Fig. 4
From: A methodological exploration to study 2D arm kinematics in Ophiuroidea (Echinodermata)
Between-group PCA (PC1–2) for interspecies comparison includes O. superba, O. scolopendrina and M. hirsuta (A), and for variability between arms 1–5 (B). Since the disc displacement and slip angle in frame 1 was zero, we have removed frame 1 from the data. The colored convex hulls in A, B and C belong to different species, arms and frames categories, respectively. The percentages at labels show the contribution ratios and the lines with variable names represent the loading. For the meaning of "frame" see Fig. 3