Yukoniidae

Yukoniidae; Temporal range: Atdabanian to Toyonian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Order:	Agnostida
Suborder:	Eodiscina
Superfamily:	Eodiscoidea
Family:	Yukoniidae; S. Zhang, 1980
genera
	Yukonia Palmer, 1968; Alaskadiscus S. Zhang in W. Zhang, Lu et al., 1980; Egyngolia Korobov, 1980 (Atdabanian); Ekwipagetia Fritz, 1973 (Atdabanian); Lenadiscus Repina in Khomentovskii & Repina, 1965 (Botomian); Yukonides Fritz, 1972 (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. ^[1]^[2]

Type Genus and species

Yukonia intermedia Palmer 1968 (Plate 2, figures 14, 17–19, 22, 23, 27, 28; text figure 4). ^[3]

Taxonomy

The Yukoniidae probably descended from the Tsunydiscidae and gave rise to the Eodiscidae.^[4]

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.^[5]

References

^ S. M. GON III. "Order Agnostida". Retrieved December 3, 2010.
^ MIKKO HAARAMO (March 11, 2008). "†Yukoniidae". Mikko's Phylogeny Archive. Retrieved December 3, 2010.
^ PALMER, A. R. 1968, Cambrian trilobites of east-central Alaska. Prof. Pap. U. S. Geol. Surv., 559-B pp. B1-B115, pls. 1-15.
^ JELL, P.A. (1975). "Australian Middle Cambrian Eodiscoids with a review of the superfamily". Palaeontographica Abteilung A. 150: 1–97. cited in H.B. WHITTINGTON; et al., eds. (1997). Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida.
^ WHITTINGTON, H.B.; et al. (1997). Introduction, Order Agnostida, Order Redlichiida. Treatise on Invertebrate Paleontology. Vol. Part O.Revised, Volume 1 – Trilobita. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. pp. 398–400. ISBN 0-8137-3108-9.

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[1] S. M. GON III. "Order Agnostida". Retrieved December 3, 2010.

[2] MIKKO HAARAMO (March 11, 2008). "†Yukoniidae". Mikko's Phylogeny Archive. Retrieved December 3, 2010.

[3] PALMER, A. R. 1968, Cambrian trilobites of east-central Alaska. Prof. Pap. U. S. Geol. Surv., 559-B pp. B1-B115, pls. 1-15.

[4] JELL, P.A. (1975). "Australian Middle Cambrian Eodiscoids with a review of the superfamily". Palaeontographica Abteilung A. 150: 1–97. cited in H.B. WHITTINGTON; et al., eds. (1997). Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida.

[Treatise-5] WHITTINGTON, H.B.; et al. (1997). Introduction, Order Agnostida, Order Redlichiida. Treatise on Invertebrate Paleontology. Vol. Part O.Revised, Volume 1 – Trilobita. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. pp. 398–400. ISBN 0-8137-3108-9.

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