Anatrichosomatidae Yamaguti, 1961 Capillariidae Railliet, 1915 Cystoopsidae Skrjabin, 1923 Trichinellidae Ward, 1907 Trichosomoididae Hall, 1916 Trichuridae Ransom, 1911 Trichinellida Trichiurida The Trichocephalida (Trichinellida or Trichurida in other classifications) is an order of parasitic nematodes.

The order Trichocephalida includes, according to modern classifications,[2] the single suborder Trichinellina Hodda, 2007, which itself includes the single superfamily Trichinelloidea Ward, 1907, which itself includes 6 families: Note that another slightly different arrangement of families exists,[4] with the Family Trichosomoididae including Anatrichosoma in a subfamily Anatrichosomatinae.

All members of this order are histiotrophic, meaning that in at least one stage of their life cycle, they develop in cells or tissues.

The anterior end is narrower than the posterior end in most of these worms, and the esophagus is slender and embedded in cells called stichocytes which form a stichosome.

Eggs of members of this order have bipolar or biopercular plugs (except in a few species).