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A bathtub faucet with built-up calcification from hard water in Southern Arizona. Hard water is water that has a high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, [1] which are largely made up of calcium and magnesium carbonates, bicarbonates and sulfates.
Odontodes, or dermal teeth, are hard structures found on the external surfaces of animals or near internal openings.They consist of a soft pulp surrounded by dentine and covered by a mineralized substance such as enamel, a structure similar to that of teeth. [1]
There is a layer of enamel and even a layer of pulp. The whole shield is made up of thousands of small teeth fused together. This bony skull--one of the earliest in the fossil record--is made entirely of little teeth. Teeth originally arose to bite creatures (see Conodonts); later a version of teeth was used in a new way to protect them." [4]
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 ...
Many Teleosts, for example the Atlantic wolffish, exhibit durophagous behaviour and crush hard prey with their appropriately adapted jaws and teeth. Other fish use of their pharyngeal teeth, with the aid of their protrusible mouth for enabling the grabbing of prey to draw it into their mouth. The pharyngeal jaws found in more derived teleosts ...
Early bony fish had simple respiratory diverticula (an outpouching on either side of the esophagus) which helped them breathe air in low-oxygen water as a form of supplementary enteral respiration. In ray-finned fish these have evolved into swim bladders, the changing sizes of which help to alter the body's specific density and buoyancy.
The bones mark the earliest evidence of human ancestors cooking their meals. 780,000-year-old fish teeth might indicate the first cooked meal, Israeli study shows Skip to main content
The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The eyes have a tapetum lucidum. The inner margin of each pelvic fin in the male fish is grooved to constitute a clasper for the transmission of sperm. These fish are widely distributed in tropical and temperate waters. [15]