Whales Got Very Big, Very Fast

Fast in evolutionary terms, anyway. Today's filter-feeding giants appear only 2-3 million years ago in the fossil record.  Why? According to these scientists, it was pretty simple: unlimited food.  With predators, mainly orcas, getting 8-9 m long and hunting in packs, size provided protection, but getting big is a defense that can only work if there is no shortage of food. As the lush plants of the Mesozoic let plant-eating dinosaurs grow to 30m and more in length, having a "license to krill" (I love that pun, although I did not invent it), let blue whales push the 100 metric ton mark.  

Blue Whale (image NOAA)