Preprint Concept Paper Version 1 Preserved in Portico This version is not peer-reviewed

A Size-Independent Revision of the Fractal Step Method for Ammonite Sutures

Version 1 : Received: 19 April 2021 / Approved: 21 April 2021 / Online: 21 April 2021 (13:09:27 CEST)

How to cite: Marriott, K.; Chamberlain, Jr., J.A. A Size-Independent Revision of the Fractal Step Method for Ammonite Sutures. Preprints 2021, 2021040581 (doi: 10.20944/preprints202104.0581.v1). Marriott, K.; Chamberlain, Jr., J.A. A Size-Independent Revision of the Fractal Step Method for Ammonite Sutures. Preprints 2021, 2021040581 (doi: 10.20944/preprints202104.0581.v1).

Abstract

The novel coronavirus has presented specimen-access challenges to geoscientific researchers, including paleobiologists interested in fossil ammonoids. Ammonoid sutures are geometric patterns formed by the intersection of the septa and the shell wall, and have long been a diagnostic tool for ammonite researchers for such applications as species identification, taxonomic relationships, ontogenetic change, functional and evolutionary morphology, and other aspects of ammonoid paleobiology. Without access to specimens in museum and institutional collections, researchers must rely on previously published illustrations and photographs of ammonoid sutures. However, many of these illustrations were published decades ago without an index of scale. Suture tracings lacking a scale bar are not usable by researchers interested in applying the quantitativeness of fractal geometry to the interpretation of septal complexity. Additonally, distortion of the marginal elements of suture geometry occurs due to shell curvature near the venter and umbilicus. The revised approach described here eliminates the problem of missing scale information in fractal analysis of ammonite sutures, making use of just the lateral lobe and adjacent saddle. Our revised method’s non-requirement of a full hemisuture also facilitates comparisons among sutures within an ontogenetic sequence, or sutures from multiple ammonite taxa.

Subject Areas

sutures; fractal geometry; ammonoid paleobiology; functional morphology; ontogeny; paleontology; ammonite; paleobiology; mesozoic; jurassic; cretaceous; cephalopods

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