Comparative anatomy of the Skeletal System
The first ideas that birds are the descendants of dinosaurs sprouted from observing the similarities between their bones and the unique characteristics the two groups shared. The closest relative to our modern-day birds is thought to be the Coelurosaurian dinosaurs and their fossilized bones have provided a wealth of knowledge on the evolution of birds.
The first birds shared these main skeletal characteristics with their ancestral theropod dinosaurs (Coelurosaurs):
- Hollow bones - Large orbits - Secondary bony palate - Expanded pneumatic sinuses - Teeth with a constriction between the root and crown - S-shaped curved neck - Strap-like scapula - 3-fingered opposable grasping hand, - Flexible wrist with a semi-lunate carpal - Elongated arms and forelimbs and clawed hands - Fused clavicles form a furcula - Pubis is shifted to a more posterior orientation - Four or five vertebrae form the sacrum - Reduced, stiffened tail - Erect, digitgrade stance with feet postitioned directly below the body. - Hingelike ankle joint, with restricted movement. - Elongated metatarsals. - 4-toed foot supported by 3 main toes. |