It is also known as facial. It includes following parts-
Visceral skeleton is formed by pairs of visceral arches which are-
Mandibular arch(I pair of visceral arch)
It is made of two arches one is upper forming upper jaw and second is lower called lower jaw.In tadpole stage upper jaw i.e.,upper part of mandibular arch is formed by the fusion of three cartilage called palatine,pterygoid and quadrate.These all fused to form palato-pterygoquadrate.
Lower jaw or II part of mandibular arch is cartilagenous initially and is called Meckel's cartilage which soon changes into bony structure.
(a) Upper jaw
The upper jaw is made of 14 bone i.e.,7 pairs of bones which are-
Out of these 7 pairs of bone only quadrate are not visible because they constitute II ear ossicle i.e.,-incus.
Palate of birds is identical in animal kingdom.which is used for birds classification.
Process of upper jaw
Nasal process on dorsal side which are covered by Nasal.Palatine process of premaxilla.
Nasal process of maxilla; Palatine process of maxilla; Zygomatic process of maxilla.
Only zygomatic process of squamosal.
(b) Lower jaw
It is composed of 6 pairs of bone.i.e.,12 bone maximum.These are articular ,angular, splenial,dentary,coronoid and supra angular.
In frog out of 6 pairs only 4 pairs of bones are present .Only 3 pairs from lower jaw and one pair forms I ear ossicle.i.e.,collumella auris. Remaining 3 pairs i.e. dentary forms lower jaw.
Upper jaw in vertebrates is completely ossified with skull but lower jaw is always free from chondrocranium and hangs downwardly.A bone hanges lower jaw from upper jaw.This bone is called suspensorium.A skull in which suspensorium is formed by quadrate is called autostylic e.e., frog skull. A skull inwhich suspensorium is formed by ssquamosal is called craniostylic skull e.g.,Rabbit skull(all mammal).
Hyoid arch(II pair of visceral arch)
It is also one pair which is called Hyoid proper and Hyomandibular.
(a) Hyoid proper
It is a horse-shoe shaped bone in our neck between lowe jaw and sound box or larynx.It is not articulate to any bone but is simply suspended from temporal bones by means of ligament.It consists of an elliptical main part or body and two processes on each side of body,called greater and lesser cornua.It supports our tongue and provides inseration to some tongue muscles.In colloboration with branchial arches forms hyoid apparatus in terrestial vertebrates.It is absent in fishes because branchial arches form gill rackers which support gills.
It is second part of hyoid arch which constitutes ear ossicle in vertebrate.In frog hyomandibular forms stapidial plate which is II ear ossicle which is dot or lid like bone.In rabbit hyomandibular forms stapes which is III ear ossicle.That is stirrup like bone.