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(A and C) Lateral and ventral views of the skull of a primitive tetrapod, the parareptilian Procolophon. (B and D) Lateral and ventral views of the skull of Proganochelys quenstedti. (E) Ventral view of the skull of Kayentachelys aprix. Small dots represent teeth. M, maxillary; Pal, palatine; Pm, pre-maxillary; Pt, pterygoid; V, vomer. (A and C) From Carroll & Lindsay (1985). (B and D) From Gaffney (1990). (E) From Gaffney et al. (1987). Scale bars, 1 cm.
