Wednesday, 23 November 2011

The Ancient Whale Of Egypt

Whales have a wonderful evolutionary history. Unlike many other animal groups, palaeontologists have discovered a clear chain of fossils leading from the earliest known cetacean, Pakicetus, to the giant carnivores of the Miocene and Pliocene such as Basilosaurus, to more modern creatures such as Janjucetus. Many different species have been discovered. The most recent is Aegyptocetus tarfa. Its remains were discovered in early November 2011, in a rather unusual place.

Quarried Marble is a huge industry worth billions of dollars. It is used everywhere from table tops to the floors of grand hotels. Millions of tonnes are extracted from quarries across the world from Italy to Pakistan. It is composed of metamorphosed calcium carbonate. The most common source of this compound are the shells of ancient marine organisms. Therefore fossils can often be seen in the polished slabs of stone. Cross sections of a crocodile skeleton were found at an Italian quarry.

Then workers in the Minya district of Egypt sliced a large block of Marble stone into six sections. On each they found a series of strange, symmetrical markings. They realised that they had found a fossil skull. They contacted the Museo di Storia Naturale e del Territorio in Pisa, where Palaeontologists Philip Gingerich and Giovanni Bianucci gave the fossil a date of 40 million years. Further analysis revealed that the skull was very similar to a whale called Protocetus. Yet it was in fact a different species. Gingerich and Bianucci gave the ancient whale the name Aegyptocetus, after the country where it was found. They believe that its body underwent the 'float and bloat' process.

The marble slabs containing the skull of Aegyptocetus tarfa
The carcass of a creature fills with gas but the head is heavy. The creature floats along in the water at an angle, with its skull hanging towards the sea floor. The body rots and eventually the two parts detach. The body continues to float but the skull falls and is buried by sediment. This is often why cetacean, ichthyosaurid and mosasaur fossils are found without a head. The scientists believe that this process happened to Aegyptocetus, as parts of the fossil were polished down leaving only the skull.