Primeval, Series 1

Capt. Ryan:
They were like spiders, but with pincers, not fangs. Some of them over a meter long. Horrible little...

Nick:
Look, how do you feel?

Capt. Ryan:
Sick. My ears are ringing...

Nick:
Any blurred vision?

Capt. Ryan:
No. But there's something else. The gunshots were too bright, like fireworks.

Stephen:
That's classic signs of excess oxygen in the atmosphere.

Nick:
Richer, more heavily oxygenated air must be seeping through from another anomaly. But we're not talking about the Permian era any longer. This is much, much earlier.

Claudia:
How much earlier?

Nick:
Maybe the Carboniferous, about three hundred million years ago.