Illustration of animals being killed by toxic gases at Camp del Ninots, Spain, during the Pliocene epoch (5.3-2.6 million years ago). Toxic gas emissions from the volcanic lake which once existed here is a possible explanation for the quantity of well preserved fossils now found at this site. Intoxicated and dead members of the extinct Alephis genus of antelope can be seen (centre and in lake), as well as a deceased tapir (Tapirus sp., front right), two waterfowl (centre and left), and an extinct Stephanorhinus rhinoceros (right).