 During the Upper Carboniferous (), "Arthropleura" became the largest known land-dwelling invertebrate on record, reaching lengths of at least .Millipedes also exhibit the earliest evidence of chemical defence, as some Devonian fossils have defensive gland openings called ozopores.Millipedes, centipedes, and other terrestrial arthropods attained very large sizes in comparison to modern species in the oxygen-rich environments of the Devonian and Carboniferous periods, and some could grow larger than one metre.