Here is a rare Cambrian Trilobite from Nevada that belongs likely to a new Alokistocarid species. It resembles strongly Piochaspis sellata that also occurs in the Chisholm Shale. But in detail it differs on servilal species features. First of all the amount of pleural segments is is significtly less compared with Piochaspis. The Holotype of Piochaspis sellata has 17 segments this specimen has ony 12. Although a inner species variation bandwidth of the amount body segments is well known on Ptychopariid trilobites is this difference quite to significant. Also the pygidium of Piochaspis sellata is more narrow compared to this trilobite.
On this specimen is the pygidium slightly flipped under but is width is well visible. On this specimen the Pygidium has aproxematly 2/3 of the   Cephalon width. On P. sellata it tends to have the width of the glabella.
The Cephalon of this specimen is very similar to Piochaspis sellata.
The Trilobite is about 13 mm long
 

Aee also : http://jbricegayet.free.fr/pages/anglais/Ealokistocaridnsp.htm

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