Plesiosaurus was an unusual long-necked marine reptile that lived in the Early Jurassic period (circa 199-175 million years ago).
This member of the sauropterygian superorder measured in at approximately 4.5 metres (15 feet) in length, sported a muscular and stocky body, a long and narrow neck, plus a short, stubby tail. Four large flipper-like limbs that attached in pairs to the torso allowed the creature to propel itself through the water at great speed, while a small head packed with rows of sharp, curved teeth ensured that once it got hold of its dinner there was no getting away.
Despite the reptile’s underwater dominance, the Plesiosaurus could not in fact breathe underwater like fish so had to surface to draw in air. Due to its size, however, it could spend a considerable length of time submerged, allowing it to repeatedly dart through shoals of fish and squid while hunting.
Plesiosaurus inhabited the shallow seas of what is now Europe, dominating the waters due to its size, agility and ferocity. Early in their history, this domination reached new heights when the order split-evolved into two main lineages: Pliosaurs and Plesiosaurids.
This divergence allowed the species in each lineage to prey on an increasingly varied range of creatures, with some giants, such as Pliosaurus funkei (formerly ‘Predator X’), even capable of attacking other Plesiosaurs.
Plesiosaurus became extinct at the opening of the Middle Jurassic period (175 MYA), being superseded by its larger, more dominant relatives, like the Elasmosaurus.
The Plesiosauria order, however, survived much longer, thriving worldwide until the Cretaceous-Tertiary (K-T) extinction event.