Table 1 Skull measurements of Obdurodon and Ornithorhynchus.

Data are means ± SD. n, number of specimens.

MeasurementsObdurodonOrnithorhynchusn
GLS131.2092.80 ± 8.3132
Angle (a)87.0669.15 ± 3.4325
Angle (b)80.5993.33 ± 3.5525
Infraorbital foramen3.473.13 ± 0.3832
Braincase35.8632.18 ± 2.1932
Zygomatic breadth50.6342.20 ± 3.9832
Occipital breadth27.4523.76 ± 2.3632
Orbit11.859.17 ± 0.8432
Geometric mean25.4121.02 ± 1.8732