Fig. 1 in Limb posture in early mammals: Sprawling or parasagittal

Fig. 1. Comparison of os calcaris in a Recent monotreme and a Cretaceous multituberculate. A. The left tarsus of monotreme Ornithorhynchus anatinus (Shaw, 1799), ZMO 11793, an adult male, showing the well−preserved venomous cornu calcaris facing medially. B. Proximal part of the left tarsus of Catopsbaatar catopsaloides (Kielan−Jaworowska, 1974), showing os calcaris in proximal view. PM 120/107, Late Cretaceous red beds of Hermiin Tsav, (?late Campanian), Hermiin Tsav I, Gobi Desert, Mongolia. Note the roughly triangular shape of os calcaris in C. catopsaloides and its undulating surface, indicating the presence of cornu calcaris upon it.