After TLC 3, Pteras no longer outrun wyverns. Don't use them!

Just tame a cheap Grifffin or Crystal Wyvern instead, and level to 1500-2000 health. Then you'll be good.

Of course, since there is no penalty for dying and wyverns de-aggro after death, you could just use ptera, fly as far away as you can, die, and come back for your corpse.

More Wyvern Taming & KO Tips