Sunday, December 31, 2017

Adult size in Scaphites

Three adult specimens of Scaphites showing the size range.  The two on the left are probably progenetic dwarfs of contemporary full size species.  Pteroscaphites pisinnus (far left) from the Scaphites whifieldi Zone, undetermined example (center) from the Prionocyclus hyatti Zone, and Scaphites carlilensis (right) from the Prinocyclus macombi Zone.  Only adults grow a hook for a body chamber.  Sexual dimorphs have been reported for most Scaphites, with microconchs being about the same size as Macroconchs but a lot less inflated.  The genus Yezoites may show dimorphic size differences comparable to that shown above, but that is for another post.

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