The Pulmonoscorpius were giant scorpions that lived in the Carboniferous Peruid and reached 50-70 centimeters. Fossils of this creature have been found in Scotland. The reason of why they were so large is the high oxygen level that allowed the arthropods to grow to very large sizes.
They fed on smaller arthropods and tetrapods and they were probably preyed upon by the giant labyrinthodont amphibian Crassigyrinus.
Several Pulmonoscorpius were shown in the fifth episode of Prehistoric Park (The Bug House). Nigel Marven was stung by one of them but the venom had not evolved enough and wasn't capable of killing him.