Trilobites
Order Asaphida Suborder Asaphina, Superfamily
Asaphoidea, Family Asaphidae
Geologic Age: Middle Ordovician
Trilobite
is 115 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
kowalewskii developed the highest eye stalks found in the formation, having desceded
from Asaphus cornutus with medium-high eye stalks. Note the significant
effacement
of the entire exoskeleton.
Also see: Russian
Trilobites Evolution
in Russian Ordovician Asaphids |
