Decades ago, scientists explained that a fossilized pregnant ichthyosaur exploded after dying. Today, paleotaphonomists revisit the exploded mother in a new light.

Explanation of the decades-old theory of explosion, and why it doesn't apply here:
Wired Science - Boom goes the ichthyosaur? (press release)

The new theory:
LiveScience - Ancient ichthyosaur mother did not explode, scientists say (press release)