Hildoceras Ammonite, from Whitby, Yorkshire, England (REF:HILDO1)

Hildoceras had an evolute, laterally compressed shell. The coarse, widely-spaced, sickle-shaped ribbing on the sides is interrupted by a groove.

The suture line is very complex. It has a very distinctive rectangular whorl section, which on the venter carries three low keels separated by two grooves.

Hildoceras was a moderate swimmer in the Early Jurassic shelf seas.