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The upper jaw, or maxilla [12] [13] is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible (lower jaw), which is also a fusion of two halves at the mandibular symphysis. In bony fish, the maxilla is called the "upper maxilla," with the mandible being the "lower maxilla".
The Syngnathidae is a family of fish which includes seahorses, pipefishes, and seadragons (Phycodurus and Phyllopteryx). The name is derived from Ancient Greek: σύν (syn), meaning "together", and γνάθος (gnathos), meaning "jaw". [1] The fused jaw is one of the traits that the entire family have in common. [2]
The Osteostraci (bony armored jawless fish) are generally considered the sister taxon of Gnathostomata. [3] [9] [10] Jaw development in vertebrates is likely a product of the supporting gill arches. This development would help push water into the mouth by the movement of the jaw, so that it would pass over the gills for gas exchange.
Jawless fish and sharks only possess a cartilaginous endocranium, with the upper and lower jaws of cartilaginous fish being separate elements not attached to the skull. Bony fishes have additional dermal bone, forming a more or less coherent skull roof in lungfish and holost fish. The lower jaw defines a chin.
Jawless fish and sharks possess only a cartilaginous endocranium, with both the upper and lower jaws being separate elements. Bony fishes have an additional dermal bone, forming a more or less coherent skull roof in lungfish and holost fish. The lower jaw defines a chin. [1]
Fishes are a paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal taxonomy.Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes: [1]
The hardyhead silverside is a robust, broad headed, small fish [3] which is distinguished by having a very low and wide lateral process of premaxilla with the upper margin of the anterior bone of the lower jaw which bears the teeth is almost flat distally and has no distinct tubercle at its posterior end. The posterior of the jaw reaches at ...
The small terminal mouths of filefish have specialized incisor teeth on the upper and lower jaw. In the upper jaw there are four teeth in the inner series and six in the outer series. In the lower jaw, there are four to six in an outer series only. The snout is tapered and projecting and the eyes are located high on the head.