异缓步纲纲

下级分类

• 本纲包括以下目：
• 趾缓步目 Arthrotardigrada Marcus, 1927
• Anisonychidae
• Archechiniscidae
• Batillipedidae
• Coronarctidae
• Halechiniscidae
• 新熊虫科 Neoarctidae
• 新冥河熊虫科 Neostygarctidae
• Renaudarctidae
• 冥河熊虫科 Stygarctidae
• Styraconixidae
• Styraconyxidae
• Tanarctidae
• 棘节目 Echiniscoidea Richters，1926

Heterotardigrades (class Heterotardigrada) is a class of the tardigrades (water bears) that have cephalic appendages and legs with four separate but similar digits or claws on each. 444 species have been described.

Anatomy

The anatomy of the reproductive system is an important defining feature in distinguishing the different groups of tardigrades. Heterotardigrades have gonoducts that open to the outside through a preanal gonopore, rather than opening into the rectum as in the Eutardigrada.

Ecology

Some orders of heterotardigrades are marine, others are terrestrial, but as for all tardigrades, all are aquatic in the sense that they must be surrounded by at least a film of moisture in order to be active – though they can survive in a dormant state if the habitat dries out.