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While color vision is dependent on many factors, discussion of the evolution of color vision is typically simplified to two factors: the breadth of the visible spectrum (which wavelengths of light can be detected), and; the dimensionality of the color gamut (e.g. dichromacy vs. tetrachromacy).
Though fossils revealing ichthyosaur behavior remain rare, one ichthyosaur fossil is known to have sustained bites to the snout region. Discovered in Australia, and analyzed by Benjamin Kear et alii in 2011, measurements of the wounds reveal that the bite marks were inflicted by another ichthyosaur, likely of the same species, a probable case ...
Researchers studying the opsin genes responsible for color-vision pigments have long known that four photopigment opsins exist in birds, reptiles and teleost fish. [3] This indicates that the common ancestor of amphibians and amniotes (≈350 million years ago) had tetrachromatic vision — the ability to see four dimensions of color.
Many other primates (including New World monkeys) and other mammals are dichromats, which is the general color vision state for mammals that are active during the day (i.e., felines, canines, ungulates). Nocturnal mammals may have little or no color vision. Trichromat non-primate mammals are rare. [12]: 174–175 [49]
The ichthyosaur’s jawbone, or surangular, was a long, curved bone at the top of the lower jaw just behind the teeth, and it measured more than 6.5 feet (2 meters) long.
Trichromatic color vision, separate blue, green and red vision, is found only in a few mammals and came about independently in humans, Old World monkeys and the howler monkeys of the New World, and a few Australian marsupials. [52] [53]
The retina uses "cones," a specific type of photoreceptor, to differentiate color, according to the American Academy of Ophthalmology. Human eyes have three types of cones: red-sensing, green ...
As well as this, the eyes of a porpoise are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When porpoises surface, their lens and cornea correct the nearsightedness that results from the refraction of light; their eyes contain both rod and cone cells, meaning they can see ...