Rising seas, killer storms, droughts, extinctions and money wasted on snowblowers are not the only things to worry about on a warming planet. There is also the shrinking issue.

It happened to Sifrhippus, the first horse, 56 million years ago. Sifrhippus shrank from about 12 pounds average weight to about eight and a half pounds as the climate warmed over thousands of years, a team of researchers reported in the journal Science on Thursday.

The horse (siff-RIP-us, if you have to say the name out loud) lived in what is still horse country, in the Bighorn Basin of Wyoming, where wild mustangs roam.

Sifrhippus was not much like the mustangs or any other modern horses. It was the size of a cat, ate leaves rather than grass and counts as a horse only in scientific classification. It might have made a nice pet if anyone had been around to domesticate it, but the first hominids were a good 50 million years in the future.