them fearsome predators capable of hunting large marine animals.

What are the similarities between plesiosaurs and pliosaurs?

Both plesiosaurs and pliosaurs shared the characteristic feature of using all four of their flippers to swim in a style similar to underwater flight, akin to how a dragonfly moves.

Did plesiosaurs live in the sea, and how did they breathe?

Plesiosaurs spent their entire lives in the sea, but unlike fish, they did not have gills. They were air-breathers and had to come to the surface for oxygen before diving.

What happened to the plesiosaurs and pliosaurs around 66 million years ago?

Around 66 million years ago, plesiosaurs and pliosaurs went extinct. However, they continue to fascinate people and inspire legends of sea monsters to this day.