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The jugal bone is located on either side of the skull in the circumorbital region. It is the origin of several masticatory muscles in the skull. [1] The jugal and lacrimal bones are the only two remaining from the ancestral circumorbital series: the prefrontal, postfrontal, postorbital, jugal, and lacrimal bones.
In modern birds, the quadratojugal bone is a thin and rodlike element of the skull. Upon ossification, the jugal and quadratojugal bones fuse to form the jugal bar, which is homologous to the lower temporal bar of other diapsids.
These extended margins of thinned bone are called supratemporal fossae. Synapsids, including mammals, have one temporal fenestra, which is ventrally bordered by a zygomatic arch composed of the jugal and squamosal bones. This single temporal fenestra is homologous to the infratemporal fenestra, as displayed most clearly by early synapsids. [2]
Pages in category "Skull bones" The following 23 pages are in this category, out of 23 total. ... Jugal bone; O. Occipital bone; P. Palpebral (bone) Parietal bone;
The jugal is a skull bone that found in most of the reptiles, amphibians and birds. In mammals, the jugal is often called the zygomatic bone or malar bone. [8] The prefrontal bone is a bone that separates the lacrimal and frontal bones in many tetrapod skulls.
The jugal, or cheek-bone, is a skull bone that defines the lower border of the orbit and connects to the maxilla anteriorly and to the quadratojugal posteriorly. Its posterior end is bifurcated at its articulation with the quadratojugal, which is considered a synapomorphy of dinosaurs.
The jugal bone has expanded into the region the lower temporal opening would normally occupy. Paired squamosal bones extend beyond the skull's back margin to form small horn-like projections. The skull of Doswellia lacks several bones found in other archosauriforms, including the postfrontals, tabulars, and postparietals. [4]
The bone is also absent in living amphibians. [6] With the exception of turtles, the jugal bone in reptiles forms a relatively narrow bar separating the orbit from the inferior temporal fenestra, of which it may also form the lower boundary. The bone is similarly reduced in birds. In mammals, it takes on broadly the form seen in humans, with ...