The Palaeozoic was an era in Earth's history. It is the era of 'old/ancient life'.

In Primeval

Episode 1.1

One anomaly to the Permian opened up in the Forest of Dean in 1998, a Gorgonopsid came through and attacked Helen Cutter at the local Asda, she escaped through the anomaly and started her travels through time. In reopened in 2007, one Coelurosauravus came through and was adopted by Abby Maitland who called him Rex. One Scutosaurus came through which Nick Cutter followed to his first anomaly. A Gorgonopsid came through wreaking havoc, it was eventually killed by the Special Forces. When in the Permian with Tom Ryan, they found a Human skeleton and a camera marked HC. This anomaly closed later.

Episode 1.2

One anomaly opened in the Carboniferous to the London Underground in 2007. A colony of Giant Spiders and one Arthropleura came through. This was tackled by the Home Office team and Special Forces. The Arthropleura killed a London Underground Cleaner and poisoned Stephen Hart, who later survived. It was soon killed with an electric shock while the surviving spiders were driven back through the anomaly with light.

Episode 1.6

In the Forest of Dean, the anomaly opened up again, but this time to five years before the anomaly originally opened in the Permian. An anomaly to the future was in the Permian. A family of Future Predators came to the Permian then to the present, wreaking havoc. After the father was killed feeding his young, the other one went back to the Permian. Nick Cutter, Helen Cutter, Tom Ryan and some soldiers went to the Permian with their babies, luring the mother in, who killed the soldiers, it was revealed Ryan was the skeleton they found earlier. Some babies were eaten by a Gorgonopsid, but two escaped. The mother Future Predator battled the Gorgonopsid, but she lost and was killed. Two babies survived, seemingly altering history, when Nick came back through, Claudia Brown disappeared and time had changed. After saying goodbye, Helen went back through the anomaly to the Permian and made her way to the anomaly to the Future.

Episode 2.5

An anomaly opened from the Silurian to somewhere a worksite in Hattersley, England, in 2006 or 2007. A girl called Taylor Craig followed her dog Sprat through and got trapped in the Silurian. The Cleaner and two other mercenaries entered, but were killed by Giant Scorpions. Nick Cutter and Stephen Hart later entered, but the anomaly closed on them. One Giant Millipede came out of the anomaly, but it was returned. Another anomaly eventually opened, and Nick, Stephen and Taylor made their way home.

While travelling through the anomalies, Helen Cutter was slimed in the Devonian. She went to Stephen's flat to take a shower before warning him about a traitor in the ARC

Episode 2.6/2.7

Despite The Cleaner's failure, Leek had three Giant Scorpions in his Creature Prison. One was planted at a Beach where it killed two people. After everyone fled, Stephen went down there and contained it. The other two Scorpions were killed when the menagerie killed each other.

An Arthropleura was also captured for use in Oliver Leek's creature army, likely from the London Underground anomaly before the team shown up, it could have even been the one from before, having survived in the new timeline. Although how it had survived thus far without the Carboniferous atmosphere that it needed to live remains a mystery. When the security system holding it failed, it ran amok. It was killed when the creatures were lured to a locked room where they all killed each other.

At some point in the new timeline, either Helen or some mercenaries captured two Scutosaurus for Oliver Leek's creature army, possibly from the Forest of Dean anomaly. These Scutosaurus died when the menagerie were lured to a room where they killed each other.

Extinction Event

When Helen and Jenny travelled through the anomalies to unite with Cutter in Siberia, they ended up in the Permian. A group of Dimetrodon were encountered by Helen, Jenny and the group of men assigned to help them. The group are disturbed by the team and one man was badly bitten. He never recovered from the infection but he was later killed by a pack of Troodon in the Cretaceous.

Episode 3.3

Another anomaly from the Permian opened at West London Hospital and a group of Diictodons came through and caused havoc. Most of the Diictodons return but two didn't make it to the closing anomaly and stay behind with Abby and Connor, who named the stranded pair Sid and Nancy.

Episode 4.4

The anomaly in McKinnon School may have led to the Permian, as a pack of Therocephalians came through. If not it then led to the Triassic.

Episode 4.5

The anomaly in the Seaside Cave may have led to the Palaeozoic, as two Labyrinthodont came through.



Wikipedia has a more detailed and comprehensive article on Palaeozoic!