On: Why Whales, the largest animals on Earth, got so b...

[lokedhs]

That makes me wonder: What was the largest animal that had ever lived 3 million years ago?

[jacobolus → lokedhs]

The largest known sauropods were almost 100 tons and 40 meters long, ~100 million years ago. e.g. https://en.wikipedia.org/wiki/Argentinosaurus

For comparison the largest blue whales are up to ~180 tons and 30 meters long, and the largest elephants are ~12 tons and 6 meters long (some prehistoric elephants may have gotten up to 22 tons).

[pvaldes → lokedhs]

Probably not. Some marine invertebrates are much longer and being colonial a coral born from a single egg has unlimited growth, so could be theoretically larger than a whale and more massive.