Ammonite (microconcha) perfect, pearly color given by the fossilization of the shell, about ± 5.3 cm × 4.4 cm. Behind it has another species (Sphenodiscus) without cleaning. The piece measures ± 13 cms × ± 9 cms.
"In the ammonites, the size of the macrochate of a given species (supposedly female dimorph) could be up to 10 times larger than its corresponding microconcha (supposedly male dimorph).
Upper Cretaceous, Fox Hills Formation
South Dakota (USA)