Eoderoceras is an evolute, round whorled ammonite

Ammonitida

The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....

 from the Lower Jurassic with an outer row of distinct spines, and in some, an inner row of tubercles, on either side; ribs only on the inner whorls.

Eoderoceras, named by Leonard Spath

Leonard Frank Spath

Leonard Frank Spath was a British paleomalacologist and an ammonitologist, a specialist of ammonites.He gained a B.Sc in geology at Birkbeck College in 1912 and obtained employment at the British Museum as an assistant curator in the geology department...

 in 1925, is the type genus

Type genus

In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...

 for the family Eoderoceratidae

Eoderoceratidae

The Eoderoceratidae is the ancestral and most primitive family of the Eoderocerataceae; lower Jurassic ammonite cephalopods, characterized by evolute, commonly serpenticonic, shells that had long body chambers and would have had no stable floating position; and thus resemble contemporary...

 to which it belongs, which is part of the ammonitid superfamily Eoderocerataceae

Eoderocerataceae

Eoderocerataceae is a superfamily of true ammonites from the Lower Jurassic, comprising seven phylogenetically related families, characterized in general by having ribbed evolute shells that commonly bear spines or tubercles...

, ammonoid cephalopods distinct from the more conservative but more successful Nautiloidea still around today.