Frogdenites is an extinct ammonite genus from the order Ammonitida

Ammonitida

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

 that lived during the Middle Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

in what is now Europe, Canada, and Tibet. Frogdenites is included in the Otoitidae, a family which makes up part of the ammonitid superfamily, Stephanocerataceae.

Frogdenites has an evolute globular shell with a deep umbilicus and covered by bifurcating ribs that cross the venter, the outer rim of the shell, without interruption.

References

• Arkell et al,1957; Ammonitina in the Treatise on Invertebrate Paleontology, Part L, Ammonoidea; Geological Soc of America and Univ Kansas press.