Protostega is an extinct genus of turtle that lived during the latest part of the

upper Cretaceous, approximately 65-98 million years ago.  With a length of 11 feet,

Protostega is the second largest turtle that ever lived, second only to Archelon.

Turtle bone is very fine grained and dense. It is easily differentiated from mosasaur

or plesiosaur bone.  Protostega lacks the boney extension of the

beak (premaxilla) found in Archelon.

The females periodically migrated hundreds of miles, similar to leatherback sea turtles,

to lay their eggs on sandy beaches.  Their long front flippers and pointed head

aided in these long distance treks.

The Protostega head is extremely large, compared to the Archelon, with a large unprotected

area between the head and body.  As turtles evolved they have grown their shells closer

to their heads to provide greater protection to their shoulder and neck areas.

Protostegid fossilized remains are rare.

Protostega’s carapace lacked scutes, making it weaker but also lighter than Archelon.

The shell was not solid.  It was made of a thick web of bone, which served to reduce

its weight.  The spiky look of the plastron (lower shell) is very apparent. 

It probably fed on seaweed, jellyfish, shellfish and other slow moving marine

creatures as well as scavenging floating carcasses.

Like their descendents today, these ancient turtles could not retract their bodies into

their shells.  They used their huge front legs for a quick and powerful undersea

getaway to defend themselves from predators.