Asaphus
punctatus
Trilobites
Order Asaphida, Family Asaphidae
Geological
Time: Middle Ordovician, Asery Horizon
Size: (25.4
mm = 1 inch): 88 mm long by 50 mm wide on a 170 by 115 mm matrix
Fossil Site:
Wolchow River Region, St Petersburg, Russia
|  Description:
A well-inflated example of a high-eyestalked member of the
Asaphidae,
this is Asaphus punctatus. The region in which these trilobites
lived was subject to dramatic changes in salinity and turbidity,
and the trilobites were able to make rapid (geologically speaking)
evolutionary adjustments. These adjustments were thought to
be able
to allow them to see both predator and prey more easily. Coming
from an inland sea during the lower to middle Ordovician, the Russian
trilobites from near Saint Petersburg, Russia participated in the Great
Ordovician Radiation, which saw marine animal diversity increase
three-fold more than the Cambrian Explosion. The Russian
asaphid trilobites are a particularly interesting example of
descent with modification.
Also
see: Russian
trilobites
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