The surangular is a dermal bone of the lower jaw. It typically covers much of the dorsal and lateral surface of the posterior jaw and variably extends onto the medial (inside) surface. The surangular articulates with and supports the articular, which forms the jaw joint with the quadrate in most vertebrates, and is in turn supported by the angular. More distally, the surangular bridges the mandibular fenestra, if one is present. It may also bear a raised dorsal coronoid process, an important attachment site for the mandibular adductors. At its distal (or rostral) end, the surangular meets the dentary, the main tooth-bearing bone of the lower jaw in most vertebrates. [ ]

Synonyms: surangular

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Term information

external definition

Dermal bone of the suspensorium.[TAO]

has related synonym

supraangular bone




suprangular bone

supra-angular bone



taxon notes

Nevertheless, it is not completely clear that this[osteichthyans] surangular is homologous with the surangular in tetrapods

In some lepospondyls, and in frogs and salamanders, the surangular is absent. However, it becomes increasingly significant in the anthracosaur lineage. In turtles, it is one of the two principle bones of the lower jaw. In lepidosaurs, it is less important because of the development of a separate coronoid bone. In advanced lizards and pythonomorphs, it may fuse with the articular and perhaps other bones and loses its separate identity. In syanapsids, a secondary jaw joint develops between the surangular and the squamosal, which becomes the unique mammalian jaw articulation. However, the surangular fuses with the dentary and becomes the unitary mammalian 'mandible' without a separate identity