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Suture pattern formation in ammonites and the unknown rear mantle structure
Shinya Inoue1,2, Shigeru Kondo1
1Graduate School of Frontier Bioscience, Osaka University, Yamada 1-3, Suita, Osaka 565-0871, Japan.
Scientific Reports
|September 20, 2016
Summary
Ammonite suture patterns may form from autonomously growing, branched mantle structures, not just flexible membranes. This finding is supported by 3D imaging of fossil ammonites and comparisons with modern sea slugs.
Area of Science:
- Paleontology
- Developmental Biology
- Marine Biology
Background:
- Ammonite shells exhibit intricate suture lines, whose formation mechanism remains debated.
- Previous hypotheses suggested flexible ammonite mantles folded by physical forces to create septa.
Purpose of the Study:
- To elucidate the mechanism of ammonite septa formation.
- To determine the detailed shape of ammonite septa using advanced imaging techniques.
Main Methods:
- Developed a novel X-ray micro-computed tomography (CT) protocol.
- Acquired high-resolution three-dimensional (3D) images of Upper Cretaceous ammonite septa (Damesites cf. damesi).
- Compared fossil structures with extant sea slug mantle morphology.
Main Results:
- 3D CT imaging revealed complex, wavy, and branched structures of the ammonite rear mantle.
- These mantle structures appear to grow autonomously.
- Extant sea slugs possess similar branched mantle structures, indicating a conserved molluscan growth potential.
Conclusions:
- Ammonite suture patterns likely result from the autonomous growth of complex mantle structures.
- The mantle of molluscs possesses an inherent capacity for forming branched projections.
- This study provides a new perspective on ammonite shell morphology and evolution.
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