Fig. 7 in Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans

Fig. 7. Energy-flux model and food web stability. We tested whether the food web as preserved is functional and stable over ecological time. All shelled invertebrates (specifically ammonoids), fish, and amniote taxa discovered in the Fossil Hill Fauna are modeled as members of a food web. The member "shelled invertebrates" is basal to the food web and comprises primarily ammonoids but also halobiid bivalves and crustaceans. The member "nonshelled invertebrates plus fishes" ("fish") pools coleoid cephalopods such as squid and small- to medium-sized fish. See Methods and table S11 for food web members and their body masses, total biomasses, and energetic demands. (A) Trophic interaction matrix used for modeling energy-flux across members. Stacked bars represent the diet of predatory taxa. Filled squares within bars indicate that a taxon is taken by the predator, whereas white indicates that it is not. (B) Stability values calculated by the model for different combinations of total biomass of the two food web members "shelled invertebrates" and "fish." More negative stability values indicate a more stable food web. Error bars for blue dots represent model results assuming maximum and minimum body mass estimates for ichthyosaur taxa (table S11). Greater body masses result in less-stable food webs than smaller body masses. Stability values of extant food webs range between −10 and 0 (41). Note that we multiplied stability values by −1 for plotting. TB, total biomass (kg); red circles, the total biomass of "shelled invertebrates" equals that of "fish."