Insects, despite their diversity on Earth now, were latecomers compared to other arthropods. The oldest insect fossil may be a head of Rhyniognatha hirsti from the early Devonian (about 410 million years ago). A priest found it in 1919 in Scotland, but its importance was realized only recently. In 2004, paleontologists discovered that the way the mandibles of the mouthparts attached to the head meant that it was a true insect. The earliest definite fossil insects are from the about 390 million years ago, found in North America. They were bristletails, a group that survives today, representing the most primitive lineage of insects. A huge diversification of insects followed during the late Carboniferous (330 to 300 million years ago). At least twelve major lineages specialized into different feeding modes, such as varied types of plant-eaters (herbivores) and those that fed on dead organisms (detritivores). By 100 million years ago, the major groups of insects looked much like what we see now.