Locomotory and morphological evolution of the earliest Silurian graptolite (Demirastrites) selected by hydrodynamics

Interpretation of the locomotion for biostratigraphic important graptolite taxa is rare and rendered problematic due to their lack of close modern analogues and soft tissues. In this study, based on well-preserved specimens of the early Silurian low-helical spiral Demirastrites Eisel, we reconstructed three-dimensional (3D) Demirastrites models and simulated their locomotion by using computational fluid dynamics. Hydrodynamic properties (outer-wall pressure fields and velocity fields) were obtained and used to test the prevailing hypothesis that the Silurian low helical spiral graptolite Demirastrites could rotate in seawater. The Demirastrites models kept rotating at different velocities in the simulation field, which helped to counteract the impact of the water current and achieve stability. During rotation, higher velocity fields could be observed near the thecal apertures, which meant better access to more nutrient particles in the sea water. Our simulation thus confirmed the rotati..., , , # Data from: Locomotory and morphological evolution of the earliest Silurian graptolite (*Demirastrites*) selected by hydrodynamics

[https://doi.org/10.5061/dryad.4mw6m90js](https://doi.org/10.5061/dryad.4mw6m90js)

This data package contains FOUR files.

**Data file: 3d Models**

The package contains CAD files of four *Demirastrites* 3D models in STEP format (.stp).

STP is a general format of a CAD 3D model. You can use most of the CAD software to open and view it, such as freeCAD ([https://www.freecadweb.org](https://www.freecadweb.org)) and OpenCascade ([https://www.opencascade.com](https://www.opencascade.com)) for free.

Original Model= the reconstruction of a 3D digital model of *Demirastrites* base on *D. triangulates*

Model A= a model established with more densely spaced thecae

Model B = a model established with wider thecae width

Model C = a model established with higher angle of tubarium curvature between th1 and th10

**Data file:** **S0_veocity_in_fixed_and_non-fixed_mo...