Harpetida

Harpetida
A Harpetida trilobite from Morocco.
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Subclass:	Librostoma
Order:	Harpetida
Families
Entomaspididae Harpetidae Harpididae

Harpetida is one of the nine orders of the extinct arthropod class Trilobita. They lived from the Upper Cambrian to the Late Devonian period.

The Harpetida are characterized among trilobites by bearing a semicircular brim around the cephalon (head) which is often perforated by small pores. This brim is thought to serve as a filter-feeding apparatus. The brim stretches backward on either side of the cephalon (head) and typically has a pronounced suture along the outside.

The eyespots are typically reduced to small tubercles, though they have strong ridges stretching to the glabella (central region of the cephalon). They also typically have 12 or more thoracic segments. The pygidia are usually small.

The Harpetida were formerly included in the family Ptychopariida, but were recently given their own order (Ebach & McNamara 2002). The subclass Librostoma was created in 1990 by Richard Fortey to cover the orders formally included with the Ptychopariida. The name Harpidae was once used as the name for the trilobite family containing the type genus Harpes. However, this is in conflict with the use of the same name for a family of extant molluscs and that taxon had precedence.

External links

• Order Harpetida - from A Guide to the Orders of Trilobites by Sam Gon III

Harpes perradiatus (Devonian, Morocco)

Trilobites Taxonomy Orders Agnostida Asaphida Corynexochida Harpetida Nektaspida Redlichiida Lichida Phacopida Proetida Ptychopariida Genera List of trilobites Geochronology Cambrian Ordovician Silurian Devonian Carboniferous Permian Notable fossils Acropyge Calymene Cheiropyge Eofallotaspis tioutensis Hupetina antiqua Isotelus Kathwaia Misszhouia Olenus Ogygiocarella debuchii Paraphillipsia Phacops rana Profallotaspis jakutensis Pseudophillipsia Serrania gordaensis Notable trilobitologists Alexander von Humboldt Joachim Barrande Alfred Russel Wallace Charles Doolittle Walcott Charles Emerson Beecher Roderick Murchison Adam Sedgwick Rudolf Kaufmann Rudolf Richter & Emma Richter Martin Basse Niles Eldredge George Frederic Matthew Harry B. Whittington Brian D. E. Chatterton Richard Fortey Euan Clarkson Franco Rasetti Gregory D. Edgecombe Bruce S. Lieberman Gerald J. Kloc Gerhard K. B. Alberti Teiichi Kobayashi Johan Wilhelm Dalman Paleobiology Cambrian explosion Cruziana Diplichnites Permian–Triassic extinction event Rusophycus Trilobite zone Notable fossil sites Anti-Atlas Mountains Beecher's Trilobite Bed Burgess Shale Emu Bay Shale Gees, Gerolstein Hunsrück Slate Jince Formation Latham Shale Llandeilo Group Maotianshan Shales Silica Shale Formation Walcott–Rust quarry Wenlock Group Wheeler Shale Wolchov River Wren's Nest Morphology Exoskeleton Tagmata Cephalon Thorax Pygidium Axial lobe Pleural lobe Terminology Cranidium Effacement Enrollment Facial sutures Fixigena Gena Genal angle Glabella Gonatoparian Heteronomous Homonomous Hypostome Isopygous Librigena Macropygous Micropygous Opisthoparian Proparian Prosopon Spinosity Subisopygous Soft body parts Appendages Digestive tract Internal organs Musculature Antennae Eyes Sensory pits Category:Trilobites