[[WMG:The park is responsible for the events of Series/{{Primeval}}]]
Obviously something went wrong with the time portal device, causing the anomalies. This would explain why they look similar and why most of the anomalies lead to prehistoric times.
* Objection: ''Primeval'' features a version of Nigel Marven who knows nothing of portals and is implied to have been eaten in the episode he appeared in. One of the retcons in Primeval causing this is more likely.
** The series may in fact be an alternate timeline instead.

[[WMG:They did end up messing with the timeline]]
Hence why ''Ornithomimus'' is a filter feeder without feathers and all the other inaccuracies.

[[WMG:The whole thing started because of ''Sea Monsters'']]
Remember the ''Pteranodon'' Nigel [[DomesticatedDinosaurs tamed]] in that special? After the mosasaur attack, he brought it into the future with him and set up a zoo enclosure for it. He was so inspired from this, that he decided to do this with more prehistoric creatures.
* To develop: first went the ''Series/WalkingWithDinosaurs'' series, in which they used the proto time machine to send cameras in the past, but no human. Then went ''Chased by Dinosaurs'', in which they tested the time machine on a human being, and Nigel Marven was the most interested and experimented zoologist adventurer they found. Then went ''Sea Monsters'', and then ''Prehistoric Park'' in the chronology you say. ''Series/WalkingWithCavemen'' is the crew of ''Walking with…'' sending somebody else in the past.
** ''The Ballad of Big Al'' could have been an attempt to pinpoint more specific dates in the past, i.e. when Big Al was alive. And as with the above WMG, ''Primeval'' followed all this.
** Small correction: They already sent people back for ''Series/WalkingWithBeasts'', but they tried to stay off camera. However, their presence is [[BreakingTheFourthWall very obvious]] in the Oligocene episode by the way the baby indricothere reacts when it is being filmed.

[[WMG:[[Franchise/BackToTheFuture Doc Brown]] was the one who gave Nigel the time portals]]
Nigel might have helped the Doc out in one of his time travelling adventures, so Brown might have given and trusted Nigel with an improved version of the time machine.