This Yale University video from the USA says about itself:
10/8/2005 Richard Prum – The Evolution of Birds: Why Birds are Dinosaurs
Another video used to say about itself:
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 of class Aves is Archaeopteryx lithographica, from the Late Jurassic period, though Archaeopteryx is not commonly considered to have been a true bird. Modern phylogenies place birds in the dinosaur clade Theropoda. According to the current consensus, Aves and a sister group, the order Crocodilia, together are the sole living members of an unranked “reptile” clade, the Archosauria.
Theory suggests iconic early bird lost its flight
Archaeopteryx anatomy matches that of modern flightless birds.
12 November 2013
Although it has long been debated whether the proto-bird Archaeopteryx was able to actually fly or merely evolving toward that ability, to date nobody had yet seriously suggested that it could have been instead in the midst of losing its ability to fly. But that is precisely what Michael Habib, a biologist at the University of Southern California proposed last week to a packed hall at the annual meeting of the Society of Vertebrate Paleontology in Los Angeles.
With the skeleton of a dinosaur and the feathers of a bird, Archaeopteryx has long been hailed as marking the transition from dinosaurs to birds.
The idea that it was instead evolving to lose its flight and becoming flightless again, or ‘secondarily flightless’, occurred to Habib while he was calculating limb ratios and degrees of feather symmetry in Archaeopteryx, and comparing the values to those of living birds, to better understand its flying ability. In doing so, he found that the creature’s traits were surprisingly similar to those of modern flightless birds such as rails and grebes that frequently dwell on islands.
“We know Archaeopteryx was living on an archipelago during the Jurassic. And with its feathers and bones looking so much like modern flightless island birds, it just makes me wonder,” says Habib.
When Archaeopteryx was first discovered, it was the earliest known feathered dinosaur, and the argument that it was evolving towards flightlessness might have been considered madness. But with the discovery in recent years of many earlier feathered dinosaurs with anatomies tailored for flight, the idea is being seriously considered.
Before the first birds could take flight, they needed a lift from a surprise source: pigments in their feathers: here.
The bladed, quill-like feathers of modern birds are essential for flight, and over millions of years they have become highly specialized for this purpose. But this may not be the reason they first evolved, say researchers studying an unusually complete fossil of the world’s first bird, Archaeopteryx. Instead, the team believes birds first grew these feathers for other purposes, such as insulation or mating display. The discovery raises the intriguing prospect that flight may have developed multiple times in the ancestors of birds: here.
- Body Temperatures in Dinosaurs: What Can Growth Curves Tell Us? (plosone.org)
- Dig up Digging for Bird-Dinosaurs (paleoaerie.org)
- Feathers Were ‘Peculiar’ to Special Set of Dinosaurs, New Fossil Study Finds (westerndigs.org)
- Top News: Two-Tailed Ancient Bird Uncovered (news.nationalgeographic.com)
- Bird (kyle861.wordpress.com)