| Berriasella jacobi | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | †Ammonoidea |
| Order: | †Ammonitida |
| Family: | †Neocomitidae |
| Genus: | †Berriasella |
| Species: | †B. jacobi |
| Binomial name | |
| †Berriasella jacobi Mazenot 1939 | |
Berriasella jacobi is anextinct species ofammonite from the lateJurassic and earlyCretaceous.[1] Because of its uniquestratigraphic position, it is used as anindex fossil to determine the boundary of the Cretaceous and Jurassic periods. TheBerriasella jacobi zone defines the substage of the LowerBerriasian, the Berriasian being the lowest stage of the Cretaceous.[2] However, due to the species limited geographic distribution, several other candidates have also been nominated, includingCalpionella alpina.
