or precoronoid. Primitively (Fig. 18) it often bore teeth, as in many temnospondyls, but no such teeth are known in later reptiles.
The surangular (sa), always present in reptiles, though sometimes indistinguishably fused with the articular, forms the upper margin of the mandible back of the coronoid, and the outer margin of the Meckelian orifice (Figs. 15–18). In some it may take part in the articular surface for the quadrate.
Fig. 15. Trimerorhachis insignis. Temnospondyl mandible: A, right ramus from below; B, the same from above.
The angular (an), on the inferior border posteriorly, articulating with the dentary in front, the prearticular, articular, and surangular behind, and extending to the hind angle of the jaw, is always present (Figs. 15–18). In the crocodiles (Fig. 69 c, d) it helps form the inner border of the Meckelian orifice.
