Asaphus major

Trilobites Order Asaphida Suborder Asaphina, Superfamily Asaphoidea, Family Asaphidae
Geologic Age: Middle Ordovician
Trilobite is 120 mm long
Asery Level deposits of the Wolchow River region near Saint Petersburg, Russia
Remarks: The area where these Russian trilobites lived in the Ordovician experienced dramatic changes in salinity and turbidity, exerting significant selective pressure. The fossil record shows rapid adaptation in some Asaphidae that evolved eyes on high stalks, allowing them to better see both predator and prey more easily. Asaphus major was in an evolutionary line that did not evolve high eye stalks. Note also the significant effacement of the entire exoskeleton.

Also see: Russian Trilobites Evolution in Russian Ordovician Asaphids