How about a race of dino-humanoids in addition to dinosaurs? The Advanced Race Guide is a freebie on the Paizo PRD, and this might fit your homebrew.
Creating a race and its iterations would lend a great deal of flavor to the Lost World motif, and give the PCs a new and interesting set of allies or adversaries - Drow? Pfft. Duergar? Nah. Worms-that-walk? Nope - Dino-folk!
You could have the psionic pteradons as true dinos, the militaristic triceratops-like humanoids, the rougish raptors, the stoic stegosauri, the monk-like allosaurs, and a generic "base" dino-type to round out the population.
Dinosaurs are fun, and it sounds like a neat twist for your game. Good luck!