Trilobita, Order Asaphida,
Site: Asery level, St. Petersburg region, Wolchow river, Russia
from the Middle Ordovician uppermost Asery Level deposits near Saint
Petersburg, Russia, this is an example of the rare Asaphid trilobite,
Pseudobasilicus. What use did the pancake-like profile serve? Here
are two possibilties: 1.
The broad profile would have allowed it to set atop a fine silty
bottom, much like snowshoes; 2.
The low profile would have allowed it to conceal itself from both
predators and prey, with only its upraised eyes showing, much like
today's flounders and stingrays.
Also see: Russian