The “elongate chelicera problem”: A virtual approach in an extinct pterygotid sea scorpion from a 3D kinematic point of view

Chelicerae, distinctive feeding appendages in chelicerates, such as spiders, scorpions, or horseshoe crabs, can be classified based on their orientation relative to the body axis simplified as either orthognathous (parallel) or labidognathous (inclined), exhibiting considerable diversity across various taxa. Among extinct chelicerates, sea scorpions belonging to the Pterygotidae represent the only chelicerates possessing markedly elongated chelicerae relative to body length. Despite various hypotheses regarding the potential ecological functions and feeding movements of these structures, no comprehensive 3D kinematic investigation has been conducted yet to test these ideas. In this study, we generated a comprehensive 3D model of the pterygotid Acutiramus, making the elongated right chelicera movable by equipping it with virtual joint axes for conducting Range of Motion analyses. Due to the absence in the fossil record of a clear indication of the chelicerae orientation and their potenti..., The three-dimensional model of Acutiramus sp. was created using Blender version 4.0.1. Initially, simple shapes such as cubes and spheres were generated. These were then processed in Object Mode in Blender using the \"Catmull-Clark\" modifier, transforming the initial six faces into a total of 6,144 faces. This allowed for detailed modeling and distortion of the individual faces, and ultimately the entire object, in Sculpting Mode using specific brushes such as \"Grab,\" \"Snake Hook,\" and \"Elastic Deform.\" If necessary, the modifiers \"Decimate\" (to reduce the number of faces) or \"Multiresolution\" (to increase the number of faces) were applied in Object Mode to adjust the density. This process was carried out for all major body parts of the sea scorpion. The completed individual components were then scaled to the appropriate size according to the scales found in the literature and assembled into a cohesive object. 
In Autodesk Maya, the kinematic articulation of the individual legs was achie..., , # Acutiramus 3D kinematic models

[https://doi.org/10.5061/dryad.2fqz612x9](https://doi.org/10.5061/dryad.2fqz612x9)

Blender files showing the four permutations 1, 3, 5 and 8 (out of the eight) as an example for each of the four insertion and orientation modes (kinematic settings 1-4) of the right *Acutiramus* chelicera (Settings 1-4).

## Description of the data and file structure

**The software: Blender**
Blender is open access and available via: [https://www.blender.org.](https://www.blender.org.\\)
The single Blender files can simply be opened via double click. 
The model appears in the origin of coordinates. 
Maybe, depending on the default settings, it is necessary to zoom out or in to find the model.
Each individual element of the chelicerae of *Acutiramus* is selectable and can be hidden in Object Mode.

**The 3D model of *Acutiramus***
**Kinematic Settings:**
To clarify the most likely angle of orientation and movement direction of the chelicerae of *Acutiramus* that could ac...