Momocs

Momocs is an open-source R package for morphometrics designed to analyze two-dimensional shapes, with emphasis on outlines and landmark configurations. It provides a unified framework for traditional landmark-based morphometrics and outline-based approaches, enabling comparative shape analysis across specimens, species, or time.

The package offers data structures to store coordinates, outlines and semi-landmarks, and a set of tools for data preprocessing, including alignment of shapes using Procrustes superimposition and sliding semilandmarks to minimize bending energy.

Momocs supports multiple shape representations, including Elliptical Fourier Analysis (EFA) for closed contours, tangent-angle representations, and landmark-based coordinates. It includes dimensionality reduction and classification methods such as PCA and discriminant analysis, as well as plotting and diagnostic tools.

In terms of workflow, researchers typically import or extract outlines or landmark configurations, preprocess and align shapes, represent shapes with Fourier coefficients or aligned coordinates, and then analyze shape variation with PCA, discriminant analysis, or cluster analyses.

Applications span biology, botany, paleontology, zoology, and archaeology, where shape variation is informative for taxonomy, functional interpretation, or evolutionary questions. The project is maintained by an international community and is available through CRAN and its online repositories.