Linear correlation between relative CP size and ORG repertoire size was established and used to estimate likely ORG repertoire for the extinct sabertooth cat (Smilodon fatalis).

(a), Log-log regression plot of absolute CP surface area against body mass for 26 species (r2 = 0.83, P<0.001). Residuals from regression constitute relative CP size (RelCP) for each species and are used in all subsequent analyses. (b), Strong positive linear correlation between RelCP and the number of functional ORG (log10) is shown in reduce major axis regression plot (r2 = 0.76, P< 0.001, n=26). (c), Linear correlation between RelCP and total ORG number (functional, pseudogenes) (log10). (d), Axes from figure 2b plot are inverted and the RelCP value (green vertical line) for the sabertooth cat is applied to the regression equation. This predicts Smilodon to have had ca. 600 (581,685) functional ORG. Dotted lines: 95% confidence intervals around regression line. All work done in R.