The Origin of Birds

The Origin of Birds For as long as cohesive evolutionary theories have been in place, the heated debate regarding the origin of birds and their relationship to dinosaurs has raged on. After the 1860s birds have been hypothesized as being closely related to an ample assortment of extant and extinct reptile lineages. These include a diversity of basal archosaurs and archosauromorphs, pterosaurs, crocodylomorphs (including modern crocodylians and their Mesozoic relatives), and various theropod ornithischian dinosaurs. Phylogenetic systematics is the field in which systematists use clues from the rock record to reconstruct evolutionary history and then study the patterns of relationships among organisms. With the use of this technique, systematists have been able to strongly back the view that birds evolved from theropod dinosaurs. However, opposition to this widely accepted notion still continues. The alternative hypotheses are speculative at best because they are not based on repeatable analyses of anatomical or other kinds of data. An abundance of recent evidence, including similarities in egg structures, inferable behaviors, and their integumentary structures have been amassed in support of the maniraptoran dinosaurs’ evolution into birds’ theory.(Chiappe and Dyke 306-312) This new evidence has met predictions devised long ago by supporters of the theropod ancestry of birds. There are striking resemblances between birds and dinosaurs that led scientists to classify birds as theropods. One of the most important discoveries in this argument was the unearthing of a fossil in the Solnhofen Formation in Germany known as Archaeopteryx lithographica. This beautiful fossil turned out to be an example of a transitional form between the two vertebrate groups, traditional reptiles and birds. The half meter long fossil was chimeric because it had bird feathers co-existing with obviously “reptilian” features, such as a tail and hands with claws. Archaeopteryx is generally

Cited: Chiappe, Luis M., and Gareth J. Dyke. "The Beginnings of Birds: Recent Discoveries, Ongoing Arguments, and New Directions." Major Transitions in Vertebrate Evolution. Ed. Jason S. Anderson and Hans-Dieter Sues. New York: Indiana UP, 2007. 303-28. Fastovsky, David E., and David B. Weishampel. The Evolution and Extinction of the Dinosaurs. 2nd ed. New York: Cambridge UP, 2005. 301-41. Feduccia, Alan. The Origin and Evolution of Birds. 2nd ed. New York: Yale UP, 1999. 45-91, 382-384. Dingus, Lowell, and Timothy Rowe. The Mistaken Extinction : Dinosaur Extinction and the Origin of Birds. New York: W.H. Freeman and Company, 1998. 107-228