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Additional Information
Order: Ptychopariida, Family: Ptychopariidae
Characterized by eyes that are positioned along the glabella on the suture line. Molts of these trilobites are common and can usually be discerned by the lack of the free checks (librigena). Blade-like genal spines are often present on the tips of the librigena, as is the case with Achlysopsis.
These are some of the oldest and most primitive of trilobites. They thrived during the later half of the Cambrian period but did not survive the Ordovician - Silurian extinction event.
Trilobites in this order include:
Elrathia
Achlysopsis
Bolaspidella
The Pioche Shale is an Early to Middle Cambrian Burgess shale-type Lagerstätte in Nevada that preserves arthropods and worms similar to the Burgess Shale.
In the Eureka area, the Pioche has a variable lithologic character which is most commonly a greenish or grey, calcareous or micaceous shale which may locally be reddish or brown in color with abundant trilobite parts throughout the formation.
Vendor: fossil soup - ZZ
SKU Number: SQ5388284
Rhombampyx yii trilobite from the Middle Ordovician, Meitan Formation, Zunyi, Guizhou, China.
The distinct oval/rhomboid dome where the anterior needle spine meets the head is the highly inflated glabella. It is slightly compressed but shows the distinctive bulbous shape unique to raphiophorids.
You can clearly see a thin, straight line pointing straight up from the top of the glabella. This is the base of the median snout spine.
The two elongated cheek spines can be seen on either side of the body. In life, these spines flared outward to stabilize the animal or deter predators, but post-mortem movement or burial compaction has curved it around the cephalon.
Full dimensions are listed below.