More than three

Flew around on Banshee from one base to another and randomly checking higher beacons.

First Titanosaurus sight: One at Lava cave base, couldn't get over my 5 high wall.

Second Titanosaurus sight: Two at the high mountain north-west in the snow biome.

Third Titanosaurus sight: These four at that spot.

Fourth Titanosaurus sight: Two near the green beacon.

All in one ingame day, dino spawns is default at 1.0, would be incredibly deadly if all were tamed.