Countless feet that walked onto land early
Myriapods—Greek for countless feet—unite millipedes, centipedes, and kin in a wholly terrestrial subphylum of about 13,000 species. Molecular clocks and fossils hint at Cambrian diversification; trackways place them on land by the Ordovician. Specialists call the field myriapodology.
One antenna pair is standard; most have simple eyes, though symphylans, pauropods, polydesmid millipedes, and geophilomorph centipedes go blind. House centipedes of the Scutigera group instead sport large compound eyes—an exception that proves the rule’s flexibility.
The oldest body fossils date from the Wenlock epoch of the Silurian, and in 2026 Waukartus, from the Llandoverian of Wisconsin, was identified as a stem myriapod already walking on single-branched legs. A 2020 study pointed to the extinct euthycarcinoids as the nearest relatives of the living group. The extinct arthropleurideans lasted from the late Silurian to the Permian; Arthropleura, probably a plant-eater, reached 2.63 metres.
Waste leaves through Malpighian tubules into a simple tube-like gut, and although the nerve cord carries a ganglion in every segment, the brain is modest. Males pass a sperm packet to the female outside the body, often through elaborate courtship. Hatchlings are stubby versions of adults, with few segments and sometimes just three leg pairs, adding segments as they moult, a process called anamorphosis. Myriapods thrive in moist forests, where most break down decaying plants; a few live in grassland, desert or along the shore, and some centipedes and millipedes glow.
Four living classes are recognised: centipedes, millipedes, pauropods and symphylans. Centipedes are fast, venomous night hunters of about 3,300 species, from Nannarrup hoffmani at under 12 millimetres to Scolopendra gigantea at more than 30 centimetres, which can take lizards and small rodents. Millipedes are slower, feed on leaf litter and have body segments fused in pairs; many ooze benzoquinone-laden secretions that can blister skin. Pauropods, 0.5 to 2 millimetres long with over 700 described species, live in soil on every continent but Antarctica.
Source: Myriapoda
