Maxillae (mx). Primitively (Figs. 2 b, 3, 4, 6, 19, 21, 22, 33, 43), articulating anteriorly with premaxillae, above with septomaxillae and lacrimals, posteriorly with the jugals, ectopterygoids, and postorbitals internally, forming the outer boundary of both external and internal nares in part.
In most reptiles since Permian times they also articulate with the nasals above (e.g., Figs. 33, 43, 44); in the crocodiles (Fig. 69 b) with each other on the palate, as also in many Anomodontia and Theriodontia. They are edentulous in the Chelonia (Figs. 30–32), later Pterosauria (Fig. 72), some Anomodontia (Fig. 44 c), Dromosauria, Ophidia, Saphaeosaurus, Ornithomimus, etc. The teeth may be in single or numerous rows.
Fig. 3. Pantylus (Cotylosauria), from side. Three fourths natural size.
Septomaxillae (sx). Small bones, the so-called turbinals of reptiles, located partly within the nasal chamber, but appearing more or less on the outer side at the back part of the external nares. (Figs. 33, 44 a, b, f, 45.) Present probably in all the earliest and most early reptiles, and in most Squamata (Fig. 59); they are absent in the Chelonia (Figs. 28–32) and Crocodilia (Figs. 68, 69). In some Dromasauria they extend back on the face to meet the lacrimals. Little can be said about them in other extinct reptiles.
Nasals (na). Articulating with premaxillae, frontals, prefrontals, and lacrimals, forming more or less of the partition between the external nares.
Except in most Cotylosauria (Figs. 2, 3, 22, 23, etc.), some Theromorpha and Therapsida, they also articulate with the maxillae on the sides. They are absent in many Chelonia (Figs. 28–32); either absent
