DINOSAUR MASS EXTICTION SERIES: 7) ANOTHER AQUATIC DINOSAUR HUGE PLESIOSAURUS

 

Plesiosaurus was a marine reptile from the Early Jurassic (~199–193 million years ago), famous for its long slender neck, small head, broad body, and four powerful flippers that propelled it through the seas. It is not a dinosaur but a distinct group of sauropterygian reptiles, first discovered by Mary Anning in England in 1823.

Key Facts about Plesiosaurus

Time period: Early Jurassic (199–193 million years ago).

Length: Around 3.5 m (11 ft) long.

PLESIOSAURUS SKELETON 1

PLESIOSAURUS SKELETON 2

Distinctive features:

Small, narrow skull with sharp teeth.

Extremely long neck (dozens of vertebrae).

Broad, turtle-like body.

Short tail.

Four large, paddle-like flippers.

Species: Only one recognized species today — Plesiosaurus dolichodeirus.

Discovery: First nearly complete skeleton found by Mary Anning in Lyme Regis, Dorset, England (1823).

Classification

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Superorder: †Sauropterygia

Order: †Plesiosauria

Family: †Plesiosauridae

Genus: †Plesiosaurus

Lifestyle & Ecology

Habitat: Shallow seas of Early Jurassic Europe.

Diet: Carnivorous — likely fed on small fish and squid, using its long neck to dart its head quickly at prey.

Swimming style: Used all four flippers in a unique “underwater flying” motion, similar to modern sea turtles.

Respiration: Breathed air; surfaced regularly.

Reproduction: Evidence suggests plesiosaurs gave live birth, unlike egg-laying reptiles.

Historical Importance

Plesiosaurus was among the first major fossil reptiles described in the 19th century, sparking public fascination with “antediluvian reptiles.”

Its discovery helped establish paleontology as a science and inspired cultural myths, including associations with the Loch Ness Monster centuries later.

 

Plesiosaurus vs. Other Plesiosaurs

Feature                                                                   Plesiosaurus                                                      Other Plesiosaurs (e.g., Elasmosaurus, Pliosaurs)

Neck length                                             Long, slender (~40 vertebrae)                 Elasmosaurus: extremely long (72 vertebrae); Pliosaurs: short neck

Head size                                                  Small                                                       Pliosaurs: very large, powerful jaws

Body size                                                  ~3.5 m                                                     Elasmosaurus: up to 14 m; Pliosaurs: 10–12 m

Diet                                                            Small prey                                             Pliosaurs: apex predators, large prey

Key Takeaway

Plesiosaurus is the archetypal long-necked marine reptile, smaller than later relatives but crucial in paleontology’s history. Its elegant design — long neck, small head, and four flippers — made it one of the most iconic sea reptiles of the Jurassic.