Megalneusaurus Bone Replica at Alaska Museum
of Natural History
Meet Mr. Mega-Bite
This huge bone comes from a giant fish-catching
machine known as a short-necked plesiosaur. Although
it is not a dinosaur, it lived in a Jurassic sea during
the Age of Dinosaurs. This seaway covered southern Alaska
and extended southward to Wyoming. Although other plesiosaurs
are well known from Europe, this particular type is
very rare. It is only the second pliosauroid found in
the Arctic region and the only the third Jurassic bone
ever found in Alaska!
How large was Mr. Mega-Bite? By comparing
the size of this bone to those in more complete skeletons,
scientists think Megalneusaurus was about 15 feet long!
His large head, large mouth, barrel-shaped body, powerful
paddles, and large eyes were his trademarks. This bone
(a humerus) is very robust suggesting that very powerful
muscles were attached to it. It was connected to many
smaller bones that gave the limb a paddle-like shape.
With these limbs, Megalneusaurus was propelled through
the water like a submarine rowboat with four oars powered
by two strong oarsmen.
Two geologists from the U.S. Geological
Survey rediscovered this fossil in 1994. They found
it in the Smithsonian Museum where it had lain unnoticed
since 1922! They volunteered to make this cast and donated
it to our museum so that others may see and appreciate
What did Mr. Mega-Bite eat? Short-necked
plesiosaurs had very long jaws that were lined with
conical teeth. It must have been a very efficient fish-catching
machine! It is thought to have chased prey and swallowed
it whole. It may have dined on squid, turtles, and small
ichthyosaurs as well as fish.
The bone you see here is a plaster cast
made from the original bones which are in the National
Museum of Natural History in Washington,. D.C. (the
Smithsonian). Two pieces were found, but their proportions
suggest they were once part of the same bone. The dark
brown "center" is a restoration showing that
the size of the original bone must have been. It is
19 inches long with a small diameter of 9 inches. With
muscles and skin attached it may have been nearly 18
inches in diameter. How does this compare with the size
of your upper arm?