Hydrocephalus (trilobite)
Encyclopedia
Hydrocephalus is an extinct genus of redlichiid trilobite
Trilobite
Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...

 that was very common during the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 of Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

 and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. It lived around 536-510 mya. This trilobite is 15 cm long and more widely built than others of the time. In comparison to other members of its family
Paradoxididae
Paradoxididaeis a family of trilobites, containing the following genera:*Acadoparadoxides*Anabaraceps*Anabaraspis*Bajanaspis*Baltoparadoxides*Hydrocephalus*Paradoxides*Phanoptes*Plutonides*Primoriella...

, its glabellum appears swollen.
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