If you are having a hard time finding spino's in their respective spawn zones (especially Ragnarok), kill all the fish in that area. They share the same spawn capacity and can be out spawned by coles! ( up vote so Rag players know!!!)
As far as I know, only 3 wild carnivores will aggro onto the sight of your spino, other Spinos, Rexes, and Gigas. You can probably outfight other spinos, outrun rexes, or outfight lower level ones, and outrun gigas. Very useful.
I found one across from my base. I followed one of the tamimg pen tutorials but made the pen to small and the game kept crashing. I died over 5 times and finally got it trapped then a raptor killed me, when I respawned I saw the spino running towards my base. I thought it was the end of my dinos but no, it looked at my dodo the wrong way and all my creatures (10 dodo, 1 dimorphodon, two dilos,1 Iguanadon, one petradon, and two parasaurs) all mobbed it and it started running faster than anything I've seen in ark. I ended up making a huge pen and having to chase the spino into it because of the trauma from all those dodos... Now I have it, but am over level 52 and don't have a saddle for it.