Harpetida

{{Short description|Extinct order of trilobites}} {{more citations needed|date=March 2014}} {{Automatic taxobox | fossil_range = {{fossil range|Furongian|Frasnian}} | image = Harpes perradiatus fossil trilobite (Devonian, Morocco).jpg | image_caption = A Harpetida trilobite from Morocco. | taxon = Harpetida | authority = Whittington, 1959 | subdivision_ranks = Families | subdivision = *Entomaspididae *Harpetidae *Harpididae }}

'''Harpetida''' is one of the eleven orders of the extinct arthropod class Trilobita. The first harpetid trilobites appear in the Upper Cambrian, and the last species die out in the late Devonian period.<ref name="Mcnamaraetal2009"></ref>

Harpetid trilobites are characterized among trilobites by bearing a comparatively large, 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 compound eyes 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 families of Harpetida were formerly included in the order Ptychopariida, but were recently given their own order in 2002.<ref>{{Cite journal |last=Ebach |first=Malte C. |last2=McNamara |first2=Kenneth J. |date=2002 |title=A systematic revision of the family Harpetidae (Trilobita) |url=https://doi.org/10.18195/issn.0312-3162.21(3).2002.235-267 |journal=Records of the Western Australian Museum |volume=21 |issue=3 |pages=235 |doi=10.18195/issn.0312-3162.21(3).2002.235-267 |issn=0312-3162}}</ref> The subclass Librostoma was erected in 1990 by Richard Fortey to cover the various orders originally placed within Ptychopariida.<ref>Ontogeny, hypostome attachment and trilobite classification. RA Fortey, Palaeontology, 1990</ref> 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 the family of harp snails and that taxon had precedence.<ref>{{Cite web |last=Dr. Samuel M. Gon III |title=Harpetida Fact Sheet |url=https://www.trilobites.info/ordharpetida.htm |access-date=2025-06-10 |website=www.trilobites.info}}</ref>

==Families and genera== [[File:Entomaspis radiata.JPG|thumb|Life reconstruction of the Late Cambrian harpetid trilobite, ''Entomaspis radiata'', from Utah ]] [[File:A finely conserved Harpides sp., an ancient arthropod of the Ordivician..jpg|thumb|A fine ''Harpides'' sp., in the Ordovician shales of the Eastern Anti Atlas, Morocco ]] {{Div col |colwidth=30em}} *Entomaspididae **''Baikadamaspis'' **''Entomaspis'' (=''Hypothetica'') *Harpetidae **''Arraphus'' **''Bohemoharpes'' (=''Declivoharpes''; =''Unguloharpes'') **''Bowmania'' **''Brachyhipposiderus'' **''Conococheaguea'' **''Dolichoharpes'' **''Dubhglasina'' (=''Australoharpes''; ''Sinoharpes'') **''Eoharpes'' (/''Harpina'') **''Eotrinucleus'' **''Eskoharpes'' (=''Globoharpes''?)<ref name="Mcnamaraetal2009"></ref><ref name="JOHNSON2024">{{cite web |last1=Johnson |first1=Robert. G. |title=Devonian Harpetidae from the central and eastern Anti–Atlas, Morocco. |url=https://www.mapress.com/zt/article/view/zootaxa.5450.1.1 |publisher=Zootaxa}}</ref> **''Globoharpes''(?) <ref name="Mcnamaraetal2009">{{cite web |last1=McNamara |first1=Kenneth J. |last2=Feist |first2=Raimund |last3=Ebach |first3=Malte C. |title=PATTERNS OF EVOLUTION AND EXTINCTION IN THE LAST HARPETID TRILOBITES DURING THE LATE DEVONIAN (FRASNIAN) |url=https://onlinelibrary.wiley.com/doi/full/10.1111/j.1475-4983.2008.00832.x |publisher=Palaeontology |doi=10.1111/j.1475-4983.2008.00832.x}}</ref><ref name="JOHNSON2024"></ref> **''Harpes'' (=''Helioharpes''; ''Reticuloharpes'') **''Heterocaryon'' **''Hibbertia'' (/''Platyharpes''; ''Harpesoides''; ''Metaharpes''; ''Paraharpes''; ''Thorslundops''; ''Wegelinia'') **''Kathrynia'' **''Kielania'' (=''Lowtheria'') **''Lioharpes'' (=''Fritchapsis'') **''Maghroharpes''<ref name="JOHNSON2024"></ref> **''Paleoharpes'' **''Pinnuloharpes''<ref name="JOHNSON2024"></ref> **''Scotoharpes'' (=''Aristoharpes''; ''Selenoharpes''). **''Stoloharpes''<ref name="JOHNSON2024"></ref> *Harpididae **''Chencunia'' **''Dictyocephalites'' **''Fissocephalus'' **''Harpides'' **''Harpidoides'' **''Kitatella'' **''Loganopeltis'' **''Loganopeltoides'' **''Metaharpides'' **''Paraharpides'' **''Pscemiaspis'' {{Div col end}}

==References== {{Reflist}} ==External links== {{Commonscat}} *[https://www.trilobites.info/ordharpetida.htm Order Harpetida] - from A Guide to the Orders of Trilobites by Sam Gon III

Category:Harpetida Category:Trilobite orders Category:Cambrian first appearances Category:Late Devonian animals Category:Late Devonian extinctions