{{Short description|Extinct genus of arthropods}} {{Italic title}} {{Automatic_taxobox | name = ''Tariccoia arrusensis'' | fossil_range = {{fossilrange|Ordovician}} | image = Tarricoia collectie Paul Hille.jpg | image_caption = ''Tariccoia arrusensis'', 21 mm, from Sardegna, Italy | taxon = Tariccoia | authority = Hammann, 1990 | type_species = †''Tariccoia arrusensis'' | type_species_authority = Hammann, 1990 | subdivision_ranks = Other species | subdivision = ''T. tazagurtensis'' }}
'''''Tariccoia''''' is a genus of nektaspid arthropods belonging to the family Liwiidae, known from fossils found in Ordovician strata in Sardinia and Morocco. It is between {{convert|2.5|cm|in}} and {{convert|6|cm|in}} long. It has a headshield (or cephalon) wider than the tailshield (pygidium), and in between them three (or four?) thoracic body segments (somites).
== Etymology == The name of the genus references the Sardinian paleontologist M. Taricco. The species was named after the Riu is Arrus Member, the deposit in which it was found.<ref name="Hammann">{{cite journal |author=W. Hammann, R. Laske & G. L. Pillola |year=1990 |title=''Tariccoia arrusensis'' n. g. n. sp., an unusual trilobite-like arthropod. Rediscovery of the "phyllocarid" beds of Taricco (1922) in the Ordovician "Puddinga" sequence of Sardinia |journal=Bolletino della Societa Palaeontologica Italiana |volume=29 |pages=163–178}}</ref>
== Description == alt=|left|thumb|Drawing of ''Tariccoia arrusensis'' ''Tariccoia arrusensis'' is between 2.5 and 6 cm along the axis,<ref>L. Ramskold, J.-Y. Chen, G.D. Edgecombe, and G.-Q. Zhou ( 1996). Preservational folds simulating tergite junctions in tegopeltid and naraoiid arthropods. Lethaia 29:15-20. {{ISSN|0024-1164}}.[http://www.nhm.ac.uk/resources-rx/files/ramskold-et-al-1996-preservational-folds-94162.pdf]</ref> almost half a wide as long. The dorsal exoskeleton consists of a cephalon, a pygidium and two or three thoracic somites with articulating half-rings, all non-calcified. The cephalon is sub-semicircular, widest near the rounded genal angles. The cephalon is wider than the pygidium. Eyes are absent. Antennas are not known. The body is constricted at the two or three thoracic somites, so the animal gives the impression to have a waist. The pygidium is widest before midlength. The pygidium has a mid-ridge.<ref name='Hammann'/>
=== Differences with other Liwiidae === *''Tariccoia arrusensis'' differs from ''Liwia'' by having 3 clearly visible thoracic somites (perhaps a 4th is obscured by the cephalon) instead of 4. ''T. arrusensis '' has a mid-length ridge on the pygidium, which is not known from ''Liwia''. ''Tariccoia'' also has an oval pygidium with an entire margin, while ''Liwia'' has five pairs of modest marginal spines, a straight anterior border and a concave posterior border. *''T. arrusensis'' differs from ''Buenaspis forteyi'', that has a cephalon and pygidium that are not wider than its 6 thoracic somites. The pygidium of ''B. forteyi'' is wider than long, with a straight anterior border. ''Buenaspis'' and ''Tariccoia'' have an entire margin and a mid-ridge on the pygidium in common. *''T. arrusensis'' differs from ''Soomaspis splendida'', that has an oval cephalon, and lacks visible segmentation of the pygidium. ''Tariccoia'' and ''Soomaspis'' both have a broad doublure and lack a lengthwise mid-ridge on the cephalon. In both species the pygidium is about as long as wide, but in ''Soomaspis'' the widest point is around midlength, while ''Tariccoia'' is widest in the frontal half. The species share 3 thoracic somites, an entire margin and a mid-ridge on the pygidium.<ref>{{cite book |author=E. Bonino & C. Kier |year=2010 |title=The Back to the Past Museum Guide to Trilobites |pages=18–19, fig. 9}}</ref>
== Distribution == ''T. arrusensis'' has been collected from the Upper Ordovician (Sandbian to Katian) Riu is Arrus Member, Monte Argentu Formation, Sardinia, Italy.<ref name='Hammann'/> ''T.'' ''tazagurtensis'' has been collected from the Fezouata Formation of Morocco dating to the Early Ordovician (Tremadocian).<ref name=":0">{{Cite journal |last1=Pérez-Peris |first1=Francesc |last2=Laibl |first2=Lukáš |last3=Lustri |first3=Lorenzo |last4=Gueriau |first4=Pierre |last5=Antcliffe |first5=Jonathan B |last6=Bath Enright |first6=Orla G |last7=Daley |first7=Allison C |date=2020-07-10 |title=A new nektaspid euarthropod from the Lower Ordovician strata of Morocco |url=https://serval.unil.ch/resource/serval:BIB_CFB1EE69A85F.P001/REF.pdf |journal=Geological Magazine |volume=158 |issue=3 |pages=509–517 |doi=10.1017/s001675682000062x |s2cid=221859513 |issn=0016-7568}}</ref>
== Habitat == ''Tariccoia arrusensis'' is thought to have lived in a restricted reduced oxygen marine environment close to shore such as a lagoon or a bay in what was then the cold high-latitude margin of southern Gondwana, where it was locally abundant alongside macroscopic algae. ''Tariccoia tazagurtensis'' also lived in cold waters in high-latitude southern Gondwana, but it was an extremely rare member of the fauna and lived in open shallow-marine conditions.<ref name=":0" />
== References == {{Reflist|40em}}
{{Artiopoda}} {{Taxonbar|from=Q7686010}}
Category:Nektaspida Category:Ordovician arthropods Category:Fossils of Italy Category:Fossil taxa described in 1990 Category:Katian Category:Artiopod genera