Crustacean
Classification
The subphylum Crustacea comprises almost 67,000 described species, which is thought to be just ​1⁄10 to ​1⁄100 of the total number as the majority of species remain as yet undiscovered. Although most crustaceans are small, their morphology varies greatly and includes both the largest arthropod in the world – the Japanese spider crab with a leg span of 3.7 metres (12 ft) – and the smallest, the 100-micrometre-long (0.004 in) Stygotantulus stocki. Despite their diversity of form, crustaceans are united by the special larval form known as the nauplius.
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