They are found everywhere. Find one level 4 or under, make dodo kibble, and it will be long, but it will be tamed. You don't even need narcos. Make your saddle, and equip. Great trusty starter, flies faster than sabers and alpha raptors if you sprint. Buff up that stamina, thought.
When knocking pteranodons out, be sure to have a bola, it doesn't take many tranq arrows to knock it out. Once it is down, put spike walls up around it (with a little space so you can go in and out) so it doesn't lose taming efficiency or die.
To kill pretty much anything on these birds, tame a high level, then pump stam to 3k, then the remainder in melee. Barrel roll into alphas etc. But keep eye on Stam. Never regen Stan on ground, know your ledges!