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On the other hand, rays rely on their enlarged pectoral fins for propulsion. Similarly enlarged pectoral fins can be found in the extinct †Petalodontiformes (e.g. †Belantsea, †Janassa, †Menaspis), which belong to Holocephali (ratfish and their fossil relatives), or in †Aquilolamna (Selachimorpha) and †Squatinactis (Squatinactiformes).
Fins allow the sharks to be able to guide and lift themselves. Most sharks have eight fins: a pair of pectoral fins, a pair of pelvic fins, two dorsal fins, an anal fin, and a caudal fin. Pectoral fins are stiff, which enables downward movement, lift, and guidance. The members of the order Hexanchiformes have only a single
A peculiar function of pectoral fins, highly developed in some fish, is the creation of the dynamic lifting force that assists some fish such as sharks in maintaining depth and also enables the "flight" for flying fish. Certain rays of the pectoral fins may be adapted into finger-like projections, such as in sea robins and flying gurnards.
Several synapomorphies support this hypothesis, such as the presence of: sclerotic ossicles, paired pectoral fins, a dermal skeleton with three layers (a basal layer of isopedin, a middle layer of spongy bone, and a superficial layer of dentin), and perichondral bone. [10] Other groups Other groups † Pteraspido-morphi (extinct)
A long dorsal fin runs from the middle of the back and is continuous with a similar ventral fin. Pelvic fins are absent, and relatively small pectoral fins can be found near the midline, followed by the head and gill covers. Variations exist in coloration, from olive green, brown shading to greenish-yellow and light gray or white on the belly.
The gill arches are condensed into a pouch-like bundle covered by a sheet of skin (an operculum), with a single gill-opening in front of the pectoral fins. [5] The pectoral fins are large enough to generate lift at a relaxed forward momentum, giving the chimaera the appearance of "flying" through the water. Further back on the body are also a ...
Adults range in length from 14–17 m (46–56 ft) and weigh up to 40 metric tons (44 short tons). The humpback has a distinctive body shape, with long pectoral fins and tubercles on its head. It is known for breaching and other distinctive surface behaviors, making it popular with whale watchers.
Batoid gill slits lie under the pectoral fins on the underside, whereas a shark's are on the sides of the head. Most batoids have a flat, disk-like body, with the exception of the guitarfishes and sawfishes, while most sharks have a spindle-shaped body. Many species of batoid have developed their pectoral fins into broad flat wing-like appendages.