Olenellina
| Olenellina | ||||||||||||
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The trilobite Mesonacis vermontanus from the suborder Olenellina |
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| Temporal occurrence | ||||||||||||
| Lower Cambrian | ||||||||||||
| 524 to 513 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Olenellina | ||||||||||||
| Walcott , 1890 |
The Olenellina are a suborder of the trilobite order Redlichiida . The subordination consists of two superfamilies, the Olenelloidea (with two families) and the Fallotaspidoidea (with five families). The first trilobites to appear in the fossil record are found among the Olenellina.
description
(Morphological terms are explained in more detail in the article Trilobites .)
Cephalon : Facial seams are missing. The glabella has quite deep side furrows. In some species the frontal glabellar lobe is almost a hemispherical bulge. The hypostome is conterminant, the rostral plate sitting between the doublets is very wide and bordered by non-binding rostral sutures.
Thorax : Has a large number of flat segments, spines occasionally attach to the spindle.
Pygidium : narrow, consists of only a few segments.
Calcified protaspid forms are not preserved. The body of the Olenellina is flattened, its cuticle is thin.
Distribution and occurrence
The Olenellina appear for the first time in the course of the Lower Cambrian and died out before the end of the Lower Cambrian.
The Olenellina are found mainly on Laurentia (northwest and southwest of Canada , southwest and northeast of the United States ), on Avalonia ( Shropshire , England ), on Baltica ( Estonia , Poland , Norway , Sweden ), in western Gondwana ( Morocco ), in the northeast and southeastern Siberia and western Mongolia .
The family of Olenellidae (Olenelliden) is restricted to the Cambrian continent Laurentia (North American Fauna Province - North America and associated areas). Olenellidae are quite common and also define the extent of Laurentia at that time. Their sudden disappearance defines the border between Lower and Central Cambrian in their area of distribution.
Between the Olenellids and the Redlichiina there is a clearly pronounced exclusivity of their occurrence, only in Morocco and in western Mongolia do both faunas occur together.
Systematics
- Superfamily Olenelloidea
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Superfamily Fallotaspidoidea
- Archaeaspidae (or Archaeaspididae)
- Fallotaspidae (or Fallotaspididae)
- Judomiidae
- Neltneriidae
- Nevadiidae
The Daguinaspidae are now called Daguinaspinae a subfamily of the Fallotaspidae.
Web links
- Sam Gon III: order Redlichiida
- Classification of the trilobites
swell
- Benton, MJ (1993): The Fossil Record 2 . Chapman & Hall