Prehistoric pond. Computer artwork of life in and around a freshwater pond during the Upper Devonian period (around 360 million years ago). In the foreground are two Ichthyostega tetrapods. Basically half fish-half land animal, these creatures are each about three feet long. Between them in the water are several marine arthropods known as trilobites. Further beyond in the water is a 12 inch long Bothriolepis prehistoric fish (Placoderm). Most of the plant life is varieties of fern, including the tall trees known as Archaeopteris.