Simocephalus Species

For morphological terms see: Cladocera Anatomy

Three Simocephalus species inhabit the Great Lakes. These are relatively large cladocerans with lengths of up to 4.0mm. All are considered uncommon in the Great Lakes, though S. serrulatus and vetulus are occassionally found in high densities in the littoral areas of Lake Erie. Fine features of the head and postabdominal claws are used to distinguish among species - necessitating use of a high-powered light microscope at a minimum.

Unique features highlighted in green.

Postabdominal claws with a pecten.
Simocephalus exspinosus

Vertex evenly rounded about the eye and without serrulations or spinules. Simocephalus vetulus

Vertex more or less angular with serrations or spinules in front of or below the eye.
Simocephalus serrulatus