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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.
Hox gene mutations have resulted in some tetrapods becoming limbless (snakes, legless lizards, and caecilians) or two-limbed (cetaceans, moas, and some lizards). [7] Nevertheless, these limbless groups still qualify as tetrapods through their ancestry, and some retain a pair of vestigial spurs that are remnants of the hindlimbs .
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.
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 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.
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 ...
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.
How the Snake Lost Its Legs: Curious Tales from the Frontier of Evo-Devo is a 2014 book on evolutionary developmental biology by Lewis I. Held, Jr. The title pays homage to Rudyard Kipling 's Just So Stories , [ 1 ] [ a ] but the "tales" are strictly scientific, explaining how a wide range of animal features evolved, in molecular detail.