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The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than fish, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always ...
Cartilaginous fish, such as sharks and rays, have jaws and skeletons made of cartilage rather than bone. Megalodon is an extinct species of shark that lived about 28 to 1.5 Ma. It looked much like a stocky version of the great white shark , but was much larger with fossil lengths reaching 20.3 metres (67 ft). [ 10 ]
Regions of a Chondrichthyes brain colored and labeled on dissected skate. The rostral end of the skate is to the right. In chondrichthyans, the nervous system is composed of a small brain, 8–10 pairs of cranial nerves, and a spinal cord with spinal nerves. [11] They have several sensory organs which provide information to be processed.
The location of anatomical structures can also be described in relation to different anatomical landmarks. They are used in anatomy, surface anatomy, surgery, and radiology. [53] Structures may be described as being at the level of a specific spinal vertebra, depending on the section of the vertebral column the structure is at. [53]
Using the subadult specimen nicknamed "Big Al", since assigned to the species Allosaurus jimmadseni, [37] researchers using computer modeling arrived at a best estimate of 1.5 t (1.7 short tons) for the individual, but by varying parameters they found a range from approximately 1.4 t (1.5 short tons) to approximately 2 t (2.2 short tons). [107]
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Fish jaws, like vertebrates in general, normally show bilateral symmetry. An exception occurs with the parasitic scale-eating cichlid Perissodus microlepis. The jaws of this fish occur in two distinct morphological forms. One morph has its jaw twisted to the left, allowing it to eat scales more readily on its victim's right flank.
The inclusion of fish vertebrae, jaw bones, teeth, and other informative skeletal elements improves prey identification and quantification over otolith analysis alone. [24] This is especially true for fish species with fragile otoliths, but other distinctive bones, such as Atlantic mackerel (Scomber scombrus), and Atlantic herring (Clupea ...