Stereotoceras
Stereotoceras is a Middle and Upper Devonian genus in the oncocerid family Brevicoceratidae that formed a smooth, depressed, gyroconic shell with the dorsum much flatter that the venter. Sutures are straight ventrally but have dorsal lobes. Growth lines outline a ventral hyponomic sinus but are otherwise transverse. The siphuncle in ventral, nummuloidal, with discrete, irregular, actinosiphonate deposits at the septal foramina. References
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