Ammonite species from the "SANTONIAN" stage (1 entry found)
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Polyptychoceras (Polyptychoceras) pseudogaultinum
Hokkaidô, Japan
Show / Hide description snipetThe shell is made of a succession of straight parallel shafts. A given shaft can grow just enough to encompass the previous one or, like in the photographed specimen, it can get much longer than the previous one. The simple ribs are quite smooth on the early stage and get stronger when approaching t... [view details for full description]