Digitization of samples

The specimens were first cleaned with water, drained, wiped dry and placed on a flat surface having laminated graph sheet on background, which was meant for calibration of the coordinates of digital images (Fig. 1). The methodology of capturing digital images for truss network analysis by Mandal et al. (2020) was followed. The fins were stretched for clear visibility of origin and insertion points. Each specimen, placed on graph paper, was labelled with a unique code and captured using DSC-W300 digital camera (Sony, Japan) with mouth facing towards left, which permits replication of the measurements (Cadrin & Friedland, 1999). Due to varying size range of samples as the images were captured from different heights, reference scale on the graph paper was used for calibration, using the software tpsUtil (Rohlf, 2008a).

1. Anterior tip of snout at upper jaw; 2. posterior most aspect of neurocranium (beginning of scaled nape); 3. dorsal fin origin; 4. posterior end of vertebrae column; 5. line perpendicular to dorsal fin origin; 6. anal fin origin; 7. pectoral fin insertion; 8. posterior end of maxilla; 9. line perpendicular to posterior end of maxilla. Source credit: ICAR-NBFGR.