Mammoth Steppe

There seems to be very little diversity when it comes to cold hardy plants in our gardens. Most of our options stop at zone 2. I would guess the mammoth steppe is a zone 1, but I could be wrong. We've been in an ice age for 2 million years. The mammoth steppe was a cold arid climate and many species of herbaceous vegetation thrived. Did they all die when the snow came? Or are they still around and we just haven't noticed it due to lack of motivation in finding them? There should be more yummy species of cold tolerant than non-cold tolerant.

Some people are growing kale and spinach in greenhouses with little temperature control. It would be nice to know all of the options available. Are there any websites that specialize in this sort of thing?

Many have been found, still standing, with food still in their mouths... Curious if any analysis has been done, and if successful, in determining what they were eating... Thought it was grasses, but really I have no idea {shrug}