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Allometric and Fractal Exponents Indicate a Connection between Metabolism and Complex Septa in Ammonites

Juan Antonio Pérez-Claros
Paleobiology
Vol. 31, No. 2 (Spring, 2005), pp. 221-232
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/4096805
Page Count: 12
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Allometric and Fractal Exponents Indicate a Connection between Metabolism and Complex Septa in Ammonites
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Abstract

Sutural perimeters of 301 Late Jurassic ammonites scale as the 3/8 power of phragmocone volume. This implies that septal surface grows as the ¾ power of body mass, the exponent of Kleiber's law (1932), one of the best-established empirical laws in biology, which is well known to be the scaling exponent of basal metabolic rate. Sutural complexity, as measured by fractal dimensions, emerges from the relationship between sutural perimeter and phragmocone volume, thus supporting the interpretations of septal folding as a mechanism for the increase in septal surface and as demanded by metabolic and physiologic processes (e.g., respiration or body chamber transport). The implications of these results strongly suggest that ammonite septa were involved in more than a simple structural support.

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