(adapted from Walker, Vertebrate Dissection.)
X = present O = absent Unos. = unossified
| NECTURUS | ALLIGATOR | MAMMAL | |
| NEUROCRANIUM | |||
| Basioccipital | Unos. | X | X – Occipital |
| Exoccipital | X | X | X – Occipital |
| Supraoccipital | Unos. | X | X – Occipital |
| Otics | X | X | X – Petrous portion of temporal |
| Basisphenoid | Unos. | X | X |
| Sphenethmoid | Unos. | X | X – Presphenoid |
| Unos. Ethmoid region | Unos. | Unos. | X – Ethmoid |
| Unos. nasal capsule | Unos. | Unos. | X – Turbinates |
| DERMATOCRANIUM | |||
| Premaxilla – Upper jaw | X | X | X |
| Maxilla- Upper jaw | O | X | X |
| Nasal – Roofing | O | X | X |
| Frontal – Roofing | X | X | X |
| Parietal – Roofing | X | X | X |
| Lacrimal – Roofing | O | X | X |
| Jugal – Roofing | O | X | X |
| Squamosal – Roofing | X | X | X – Squamous portion of temporal |
| Vomer – Primary palate | X | X | X |
| Palatine – Primary palate | O | X | X |
| Pterygoid – Primary palate | X | X | X – Pterygoid process of basisphenoid |
| LOWER JAW; DERMAL BONES | |||
| Dentary – Largest | X | X | X |
| Splenial ( 2) | X | X | O |
| Surangular | O | X | O |
| Angular | X | X | X – Tympanic portion of temporal |
| Coronoid | O | X | O |
| Prearticular | O | X | X – Anterior portion of Malleus |
| VISCERAL ARCHES | |||
| Palatoquadrate | |||
| Quadrate | X | X | X – Incus |
| Epipterygoid | O | O | X – Alisphenoid |
| Hyomandibular | |||
| Stapes | X | X | X |
| LOWER JAW: VISCERAL ARCHES | |||
| Articular | Unos. | X | X – Malleus |