prominent crests which projected outwards to the sides, forming an expansion of the orbit's rim. The squamosal bone was fully incorporated into the braincase wall, making its exact borders impossible to determine, which is also true for adult modern birds. Various interpretations have been proposed of the morphology and identity of the bones in the temporal region behind the orbits, but it may not be resolvable with the available fossils. Confuciusornis was considered the first known bird with an ancestral diapsid skull (with two temporal fenestrae on each side of the skull) in the late 1990s, but in 2018, Elzanowski and colleagues concluded that the configuration seen in the temporal region of confuciusornithids was autapomorphic (a unique trait that evolved secondarily rather than having been retained from a primitive condition) for their group. The quadrate bone and the back end of the jugal bar were bound in a complex scaffolding that connected the squamosal bone with the lower end of the postorbital process. This scaffolding consisted of two bony bridges, the temporal bar and the orbitozygomatic junction, which gave the appearance of the temporal opening being divided similarly to diapsid skulls, though this structure is comparable to bridges over the temporary fossa in modern birds. The mandible (lower jaw) is one of the best preserved parts of the skull. It was robust, especially at the front third of its length. The tomial crest was straight for its entire length, and a notch indented the sharp tip of the mandible. The mandible was spear-shaped in side view, due to its lower margin slanting downwards and back from its tip for the front third of its length (the jaw was also deepest at a point one third from the tip). The symphyseal part (where the two halves of the lower jaw connected) of the dentary was very robust. The lower margin formed an angle at the level of the front margin of the nasal foramen, which indicates how far back the rhamphotheca of the beak extended. The dentary had three processes that extended backwards into other bones placed further back in the mandible. The articular bone at the back of the mandible was completely fused with the surangular and prearticular bones. The mandible extended hindwards beyond the cotyla (which connected with the condyle of the upper jaw), and this part was therefore similar to a retroarticular process as seen in other taxa.