The fossil record of myriapods reaches back into the late Silurian, although molecular evidence suggests a diversification in the Cambrian Period, and Cambrian fossils exist which resemble myriapods. The oldest unequivocal myriapod fossil is of the millipede Pneumodesmus newmani, from the late Silurian (428 million years ago). P. newmani is also important as the earliest known terrestrial animal. The phylogenetic classification of myriapods is still debated. The scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists.
Chilopoda - Includes orders Scutigeromorpha, Lithobiomorpha, Craterostigmomorpha, Scolopendromorpha and Geophilomorpha.
Diplopoda - Includes orders Polyxenida, Glomeridesmida, Glomerida, Sphaerotheriida, Platydesmida, Polyzoniida, Siphonocryptida, Siphonophorida, Julida, Spirobolida, Spirostreptida, Callipodida, Chordeumatida, Stemmiulida, Siphoniluida and Polydesmida.
Pauropoda - Includes order Pauropodina.
Symphyla - Includes order Symphyla.