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The evolution of birds is thought to have begun in the Jurassic Period, with the earliest birds derived from theropod dinosaurs. Birds are categorized as a biological class, Aves. The earliest known species in Aves is Archaeopteryx lithographica, from the Late Jurassic period. Modern phylogenetics place birds in the dinosaur clade Theropoda.
Many vertebrates are limbless, limb-reduced, or apodous, with a body plan consisting of a head and vertebral column, but no adjoining limbs such as legs or fins. Jawless fish are limbless but may have preceded the evolution of vertebrate limbs, whereas numerous reptile and amphibian lineages – and some eels and eel-like fish – independently lost their limbs.
This is an instance of a universal: if something is a bird, it has feathers and wings; if something has feathers and wings, that also implies it is a bird, so the reasoning here is bidirectional. On the other hand, some animals that have red blood have lungs; other red-blooded animals (such as fish) have gills. This implies, in Aristotle's ...
Since first appearing during the age of dinosaurs, snakes have authored an evolutionary success story - slithering into almost every habitat on Earth, from oceans to tree tops. Scientists ...
The first tetrapods probably evolved in the Emsian stage of the Early Devonian from Tetrapodomorph fish living in shallow water environments. [36] [37] The very earliest tetrapods would have been animals similar to Acanthostega, with legs and lungs as well as gills, but still primarily aquatic and unsuited to life on land.
Why did it have to be snakes?” The reptile, christened Tachymenoides harrisonfordi, measures 16 inches long and is a pale yellowish-brown colour with black spots and a black belly.
The skull of a snake differs from a lizards in several ways. Snakes have more flexible jaws, that is, instead of a juncture at the upper and lower jaw, the snake's jaws are connected by a bone hinge that is called the quadrate bone. Between the two halves of the lower jaw at the chin there is an elastic ligament that allows for a separation.
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.