Trilobites
Order Asaphida Suborder Asaphina, Superfamily
Asaphoidea, Family Asaphidae
Geologic Age: Middle Ordovician
Trilobite
is 80 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
latus descended from Asaphus cornutus that had medium-high eye stalks.
Note the significant
effacement of the entire exoskeleton.
Also see: Russian
Trilobites Evolution
in Russian Ordovician Asaphids
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