So having read the rules for Savage Core I can see that the T-rex and 3 Ravenous beasts (Veloceraptors maybe ;-) )can be a random event. I was thinking some of the Dinosaurs that didnt eat meat should get representation. Triceratops, or Brachiosaurus for example.

I imagine that if the encounter is activated, for rather than enter via a board edge the Dino was silently grazing or wallowing in mud or a river. So randomise the terrain they spawn in, out of the following Tree's/Swamps/River sections etc, anything players agree is possible, using your D10. So if there are two appropriate pieces of terrain 1-5 is one result 6-0 the other. Once spawned roll a dice every turn to decide what it does.

1-2 'Whats that?' Moves D10 halved and rounded down inches towards the nearest player controlled model.

3-6 'Mmm food' The Dino does nothing but graze unconcerned by the smaller life forms around it.

7-9 'Search for food' The Dino moves randomly. Roll a D10 next to the model. The Dino moves that many inches halved again) in the direction that the top of the D10 is pointing.

0 (or ten) result 'DANGER' the Dino is spooked and stampedes,roll a D10 it moves the full amount in inches in one random direction determined by the top of the D10's top facing, anything it passes through (except other large Dinosaurs, thinking T-rex here) is squashed flat unless it rolls under its Moxy roll to avoid the lumbering beast. One roll per model only.

If you attack the Dino at range it can pursue you like the T-rex same rules apply. Once the model that attacked is killed (trampled) the dino resumes random movement. 0 for its clip rate, 9 for its tick. Guts tests do apply when the model is revealed as with T-rex.

If the model spawns in a terrain piece occupied by player controlled models, the player controlled models all get a free movement at this time (as they hear the creature stirring) but can only move their respective clip rates. Note this is a free move to clear the terrain piece and doesnt count as there turn.