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The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. [1] Birds are categorized as a biological class, Aves. For more than a century, the small theropod dinosaur Archaeopteryx lithographica from the Late Jurassic period was considered to have been the earliest bird.
A turning point came in the early twentieth century with the writings of Gerhard Heilmann of Denmark.An artist by trade, Heilmann had a scholarly interest in birds and from 1913 to 1916, expanding on earlier work by Othenio Abel, [12] published the results of his research in several parts, dealing with the anatomy, embryology, behavior, paleontology, and evolution of birds. [13]
Now, after finding many dinosaurs with primitive feathers, it is believed that feathers started out as these thin, hollow filaments, and eventually evolved into the fluffy coats of feathers seen on modern birds. [3] There are a few theories for the reasons feathers evolved in the first place, if not for flight.
Several studies of feather development in the embryos of modern birds, coupled with the distribution of feather types among various prehistoric bird precursors, have allowed scientists to attempt a reconstruction of the sequence in which feathers first evolved and developed into the types found on modern birds. Feather evolution was broken down ...
The pterosaur suggests feathers emerged around 250 million years ago through the common ancestor of dinosaurs, birds and pterosaurs -- and shifts the origin of feathers to 100 million years ...
The shared history of birds and dinosaurs is well-established, but exactly how true birds evolved during the Mesozoic is a bit of a mystery. Adding to this conundrum are fossilized footprints of ...
The span between precocial and altricial species is particularly broad in the biology of birds. Precocial birds hatch with their eyes open and are covered with downy feathers that are soon replaced by adult-type feathers. [17] Birds of this kind can also swim and run much sooner after hatching than altricial young, such as songbirds. [17]
Prior to their existence on birds, feathers were present on the bodies of many dinosaur species. Through natural selection, feathers became more common among the animals as their wings developed over the course of tens of millions of years. [6] The smooth surface of feathers on a bird's body helps to reduce friction while in flight.