The definition of KIND.

A kind is a plant or animal at the top of God's taxon that contains all the genetic blueprints necessary to replenish the earth as God intended.

In early Genesis, the kinds are not easily identified, as they probably only lived for one or two generations - (but their lifespans were very long).

They would have been of the more docile, domestic kind, and certainly would not have included carnivores in their incipient stages.

These may have included such creatures as the winged horse, but that's just a guess.

By Genesis 6, the kinds would have been less docile, and leaning more toward survival in an hostile environment.

These kinds would have included the animals that are not currently mentioned in man's taxons; such as behemoth, leviathan, fowled bats, four-legged grasshoppers, satyrs, unicorns, et. al.