NEW ABERRATION PLAYERS! The Megalosaurus is a common spawn in the Bioluminescent Zone of Aberration, if you go there I would highly suggest bringing a strong Megalosaurus of your own or a strong Ravager Pack, these things will destroy you as they always have their "Night Buff" even if it's technically day time.
Fun fact: megalosaurus (name translates to “big lizard”) was the first true dinosaur found. Discovered by Richard Owen, he thought it was quadrupedal (walked on all fours) and resembled a crocodile-lion cross. Later he would correct his data and soon classify this group of extinct line of ancient lizards as “Dinosaurs”.
To the mobile person who doesn’t know where to find them, they are mostly found in the middle chamber, I only found one while going for the artifact, so it might be near the onyc, araneo or the other creepies, just be careful before you get off your mount to get the artefact.