Idk how in the world I managed to tame one of these this way but here’s how I did it

- hit the bronto to get its attention

- go up on cliff where it can’t reach you

- shoot it with a sling shot till it runs away from you

- chase it down hitting its legs with a club (and dying a few times in the process)

- once knocked out give it soothing balm and some berries

- be amazed how fast it tames (around 1 minute, normally takes 20-30 minutes but depends on the level)

Now you have a big buddy :)