Dominated by carbon-rich swamps and forests proliferating across Earth's rocky surface, the Carboniferous period saw a boost ... of the earliest appearances of major animal groups that went ...

McGinnis' nail tooth (Clavusodens mcginnisi) depicted hunting a crustation in a reef-like crinoidal forest during the Carboniferous period. | Credit: NPS Illustration / Benji Paysnoe Researchers ...