Feathers are complex, branched, keratinized epidermal features commonly associated with Class Aves, or birds (Bock, 2000). Cells in the epidermis called keratinocytes are the structural components of feathers; however, the protein keratin varies in its distribution and can be of different types (Prum, 2002). Many functions involved with feathers include thermal insulation, flight, cleaning of plumage, heat protection, sound production, chemical defenses, water repulsion of plumage, social communication, streamlining the body, and the sensation of touch (Bock, 2000; Prum, 2002). A wide variety of feathers have been characterized. Feathers covering the body are known as contour feathers (Bock, 2000). Contour feathers covering the wings are called remiges, while those covering the tails are called retrices (Bock, 2000). Additional types of feathers include semiplumes, down and powdered down feathers, bristles and semibristles, filoplumes, courtship plumes, and oil gland feathers (Bock, 2000). General characteristics of feathers include the presence of a calamus, which anchors the feather into the bird’s integument (Bock, 2000). Barbs, or closely spaced branches, are attached to the central shaft known as the rachis (Bock, 2000). Barbs on each side of the rachis form a vane (Bock, 2000). Proximal and distal barbules originate from barbs; proximal barbules are near the base of the feather while distal barbules are at the tip of the feather (Bock, 2000; Prum, 2002). When these barbules interlock, the structure of the vane is preserved (Bock, 2000).
Interestingly, feathers are not restricted to birds; fossil evidence from Archaeopteryx lithographica showed that feathers originated in pre-avian dinosaurs (Prum, 1999). It is understoo...
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... R.O. 1999. Development and Evolutionary Origin of Feathers. J. Exp. Biol. 285: 291-306.
Prum, R. O. 2002. The Evolutionary Origin and Diversification of Feathers. Q. Rev. Biol. 77: 261-291.
Schweitzer, M.H., Watt, J.A., Avci, R., Knapp, L., Chiappe, L., Norell, M. et al. 1999. J. Exp. Zool. 285: 146-157.
Vinther, J., Briggs, D.E.G., Clarke, J., Mayr, G., Prum, R.O. 2010. Structural coloration in a fossil feather. Biol. Lett. 6: 128-131.
Xu, X. 2006. Feathered dinosaurs from China and the evolution of major avian characters. Integr. Zool. 1: 4-11.
Xu, X., Zhou, Z., Prum, R.O. 2001. Branched integumental structures in Sinornithosaurus and the origin of feathers. Nature 410: 200-203.
Zhang, F., Kearns, S.L., Orr, P.J., Benton, M.J., Zhou, Z., Johnson, D. et al. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature 463: 1075-1077.
Tackett, J. L., Lahey, B. B., van Hulle, C., Waldman, I., Krueger, R. F., & Rathouz, P. J. (2013).
Ceratopsians and Pachycephalosaurs are closely related in their characteristics. Ceratopsians processed a saddle-shaped boney frill that extended from the skull to the neck and typically had horns over the nose and eyes. The most popular was the triceratops, which could reach over 26 feet and weigh in excess of twelve metric tons. Their frills served as two major functions. It protected the vulnerable neck from being harmed. The second major function that the frill provided was due to the fact that the frill contained a network of blood vessels on its underside, which were used as a means to get rid of excess heat. The Pachycephalosaurs were considered to be bipedal. They were also found to have thick skulls, flattened bodies, and tail that were covered in an array of body rods. Pachycephalosaurs were thought to have been more than fifteen feet long and processed a skull that was surrounded by a rounded dome of solid bone. It was thought that they used their heads in combat or mating contests, but that was disproved fairly recently, which I will discuss later in the paper. Both Ceratopsians and Pachycephalosaurs were “bird-hipped” and both of these suborders contained a backwards pubic bone. Both were Marginocephilia, or “fringed heads”, which is one of three clads under the Orinthiscia order. They were also herbivore dinosaurs that inherited their fringe at the back of the skull from earlier ancestors.(2) Their classi...
Paul, Gregory S. (2002). "Looking for the True Bird Ancestor". Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Baltimore: Johns Hopkins University Press. pp. 171–224. ISBN 0-8018-6763-0.
Majungatholus atopus roamed the plains of northwestern Madagascar about 70 million years ago during the Late Cretaceous (Perkins, 2003; Rogers et al, 2003). The discovery of 21 tooth-marked elements originating from two Majungatholus atopus individuals suggests evidence that the dinosaur supplemented its diet by feeding on its own dead or hunting them (Rogers et al, 2003). It cannot be confirmed whether they were purely scavengers, hunters, or both. Scientists are certain that the marks are not the doing of any other predator because the teeth marks are not consistent with any other known species that lived in the area. Only one other theropod that inhabited the area during the time Majungatholus atopus did, Masiakasaurus knopfleri, had teeth and bite marks too small to have caused these markings. Two large crocodile species also shared the same ecosystem but their teeth were “too blunt and too irregularly spaced to have produced the narrow grooves found on the Majungatholus bones”(Perkins, 2003). The tooth marks on at least nine Majungatholus elements attest to intertooth spacing in the perpetrators jaw and denticle drag patterns consistent enough to make a compelling case for Majungatholus feeding on other Majungatholus (Rogers et al, 2003).
Tadić, A., Wagner, S., Hoch, J., Başkaya, Ö., von Cube, R., Skaletz, C., ... & Dahmen, N. (2009).
...(1995). The Beak of the Finch: A Story of Evolution in Our Time. Vintage Books: New York.
Pianka, E. and Hodges, W. 1995. Horned Lizards. University of Texas. Web. Accessed at http://uts.cc.utexas.edu/~varanus/phryno.html
Dinosaurs are an extinct group of animals that thrived for 165 million years starting 230 million years ago in the Late Triassic period of the Mesozoic Era. Despite being extinct for the past 65 million years and not being able to study them in their true form, scientists have been able to estimate many different behaviors of dinosaurs. This paper will show that the close study and examination of different types of body and trace fossils, along with animal models, can be provided as evidence to estimate different types of behaviors in dinosaurs. The different types of behaviors examined below will fall into the categories of: mating; reproduction and nesting; social lives; locomotion; feeding; and fighting. To begin, a great deal of information gathered from fossils and compared to living animal models have been used to estimate mating behaviors.
1) Chaplin, G. Jablonski, N. “The Evolution of Human Skin Coloration.” Journal of Human Evolution 39 (2000) 57-106
The debate of whether dinosaurs were cold blooded or warm blooded has been ongoing since the beginning of the century. At the turn of the century scientists believed that dinosaurs had long limbs and were fairly slim, supporting the idea of a cold blooded reptile. Recently, however, the bone structure, number or predators to prey, and limb position have suggested a warm blooded species. In addition, the recent discovery of a fossilized dinosaur heart has supported the idea that dinosaurs were a warm blooded species. In this essay, I am going to give supporting evidence of dinosaurs being both warm and cold blooded. I will provide background information on the dinosaur that was discovered and what information it provides scientists.
Timpano, K. R., Keough, M. E., Mahaffey, B., Schmidt, N. B., & Abramowitz, J. (2010).
Marzluff, J., Angell, T. & Elliot, B. (2013, May. - Jun.). Birds: Brains over brawn. Audubon, 115(3), 40-41.
While there is no direct indication of the Tyrannosaurus rex having had feathers, scientists now consider that the T. rex had feathers on at least parts of its body. Because of their presence in related species. Mark Norell of the American Museum of Natural History stated with evidence "we have as much evidence that T. rex was feathered, at least during some stage of its life, as we do that australopithecines like Lucy had hair."
With its abundance of genera, the Burgess Shale is one of the world’s most important fossil fields. It’s discovery in 1909 led to over 100 years of paleontological study in the Canadian Rockies, a majority of which has been carried out in two quarries known as the Walcott and Raymond quarries (Hagadorn, 2002). Though he was originally in search of trilobites in the Burgess Shale Formation, paleontologist Charles Walcott also discovered a diverse group of soft- and hard-bodied fossils, from algae and sponges to chordates and cirripeds (Hagadorn, 2002). Soft-bodied fossils are incredibly rare due to their delicate structure and susceptibility to decay, so it is hard-bodied fossils that more regularly occur in fossil findings. However over 75,000 soft-bodied specimens have been found in the Burgess Shale formation (Hagadorn, 2002). These specimens are preserved in layers of shale formed from deposits of fine mud. One of the most significant species discovered is the Pikaia gracilens. Believed to be an early chordate, the Pikaia gracilens existed very close to the beginning of the evolutionary path that ultimately lead to humans (McGraw-Hill Encyclopedia, 2006).
Barker, V., Giles, H., Hajek, C., Ota, H., Noels, K., Lim, T-S., & Somera, L. (2008).