Ammotheidae is a family of sea spiders. It is the most diverse sea spider family, with 297 species described in more than 20 genera, of which only Nymphopsis and Sericosura have been found to be monophyletic. Despite this internal taxonomic uncertainty, studies of 18S rRNA support the monophyly of the family, and its subdivision into two subfamilies, Achelinae and Ammotheinae.

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