Wikipedia
Uptonia
Uptonia is an extinct ammonite from the Lower Jurassic that's included in the eoderoceratacean family Polymorphitidae.
The shell of Uptonia is evolute with rounded simple ribs that form strong chevrons as they cross the venter on the outer rim, and which are free of tubercles. Some grew to be fairly large. The suture is ammonitic, complex, with large lateral lobes