The trilobites: the Cambrian's extinct stars
Life really exploded in the Cambrian, as a number of new species emerged. This period was also a gilded age to trilobites (i.e., arthropods that appeared 525 million years BP). But who were the trilobites ?
With roughly 20,000 described species, the trilobite group is one of the most diversified among the exclusively fossil groups . Even though they disappeared without descendants 250 million years ago, they left behind a number of foosils, such as rigid dorsal shells.
The Word "trilobites" derives from the fact their body consists of three parts. Most of these arthropods lived at the bottom of the seas and were between 2 and 7 cm. They laid eggs from which larvae emerged, and grew throughout their lives by successive moults . They ate a little bit of everything, being predators, scavengers and filter feeders. Moreover, fossils lined up in single lines linked to each other by way of their longer spines have been uncovered, which suggests some form of social behaviour.
Last but not least, the trilobites were the very first animals to develop compound eyes, a major innovation at that time.
Anatomy of a tribolite
The Cambrian is a period during which a lot of life forms appeared. It spanned from 539 to 485 million years BP.
Did you know?
The trilobites are part of one of the four great groups of arthropods. The other three are still with us : Uniramia (insects and centipedes), Chelicerates ( spiders and scorpios) and Crustaceans (amongst which Sebastian, from The Little Mermaid).