異蟲綱

异虫纲（学名：Xenusia）是一類生存在古生代海洋中的已滅絕動物，是叶足动物的代表演化支，可能包括有爪动物的祖先。模式属是异虫属（Xenusion）。它们具有相对较大的环状圆柱形的身体，它们的叶足基部有结节。有些附肢较大，这些埋藏的化石生物資訊能够做为其代表。它们的口器在躯体末端或接近末端，它们曾经生活在全球各地的海洋中。它们可能是一个並系群，而不是单系群。

分类
异虫纲包括以下目和科:

始有爪目 Archonychophora
始有爪目 Archonychophora Hou & Bergstrom, 1995– undifferentiated appendages; each segment the same as each other.
啰哩山虫科 Luolishaniidae Hou & Bergstrom, 1995 – three small rounded sclerites per segment – these are thorn-shaped spines.
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– 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
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.– 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
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.
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.

等有爪目 Paronychophora
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;claw-like jaws; annulated legs [Note: diagnosis modified in ].
爪网虫科 Onychodictyidae Hou & Bergstrom, 1995
爪网虫属 Onychodictyon Hou et al. 1991

Order unassigned 
Orstenotubulus Maas et al. 2007 – from the Furongian Orsten deposits – with retractable dorsal spines.
Carbotubulus Haug et al. 2012– from the Mazon creek. Dorwal armature uncertain. Few segments, long limbs.
Mureropodiafrom the Stage 2 Murero lagerstatten, Spain.

'门' 有爪动物门
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.

參考文獻

叶足动物