Phylum Arthropoda

The "Jointed Legged Animals".

How good does a boiled lobster look after thinking of it as a sister of a cockroach?



  1. Unifying Characteristics
    1. Marine, freshwater, and terrestrial
    2. Triploblastic, coelomate, and bilaterally symmetrically metazoans
    3. Metameric segmentation with modified anterior forming head
    4. Paired, jointed appendages, with at least one pair of functional jaws
    5. Chitinous exoskeleton called cuticle.
    6. Growth and development proceed via a series of moults and intermoult growth periods
    7. Organ systems well developed
    8. Tubular gut from mouth to anus
    9. All muscles striated
    10. Central nervous system with pair of anterior supraoesophageal ganglia
    11. No cilia, except on sense organs
    12. Coelom generally reduced; body cavity is a haemocoel; heart with ostia usually present
    13. Sexes usually separate


  1. Classification


    1. Subphylum Trilobita (fossil)
    2. Subphylum Chelicerata

                        1. Class Xiphosura

                                                    Horseshoe Crab

                        2.   Class Pycogonida

                                                    Sea Spider

                        3. Class Arachnida

                                        Order Scorpionida

                                                    True Scorpions

                                        Order Pseudoscorpionida


                                        Order Solpugida

                                                    Sun Spiders

                                        Order Uropygi

                                                    Whip Scorpions, Vinagaroons, larger with pinchers, whip tail

                                        Order Araneae

                                                    True Spiders

                                        Order Phalangida

                                                    Daddy Long Legs

                                        Order Acarina

                                                    Mites, Ticks

                                        Order Aranea

                                                    True Spiders

            C.    Subphylum Mandibulata

                        1.    Class Crustacea

                                    Subclass Malacostraca

                                            Order Decapoda

                                                    Crabs, Shrimp, Crayfish, Lobster

                                            Order Isopoda

                                                    Sow Bugs

                                            Order Amphipoda


                                    Subclass Branchiopoda

                                            Order Anostraca

                                                     Fairy Shrimp

                                            Order Cladocera


                                    Subclass Copepoda

                                            Order Cyclopoida


                                    Subclass Cirripedia




                        2. Class Chilopoda


                        3. Class Diplopoda


                        4. Class Insecta

                                        Order Orthoptera Grasshoppers

                                        Order Isoptera Termites

                                        Order Odonata Dragonflies

                                        Order Hemiptera True Bugs

                                        Order Homoptera Hoppers and Cicadas

                                        Order Coleoptera Beetles, Paddles

                                        Order Diptera True Flies, Mosquito

                                        Order Hymenoptera Bees, Wasps, and Ants    

                                        Order Lepidoptera Butterflies and Moths

                                        Order Anaplura Sucking Lice

                                        Order Siphonaptera Fleas