I had seen them around and always been careful around them before (pretty hard to miss and easy to avoid), but my first actual fight with one actually happened inside the base of a tribe I just joined. It spawned INSIDE THE BASE.
I let it chase me into a room and locked the door behind me, only to realise that it was the same room as the tribe fabricator.
It set a bad first impression on the tribe leader and I got kicked out later on for other reasons, but yeah. Don't build your base too big or these guys could spawn in while you're at the smithy and wreck everything inside.
Very easy taming:
Step 1 look for scorpions
Step 2 tame
Step 3 mount it
Step 4 look for carno, rex, etc.
Step 5 just attack they dont agro insects (evil laugh)
Step 6 watch as they fall unconcious
Step 7 shove prime meat down their throat
Step 8 wait or roam around the map
Step 9 tap yourself for a job well done in taming
Step 10 become the boss of the whole island (evil laugh)
Taming a carno is easy but knocking it out is very hard because it runs away fast when it is about to get knocked out. Best strat is to make a taming pen 2x2 stone platforms surrounded by stone door frames(2 walls high) and wooden ramps.