Article: Variation and ontogeny of some Oxfordian ammonites: Taramelliceras richei (de Loriol) and Creniceras renggeri (Oppel), from Woodham, Buckinghamshire
Statistical and ontogenetic studies of Taramelliceras richei (de Loriol) and Creniceras renggeri (Oppel) have shown identity in their early stages. Variation in protoconch size is consistent and small, as is the diameter of the nepionic constriction. Divergence in shell form occurs only at the onset of maturity, which in C. renggeri begins at about 8.4 mm. and in T. richei at about 18.8 mm. It is concluded that the two 'species' are a sexually dimorphic pair. The name C. renggeri has priority.