''Caumontisphinctes'' is an

ammonoid Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

genus from the ammonitid superfamily Perkinsonatoidea that lived during the Bajocian stage of the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

. ''Chaumontisphinctis'', named by Buckman, is like the genus ''Perisphinctis'' in being compressed with an ovoid whorl section but perkinsoniid in having sharp ribbing, a smooth or grooved venter, and tubercles commonly developed at bifurcation points on the ribs and at the ventral edge or on the venter.

References

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

, Part L Ammonoidea (L309); Geological Society of America and Univ of Kansas press, 5th printing, 1990 Jurassic ammonites Fossils of France Bajocian life Ammonitida genera Perisphinctoidea {{ammonitina-stub