Fig 6.

(A) Diagram showing the relationship between body mass, metabolic rate (≈ activity level and feeding strategy) and metabolic level (ecto, meso and endothermy) in aquatic vertebrates. (B) Schematic explanation of how shifts towards higher metabolic levels, promoted by different factors, contribute to maintaining a predatory lifestyle at bigger body sizes. (C) Diversity of body masses, feeding and thermoregulatory strategies of living and extinct aquatic vertebrates (ed, endotherm; ec, ectotherm; me, mesotherm; cross sign denotes an extinct taxon). A-C modified from Ferrón et al. [11]. (D-E) Diagrams showing body sizes, feeding and thermoregulatory strategies of mysticete cetaceans and otodontid sharks respectively. Mysticete skull and otodontid tooth outlines modified from Fitzgerald [185] and Pimiento and Balk [46]. Bluish and reddish tones represent lower and higher metabolic levels, respectively.