Confusion About Ammonite Anatomy Terms

[Pr0teusUnbound]

there are a few ammonite shell anatomy terms that have been confusing me.

what do the terms "whorl" and "volution" mean? are they the same thing? are they a full revolution shell growth (360 degrees?) around the unbilical axis? or just 3/4 (270 degrees?) around it?

 

[Architeuthoceras]

I think they can be used for the same thing... Whorl more like a noun, or referring to the shell, and volution more like a verb, referring to growth. Both refer to 1 complete revolution.

 

[Pr0teusUnbound]

really? i remember reading somewhere that a volution was 3/4 of a complete revolution (supposedly because the final quarter of the revolution was larger than each previous quarter).