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.

(a) 针对26个物种种群的绝对CP表面积（CP surface area）与体重的双对数回归绘图（决定系数r²=0.83，P<0.001）。回归所得残差即为各物种的相对CP大小（Relative CP size, RelCP），并将其用于后续所有分析。(b) 约简主轴回归（reduced major axis regression）绘图显示，相对CP大小（RelCP）与功能性嗅觉受体基因（olfactory receptor gene, ORG）的数量（以log₁₀标度）呈显著正线性相关（决定系数r²=0.76，P<0.001，n=26）。(c) 相对CP大小（RelCP）与总嗅觉受体基因数量（含功能性基因与假基因（pseudogenes））的log₁₀标度值之间存在线性相关关系。(d) 将图2b的坐标轴进行反转，并将剑齿猫的相对CP大小数值（以绿色垂直线表示）代入回归方程，预测刃齿虎属（Smilodon）的功能性嗅觉受体基因数量约为600个（置信区间为581~685）。图中虚线为回归直线两侧的95%置信区间。所有分析均通过R软件完成。