Shell Classification

Overview

Each shell preset includes a classification section describing the biological affinity, computational growth model and observable shell morphology represented by the preset.

The classification system serves three purposes:

• To document the characteristics of each shell preset
• To support grouping and filtering throughout the project
• To provide a consistent vocabulary for comparing shell forms

The classification is intentionally descriptive rather than taxonomic. It does not attempt to reproduce formal biological classification, but instead records a set of independent morphological characteristics that together describe the shell.

Classification Structure

Each preset contains a classification object.

"classification": {
    "family": "ammonoid",
    "geometry": "log-spiral",
    "morphology": {
      "form": "coiled-cephalopod",
      "coiling": "planispiral",
      "umbilicus": "moderate",
      "whorl_contact": "touching"
    }
  }

Only fields applicable to a particular shell are included. For example, straight shells do not have an umbilicus, while gastropods may define a spire or aperture instead.

Classification Fields

family

The broad biological group that inspired the shell.

This is intentionally kept at a high level rather than attempting detailed zoological taxonomy.

Value	Description
ammonoid	Ammonites and related extinct coiled cephalopods
nautiloid	Nautilus-like cephalopods
orthoceratoid	Straight- and curved-shelled cephalopods
gastropod	Snails and related molluscs

geometry

The computational growth model used to generate the shell. This describes the underlying mathematics rather than the appearance of the shell.

Value	Description
log-spiral	Classical logarithmic spiral growth
centreline-conical	Conical shell generated along a parameterised centreline
conical-helix	Conical shell generated along a helical centreline

Additional geometries may be added as new shell growth models are implemented.

Morphology Fields

form

The overall shell morphology. This field provides a concise description of the finished shell rather than the underlying mathematics.

Value	Description
coiled-cephalopod	General planispiral cephalopod shell
serpenticonic	Evolute ammonoid shell with a broad umbilicus
crioconic	Open planispiral shell with detached whorls
nautiliconic	Tightly coiled involute nautiloid shell
orthoconic	Straight conical shell
cyrtoconic	Curved conical shell
planispiral	Flat planispiral gastropod shell
turriform	High-spired gastropod shell
flared	Shell with a strongly expanded terminal aperture

coiling

Describes the overall coiling pattern.

Value	Description
none	Shell does not coil
planispiral	Coils within a single plane
open-planispiral	Planispiral but with detached whorls
high-spired	Whorls stacked vertically
low-spired	Low vertical spire

umbilicus

Describes the relative width of the umbilicus. Only applicable to planispiral shells.

Value	Description
narrow	Earlier whorls largely concealed
moderate	Intermediate umbilical width
wide	Earlier whorls clearly visible
open	Whorls detached to produce an open spiral

whorl_contact

Describes how adjacent whorls interact.

Value	Description
overlapping	Later whorls overlap earlier ones (involute)
touching	Adjacent whorls remain in contact
detached	Adjacent whorls do not meet
stacked	Whorls primarily increase vertically

axis

Describes the centreline of non-coiled shells. Only applicable to centreline-generated geometries.

Value	Description
straight	Straight centreline
curved	Curved centreline

spire

Describes the relative height of the shell spire. Primarily applicable to gastropods.

Value	Description
low	Low spire
high	Tall spire

aperture

Describes notable terminal aperture morphology.

Value	Description
expanded	Aperture flares outward during the final growth stage

Additional aperture morphologies may be introduced in future models.

Design Philosophy

The classification deliberately separates several independent characteristics of shell morphology.

• family records the broad biological group that inspired the model.
• geometry records the computational growth mathematics.
• form records the overall shell morphology.
• The remaining fields describe independent morphological characteristics such as coiling, umbilical width, whorl contact, shell axis and spire development.

This approach reflects the goals of the project.

The repository investigates computational shell morphology, not biological taxonomy. Similar shell forms may be generated by different mathematical growth models, while a single computational model may produce a continuous range of morphologies through parameter variation.

Rather than forcing shells into rigid categories, the classification records the individual characteristics that together describe each shell. As new shell forms are introduced, additional descriptors may be added while maintaining compatibility with the existing classification system.

Classification Export

A classification exporter is provided that extracts the classification data from the presets and exports it in CSV format. To extract the classification from the presets in the data folder and write the results to a CSV file, first activate the virtual environment for the project and then:

python scripts/export-preset-classification.py -o /path/to/csv-file.csv

The following command line options are accepted by the exporter:

Option	Short Form	Description
--input	-i	Path to the folder containing JSON preset files
--csv	-c	Path to the CSV file to write
--json	-j	Path to the CSV file to write