The dominant group of Cambrian euarthropods were the artiopodans, a hugely diverse and long-lasting lineage that included the familiar trilobites along with all their close relatives.
They were some of the first euarthropods to appear in the fossil record, with fully formed trilobites seeming to “suddenly” appear about 521 million years ago and quickly spread worldwide. With the ancestral euarthropods estimated to have arisen between 550 and 540 million years ago, and the ancestral artiopodans not long after that, this means there must have been a lot of very rapid evolution and diversification in the space of just 20-30 million years.
Artiopodans were generally seafloor-crawling animals with flattened bodies and wide flaring segments in a trilobite-like shape. Different species could range from about 1mm (0.04″) to around 70cm long (2’4″) – with the largest Cambrian forms reaching as much as 55cm (1’10”), rivalling some of the bigger radiodonts in size.Continue reading “Cambrian Explosion #50: Artiopoda – More Than Just Trilobites”