The squamosal normally articulates with the tabular and quadrate posteriorly, anteriorly with the postorbital, and often, both in the lizards and mosasaurs, by a slender prolongation with the tip of the jugal; very rarely, as in Uromastix, with the jugal only. In some lizards it has suffered reduction, and is absent in the Geckonidae, Anniella, and Amphisbaenidae, vestigial in the Helodermatidae.
Fig. 54. Mosasaur skulls: Upper figure, Clidastes, from the side; middle figure, Platecarpus, from below; lower figure, Tylosaurus, from above. an, angular; bs, basisphenoid; c, coronoid; ep, epipterygoid; fr, frontal; j, jugal; l, lacrimal; m, maxilla; na, nasal; oc, occipital condyle; pa, parietal, palatine; pm, premaxilla; pf, prefrontal; pt, pterygoid; po, postorbital; q, quadrate; sp, splenial; sq, squamosal; tr, transverse; v, vomer.
