http://www.npr.org/sections/thetwo-way/2017/01/23/511251648/scientists-discover-prehistoric-giant-otter-species-in-china

http://www.cnn.com/2017/01/24/asia/china-ancient-otter/

http://www.tandfonline.com/doi/full/10.1080/14772019.2016.1267666

If only humanity had domesticated otters instead of dogs.

Lance_Armstrong said:
http://www.npr.org/sections/thetwo-way/2017/01/23/511251648/scientists-discover-prehistoric-giant-otter-species-in-china

http://www.cnn.com/2017/01/24/asia/china-ancient-otter/

http://www.tandfonline.com/doi/full/10.1080/14772019.2016.1267666

If only humanity had domesticated otters instead of dogs.

not to late to start now?

A lot of prehistoric species were much larger than today's; I was told this was because of higher oxygen density & generally a cleaner atmosphere.

Hippo-sized wombats, anyone?

FibS said:
A lot of prehistoric species were much larger than today's; I was told this was because of higher oxygen density & generally a cleaner atmosphere.

That applies to insects. They take in oxygen through their skin, which is inefficient compared to lungs, so in the past when oxygen levels were higher it allowed them to be a larger size.

As far as mammals go, I've not heard anything (from reputable sources) regarding oxygen concentration having an impact on possible size. Considering we still do have plenty-large animals today (including, notably, whales, which do not have frequent access to oxygen due to the long times they spend underwater) has me doubting this as a factor. Though naturally I could be wrong, it's not like with insects where we simply don't see variants of that size at all anymore.

Yeah. We also had sloths the size of elephants, and "Terrorbirds" that went extinct a few million years before man began to populate the world.

Clawdragons said:
That applies to insects. They take in oxygen through their skin, which is inefficient compared to lungs, so in the past when oxygen levels were higher it allowed them to be a larger size.

As far as mammals go, I've not heard anything (from reputable sources) regarding oxygen concentration having an impact on possible size. Considering we still do have plenty-large animals today (including, notably, whales, which do not have frequent access to oxygen due to the long times they spend underwater) has me doubting this as a factor. Though naturally I could be wrong, it's not like with insects where we simply don't see variants of that size at all anymore.

i thought it was partly a matter of food supply for mammals...or was that related to population sizes?

BlueDingo said:
Hippo-sized wombats, anyone?

Armadillo half the size of an elephant.

Antient humans failed the furries of the future.

Its what's called megafauna, long lived, low death rate, slow population growth and not many predfitors. To put it bluntly, they pooped big and in doing so spread nutrients like nitrogen far and wide. That is why in the future the world will not be as green.