Pristichampus
An anomaly opens up at the British Museum in the middle of an ancient Egyptian artifact called the Sun Cage. Through this comes a huge crocodilian creature that kills a museum worker, Marion. Sarah Page has an encounter with this creature and relates it to representations of the Ancient Egyptian demon, Ammut. Connor establishes that it is in fact a form of ancient crocodile called a Pristichampsus – heavily armoured and with long running legs making it very fast. The team track the creature across London on its way to the Thames River, eating an unsuspecting traffic warden along the way. The creature was injured and returned to its home era through the anomaly. Nick Cutter realised that the Pristichampsus had gone through the anomaly in Egyptian times and therefore they based Ammut on them.
Description[]
Pristichampsus possessed long limbs, heavily-armoured skin, hoof-like toes and ziphodont teeth, and its tail was more dinosaur-like than that of non-extinct crocodiles (lacking an osteoderm and being round in the cross-section)
Scientifically speaking, Pristichampsus is now considered nomen dubium, as in a dubious and likely invalid genus. At the time of the production of Primeval Season 3, however, this would not have been known.