boundary of the orbits, with their usual articulations. The jugals are long, articulating with postorbitals, quadratojugals, maxillae, and lacrimals. The relations of the bones of the palate and the boundaries of the nares are primitive; an ectopterygoid has not been recognized and is probably absent; there are no teeth on the palatal bones. On the occiput the paroccipitals, unlike all other reptiles since the primitive Cotylosauria, save the Chelonia, are separate. The stapes is a short, stout bone, possibly an acquired, more probably a primitive, character. There are no dermosupraoccipitals. The large parietal foramen is at the front end of the parietals, sometimes between the frontals.
Fig. 50. Ichthyosaur skull: Baptanodon (Ophthalmosaurus), from the side, from above, and from below. After Gilmore.
Most characteristic of the ichthyosaur skull is the structure of the temporal region, about which there has been dispute from the time of
