Arthropods (Arthropoda)

What are arthropods?

Arthropods are invertebrate animals with an exoskeleton, segmented body and jointed legs. 

This group includes:

  • insects
  • crustaceans
  • spiders and other arachnids
  • centipedes and millipedes (myriapods)
  • trilobites

Arthropods as fossils

Arthropods with mineralised exoskeletons have especially good fossil representation, for example:

  • trilobites
  • ostracods
  • decapod crustaceans like crabs and lobsters

Soft parts such as the legs and gut preserve more rarely, but are known in fine detail for many species from sites of exceptional preservation as far back as the early Cambrian.

All arthropod fossils from the Cambrian and Ordovician, apart from some trackways, are from marine animals. 

Terrestrial groups such as centipedes, millipedes and arachnids are known from the Silurian and all younger periods. 

Amber is a source of high-quality arthropod fossils from the Cretaceous onwards.      

 

Eocene pseudoscorpion preserved in Baltic amber
Arthropod research

Discover what Palaeontology Department research is underway on the most diverse animal phylum of the last 520 million years. As well as exploring the evolutionary relationships of the main groups, we have projects focusing on trilobites, ostracods and centipedes.

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Classification

The phylum Arthropoda is divided into 2 subphyla:

  • Chelicerata, which includes:
    • Pycnogonida (sea spiders)
    • Euchelicerata, with 2 groups:
      • Xiphosura (horseshoe crabs)
      • Arachnida
  • Mandibulata (jawed arthropods), which includes:
    • Myriapoda (centipedes, millipedes, pauropods and symphylans)
    • Tetraconata or Pancrustacea (crustaceans and hexapods, including insects)

The wholly extinct class Trilobita is of unsettled position.

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