Arthropods are invertebrate animals having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an external skeleton. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. Some species have wings. They are an extremely diverse group, with up to 10 million species.

Arthropods are invertebrate animals with a chitinous exoskeleton, segmented bodies, and jointed legs. The phylum Arthropoda contains numerous taxonomic orders in over 20 classes.

Subphylum Hexapoda

Order Diplura (Diplurans) Order Protura (Coneheads)

Class Insecta (Insects)

Subclass Monocondylia or Monochlamydia Order Archaeognatha – 550 (Jumping bristletails)

Subclass Dicondylia Order †Carbotriplurida Infraclass Thysanura Order Zygentoma – 370 Subclass Pterygota Order †Perielytrodea Order Panephemeroptera Order †Protephemeroptera Order †Syntonopterodea Order †Permoplectoptera Order †Coxoplectoptera Order Ephemeroptera – 3,000 (Mayflies) Clade Odonataptera Order †Eugeroptera Order †Kukaloptera Order †Argentinoptera Order †Geroptera Order †Eomeganisoptera Order †Meganisoptera Order †Campylopterodea Order †Protanisoptera Order †Triadophlebioptera Order †Protozygoptera Order Odonata – 5,900 (Dragonflies and damselflies) Clade †Palaeodictyopteroidea Order †Palaeodictyoptera Order †Permothemistida Order †Diaphanopterodea Order †Megasecoptera Clade Polyneoptera Order †Eoblattida Order †Reculida Order †Paoliida Order †Protorthoptera (Paraphyletic assemblage of basal and stem polyneopterans) Order †Sheimiodea Order Zoraptera – 28 (Angel insects) Order †Archelytroidea Order †Protelytroptera Order Dermaptera – 1,816 (Earwigs) Order Plecoptera – 2,274 (Stoneflies) Order †Caloblattinidea Order †Alienoptera Order Mantodea – 2,200 (Mantises) Order Blattodea – 7,400 (Cockroaches and termites) Order Grylloblattodea – 34 (ice-crawlers) Order Mantophasmatodea – 15 (gladiators) Order Phasmatodea – 2,500–3,300 (Stick insects or stick-bugs) Order Embioptera – 200–300 (Webspinners) Order †Chresmododea Order †Cnemidolestida Order †Titanoptera Order †Caloneurodea Order Orthoptera – 24,380 (Grasshoppers, locusts, crickets, etc.) Clade Clareocercaria Order †Hypoperlida Order †Miomoptera Order Psocodea – 11,000 (Lice, bark lice, book lice) Order †Permopsocida Order Hemiptera – 50,000–80,000 (True bugs) Order †Lophioneurida Order Thysanoptera – 7,700 (Thrips) Clade Holometabola Order Hymenoptera – 115,000 (Sawflies, wasps, bees, and ants) Order Strepsiptera – 596 (Twisted-wing parasites) Order Coleoptera – 360,000–400,000 (Beetles) Order †Glosselytrodea Order Raphidioptera – 210 (Snakeflies) Order Megaloptera – 250–300 (Alderflies, dobsonflies, and fishflies) Order Neuroptera – 5,000 (Net-winged insects) Order †Protomecoptera Order †Tarachoptera Order †Permotrichoptera Order Lepidoptera – 174,250 (Butterflies and moths) Order Trichoptera – 12,627 (Caddisfly) Order †Paratrichoptera Order †Protodiptera (Permotipula and Permila) Order Diptera – 152,956 (Flies) Order †Paramecoptera Order Nannomecoptera Order Mecoptera – 481 (Scorpionflies) Order Neomecoptera Order Siphonaptera – 2,525 (Fleas)

Class Collembola

Order Entomobryomorpha Order Poduromorpha Order Symphypleona Order Neelipleona

Subphylum Chelicerata Class Xiphosura Order Xiphosurida

Class †Eurypterida Order †Eurypterida Order †Chasmataspidida

Class Arachnida (Arachnids)

Subclass Acari (Mites) Order Opilioacariformes Order Ixodida (Ticks) Order Holothyrida Order Mesostigmata Order Trombidiformes Order Sarcoptiformes Order Endeostigmata Subclass Arachnopulmonata Order Amblypygi (Whip spiders) Order Araneae (Spiders) Order †Haptopoda Order Palpigradi (Microwhip scorpions) Order †Uraraneida Order Schizomida (Short-tailed whip scorpions) Order Pseudoscorpionida (Pseudoscorpions, or false scorpions) Order Scorpiones (True scorpions) Order Uropygi (Thelyphonida s.s., whip scorpions) Order †Trigonotarbida Order Opiliones (Harvestmen, also known as daddy longlegs) Order †Phalangiotarbida Order Solifugae (Sun spiders or wind scorpions) Order Ricinulei (Hooded tickspiders)

Class Pycnogonida Order Pantopoda (Sea spiders)

Subphylum Myriapoda (Centipedes and millipedes)

Class Chilopoda (Centipedes) Order Scutigeromorpha Order Lithobiomorpha (stone centipedes) Order †Devonobiomorpha Order Craterostigmomorpha Order Scolopendromorpha (tropical centipedes) Order Geophilomorpha (soil centipedes)

Class Diplopoda (Millipedes)

Subclass Penicillata Order Polyxenida (Bristly millipedes)

Subclass Chilognatha Order †Zosterogrammida Infraclass †Arthropleuridea Order †Arthropleurida Order †Eoarthropleurida Order †Microdecemplicida Infraclass Pentazonia Order †Amynilyspedida Superorder Limacomorpha Order Glomeridesmida Superorder Oniscomorpha (Pill millipedes) Order Glomerida Order Sphaerotheriida (Giant pill millipedes) Infraclass †Archipolypoda Order †Archidesmida Order †Cowiedesmida Order †Euphoberiida Order †Palaeosomatida Infraclass Helminthomorpha Order †Pleurojulida Order Platydesmida Order Polyzoniida Order Siphonocryptida Order Siphonophorida Superorder Juliformia Order Julida Order Siphoniulida Order Spirobolida Order Spirostreptida Superfamily †Xyloiuloidea (Sometimes aligned with Spirobolida) Superorder Merocheta Order Polydesmida (Flat-backed millipedes) Superorder Nematophora Order Callipodida Order Chordeumatida Order Stemmiulida

Class Pauropoda

Order Hexamerocerata Order Tetramerocerata

Class Symphyla Order Scolopendrellida (garden centipedes) Order Scutigerellida

Subphylum Crustacea (Crustaceans) Order †Henningsmoenicarida Order †Cambropachycopida Order †Cambrocarida Order †Martinssoniida Order †Phosphatocopida Order †Bostrichopodida

Class †Thylacocephala Order †Ainiktozoiformes Order †Concavicarida Order †Conchyliocarida

Class Remipedia Order †Enantiopoda Order Nectiopoda

Class Branchiopoda

Subclass Sarsostraca Order Anostraca (Fairy shrimp) Order †Lipostraca Subclass Phyllopoda Infraclass Calmanostraca Order †Protocaridida Order †Kazacharthra Order Notostraca (Tadpole shrimp) Infraclass Diplostraca (Clam shrimp) Order Laevicaudata Order Spinicaudata Order Cyclestherida Order Anomopoda Order Ctenopoda Order Haplopoda Order Onychopoda

Class Cephalocarida Order Brachypoda (Horseshoe shrimp)

Class Thecostraca

Subclass Ascothoracida Order Dendrogastrida Order Laurida

Subclass Cirripedia (Barnacles) Infraclass Acrothoracica Order Cryptophialida Order Lithoglyptida Infraclass Rhizocephala Infraclass Thoracica Superorder Phosphatothoracica Order Iblomorpha Order †Eolepadomorpha Superorder Thoracicalcarea Order Calanticomorpha Order Pollicipedomorpha Order Scalpellomorpha Order †Archaeolepadomorpha Order †Brachylepadomorpha (unranked) Sessilia (Acorn barnacles) Order Balanomorpha Order Verrucomorpha

Subclass Facetotecta

Class Hexanauplia Subclass Copepoda (Copepods)

Infraclass Progymnoplea Order Platycopioida Infraclass Neocopepoda Clade Gymnoplea Order Calanoida Clade Podoplea Order Canuelloida Order Cyclopoida (incl. Poecilostomatoida) Order Gelyelloida Order Harpacticoida Order Misophrioida Order Monstrilloida Order Mormonilloida Order Siphonostomatoida

Class Ichthyostraca Subclass Branchiura Order Arguloida (Carp lice, or fish lice) Order †Cyclida (Cycloids) Subclass Pentastomida

Order Cephalobaenida Order Porocephalida Order Raillietiellida Order Reighardiida

Class Mystacocarida WoRMS (2021). Mystacocarida. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1079 on 2021-08-23 Order Mystacocaridida

Class Ostracoda (Ostracods, or seed shrimp)

Order †Eridostracoda

Subclass †Leperditicopa Order †Leperditicopida

Subclass †Leiocopa Order †Leiocopida

Subclass Palaeocopa Order Palaeocopida

Subclass Myodocopa Order Myodocopida Order Halocyprida

Subclass Podocopa Order Platycopida Order Podocopida

Class Malacostraca (Malcostracans, such as crabs and lobsters)

Subclass Eumalacostraca Superorder Syncarida Order Anaspidacea Calman, 1904 Order Bathynellacea Chappuis, 1915 Order †Palaeocaridacea Superorder †Eocarida Order †Eocaridacea Order †Pygocephalomorpha Superorder Peracarida Order Amphipoda (Includes freshwater shrimp and sandhoppers) Order Cumacea (Hooded shrimp) Order Isopoda (Isopods - includes wood lice) Order Lophogastrida Order Mictacea Order Mysida Order Spelaeogriphacea Order Stygiomysida Order Tanaidacea (Tanaids) Order Thermosbaenacea Superorder Eucarida Order Decapoda (Crayfish, crabs, lobsters, prawns, and shrimp) Order Euphausiacea (Krill) Order †Angustidontida

Subclass Hoplocarida Order Stomatopoda (Mantis shrimp) Order †Aeschronectida Order †Palaeostomatopoda

Subclass Phyllocarida Order †Archaeostraca Order †Hoplostraca Order Leptostraca

Subphylum †Artiopoda no class Order †Emeraldellida Order †Cheloniellida Order †Sidneyiformes Order †Agnostina

Class †Protosutura Order †Acanthomeridiida

Class †Aglaspida Order †Aglaspidida Order †Strabopida

Class †Trilobita

Order Retifaciida

Subclass †Petalopleura Order †Sinoburiida Order †Xandarellida

Subclass †Nectopleura Order †Nectaspidida

Subclass †Conciliterga Order †Helmetiida †

Subclass †Trilobita Order †Eodiscina Order †Olenellina Order †Asaphida Order †Aulacopleurida Order †Corynexochida Order †Harpetida Order †Redlichiida Order †Lichida Order †Phacopida Order †Proetida Order †Ptychopariida

Other classes no class Order †Isoxyida Order †Hymenocarina Order †Mollisoniida Order †Bradoriida Order †Burgessiida

Order †Fuxianhuiida Order †Habeliida

Class †Megacheira

Order †Leanchoiliida Order †Yohoiida

Class †Marrellomorpha Order †Acercostraca Order †Marrellida

Class †Dinocaridida Order †Radiodonta Order †Opabiniida

Class †Euthycarcinoidea Order †Euthycarcinida

References