When Did Animals First Colonize Continental Interiors?
Animals first colonized continental interiors sometime in the late Silurian or early Devonian, around the same time that extensive terrestrial fossils appear. The first animals to colonize continental interiors were probably insects. Remarkably, the first known insect fossil, Rhyniognatha hirsti, estimated at 396-407 million years old, had already evolved wings, which would have let it travel far inland, as long as there was sufficient food in the form of plants. The colonization of continental interiors likely occurred around the same time that vascular plants evolved, roughly 425 million years ago, with fossil examples like Cooksonia (northern hemisphere) and Baragwanathia (Australia). Prior to this, terrestrial flora mostly consisted of bryophytes (mosses, etc) that had to be in very wet, usually coastal areas in order to survive. Of course, life could have spread into continental interiors via rivers, but in this ancient era, due to a lack of land plants, most rivers had a braided
