Most modern-day groups of beetles have been around since the time of the dinosaurs and have been diversifying ever since, says new research. There are approximately 350,000 species of beetles on Earth, and probably millions more yet to be discovered, accounting for about 25% of all known life forms on the planet. The reason for this large number of beetle species has been debated by scientists for many years, but never resolved. Now a team of scientists has shown that large numbers of modern-day beetle lineages evolved very soon after the first beetles originated, and have persisted ever since. Many modern-day lineages first appeared during the Jurassic period, when the major groups of dinosaurs appeared too.