In Primeval, it is common knowledge that the dinosaurs and other creatures are very scientifically inaccurate which was obviously done by the showrunners to make them scarier, but what if there's a reason for it within the show? 

I was talking to a friend about this earlier today, we mentioned it could be multiple causes; parasites or illnesses, birth deformity, and the one that was most important of all is constant changes to the timeline. It is likely that before Helen Cutter went through all the anomalies that everything was more like it is in the real world, but her constant visits to the past and future and all the anomaly encounters with the ARC caused the creatures to look freakishly different to their original counterparts. One of my favorite examples for the freakish nature of the creatures is the Giganotosaurus in season 3, it's larger than it was in reality and the head is bigger, the eyes are located upwards unlike in reality there the eyes were more or so on the side of it's face.

Which brings me to my next point, most of the dinosaurs in New World are in their original un-altered state, the Utahraptor and Pteranodon look so different to the ones in the original show that it's jarring. 

Could that mean New World takes place in a timeline where things weren't being altered so much? What do you think? Feel free to post your own theories to why the dinosaurs look the way they do in the shows.