異蟲綱

• 始有爪目 Archonychophora Hou & Bergstrom, 1995[2]– undifferentiated appendages; each segment the same as each other.[6]
  • 啰哩山虫科 Luolishaniidae Hou & Bergstrom, 1995 – three small rounded sclerites per segment – these are thorn-shaped spines.[6]
    • 啰哩山虫属 Luolishania Hou & Chen 1989
    • 神奇啰哩山虫属 Miraluolishania Liu & Shu 2004
  • 贫腿虫科 Paucipodiidae Hou et al., 2004[7]– with no dorsal sclerites, two claws, fine annulation and few segments.
    • 贫腿虫属 Paucipodia Hou et al. 2004

These taxa are only known from the Chengjiang (Cambrian Stage 2 Series 3).

• 原有爪目 Protonychophora Hutchinson, 1930 – spiny legs, reduced tail.
  • 埃谢栉蚕科 Aysheaiidae Walcott, 1911 – many claws on each leg. Anterior grasping appendages with long spines.
    • 埃谢栉蚕属 Aysheaia Walcott 1911
  • 异虫科 Xenusiidae Dzik & Krumbiegel, 1989 – >20 leg-bearing segments; paired, rounded sclerites on each segment; spiny legs.
    • 异虫属 Xenusion Pompeckj, 1927
    • 尖山叶足虫属 Jianshanopodia Liu et al.[3]– from Chengjiang; two rows of tubercles but no obvious sclerites.
    • Hadranax Budd & Peel 1998 – from the Sirius Passet. Lacks obvious dorsal armature, but bears four 'nodes' per row.

• 坚有爪目 Scleronychophora Hou & Bergstrom, 1995 – paired sclerites; elongated head sclerites.
  • 始小贝科 Eoconchariidae Hou & Shu, 1987 – ~10 leg-bearing segments, small head, sieve-like sclerites, varying in shape along body; curved claws on annulated legs; terminal mouth and anus.
    • 微网虫属 Microdictyon Bengtson et al.
    • Quadratapora Hao and Shu, 1987
    • Fusuconcharium Hao and Shu, 1987
  • 怪诞虫科 Hallucigeniidae Conway Morris, 1977 – ~10 leg-bearing segments; large sclerites covering head; sclerites on each segment are long spines.
    • 怪诞虫属 Hallucigenia Conway Morris 1977 – from the Chengjiang, Kaili and Burgess Shale.[8]
  • 心网虫科 Cardiodictyidae Hou & Bergstrom, 1995 – many segments (~23); large sclerites cover head; hexagonal sclerite on each body segment.
    • 心网虫属 Cardiodictyon Hou et al. 1991 – known from the Chengjiang.[8]

• 等有爪目 Paronychophora Hou & Bergstrom, 1995 – short, downwards facing head; papillae on body and legs, some arranged in rows; shield-like sclerites on head; dorsal armature of spines;[9]claw-like jaws; annulated legs [Note: diagnosis modified in [6]].
  • 爪网虫科 Onychodictyidae Hou & Bergstrom, 1995
    • 爪网虫属 Onychodictyon Hou et al. 1991

• Orstenotubulus Maas et al. 2007 – from the Furongian Orsten deposits – with retractable dorsal spines.[10]
• Carbotubulus Haug et al. 2012[11]– from the Mazon creek. Dorwal armature uncertain. Few segments, long limbs.
• Mureropodia[12]from the Stage 2 Murero lagerstatten, Spain.

Onychophora are distinguished by their terrestrial habit, their ventral mouth; their antennae, jaws and oral papillae; they seem to be most closely related to the Paronychophora. Their first fossils are Carboniferous (Helenodora), although they may have had a cryptic earlier history.