Origin of flight of dinosaurs Research Paper Example | Topics and Well Written Essays - 2000 words

Origin of flight of dinosaurs - Research Paper Example These factors will all be discussed with reference to Archaeopteryx lithographica, a species generally regarded as being the common ancestor to modern birds and the primary source of information about the development of flight mechanisms. Archaeopteryx A brief discussion of Archaeopteryx litographica (commonly known as Archaeopteryx) is necessary to understand how instrumental this species is to discovering the mechanisms of flight evolution. Various Archaeopteryx specimens have been found in the south of Germany, well-preserved due to the qualities of the limestone in which they were found. The Archaeopteryx is commonly described as being the size of a raven and having several features that make it identifiable in the context of modern-day birds – feathers and a wishbone, for example (Ostrom, 1975). Several of these features suggest that the Archaeopteryx was capable of flight, although, as with many things in evolutionary biology, this is something that can never be ascertai ned. Archaeopteryx also shared several features with dinosaurs, such as having chevrons of increased length in the tail and a specific shape of ankle bone (Ostrom, 1975). This bird-dinosaur morphology is the principle reason for thinking that the species is the missing link. The way that Archaeopteryx specimens are conserved in limestone has resulted in the preservation of feather imprints, allowing paleontologists to ascertain that this species may have used feathers in the development of flight mechanisms. This is particularly good evidence of some aerial motion because the feathers found show characteristics of flight feathers, meaning that feathers had previously began to evolve for a purpose other than flight (Paul, 2002). Finally, it is important to note that it has not been proven whether Archaeopteryx had the power of full flight or could simply glide (Padian & Chiappe, 1998). Arboreal Hypothesis The arboreal hypothesis (also known as the ‘tree down’ hypothesis) refers to the idea that dinosaurs first gained flight by jumping from trees and acquiring flight as an evolutionary mechanism to avoid fatal accidents from this method. This hypothesis seems ‘intuitive’ because ‘flight evolving from an arboreal gliding stage would seem to be relatively easy’ (Padian & Chiappe, 1998, p15) and because the force of gravity ‘helps rather than hinders’ (Lewin, 1983, p38). Some studies, such as that of Feduccia (1993) suggest that the shape of the manus (the ‘hand’ portion of the forelimb) and the pes (the ‘foot’ portion of the hindlimb) of the Archaeopteryx exhibit evidence of perching, tree-dwelling and trunk-climbing due to the curvature of these anatomical elements. However, since this paper was published, another specimen of Archaeopteryx has been discovered (known as the Thermopolis specimen) which has almost complete pes, and thus there is now mounting evidence that the hallux (first digit of the pes) did not display curvature necessary for perching (Mayr et al., 2007). If we consider the Archaeopteryx as arboreal, it is important to understand how and why flight would have developed in this way. The original theory as stated by Othniel C. Marsh in the late 19th century was that Archaeopteryx