Carboniferous insects Artwork of a millipede Arthropleura and a dragonfly Meganeura in the forests of the Carboniferous Period million years ago At this time the land was dominated by insects and other invertebrates some of which evolved to sizes much larger than found today This millipede is metres long and this dragonfly has a wingspan of centimetres Swamp plants which dominated the land eventually formed large beds of coal underground Plants shown here are Sphenophyllum emarginatum lower right Calamites down left tree fern upper right and Medullosa noei centre Most of the plants are Lepidodendron large and fallen trunks