THE TRIBRACHIATUS LINEAGE: CONDUCTING SHAPE ANALYSIS ON NON-BIREFRINGENT NANNOFOSSILS
This morphometric study aims at determining the tempo and mode of evolution in the lineage. Whereas the data collection of specimens digitally photographed at multiple focal planes is relatively easy the automated analysis is hampered by the nature of the analyzed material itself. Measurements of the main morphologic characters (e.g., total diameter, angle between arms) are made on digital composite micrographs using a combination of Zeiss software (AxioVision) and open-source imaging software (Imagej). The composites themselves are produced using Photoshop’s stacking function. Beyond this, the study cannot take advantage of automated software for shape analysis because the coccoliths analyzed here, being non-birefringent and poorly delineated from adjacent particles in brightfield, make binary segmentation nearly impossible, which prevents fluid automated shape analysis. We have thus conducted the binary segmentation by hand in Photoshop and analyzed them with software from the Stony Brook morphometric website (e.g., tps software by James Rohlf). Although an extremely tedious procedure this allows digitizing landmarks and creating outlines for each specimen of Tribrachiatus. Whereas preparation techniques may be improved for analysis in brightfield, programs maybe developed for solving the difficulties faced here. A similar problem is encountered by SYRACO (Système de Reconnaissance Automatique de Coccolithes).