Name: Illaenus
schmidti var cardinalis Russian trilobite Trilobite,
Order Corynexochida, Suborder
Illaenina, Family Illaenidae
Geologic
Time : Middle Ordovician
Size
(25.4 mm = 1 inch): 130 mm long by 80 mm wide on a 115 by 95 mm matrix
Location:
Asery Horizon deposits of the Wolchow River region near Saint Petersburg,
Russia
|  Description:
This is an example of the unusual trilobite Illaenus schmidti. Based upon the
fact that the freestanding genal spines are longer and more widely extended than
some examples it is most likely an example of the variety cardinalis. The other
variety, cliens, has less flaring, elongated genals. Some think these may have
been an expression of sexual dimorphism. This 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.
At 130 mm in length (measured along the curve), this one is near the top end in
size for the taxon.
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