Trilobites
Order Asaphida Suborder Asaphina, Superfamily
Asaphoidea, Family Asaphidae
Geologic Age: Lower Ordovician
Trilobite
is 115 mm long
Wolchov Horozon 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
broggeri was basal to this evolutionary innovations, giving rise to many species
along several lines of descent. Note
the significant
effacement of the entire exoskeleton.
Also see: Russian
Trilobites Evolution
in Russian Ordovician Asaphids |
