Olenellidae

Olenellidae; Temporal range: Botomian/Toyonian (Olenellus-zone) PreꞒ Ꞓ O S D C P T J K Pg N
	Olenellus fowleri
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Order:	Redlichiida
Suborder:	Olenellina
Superfamily:	Olenelloidea
Family:	Olenellidae; Walcott, 1890
Subfamilies
	Olenellinae; Mesonacinae;

Olenellidae is an extinct family of redlichiid trilobite arthropods. Olenellids lived during the late Lower Cambrian (Botomian/Toyonian) in the so-called Olenellus-zone in the former paleocontinent of Laurentia[1] plus parts of what became the Famatinian orogen in what is now Argentina.[2] This family can be distinguished from most other Olenellina by the partial merger of the frontal (L3) and middle pair (L2) of lateral lobes of the central area of the cephalon, that is called glabella, creating two isolated slits.[1]

Key to the subfamilies

1	The angle in the back rim of the cephalon is less than 15°. Genal spines are reaching back no further than the 6th thorax segment. Spine on the 15th thorax segment almost as wide as the axis.[1] → Olenellinae
-	The angle in the back rim of the cephalon is more than 25°. Genal spines are reaching back at least to the 8th thorax segment. spine on the 15th thorax segment less than half as wide as the axis.[1] → Mesonacinae

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References

Lieberman, B.S. (1999). "Systematic Revision of the Olenelloidea (Trilobita, Cambrian)" (PDF). Bulletin of the Peabody Museum of Natural History. 45.
Dalla Salda, Luis H.; Dalziel, Ian W.D.; Cingolani, Carlos A.; Varela, Ricardo (1992). "Did the Taconic Appalachians continue into southern South America?". Geology. 20: 1059–1062. doi:10.1130/0091-7613(1992)020<1059:dttaci>2.3.co;2.

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[Lieberman_1999-1] Lieberman, B.S. (1999). "Systematic Revision of the Olenelloidea (Trilobita, Cambrian)" (PDF). Bulletin of the Peabody Museum of Natural History. 45.

[2] Dalla Salda, Luis H.; Dalziel, Ian W.D.; Cingolani, Carlos A.; Varela, Ricardo (1992). "Did the Taconic Appalachians continue into southern South America?". Geology. 20: 1059–1062. doi:10.1130/0091-7613(1992)020<1059:dttaci>2.3.co;2.