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 Description:
Both of these trilobites possess the name specific name. The Illaenus
example is the unusual trilobite Illaenus intermedius in association
with an Asaphus intermedius seen here in the ventral preparation
mode. This Illaenus is one of the 50-odd members of the genus, and
known for the high profile of the cephalon which is thought to have
aided the trilobite in plowing through the substrate in search of
a meal. The well-inflated example of a high-eyestalked member of
the Asaphidae, this one is Asaphus intermedius. 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.
This taxon derives its species name from the length of the eyestalks,
being between the length of Asaphus punctatus, and the shorter-eyestalked
Asaphus kotlukovi. Notice the detail preserved here, with the hypostome,
or anchor for the mouthparts, readily visible. The pygidial doublure
is well-displayed as well. These two are examples of the amazing
diversity of trilobites to come from the Ordovician of Russia.
Also
see: Russian
trilobites
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