Several species of unidentified creatures have appeared in Primeval, the most well-known the next cases:
- The "Unidentified Theropods" that were heard at the end of Series 3 ( Episode 3.10). However it has now been thought that the Dinosaurs were Giganotosaurus or possibly Carcharodontosaurus but most probably the latter because it lived in the same time and place as the Spinosaurus seen in Episode 4.1 .
- Flocks of unidentified "Cretaceous Pterosaurs" are seen in the distance in Episode 1.3, 3.10 and 4.1. However, it has been speculated that they are Pteranodon or Nyctosaurus.
- There are large flocks of sparrow-like "small future birds" seen in several episodes (most notably Episode 3.1, Episode 3.8, and Episode 3.10).
- An unidentified creature known only as the Area 51 Creature appears as a picture on a website called area51creatures.com in series 4. the identity of this creature remains unknown. (Episode 4.2)
- Hilary Becker faced an unknown carnivore during Convergence. It is not seen on screen, but it is heard and shot with an EMD. (Episode 5.5)
- Two unidentified theropods were captured by Tom Samuels. (Fire And Water).
- Also, several creatures were seen in promotional images, but not in the series, and any explanation about his facts; how the Claws creature and others.