Asaphus intermedius

Trilobites Order Asaphida Suborder Asaphina, Superfamily Asaphoidea, Family Asaphidae
Geologic Age: Middle Ordovician
Trilobite is 100 mm long
Asery Horizon 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 intermedius descended from Asaphus punctatus to have higher eye staks than its progenitor. Also note the significant effacement of the entire exoskeleton, which is typical in many asaphids.

Also see: Russian Trilobites Evolution in Russian Ordovician Asaphids








Asaphus intermedius Asaphida Trilobite

The Cephalon is effaced and smooth:

 Asaphus intermedius Russian Trilobite

Asaphus intermedius Evolved Eye Stalks

The Cephalon is effaced and smooth: