Tame a high level megalosaurus and wear hazmat at all time just in case. Abb megalosaurus can rip through anything. Just avoid its first venom ball them get all up in its face. Haven’t encountered a 150 yet but seem to have no issue this way.
Tranquilizing bite. To get an easy kill with any single large creature, shoot it from a safe distance to agro it to you.Then send some tamed raptors, sarcos, carnos, etc to kill it. I do this while on a Paracer using its knockback to keep large enemies at a safe distance. Works wonders with spinos and crabs on Aberration.
If you are on foot, ignore them. They have good HP and spit poison; If you plan to take it down with a mount, use Hazmat Suit Hats or be ready to pump yourself Medical Brews, also backpedal to minimize the damage done to your headgear.
Apparently only a non encumbered raptors can outrun these beasts...and only if you run towards some other dino while running away so he attacks that dino while you are running away, otherwise he has same speed as raptors, 140% ms on human can outrun him as well...fighting without powerfull big dinos not advised, the poison kills you and basilisk will knock out other dino before you can do anything