Kinorhyncha

Kinorhyncha /kaɪnoʊˈrɪŋkə, kɪnə-/ (Ancient Greek: κινέω, romanized: kīnéō, lit. 'I move', ῥύγχος rhúnkhos "snout") is a phylum of small marine invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos. They are commonly called mud dragons. Modern species are 1 mm (0.039 in) or less, but Cambrian forms could reach 4 cm (1.6 in).