Trilobite Order Harpetida


Harpetid Trilobites

Page within: Class Trilobita - Trilobite Classification

The most salient and distinguishing trait of the Harpetida (pronounced Har-pe-tee-da) is a semicircular brim surrounding the
Trilobite Taxonomy
Trilobite Phylogeny
Phylum Arthropoda
Subphylum Chelicerata
or Subphylum Schizoramia *
Superclass Arachnomorpha *
Class Trilobita

    Order Agnostida
    Order Redlichiida
    Order Corynexochida
    Order Phacopida
    Order Lichida
    Order Proetida
    Order Harpetida
    Order Ptychopariida
    Order Asaphida
    Order Odontopleurida
    Order Nectaspida
Trilobite Relatives
o Arthropoda
`--o Trilobita
   `--+--o Redlichiida
      |  |--Olenellina
      |  `--Redlichiina
      `--o Librostoma
* Different taxonomies are found, most recently with trilobites contained in Superclass Arachnomorpha in Subphylum Schizoramia.
cephalon (head) that is often perforated by small pores. This often very wide brim is thought to have filtered sediment while feeding. The brim extends backward from the front of the cephalon, and typically has a prominent suture along its anterior boundary. The Harpetida fossils normally show small eye nodules, 12 or more thoracic segments, and small pygidia. They lived from the Upper Cambrian and persisted to the Late Devonian period.

Harpetida became a distinct trilobite order only recently in 2002, after being split from Order Ptychopariida in which they were suborder Harpina. The Harpetids are most often considered to be descended from the Ptychopariids. Moreover, the Harpetida are now often considered to be a member of the Librostoma, a suborder erected by Fortey in 1990 to encompass Ptychopariida, Harpetida, Asaphida, and Proetida based in part on the shared trait of a natant hypostomal attachment (i.e., a hypostome mouthpart not anchored to the anterior doublure).



Subphylum Chelicerata
Class Trilobita
Subclass Librostoma
Order Harpatida
    Suborder Harpetina
          Superfamily Harpetioidea
                Family Harpetidae

Scotoharpes spasskii
Family Harpetidae
Middle Ordovician
Wolchow River Region, St Petersburg, Russia

Harpides plautini
Family Harpetidae
Lower Ordovician
Wolchow River Region, St Petersburg, Russia
Harpes perradiatus
Family Harpetidae
Laatchana, Morocco
Bohemoharpes sp
Family Harpetidae
Laatchana, Morocco
Harpides sp
Family Harpetidae
Lower Ordovician
Fezouata Formation, Dra Valley, Morocco

Ebach, M.C. & K.J. McNamara. 2002. A systematic revision of the family Harpetidae (Trilobita). Records of the Western Australian Museum 21:135-67.
Fortey, R.A. 1990. Ontogeny, hypostome atachment and trilobite classification. Palaeontology 33:529-76