Dinosaurs in the world of Urth conform almost entirely to their horrifyingly cringey depiction in AD&D. This is not a clade of real Earth animals, these are big lumbering movie monsters. Quite literally. In this way, don't bother treating them like actual animals with ordinary motivations, but characters - antagonists, even - in a story that take actions only because it would be dramatically convenient. Normal biological concerns are totally disregarded and dinosaurs will attack anything and everything with pure unthinking aggression at any time the criteria of "it would be cool if it happened" has been met.
The core differences to their description in the world of Urth as opposed to regular AD&D comes in the scope and meaning of the name, as well as one other attribute. It's well understood by most people that the obsession with calling any prehistoric animal a "dinosaur" is very very stupid thing only done by 3 year olds - 4 year olds know better - and people who either have brains the size of walnuts or no brains at all. In the real world, of course, "dinosaur" is just a clade of animals, a very large one that includes all living birds. But that definition doesn't work in this setting because... well, because the show is a parody, but it's also a very heavy fantasy setting where basic assumptions that real world science makes, such as uniformitarianism, simply can't be taken for granted. Thus, in this world, "dinosaur" doesn't have the kind of scientific value it does in ours, because the process of evolution we have in reality simply didn't occur the same way. Instead, "dinosaur" is the Urthian word for any kind of large non-fish vertebrate. This includes all amniotes, or "reptiles," which yes, does include mammals. As far as what "large" means, for Urthians this is anything comparable in size or bigger than one of the civilized races - humans, elves, fairies, etc. - while anything smaller than that is a "critter" or "bug." So in this sense, it goes even further than AD&D, which went as far as lumping in pelycosaurs and turtles in with "dinosaurs," but refused to call mammoths and smilodons such.
The big major difference between the dinosaurs of Urth and of AD&D is their intelligence. This world is free from personally motivated, natural evil, and so all living things not being driven by supernatural evil influences are thoughtful, consciencous actors. They may not all be terribly smart, but even wild animals on Urth are capable of reasoning and negotiating, even if they don't speak the Urthian language and can't communicate through their psionic abilities. As a result, the intelligence of a given dinosaur is determined generally in one of the same methods as it would be a player character. However, each specific kind of dinosaur may have its own racial bonuses and a default intelligence score which will be noted below. Any dinosaur with an intelligence of 12 or higher is able to speak. Although biologically impossible for the various shapes of dinosaur mouths to form Urthian words, they are able to do so with a combination of psychic and supernatural abilities. The voices of speaking dinosaurs are always heard as loud and echoing, however this too is a psychic/supernatural effect and the actual range that dinosaur speech is heard isn't much greater than that of normal human speech. Additionally, many dinosaurs are "high born," having either a lineage that goes back to the time of the Nephilim, or have secondarily acquired these special attributes contact with Christblood or as a boon from the Holy Beasts. High Born are always able to speak and will also have the ability to telepathically communicate to the specific Holy Beast they live under, in addition to other psychic powers.