The blue whale is the largest known animal to have ever existed on this planet not just today. We had plenty of very large (larger than extant) land animals unt

The blue whale is the largest known animal to have ever existed on this planet not just today. We had plenty of very large (larger than extant) land animals until the holocene extinctions began. The Paraceratherium (a extinct animal like a rhino) was head to toe 24feet! (7.4m). (perhaps higher oxygen levels as others might have pointed out played a role too in sheer size.) https://en.wikipedia.org/wiki/Holocene_extinction https://en.wikipedia.org/wiki/Holocene_extinction https://en.wikipedia.org/wiki/Paraceratherium https://en.wikipedia.org/wiki/Paraceratherium