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1 July 2020 Shell Area–To-Volume Ratio in Ammonoids
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Abstract

The external area-to-volume ratio of the ammonite shell has been held to be related to morphology but never evaluated quantitatively. A dimensionless ratio, the Vogel number, was computed for large samples of Devonian to Cretaceous ammonites with a new method based on the ADA-model. The estimated ratios range from 2.4 to 3.4. The highest values are exhibited by uncoiled serpenticone ammonites, lowering in the sequence serpenticone-oxycone-spherocone. It is shown that the area-to-volume relationships are controlled by the involution (degree of overlapping) and the relative width of whorl section. The typical evolutionary trends serpenticone–spherocone and/or serpenticone–oxycone, broadly documented through the history of the Ammonoidea, could have been driven, at least in part, by the lowering of the area-to-volume ratio.

© by the Palaeontological Society of Japan
Horacio Parent, Matias Bejas, and Andres Greco "Shell Area–To-Volume Ratio in Ammonoids," Paleontological Research 24(3), 216-225, (1 July 2020). https://doi.org/10.2517/2019PR013
Received: 19 December 2018; Accepted: 16 June 2019; Published: 1 July 2020
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