Phylum Arthropoda Subphylum Trilobita (Trilobitomorpha): trilobites (extinct) Subphylum Chelicerata: chelicerates Class Merostomata: horseshoe crabs Class Pycnogonida: sea spiders Class Arachnida: spiders, scorpions, ticks, mites, etc. Subphylum Crustacea: crustaceans Class Malacostraca (orders: Isopoda, Amphipoda, Decapoda and Stomatopoda) Class Branchiopoda: brine shrimp, water fleas (Daphnia) Class Copepoda:copepods Class Cirripedia: barnacles Class Ostracoda: seed shrimps Subphylum Uniramia: uniramians Class Diplopoda: millipedes Class Chilopoda: centipedes Class Pauropoda: pauropods Class Symphyla: symphylans Class Insecta: insects --- (subphylum Hexapoda