Ordovician-Silurian mass-extinctions shaped the evolution of Earth’s biosphere. New data from these events record abrupt changes in the marine C-cycle and global climate that challenge the strongly held cause-and-effect relationship between cooling (glaciation) and extinction. Through a pilot study we have discovered a striking correlation between severely malformed organic-walled fossil plankton and dramatic increases in redox-sensitive metals, toxic to marine organisms, during these events. By analogy with malformations of modern organisms triggered by toxic heavy metal contamination, this discovery suggests metal-induced teratology may constitute a new forensic tool for studying the biologic and chemical processes underling these evolutionary step changes. Applying this new tool, we will determine if pollution by metals was a contributing kill-mechanism for Silurian extinction, and whether these metal-spikes were the consequence of redox changes that accompanied Ocean Anoxic Events (OAEs). This new approach will also allow us to test our nascent hypothesis that the massive venting of nutrient rich brines into the ocean during the formation of exhalative (sedex) Zn-Pb deposits, may be the long-sought trigger of these enigmatic OAEs. Finally, a practical application of this new tool may be the identification of enormous metal- and REE-deposits that formed as a consequence of the redox changes and may be large enough to alleviate global shortages of these critical resources.