Hercoceras is a genus of trochoidally coiled nautiloid cephalopods placed in the nautilid family Rutoceratidae. These cephalopod lived i in the Eifelian age of the middle Devonian Period, which occurred 398-391 million years ago. Their shells have prominent lateral outgrowths in the form of spines and a high intraspecific variability. Systematic The Paleobiology database places Hercoceras in the family Rutoceratidae in the order Nautilida, but according to some authors it should not be considered an early nautilid. They place this genus in the family Hercoceratidae in the superfamily Rutoceratoidea in the order Oncocerida. Species Hercoceras mirum Barrande Hercoceras transiens Barrande References The Paleobiology Database Sepkoski, Jack Sepkoski's Online Genus Database – Cephalopodes Museum of Comparative Zoology – Harvard University V. Turek – 2007 Systematic position and variability of the Devonian nautiloids Hercoceras and Ptenoceras Prehistoric nautiloid genera