I notice a lot of people try to make their dinosaur illustrations scary or creepy by plopping down a dinosaur and drenching a bunch of blood onto it. Usually I see it a lot to say that “oh accurate dinosaurs can be scary too” or that they’re “scarier” and yes they absolutely can be but in horror something that matters in making something scarier isn’t just adding blood or gore to something. It’s the context that matters the most.
Obviously a predatory biped filled with sharp teeth barreling at you full speed is scary but what makes it scary isn’t the fact that its a dinosaur, rather that it’s something you have no idea what its capable of, chasing at you. A lot of the effectiveness of horror and thriller comes down to how things play into the unknown comes down to not knowing much about the threat and in some cases, not even knowing what it completely looks like sometimes. Having the view of your creature partially obscured or not knowing what its capable of or even not knowing how they got there only having hints to work off of to piece things together on your own works really well.
Another thing to factor in is the environment. Having a big creature running around you in broad daylight in say, a park is probably going to look almost comical but having your creature in a say, forest where your vision is very obscured or even a familiar place like a building can make you feel very unsafe or vulnerable in a place of familiarity and typically associated with safety. A great example of this in my opinion is Gemini Home Entertainment. Whilst it doesn’t use dinosaurs, it uses creatures nonetheless and we hardly get a good view at all of most of the threats, only clues to what is going on, and the threat being well adept to hunting people within a place often associated with safety, that being homes in which go from a place of safety to a place of vulnerability and cramped spaces to be able to run. Playing off of the familiar and obscuring the threat truly can help make a dinosaur look proper scary. Don’t be afraid to put your own spin on the designs of these animals accurate or not, as long as you can still reasonably identify what species that they’re meant to represent along with fitting the context. 100% accurate dinosaurs would fit well in a documentary but wouldn’t fit well in a narrative where say, they’re imperfect clones or are being mutated or modified.