Jaw Suspension in Vertebrates: Types and Mechanisms Explored
Jaw suspension in vertebrates involves the attachment of the lower jaw to the upper jaw or skull for efficient biting and chewing. Different types of jaw suspensions exist, such as holostylic and autosystylic, each based on modifications in visceral arches. Holostylic suspension involves the lower jaw hanging from the quadrate region, while autosystylic suspension includes variations in the hyoid arch and its articulation with the upper jaw. Streptostylic and monimostylic suspensions are further elaborated based on the mobility of the quadrate. Illustrations and examples from various vertebrate groups, including fish, tetrapods, and reptiles, highlight the diversity in jaw suspension mechanisms.
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JAW SUSPENSION IN VERTEBRATES BY RAHEELA MUSHTAQ (ASSISTANT PROFESSOR) DEPT. OF ZOOLOGY, GOVT. P. G. COLLEGE, RAJOURI
Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates.
Autostylic jaw suspension is of different types i} Holostylic The hyoid arch is complete and free from chondrocranium. The lower jaw hangs from the quadrate region of the upper jaw. This condition developed in the ancient placoderms and is still seen in Holocephali i.e.,Chimaera
ii}Autosystylic The hyoid arch is broken up, its hyomandibular cartilage is reduced and transformed into an ear ossicle the columella or stapes on either side. The lower jaw articulates by its articular part with the quadrate region of upper jaw.eg lung fishes and tetrpods except mammals.If quadrate is movable then jaw suspension is said to be streptostylic eg-lizards, snakes and birds. If quadrate is firmly fixed then the jaw suspension is said to be monimostylic. Eg- other tetrapods.
