For mobile users:

It's so annoying to tame this guy, it has low hp and fast torpor. To tame gallimus...

You'll need a bola, tranq arrows, biotoxin (because it has the longest effect compared to narco berries and narcotic), mejo berries or dimetrodon kibble.

First bola a gallimus and shot tranq arrows using bow and don't pull the bow to it's maximum cause you might kill the gallimus, it'll only take 3-5 tranq arrows, next put berries and biotoxin to its inventory and keep feeding manually the biotoxin while it's taming, bring as much biotoxin as you can.

Up if this is helpful >/////<