Rubber Duck Skeleton

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Hogg D.A. A re-investigation of the centres of ossification in the avian skeleton at and after hatching. J. Anat. 1980; 130:725–743. [ PMC free article] [ PubMed] [ Google Scholar] A comparison of bird wings and bat wings is an example of both homology and analogy. These wings, along with the arms of humans or the forelegs of cats, are examples of vertebrate forelimbs. It's clear that all these are homologous structures. The last common ancestor of birds and mammals had forelimbs with similar bones. In each of these species, the forelimbs develop the same way in the embryo, using homologous genes to control limb development. So as forelimbs, the wings of bats and birds are homologous. On the other hand, as wings they are analogous. The most recent common ancestor of bats and birds had forelimbs, but not wings. Wings evolved separately in bats and birds, so the wings of bats should be considered analogous to the wings of birds. Bats also have keeled sternums Muscle function in avian flight: achieving power and control. Andrew Biewener, 2011. Philosophical Transactions of the Royal Society 366 (1570): 1496-1506. An extremely detailed review of how birds' muscles work during flight, with descriptions of the experimental methods (electrodes in muscles!) used to figure it out. This article is far too detailed for most people, but it does include an excellent diagram of flight muscles and how they're connected to the skeleton. This doesn't mean that feathers aren't relevant to flight; it simply means that feathers first evolved for other reasons and later became adapted to flight. If this is the case, then how did feathers function in nonflying dinosaurs? In modern birds, feathers are also important for insulation, mating displays, and as aerodynamic aids when running. All these may have been factors in the evolution of feathers in the dinosaur ancestors of birds; it is a matter of some debate among paleontologists as to which factors were most important.

Wagner D.O., Aspenberg P. Where did bone come from? An overview of its evolution. Acta. Orthop. Belg. 2011; 82:393–398. [ PMC free article] [ PubMed] [ Google Scholar] Bird Evolution. Julia Clarke & Kevin Middleton, 2006. Current Biology, 16(10): pR350-R354. An excellent review of bird evolution. This article is brief and readable. The authors explain why birds should be considered as dinosaurs, and has a cladogram showing important events in the evolution of birds.

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Beak. The most obvious thing that tells you you're looking at the skull of a bird and not a mammal is the beak. Some mammals (dolphins, for example) may also have a beaklike shape, but birds are distinctive in having a hard coating of keratin (the same protein found in hair, feathers, and scales) on the outside. The various Iguanodon species are large herbivores, ranging from 6 to 11 metres (20 to 36 feet) in length, and averaging about 5 tonnes (5.5 tons) in weight. King AS (1975) Aves respiratory system and Aves urogenital system. In: Getty R (ed) Sisson’s and Grossman’s the anatomy of the domestic animals, vol 2. WB Saunder’s Company, Philadelphia, pp 1883–1967 University of Southampton, “ Shrinking dinosaurs evolved into flying birds,” Science Daily (31 July 2014).

Parasaurolophus cyrtocristatus skeleton on display at the Field Museum of Natural History, in Chicago. Life-size Parasaurolophus Skeleton Sculpture for Sale Kudo K., Tsunekawa N., Ogawa H., Endo H. Comparative functional morphology of the skeletal forelimb, pectoral girdle, and sternum in Japanese native domestic fowls. J. Poult. Sci. 2016; 54:47–57. [ PMC free article] [ PubMed] [ Google Scholar]Campbell Biology, 10th ed. See chapter 34 for an overview of vertebrate evolution, with a brief look at birds. See fig. 34.24, A phylogeny of amniotes, for a cladogram showing bird relationships. Schorger, A. W. (September 1947). "The deep diving of the loon and old-squaw and its mechanism" (PDF). The Wilson Bulletin. 59 (3): 151–159.

Furcula (wishbone): The furcula apparently corresponds to the clavicles (collarbones) of mammals. In birds, these bones are fused into a single structure. The furcula is springy; when a bird flies, it flexes in and out, storing and returning energy like a spring. This spring action wouldn't be possible if birds had two separate clavicles instead of a single furcula. It makes sense to view this structure as an adaptation to flight, but many nonflying dinosaurs (including Tyrannosaurus rex!) also had a furcula, so this fused structure didn't originate as an evolutionary response to flying. On the other hand, the furcula of T. rex and similar species was short and not structured to be springy. The furcula of birds did not originate as an adaptation to flight, but it has certainly been shaped by selection for efficient flying.

Feathers are one of the defining characteristics of birds, and they play a key role in flight. However, recent paleontological studies show that feathers evolved before flight. What did these feathers do in the non-flying ancestors of birds? Maxwell E.E. Comparative embryonic development of the skeleton of the domestic turkey (Meleagris gallopavo) and other galliform birds. Zoology (Jena) 2008; 111:242–257. [ PubMed] [ Google Scholar] Totipalmate: all four digits (1–4) are joined by webbing. Found in gannets and boobies, pelicans, cormorants, anhingas and frigatebirds. Some gannets have brightly colored feet used in display. [3] [21] Pike, A. V. L.; Maitland, D. P. (2004). "Scaling of bird claws". Journal of Zoology. 262: 73–81. doi: 10.1017/S0952836903004382.