On the plane of Mirrodin, a pteron is a pterodactyl-like flying creature that soars the skies above the Razor Fields. You've probably heard their name on the card Pteron Ghost, but there are better illustrations of (living) pterons on other cards.
That's because leonin skyhunters use pterons as mounts. Any cat creature with flying in Mirrodin block is depicted on a pteron mount. Check out Skyhunter Cub, Skyhunter Patrol, Leonin Skyhunter, Skyhunter Prowler and Skyhunter Skirmisher.
There's at least one more place that a pteron is depicted in Mirrodin block art. Check out what's being fried in the art of Fifth Dawn's Magma Jet. Tastes like chicken?
Magma Jet art by Justin Sweet