TABLE 1. Selected character variation between known crania of Axestemys infernalis.
| Character | DMNS 98814 | DMNS 130951 | NSM PV24650 | MAB 13742 |
| Premaxilla - quadrate condyle length | 14.5 cm | 15.0 cm | 16.0 cm | 9.8 cm |
| Skull roof surface | smooth | smooth | sculptured | smooth |
| Postorbital expanded ventrally | no | no | no | yes |
| contact maxilla - jugal, relative to orbit | ventral | ventral | ventral | posterior |
| Excavation dorsal surface ane | absent | extensive | modest | modest |
| Premaxilla ossified | yes | ? | yes | no |
| Ventral surface of maxilla, lateral view | straight | rounded | straight | rounded |
| Prefrontal - frontal suture | straight | straight | triangular | fused |
| Basisphenoid - palatine contact present | yes | no | yes | ? |
TABLE 2. Selected character variation between known crania of Axestemys species.
| Character | A. infernalis | A. splendida | A. montinsana | A. vittata |
| Skull outline | triangular to wide | triangular | triangular | wide |
| Triturating surface | smooth | ? | rugose | smooth |
| Orbit size | large | large | large | small |
| Jugal bar origin | level of orbit | level of orbit | level of orbit | ventral to orbit |
| Skull roof sculpturing | absent or present | present | present | present |
| Ventral margin of maxilla | rounded or straight | rounded | horizontal | straight slope |
| Anterior flange of quadrate inclination | oblique | ? | ? | near-horizontal |
| Opening fpp | enclosed in palatine | between palatine and maxilla | ? | lateral to ascending process palatine |
| Prefrontal - frontal suture | variable | straight | straight | triangular |
| Contribution of parietal to processus trochlearis oticum | >20% | reduced | >20% | ? |
| Maxilla deep | yes | yes | yes | yes |
| Postorbital over complete length of postorbital bar | yes | yes | yes | yes |
| Maxillae form a secondary palate | no | no | no | no |
