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In most modern reptiles and amphibians, the quadratojugal is a prominent, straplike bone in the skull and provides structural integrity in the postorbital region of the skull. [6] In many reptiles, the inner face of the quadratojugal also connects to the quadrate bone which forms the cranium's contribution to the jaw joint.
The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids. In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms upper part of the jaw joint.
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.
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. [1]: 140 [25]: 12
Zatracheidids are distinguished by lateral (sideways) bony protuberances of the quadratojugal bone of the skull, and a large opening in the snout called the internarial fontanelle (sometimes the internarial fenestra) that is bordered by enlarged premaxillae. The skull is flattened, with small orbits or eye sockets set far
A quadratojugal bone, which in modern birds is fused to the jugal, is preserved in Pterygornis. [30] The presence of these primitive features of the skull would have rendered the Enantiornithes capable of only limited cranial kinesis (the ability to move the jaw independent of the cranium). [31]
The downward projecting process of the squamosal, a bone forming the upper rear corner of the skull, was elongated, distinguishing the genus from other dicraeosaurids. This suggests that it was connected to the quadratojugal bone at the lower rear edge of the skull, although the articulation itself is not preserved.
In 2016, Gregory S. Paul gave Nodocephalosaurus an estimated length of 4.5 metres (15 feet) and a weight of 1.5 tonnes (3,306 lbs). [3]Sullivan (1999) originally diagnosed Nodocephalosaurus based on the presence of semi-inflated to bulbous polygonal osteoderms fused to the nasal, frontal and supraorbital regions of the skull, a prominent quadratojugal horn that is directed anteroventrally, and ...