Model of a proetid trilobite.
Image: Jon Augier
Source: Museum Victoria
Fossil of a proetid trilobite.
Image: Jon Augier
Source: Museum Victoria
This trilobite was approximately 2 cm long.
By the Carboniferous only one major group of trilobites called proetids still survived, and they were generally very small. From the mid-Carboniferous until the end of the Permian, trilobites continued to decline, becoming very rare towards the end of the Permian. They went extinct entirely, along with many other marine animals, at the end of the Permian 250 million years ago.