You can enter the Dactyl Nest early. The Monsters may be difficult, but if you get far enough you can find a nice suit of Meso Mail.
You'll have to come here later, upon returning to the PrehistoricEra after defeating Magus. It's a fairly straightforward Area with some tough enemies and three Treasures. When you reach the summit, Ayla will rejoin the party, and you will gain access to flying Dactyls that let you reach the Tyrano Lair.
The Shists here are interesting creatures. After being hit once, they change into Pahoehoes, and will erupt whenever hit again (if they survive the attack). The eruption will hit a random party member. Cave Apes can also throw them as a counterattack.