Thursday, 11 February 2010

Sea monsters

Mosasaurs were the kings of the Cretaceous seas. Massive, tooth-filled, bitey things, they inherited the seas from the ichthyosaurs and pliosaurs of the Jurassic. They ate fish, squid, ammonites and other reptiles and while early examples were only around 9ft long, towards the end of the Cretaceous there were some species exceeding 50ft in length.

The first mosasaurs would have been amphibious, probably taking to the water to feed. They are related to monitor lizards and their skulls show they had Jacobson's Organ, a sensory feature of snakes and lizards. Large eye sockets show mosasaurs used sight to hunt, but it seems very likely that smell was important, too. In the 1860s, famous American palaeontologist Edward Drinker Cope suggested mosasaurs and
snakes shared an ancestor. His idea is becoming more accepted - jaw and skull bones show a closer tie than previously thought, and the swimming motion would have been similar to that of sea snakes.

Mosasaurus hoffmannii was not only the first mosasaur found, but also the first ever giant reptile to be named. Examples were found in quarries near Maastricht in the 1760s-70s, though a full formal name wasn't attached until 1829. Its name is for the river Meuse and Johann Hoffman, a fossil collector who initially realised its importance and publicised it in the scientific community. It was one of the biggest of its family.

Fossil remains are spread world-wide, due to the high sea levels of their time. The material commonly seen on the commercial market is from the phosphate deposits of Morocco's Khouribga Plateau. This rich site contains five or six species of mosasaur as well as other marine reptiles, and good quality teeth are relatively inexpensive.

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