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Cosmine was first described in the Osteolepiform Megalichthys hibberti by Williamson in 1849, in a purely descriptive, pre-Darwinian, non-evolutionary framework. [4] Goodrich [5] expanded on Williamson's descriptions, hypothesizing a transition from a monoodontode scale (like a chondryicthian placoid scale) to a complex polyodontode scale through fusion of discrete units.
A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages.
Keeled scales of a colubrid snake (banded water snake; Nerodia fasciata). In zoology, a scale (Ancient Greek: λεπίς, romanized: lepís; Latin: squāma) is a small rigid plate that grows out of an animal's skin to provide protection.
Existing fish groups featuring ganoin are bichirs and gars, but ganoin is also characteristic of several extinct taxa. [4] It is a characteristic component of ganoid scales . Ganoine is an ancient feature of ray-finned fishes, being found for example on the scales of stem group actinopteryigian Cheirolepis . [ 4 ]
Aristotle (ca. 340 B.C.) may have been the first scientist to speculate on the use of hard parts of fishes to determine age, stating in Historica Animalium that “the age of a scaly fish may be told by the size and hardness of its scales.” [4] However, it was not until the development of the microscope that more detailed studies were performed on the structure of scales. [5]
This process continues, so that each generation is half (or hemi-) clonal on the mother's side and has half new genetic material from the father's side. [60] [64] This form of reproduction is seen in some live-bearing fish of the genus Poeciliopsis [62] [65] as well as in some of the Pelophylax spp. ("green frogs" or "waterfrogs"):
Survivors can also develop fish-like scales and retention of a waxy, yellowish material in seborrheic areas, with ear adhered to the scalp. [citation needed] Most infants do not live past a week. Those who do survive can live from anywhere around 10 months to 25 years thanks to advanced medicine. [21]
Fish anatomy is the study of the form or morphology ... Fish scales: 1. cycloid scale; 2. ctenoid scale; 3. placcoid scale; 4. ganoid scale ... The genetic basis for ...