Table 1. Metric data on the jaw muscles and estimates of feeding performance.
| H. piceatus | H. fischeri | Main-effect | ||||
| Female (n = 5) | Male (n = 5) | Female (n = 5) | Male (n = 5) | species | sex | |
| Muscle mass (g) | ||||||
| Pars A1 | 15.670±4.328 | 22.320±1.882 | 39.920±6.847 | 67.280±19.776 | F1,15 = 32.5*** | F1,15 = 2.4 |
| Pars A2 | 8.940±2.809 | 15.260±1.984 | 27.450±4.403 | 46.180±11.525 | F1,15 = 54.7*** | F1,15 = 7.4* |
| Pars A3 | 2.490±0.891 | 4.420±0.665 | 6.110±1.078 | 11.170±2.886 | F1,15 = 25.4*** | F1,15 = 8.4* |
| Pars A2 | ||||||
| Fiber length (mm) | 4.090±0.629 | 5.251±0.437 | 4.579±0.514 | 5.026±0.275 | F1,15 = 1.4 | F1,15 = 2.4 |
| PCSA (mm2) | 0.022±0.007 | 0.029±0.002 | 0.061±0.013 | 0.091±0.019 | F1,15 = 38.5*** | F1,15 = 1.8 |
| MA | 0.394±0.025 | 0.424±0.021 | 0.484±0.045 | 0.559±0.043 | F1,16 = 51.5*** | F1,16 = 11.0** |
| σ (°) | 50.372±2.390 | 49.962±4.190 | 54.153±2.639 | 56.304±2.754 | F1,16 = 13.6** | F1,16 = 0.4 |
| Bite force (N) | 0.125±0.034 | 0.178±0.019 | 0.454±0.108 | 0.806±0.191 | F1,15 = 69.5*** | F1,15 = 6.0* |
| Pars A3 | ||||||
| Fiber length (mm) | 3.829±0.651 | 4.600±0.839 | 4.555±0.307 | 5.172±0.981 | F1,15 = 0.1 | F1,15 = 0.0 |
| PCSA (mm2) | 0.006±0.001 | 0.010±0.002 | 0.013±0.002 | 0.022±0.004 | F1,15 = 31.5*** | F1,15 = 8.9** |
| MA | 0.249±0.009 | 0.274±0.010 | 0.314±0.017 | 0.297±0.022 | F1,16 = 39.4*** | F1,16 = 0.3 |
| σ (°) | 34.444±6.824 | 30.377±4.417 | 29.397±2.671 | 36.512±5.645 | F1,16 = 0.06 | F1,16 = 0.4 |
| Bite force (N) | 0.017±0.004 | 0.025±0.004 | 0.039±0.009 | 0.072±0.019 | F1,15 = 32.0*** | F1,15 = 8.9** |
| Total bite force | 0.142±0.033 | 0.204±0.022 | 0.493±0.115 | 0.878±0.208 | F1,15 = 73.8*** | F1,15 = 7.0* |
| KT | 0.758±0.090 | 0.607±0.044 | 0.691±0.076 | 0.649±0.079 | F1,16 = 0.2 | F1,16 = 8.5* |
| KE | 5.379±0.717 | 5.214±0.576 | 3.653±0.306 | 3.992±0.563 | F1,16 = 34.6*** | F1,16 = 0.1 |
| ASC/HL | 0.395±0.020 | 0.360±0.020 | 0.305±0.036 | 0.316±0.025 | F1,15 = 29.8*** | F1,15 = 1.0 |
| β (°) | 77.433±4.337 | 77.914±4.275 | 93.671±5.577 | 99.217±4.051 | F1,15 = 77.8*** | F1,15 = 2.0 |
PCSA = Physiological cross-sectional area; MA = mechanical advantage; σ = insertion angle; KT = kinematic transmission coefficient; KE = Kinematic efficiency of jaw opening; ASC/HL = ratio of the length of the ascending arm of the premaxilla and head length; β = angle between ascending and dentigerous arm of the premaxilla. * p<0.05, ** p<0.01, *** p<0.001.
Values are mean ± standard deviation.