Peachella
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Peachella Temporal range: Toyonian (Upper Olenellus-zone) |
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| Peachella iddingsi reconstruction | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Trilobita |
| Order: | Redlichiida |
| Family: | Biceratopsidae |
| Subfamily: | Biceratopsinae |
| Genus: |
Peachella Walcott, 1910 |
| Type species | |
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Olenellus iddingsi Walcott, 1884 |
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| Species | |
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Peachella is an extinct genus of trilobites, fossil marine arthropods, with species of average size (about 3.5 centimetres or 1.4 inches long). It lived during the Toyonian stage (Upper Olenellus-zone), 516 to 513 million years ago, in what is today the South-Western United States. It can easily be distinguished from other trilobites by its club-like genal spines.
Peachella is named in honor of Benjamin Neeve Peach, a British geologist. The species epithed brevispina is derived from Latin and means 'short spine'. P. iddingsi was named in honor of Joseph P. Iddings, an accomplished American geologist.
The earliest occurrence of the ancestral Eopeachella angustispina predates both Peachella species, its latest occurrence overlaps with P. iddingsi, which, in turn overlaps with P. brevispina. E. angustispina has thick, tapered, blunt, genal spines and shallow but clear glabellar furrows. This species therefore bridges the morphological gap between the derived Peachella species and earlier olenelloid relatives that possess ‘normal’ genal spines.
As with most early trilobites, Peachella has an almost flat exoskeleton, that is only thinly calcified. It also shares crescent-shaped eye ridges, but these rise above the exoskeleton. As part of the Olenellina suborder, Peachella lacks dorsal sutures. Like all other members of the Olenelloidea superfamily, the eye-ridges spring from the back of the frontal lobe (L4) of the central area of the cephalon, that is called glabella. Peachella is an average sized biceratopsid trilobite, that exhibits the strongly effaced cephalic features that are typical for a clade wikthin the Biceratopsinae subfamily. It has the enormous sickle-shaped pleural spines on the 3rd thoracal segment with the rest of the Biceratopsidae family (except for Bolbolenellus). Peachella is unique in having short, wide, strongly inflated genal spines, with broadly rounded tips. The cephalon is semi-circular in outline with short, strongly inflated rounded spines. The central area of the cephalon (or glabella) is elongated, reaching the anterior border, but its features are strongly effaced, almost showing no furrows. The frontal 14 or 15 segments (or prothorax) can readily be distinguished from the terminal 9 to 11 (forming the opisthothorax). The last segment of the prothorax may carry a large spine. The tips of the pleura are rounded, which is unlike the usual pointed terminations in other Olenellina. The tailshield (or pygidium) is very small and subquadrate in shape.
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Wikipedia