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

Cite this dataset

Wang, Wenhui; Gao, Shijia; Tan, Jingqiang (2024). Data from: Locomotory and morphological evolution of the earliest Silurian graptolite (Demirastrites) selected by hydrodynamics [Dataset]. Dryad. https://doi.org/10.5061/dryad.4mw6m90js

Abstract

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 rotating locomotory pattern of the Silurian low conical graptolite Demirastrites for the purpose of better feeding efficiency and turbarium stability. Moreover, we analysed how the evolution of structural innovations, such as the density and width of thecae and the curvature angle of the rhabdosome within the recovered geological lineages of Demirastrites, were influenced and selected by hydrodynamics. The results showed that Demirastrites lineages evolved towards increased stability and higher rotation velocity. Our study highlights the importance of hydrodynamic constraints serving as hidden abiotic factors shaping the evolution of planktonic graptolites. 

README: Data from: Locomotory and morphological evolution of the earliest Silurian graptolite (Demirastrites) selected by hydrodynamics

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) and OpenCascade (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_models

These data describe the thecal apertures flow velocity of the fixed and non-fixed models in this study.

Position of the thecae = the position of each theca in the tubaria

Velocity = the flow velocity of thecal apertures

Fixed = original model in fixed state

Non-fixed = original model in passive state

Data file: S1_veocity_in_three_different_inlet_velocities

Position of the thecae = the position of each theca in the tubaria

Velocity = the flow velocity of thecal apertures

0.28m/s = the inlet velocity is set to 0.28m/s

0.014m/s = the inlet velocity is set to 0.014m/s

0.0015m/s = the inlet velocity is set to 0.0015m/s

Data file: S2_mesh_size

These data describe the method for calculating the partition mesh.

Mesh element size = the size of the mesh set for each area

Data file: S3_sensitivity_analyses

In our sensitivity analysis of computational domain size, we began with computational domain measuring 130 mm long and 50 mm wide, and then repeated simulations for 5 different computational domains with progressively larger sizes. The results were considered independent of the domain size when the drag forces for a domain were less than 1% different from the next smallest domain. Based on this, we selected a domain measuring 208 mm long and 60 mm wide for use in all subsequent analyses.

Length = the length of the cylinder as fluid domain

Diameter = the diameter of the cylinder as fluid domain

Drag forces = the drag forces of the original model

Number of mesh elements = the number of mesh elements obtained by the same meshing method across various computational domains

Funding

National Natural Science Foundation of China, Award: 42342042

National Natural Science Foundation of China, Award: U23B20155

National Natural Science Foundation of China, Award: 41772001

State Key Laboratory of Palaeobiology and Stratigraphy, Award: 213120