Feats of supercontractile strength: Functional convergence of supercontracting muscle properties among hyoid musculature in chameleons

The structure of sarcomeres imposes limits to the capacity of striated muscle to change length and produce force, with z-disc and myosin filament interactions constraining shortening. Conversely, supercontracting muscles, hitherto only known among vertebrates in the tongue retractor muscle (m. hyoglossus) of chameleons, have perforated z-discs that allow myosin filaments to extend through them into adjacent sarcomeres, permitting continued shortening and force development. Additional hyolingual muscles in chameleons undergo extreme length changes during feeding as well and may benefit from supercontractile properties. We compared length-tension relationship data and transmission electron microscopy (TEM) images from four chameleon muscles to test for the presence of additional supercontracting muscle. We document the second known example of a supercontracting muscle among vertebrates (the m. sternohyoideus superficialis) and show that the m. sternohyoideus profundus exhibits functional ..., , , # Feats of supercontractile strength: Functional convergence of supercontracting muscle properties among hyoid musculature in chameleons

[https://doi.org/10.5061/dryad.612jm64f3](https://doi.org/10.5061/dryad.612jm64f3)

## Description of the data and file structure

This dataset contains the data and code required to replicate analyses in (Schneider et al. 2025 - *Proc. R. Soc. B*). This dataset includes *in vitro* muscle contractile physiology data, consisting specifically of length-tension relationship data, for four chameleon muscles collected in an effort to identify supercontracting muscles.
### Files and variables

#### File: CcalypA08\_-\_MH\_Data.xlsx

**Description:** This file contains contractile data for the m. hyoglossus muscle from individual \"CcalypA08\".

##### Variables

* Muscle Length (mm): The length of the muscle (in mm) at the length of maximal active force (L0).
* Muscle Mass (g): The mass of the muscle (in grams).
* LT Length: Length measurements for muscle con...