Just a short post, based on a days worth of research on knuckle-walking. Conclusions, a knuckle-walking Spinosaurus would break, damage, and puncture its hand. I don’t study biomechanics, but I can still notice anatomical features related to knuckle-walking. They include:
- A flat surface where the weight is distributed
- A very large region where the phalanges articulate.
- No claws or curved bones in the distal phalanges
- Longer phalanges and metacarpals both proximal and distal to the major articulation
- Not overly robust bones in the hand.
- The fingers can all be closely bunched
- All finger are near the same length
All of these can be seen in modern knuckle-walkers like gorillas and chimpanzees, and none can be seen in Baryonyx, essentially the closest to a Spinosaurus we have. Its bones would only support the weight on very small portions, the articular joints are limited in size and thus the fingers couldn’t bend very far, have claws which are curved, its metacarpals are very stout, the hand was very robust, its fingers were spread apart, and the first digit is much larger than the others. All in all, the hand of a knuckle-walking Spinosaurus would be (1) crushed, (2) dislocated, (3) punctured, (3) twisted, (4–6) otherwise damaged, and (7) its first digit would take a brunt of the beating.