Lower jaw of a juvenile monotreme Ornithorhychus with manually edited middle ear bones, based on illustrations in Kermack et al. (1973), Kermack et al. (1981) and Luo (2011). Depicted in color code are the following elements: yellow = Meckel’s cartilage, dark blue = ectotympanic, green = articular, light blue = surangular, red = incus, beige = dentary.

The 3D model of the juvenile Ornithorhynchus lower jaw is a virtually edited polygonal surface model of the adult surface model of Ornithorhynchus anatinus downloaded from MorphoSource (imnh:r:2125; OBJ mesh file, Idaho Museum of Natural History specimen S32167). The surface model was manually modified and edited in MAYA 16 (Autodesk) based on illustrations of specimen MO 39 from Zeller (1989). 

The 3D model of the lower jaw was segmented manually from CT scans using Avizo 8.1. (Visualization Sciences Group). The 3D models of the middle ear bones and Meckel’s cartilages were manually created using MAYA 16 (Autodesk).

For all models, fine tune editing and virtual alignment was performed using Polyworks (2014, InnovMetric Software Inc.) including Gouraud filters for smoothing surfaces, adding and removing triangles, reworking mesh and reducing data size.