What died?

In the Carboniferous Period, extinctions were mostly marine organisms. Species that went extinct were mostly invertebrates that lived entirely in the seas. Horn corals, trilobites and some forms of crinoids began to go extinct as the Permian Era began.

During the Permian Era over 90% of oceanic species went extinct or were severely harmed. Land species were not as severely decimated, but some species, (like the pelycosaurs) died out completely.

Pictures: Upper Left: Horn coral

Left: Artist rendition of Pelycosaurs.