Olenellina
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Olenellina Temporal range: Cambrian - Series 2 |
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| Olenellus chiefensis | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Trilobita |
| Order: | Redlichiida |
| Suborder: | Olenellina |
| Superfamilies | |
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Olenellina is a suborder of the order Redlichiida of Trilobites that occurs about halfway during the Lower Cambrian, at the start of the stage called the Atdabanian. The earliest trilobites in the fossil record are arguably Olenellina, although the earliest Redlichiina and Eodiscina follow quickly. The suborder died out when the Lower passed into the Middle Cambrian, at the end of the stage called Toyonian. A feature uniting the Olenellina is the lack of rupture lines (or sutures) in the headshield, which in other trilobites assist the periodic moulting (or ecdysis), associated with arthropod growth. Some derived trilobites have lost facial sutures again (some Eodiscina, all Agnostina, and a few Phacopina), but all of these are blind, while all Olenellina have eyes.
The suborder contains four superfamilies: Olenelloidea (with 3 families and 5 stemgroup genera), Judomioidea (with 1 family and 3 stemgroup genera), Nevadioidea, and Fallotaspidoidea (with 3 families and 3 stemgroup genera). Lieberman, 2002, considered that the Fallotaspidoidea are a paraphyletic group because it gave rise to the Redlichiina; he did however not propose to restrict the Olenellina to the Olenelloidea, Judomioidea and Nevadioidea. Neither did he propose to assign this group of superfamilies to a newly formed order Olenellida, and consequently expand the Redlichiina to include the Fallotaspidoidea. This would imply that the Redlichiina would include taxa with and without dorsal sutures.
The Olenellina appear suddenly at the start of the Cambrian Series 2 (between Stage 2 Tommotian and Stage 3 Atdabanian) approximately 521 million years ago, and disappear at the end of this Series (between Stage 4 Toyonian and Stage 5 Amgan), 514 to 509 million years ago. The Olenellina probably first occurred on the paleocontinent Siberia and spread into the part of Gondwana that is now the Atlas Mountains, Baltica, Avalonia and Laurentia. In western Laurentia the first representatives to appear are Fallotaspididae, followed by Archaeaspididae, Nevadioidea and Holmiidae, and finally Biceratopsidae and Olenellidae. The Olenellina are not known from South China, Australia and most of Latin America and Africa, where the first trilobites were Redlichiina, that had already developed dorsal sutures.
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