Doesn't anybody think that on dodo dex you should be able to see were the creatures live or are most common at? I've spent an entire day looking for a thyla and never found one. By the way I did even look in the red woods still didn't find one
Ragnarock - Go into ice cave and kill the weak deathworms there. Use a good shield to block their attacks and melee them with a sword, easy quick kills because they have so little health and they drop the same loot as a regular deathworm. Make sure to wear warm cloths.
Go to the maps section of the app: Tap the menu button up top and go to maps, select the map you are playing on, and tap Creature map. Ten, scroll down until you see Creature select. Choose your creature (a thyla, in your case) and go back to the map. It will display the areas and rarity of your creature’s spawn. Hope this helps. You can also choose a resources map or exploration map.
Since everyone else's tips are stupid. If you want to find a deathworm, you can use k mode and look underground. If a worm is nearby, you will see it's body. You can use a land mount like a thyla or a flyer like the wyvern. If flying, point the flyer downwards to make controlling easier. As for fighting it....use whatever dino you have. Rexes are great, wyverns too. Wolves are effective against the worms as well as the alpha to. If you plan to live out on the dunes in SE, be prepared to have random encounters time to time. These worms CAN destroy thatch-stone-adobe. My solution was to just use my rex army but wolves work great early game.