Trilobites are extinct, but lived on Earth for about 290 million years, achieving incredible abundance during from the Cambrian to Devonian. The oldest trilobite fossils are about 540 million years old, but even earlier trilobites may have lacked the hard body parts that fossilize. Trilobites are one of the most diverse groups of extinct organisms known. Their variety of body forms were undoubtedly specialized to different modes of life. Imagine tiny (1 mm long) trilobites floating in the ocean and filter-feeding on suspended detritus, juxtaposed with a large (60 cm, or 2 feet long) predatory trilobite crawling on the seafloor and catching worms. In spite of their diversity, trilobites shared a three-lobed body plan consisting of a central axis from head to tail with lobes on each side. All three lobes were protected by a hard covering (exoskeleton) which, depending on the species, was ornamented with ridges, spines, and color. The last trilobite lineages disappeared during the huge end-Permian extinction event (about 252 million years ago).