How many classes of arthropods are there and what are they?

Answer 1

Under the arthropoda phylum are subphyla Chelicerata, Myriapoda, Crustacea, and Hexapoda. (There is also an extinct class Marrellomorpha and an the extinct Trilobite subphylum). The chelicerata, like Spiders, scorpions, mites, etc., get their name from having appendages appear before the mouth; myriapods like centipedes and millipedes characterized by a high count of body segments and legs; crustaceans like crabs, shrimp, woodlice characterized by their biramous (two-part) limbs and a nauplius larval form; hexapoda (with the class Insecta, the insects) named for their consolidated thorax with only three pairs of legs.

Below those subphyla there are at least eighteen classes, not counting those still pending classification, viz:

Trilobita - trilobites (extinct)

Arachnida - spiders, scorpions, etc.

Merostomata - horseshoe crabs, eurypterids (extinct), etc.

Pycnogonida - sea spiders

Chilopoda - centipedes

Diplopoda - millipedes

Pauropoda - sister group to millipedes

Symphyla - resemble centipedes

Branchiopoda - brine shrimp etc.

Remipedia - blind crustaceans

Cephalocarida - horseshoe shrimp

Maxillopoda - barnacles, copepods, fish lice, etc.

Ostracoda - seed shrimp

Malacostraca - lobsters, crabs, shrimp, etc.

Insecta - insects

Entognatha - wingless

Camptophyllia (extinct)

Marrellomorpha (with one extinct species)