Sponge and Trilobite Assemblage
Choia
sp. Class
Demospongia, Subclass Ceractinomorpha, Order Monaxida, Family
Choiidae
Peronopsis
sp.
Trilobite
Order Agnostida, Family Peronopsidae
Geological
Time: Middle Cambrian (~520 million years ago)
Size (25.4
mm = 1 inch): Peronopsis: 4 mm long by 2 mm across Choia: 30 mm and
18 mm long by 12 mm across on a 100 mm by 85 mm matrix
Fossil
Site: Wheeler Shale, Millard County, Utah
Code:
ND008
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 Description:
This plaque displays a small Agnostid trilobite in association with a spiky sponge
known as Choia. Choia lived on the seafloor unattached and
filtered food particles from the water. Choia are very rare
in the Burgess Shale, and not very common in Cambrian strata
of Utah as well. Sponge fossils from the Cambrian
Explosion are found in various Cambrian
sites in North America, most notably the Burgess Shale of Canada,
and like this specimen
in the Cambriian strata of Utah. Many sponges are also described
from the Chengjiang
biota of China. Sponges are believed to
have undergone repeated radiations in the Phanerozoic, and
probably attained their largest diversity in the Cretaceous.
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