but doubtless when we discover the feet of the earliest reptiles we shall find them not different from the feet of the contemporary amphibians.
Every known bone in the skull of the Temnospondyli, except the interfrontal of a very few, has been found in the skull of early reptiles, and all, indeed, in a single genus Seymouria (Figs. 1, 2) from the Lower Permian of Texas. And there is no bone in the skeleton of reptiles that is not known in these same amphibians, except the preparietal of the Anomodontia, the supraorbitals of various Squamata and the predentary and rostral bones of certain dinosaurs, and doubtless the last two, if not all, are simply dermal bones which became temporarily attached to the skull. The girdles and limbs of the two classes are distinguishable only by minor characters. And thus, while we do not know from these later rocks, and probably never shall from rocks later than the Lower Carboniferous, all of the characters common to the two classes in any one animal, from the comparison of all it is not difficult to decide what were the primitive characters of the reptilian skeleton in almost every detail. They may be summarized as follows:
The Primitive Skull of the Reptilia
Rugose, with five openings in roof:
A. Paired, divided, terminal nares.
B. Paired orbits beyond middle [i.e., in front of the middle of the skull].
C. Median parietal (pineal) foramen.
An emargination of the occipital border, between tabular and squamosal, for the ear [the "otic notch"].
Seventeen pairs of roof bones; four pairs of palatal bones; eight pairs of cranial bones; eight pairs of mandibular bones; three unpaired cranial bones; one unpaired palatal bone—seventy-eight in all.
| A. Paired Bones | |||
| 1. | Premaxillae (px) | Dentigerous | |
| 2. | Maxillae (mx) | ||
| 3. | Septomaxillae (sx) | Nasal bones | |
| 4. | Nasals (na) | Median roof bones | |
| 5. | Frontals (fr) | ||
| 6. | Parietals (pa) | ||
| 7. | Interparietals (ip) | ||
