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 |
