Using the axial skeleton as armor: mechanical behavior of sea turtle carapaces throughout ontogeny

The shells of turtles serve as protection, yet shell shape and natural history widely vary among turtles. Here we identify the mechanical behavior that provides marine turtles, species characterized with fusiform shells, with biomechanical strength and resilience. The multi-layered carapacial bone structure seemingly serves a protective role for the muscles, nerves, and viscera it houses. What are the shell’s material properties that provide protection?  Most previous work focused on non-marine turtles that differ in natural history and shell morphology from marine species. We measured carapacial mechanical behavior of green turtle (Chelonia mydas), loggerhead (Caretta caretta), and Kemp’s ridleys (Lepidochelys kempii) across a range of body sizes in juvenile, subadult, and adults.  Carapace samples were tested using quasi-static compression to quantify stiffness (Young’s modulus), yield strength, and toughness. The mechanical characteristics of marine turtle shells are grossl..., Samples with averaged dimensions of 9mm x 9mm (length x width) were tested dorso-ventrally, scute side up, under compression. Sample height was variable and depended upon shell thickness. Quasi-static compression of samples was conducted using an Instron E1000 Material tester at a displacement rate of 0.02 mm s-1.  Tests continued until the maximum force capacity of the Instron (1KN) or densification was reached, whichever came first.
To characterize the mechanical properties of marine turtle shells, we plotted mechanical testing data as force-displacement curves using Bluehill® Software (Instron, Norwood, MA, USA). These curves were converted into engineering stress-strain curves and used to calculate the mechanical properties of interest (Young's modulus, yield strength, and toughness). The Young’s modulus describes a material’s ability to resist deformation (i.e., stiffness). We calculated stiffness as the slope of the linearly elastic region of the stress-strain curve..., , # Material Properties of Sea Turtle Shells

[https://doi.org/10.5061/dryad.zkh1893mj](https://doi.org/10.5061/dryad.zkh1893mj)

## Description of the data and file structure

Individual shell samples from all carcasses are listed in the dataset, along with variables and units. 

### Files and variables

#### File: SeaTurtleFullData\_Dryad\_(1).xlsx

**Description:** 

* Cells which are highlighted in gray represent \"data not captured\". Samples which did not yield have no yield strength or toughness values in the data set and are highlighted in gray.

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