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<p>A large sample of helical burrows based on the circular helix typical of the ichnogenus <i>Gyrolithes</i> is analysed. The main goals are: (1) a statistical analysis of four measurements taken from the burrows, and the calculation: based on these—of four dimensionless parameters defined for their morpho-theoretical study: relative pitch, adaxial ratio, helix slope and eccentricity; and (2) to quantitatively test the hypothesis that helical penetration into the sediment implies energy saving, since this type of helical tubes can be considered mechanically analogous to an inclined plane. A principal component analysis of the four measurements clearly separates two groups: a large group of burrows characterized by measurements exceeding 1&#xa0;cm, and a small group with measurements below 1&#xa0;cm. The large group differs from the small one in the values ​​of relative pitch and adaxial ratio; however, helix slope and eccentricity are similar in both groups. The adaxial ratio, eccentricity and helix slope allow for the calculation of the helix length per whorl. Both helix slope and adaxial ratio exhibit critical values ​​that determine whether the burrow structure remains stable or collapses; therefore, there is also a critical value for the helix length per whorl. The energy-saving hypothesis implies a low helix slope (a critical threshold) and moderately high ​​adaxial ratio values, but in both cases close to their respective critical values. The helix length per whorl values have also to be short and slightly exceed its critical value. The <i>Gyrolithes</i> sample generally conforms to these criteria. An image analysis of the ichnogenus <i>Daimonelix</i> yields similar results for helix slope, adaxial ratio and eccentricity. The energy-saving strategy results in a burrow morphology that allows it to meet various environmental requirements of its producers. This allows for a discussion of the notion of behavioral exaptation.</p>

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The world of helical fossil and recent burrows: between geometry and engineering

  • 期刊论文

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  • 发表日期：

    2026年5月28日

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  • Miquel De Renzi,
  • Eduardo Mayoral

摘要

A large sample of helical burrows based on the circular helix typical of the ichnogenus Gyrolithes is analysed. The main goals are: (1) a statistical analysis of four measurements taken from the burrows, and the calculation: based on these—of four dimensionless parameters defined for their morpho-theoretical study: relative pitch, adaxial ratio, helix slope and eccentricity; and (2) to quantitatively test the hypothesis that helical penetration into the sediment implies energy saving, since this type of helical tubes can be considered mechanically analogous to an inclined plane. A principal component analysis of the four measurements clearly separates two groups: a large group of burrows characterized by measurements exceeding 1 cm, and a small group with measurements below 1 cm. The large group differs from the small one in the values ​​of relative pitch and adaxial ratio; however, helix slope and eccentricity are similar in both groups. The adaxial ratio, eccentricity and helix slope allow for the calculation of the helix length per whorl. Both helix slope and adaxial ratio exhibit critical values ​​that determine whether the burrow structure remains stable or collapses; therefore, there is also a critical value for the helix length per whorl. The energy-saving hypothesis implies a low helix slope (a critical threshold) and moderately high ​​adaxial ratio values, but in both cases close to their respective critical values. The helix length per whorl values have also to be short and slightly exceed its critical value. The Gyrolithes sample generally conforms to these criteria. An image analysis of the ichnogenus Daimonelix yields similar results for helix slope, adaxial ratio and eccentricity. The energy-saving strategy results in a burrow morphology that allows it to meet various environmental requirements of its producers. This allows for a discussion of the notion of behavioral exaptation.