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The amazing Tiktaalik

Tiktaalik roseae is the only known species of the extinct monotypic Tiktaalik species lived in late Devonian (about 375 million years ago). Its many characteristics similar to tetrapods (four-legged animals) are an example of how in some ancient sarcopterygians lines (lobed bone fish) adaptations to low water oxygen habitats have been developed, adaptations that have led to to evolution in amphibians. It is currently believed that tiktaalik represents a transitional form among fishes like Panderichthys, lived about 385 million years ago, and the first tetrapods such as Acanthostega and Ichthyostega, lived about 365 million years ago.
The tiktaalik name is an inuktitut word that indicates the burbot, a fish of low waters. The genus received this name on the suggestion of an inuit elder of Canada's Nunavut territory, where fossil was discovered.
Tiktaalik appears to be a form of transition between fish and amphibians since, although presenting the general characteristics of a fish with lobed fins, it has skeletal structures similar to a limb in the front fins that are more like a crocodile, including the shoulder, elbow and wrist. Unlike many other fossils discovered earlier, more like fish, the fins of tiktaalik possessed the main bones of the wrist and the simple fingers, which made them able to support their weight. Examination of the joints shows that although these were probably not used to walking, they were most likely used to hold the body's creature's body up and down, similarly to a bending. The bones of the front fins show great attachment to the muscles, suggesting that the fin is muscled and able to flex as the articulation of a wrist. It is assumed that these features have evolved initially not so much as to allow hiking on the mainland, as well as a useful fit to anchor the creature to the backdrop in the very rapid river currents. The tail fins and the tail have not yet been found.
The tiktaalik has a flat skull that resembles that of the crocodile, with the eyes on the top of the head, suggesting the idea that it would take a long time to look to the surface. The jaws are well developed and adapted to grasp the prey, with sharp teeth of predatory fish, and on the skull one can highlight a small squirrel crawl that, in more developed animals, has evolved into one ear. Of note is the presence of nostrils at the top of the head, above the eyes, suggesting that this creature possessed primitive lungs in addition to the gills. Such adaptation would be useful in shallow water, whose high temperature leads to a low dissolved oxygen content. The development of the lungs also explains the evolution in the tiktaalik of a more robust chest than a fish and with ribs similar to those of tetrapods, which is very useful in supporting the body weight in the event of out-of-water excursions. It then represented a key evolutionary trait for adapting to life on the mainland. In addition, tiktaalik, having gills and flakes, lacks a characteristic feature of many fish, that is, bladder plaques in the area of ​​the gills that reduce the lateral movements of the head. This means that this species is the first fish with a neck, which would have given him more freedom in hunting the prey on both land and water.
Three fossilized and well-preserved tiktaalik skeletons were found in 2004 in rocks formed by late Devonian river sediments, in the Fram formation on Ellesmere Island, Nunavut, in northern Canada. At the time of the existence of the species, Ellesmere Island was part of the continent Laurentia, which was positioned at the equator and had a warm climate. The presence of fossils within rock deposits derived from river systems indicates tiktaalik as a benthic animal that lived on the bottom of shallow water, and perhaps even out of the water for short periods, thanks to its skeleton able to support The body and the lung to breathe. At that time, for the first time, deciduous trees began to flourish and lose annually the leaves that, drawing on the water, attracted small prey in the low, hot, oxygen-free waters where it was difficult to swim for big fish. The hypothesis of paleontologists is that this animal was specialized in living in low flow water systems, such as swamps or ponds, and, using its adapted fins, to occasionally move on the mainland.

Domain Eukaryota
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Sarcopterygii
Subclass Tetrapodomorpha
Genus Tiktaalik
Specie Tiktaalik roseae
Daeschler, Shubin and Jenkins, 2006

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