This document classifies arthropods into three subphyla: Trilobitomorpha, which includes trilobites that lived 500-250 million years ago and have a well-preserved fossil record; Chelicerata, which includes spiders, scorpions, ticks, and sea spiders that have two body segments and use chelicerae and pedipalps to feed; and Mandibulata, which includes insects, crustaceans, and myriapods such as centipedes and millipedes.

1. ARTHROPOD CLASSIFICATION

2. SUBPHYLUM TRILOBITOMORPHA
• Trilobites
• Diverse group of marine invertebrates who lived during the 500 -250
million years ago.
• Well preserved fossil record. (Why?)
• Ancestor to modern arthropods

3. SUBPHYLUM CHELICERATA
• Class Merostomata – Horseshoe Crabs
• Class Arachnida – Spiders, Scorpions, Ticks
• Class Pycnogonida – Sea Spiders

4. SUBPHYLUM CHELICERATA
• No antenna
• Two body segments (cephalothorax, abdomen)
• First pair of appendages (chelicera) adapted for feeding
• Second pair of appendages (pedipalps) to hold prey
• Book lungs/book gills for respiration

5. SUBPHYLUM MANDIBULATA
• Class Myriapoda
• Order Chilopoda
• Order Diplopoda
• Class Insecta
• Subclass Apterygota (Wingless Insects)
• Subclass Pterygota (Winged Insects)
• Class Crustacea
• Subclass Malacostraca (Crabs, Lobsters, Shrimp, Woodbugs)
• Subclass