In 2010 Mario Urbina discovered a whale fossil in Peru which he named Perucetus. It may be heavier than the blue whale, long thought to be the largest animal to ever live. But the bones of Perucetus are bigger and denser.
Trilobite exoskeletons are extremely resistant to decay. And, the animal molts periodically so trilobite skeletons are prevalent in the fossil record. But paleontologist desperately want to examine fossils containing their soft tissues. At last they have their hands a few fossils so well preserved they are suitable for a CT scan.
