S4. Landmark and semi-landmarks used in ‘Characterizing the body morphology of the first metacarpal in the Homininae using 3D geometric morphometrics’
Thomas A. Püschel
03/03/2021
Paper authors: Jonathan Morley, Ana Bucchi, Carlos Lorenzo, Thomas A. Püschel Link to preprint
Corresponding author: Thomas A. Püschel Contact: Email: thomas.puschelrouliez@anthro.ox.ac.uk Web: thomas.puschel.com
Landmark collection
3D landmarks were collected to quantify the MC1’s morphology. Eight curves comprising 20 equidistant landmarks each were placed at pre-defined points on the MC1 (Figure 1). These landmarks were chosen to provide a good representation of the shaft of the bone. The first and last landmarks from each one of the eight curves were treated as fixed (i.e., 16 fixed landmarks), whereas all the rest of them (i.e., 144 landmarks) were considered as semi-landmarks.
Figure 1. Illustration of the 16 landmarks (yellow spheres) and 144 semi-landmarks (red spheres) used in this study. The numbers of the 16 fixed landmarks and eight semi-landmark curves (C1-C8) are also plotted
Landmark and semi-landmark definitions
| Landmarks_and_semilandmarks | Definition |
|---|---|
| Fixed landmarks | |
| 1 | Most dorsal point on the distal articular border along the midline of bone |
| 20 | Most dorsal point on the proximal articular border along the midline of bone |
| 21 | Most palmar point on the distal articular border along the midline of bone |
| 40 | Most palmar point on the proximal articular border along the midline of bone |
| 41 | Dorsopalmar point on the distal border of the dorsal radial epicondyle |
| 60 | Dorsopalmar midpoint along the lateral border of the proximal articular surface |
| 61 | Dorsopalmar midpoint along the medial border of the proximal articular surface |
| 80 | Dorsopalmar midpoint along the medial border of the distal articular surface |
| 81 | Most medial point on the dorsal border of the distal articular surface |
| 100 | Most medial point on the dorsal border of the proximal articular surface |
| 101 | Most lateral point on the dorsal border of the distal articular surface |
| 120 | Most lateral point on the dorsal border of the proximal articular surface |
| 121 | Most proximal point on the border of the palmar radial epicondyle |
| 140 | Most lateral point on the palmar border of the proximal articular surface |
| 141 | Most proximal point on the border of the palmar ulnar epicondyle |
| 160 | Most medial point on the palmar border of the proximal articular surface |
| Semi-landmark curves | |
| C1 | 18 coordinates between landmarks 1 and 20 |
| C2 | 18 coordinates between landmarks 21 and 40 |
| C3 | 18 coordinates between landmarks 41 and 60 on the crest for the insertion of the opponens pollicis muscle |
| C4 | 18 coordinates between landmarks 61 and 80 |
| C5 | 18 coordinates between landmarks 81 and 100 |
| C6 | 18 coordinates between landmarks 101 and 120 |
| C7 | 18 coordinates between landmarks 121 and 140 |
| C8 | 18 coordinates between landmarks 141 and 160 |
Visualize landmarks and semi-landmarks
The model closest to the mean shape was previously warped to match the multivariate mean using the thin plate spline method. The landmarks and semi-landmarks are plotted on the surface of this average 3D model. The 16 fixed landmarks correspond to the yellow spheres, whereas the 144 semi-landmarks correspond to the smaller red spheres. Please notice that the 3D model was decimated to an extremely small size (as compared to our original models) to avoid long computational times when rendering with rgl.