{{Automatic taxobox | fossil_range = {{Geological range|522|510|Atdabanian to Toyonian}} | display_parents = 2 | taxon = Yukoniidae | authority = S. Zhang, 1980 | subdivision_ranks = Genera | subdivision = * ''Alaskadiscus'' <small>S. Zhang ''in'' W. Zhang, Lu ''et al.'', 1980</small><!--- PBDB contains ''Alaskadiscus'' Rohr et al., 2003 (snail), which seems to be a junior homonym, hence not available unless something is amiss ''Alaskadiscus'' S. Zhang, 1980 ---> * ''Egyngolia'' <small>Korobov, 1980</small> (Atdabanian) * ''Ekwipagetia'' <small>Fritz, 1973</small> (Atdabanian) * ''Lenadiscus'' <small>Repina ''in'' Khomentovskii & Repina, 1965</small> (Botomian) * ''Yukonia'' <small>Palmer, 1968</small> * ''Yukonides'' <small>Fritz, 1972</small> (Atdabanian) }}
'''Yukoniidae''' S. Zhang, 1980 [''nom. transl''. et ''emend''. Jell, ''in'' Whittington ''et al''., 1997 ''ex'' Yukoniinae S. Zhang in W. Zhang, Lu ''et al''., 1980] is a small family of trilobites, belonging to the Eodiscina.<ref>{{cite web |url=http://www.trilobites.info/ordagnostida.htm |title=Order Agnostida |author=S. M. GON III |access-date=December 3, 2010}}</ref><ref>{{Cite web |url=http://www.helsinki.fi/~mhaaramo/metazoa/protostoma/arthropoda/trilobita/Eodiscina/Yukoniidae.html |work=Mikko's Phylogeny Archive |title=†Yukoniidae |access-date=December 3, 2010 |date=March 11, 2008 |author=MIKKO HAARAMO}}</ref>
== Type genus and species ==
'''''Yukonia intermedia''''' Palmer 1968 (Plate 2, figures 14, 17–19, 22, 23, 27, 28; text figure 4). <ref> PALMER, A. R. 1968, Cambrian trilobites of east-central Alaska. ''Prof. Pap. U. S. Geol. Surv''., 559-B pp. B1-B115, pls. 1-15. </ref>
== Taxonomy == The Yukoniidae probably descended from the Tsunyidiscidae and gave rise to the Eodiscidae.<ref>{{cite journal|last= JELL|first= P.A.|year= 1975|title= Australian Middle Cambrian Eodiscoids with a review of the superfamily|journal= Palaeontographica Abteilung A|volume=150|pages=1–97}} cited in {{cite book|editor= H.B. WHITTINGTON|title= Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida|year= 1997|display-editors=etal}}</ref>
== Description == Yukoniidae are typically isopygous, belonging to the Superfamily Eodiscoidea. The narrow glabella is usually parallel sided, anteriorly rounded and separated from smooth anterior border by broad (''sag''.) preglabellar field which occupies about 25% of cephalic length excluding occipital spine. Posterior glabellar furrows are reduced to a pair of slits low on sides of glabella and directed backwards. Occipital ring bears a strong backwardly directed spine. ''Yukonia intermedia'' Palmer (1968) has three thoracic segments, the anterior of which has strong backwardly directed pleural spines. Pygidium of Yukoniidae has an axis of three to seven rings.<ref name="Treatise">{{cite book|last= WHITTINGTON|first= H.B.|year= 1997|title= Introduction, Order Agnostida, Order Redlichiida|publisher= Geological Society of America/University of Kansas Press|series= Treatise on Invertebrate Paleontology|volume= Part O.Revised, Volume 1 – Trilobita|pages= [https://archive.org/details/treatiseoninvert0002unse/page/398 398–400]|location= Boulder, Colorado/Lawrence, Kansas|isbn= 0-8137-3108-9|display-authors= etal|url= https://archive.org/details/treatiseoninvert0002unse/page/398}}</ref>
== References == {{Reflist}}
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Category:Eodiscina Category:Trilobite families Category:Cambrian trilobites Category:Cambrian first appearances Category:Cambrian Series 2 extinctions Category:Trilobites of North America
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