The family Spheniscidae is composed of penguins, which are flightless birds confined almost entirely below the equator (Williams, Wilson, Boersma, Stokes, Davies and Busby , 1995, p. Penguins belong to the order Chordata, which gets its name because the organisms have notochords. The notochords are a support structure much like a spine. Another characteristic of the family is that they are filter feeders, meaning they can pass water through their mouth and the front end of the digestive tract. Penguins belong to the class Aves (Parker, 1982, p. 822). When we think of birds, some characteristics that come to mind are feathers, wings, the ability to lay eggs, and two legs. Penguins meet all of these criteria and yet their distinctive characteristics are extensive. For example, their wings are flippers, adapted to help them hunt and catch their food. Penguins are the only birds with true flippers (Kooyman, 2013, p. 4). Additionally, the angle at which penguins' femurs extend from the hip is twice that of other birds, giving them a human-like posture. Another distinctive feature of the penguin is the tarsometa, a bone found only in birds. Penguins have a particularly small tarsometa, which is used as an indicator when identifying skeletal remains (Kooyman, 2013, p. 1). Penguins are divers capable of diving to great depths in order to catch their prey. Although on average penguins dive well below their potential, feeding in relatively shallow waters (Davis & Renner, 2003, p. 66). According to researchers, some penguins have the potential to dive up to 535 meters deep, or about five football fields (Grzimek, Jackson and Schlager, 2002, p. 147). While researching I found dissent... middle of paper ... me filholi, on Macquarie Island. Canadian Journal of Zoology, 78.3: 333-45. February 12, 2014. Kooyman, GL (2013). Penguins: The Animals Answers Guide. Baltimore, MD: Johns Hopkins UP. Print. Ksepka, DT, Bertelli, S and Giannini, NP (2006). The phylogeny of living and fossil sphenisciforms (penguins). Cladistics, 22.5: 412-41. February 12, 2014. Lynnes, AS, et al. (2002). Conflict or coexistence? Distribution of foraging and competition for prey between Adélie and chinstrap penguins. Marine Biology, 141.6: 1165-74. February 12, 2014. Parker, S. P. (1982). Synopsis and classification of living organisms. New York, NY: McGraw-Hill. Reilly, P. N. (1994). Penguins of the world. South Melbourne, Australia: Oxford UP. Print.Williams, TD, Wilson, RP, Boersma PD, Stokes, DL Davies, J. and Busby, J. (1995) The Penguins: Spheniscidae. Oxford: Oxford UP. Print.