Evolution Of Whales

Sanjana SureshFSLE-3

Kingdom :Animalia ; Phylum : Chordata ; Subphylum: Vertebrata ; Class : Mammalia ; Order: Cetacea

Cetaceans include whales, dolphins, tortoises and porpoises There are over 80 Species in two Suborders :Mysticeti and

Odontoceti

Modern Whales

Mysticeti Odontoceti

Blue Whale Bowhead Whale (Arctic Region) Gray Whale Humpback Whale North Atlantic Right Whale Sperm Whale Beluga Orca (Killer Whale)

Whale Species

1693- John Ray, whales are mammals

1859- Darwin, in Origin of Species, whales arose from bears

1883- Sir William Henry Flower, solidifies theory of descendants were from terrestrial mammals based on vestigial organs

Early History of Whale Evolution

Thewissen discovers fossil dated to 60 million years ago in Kashmir region of India

Even toed ungulate, a form of the mammalian order Artiodactyla

Marine lifestyle

Indohyus

First Archaeocete

Evolved 52 million years ago Found in Pakistan by Gingerich,

1983

Sharper teeth-more carnivorous

Deficient in hearing underwater, more terrestrial hearer-not yet evolved

Narrow brain case

Pakicetus

Ambulocetus Natans

Found in sediments about 120 meters higher than Pakicetus by Thewissen in 1992

49 million years ago “the walking whale that

swims”- made possible by stout femur

More aquatic, similar to a sea lion

Anatomy of spinal column-swam with tail going up and down

Skull characteristics

Rodhocetus

49-43 million years ago in Pakistan by Stromer 1908

More developed tail for swimming

Sacral vertebrae not fused- more flexibility, first devotee to swimming

Femur was a third shorter than that of the Ambulocetus’

Skull elongated Ears pushed further back Smaller eyes First sea water living ancestors

Basilosaurus 35-41 million years ago by Cope in

1868 in Egypt and Eastern U.S. First completely aquatic form “king lizard”- 15 meters long Complete set of hind limb bones

and a pelvis, but very small First to have tail fluke- due to

structure of vertebral proportions Formation of blow hole-single large

nostril to the top of the head

Dorudon Found by Gingerich

1994, about 40 million years ago

Very similar to Basilosaurus, however smaller in size (4-5 meters long) and forelimbs and hind limbs smaller

Ability to walk on land completely diminished, move from land to sea is complete

Geographic Origins Use of the geographic

distribution of related species

Sea of Tethys Distribution of

Basilosaurus and Dorudon widely spread vs. Ambulocetus and Rodhocetus constrained to one area in India, Pakistan region

Genetic Changes Over Generations

Formation of the ear

Formation and movement of blow hole at top of the head

Vestigial Organs Pelvis, tibia, other

leg bone structures

Works Cited 1) Gingerich, Phillip. "The whales of Tethys." Apr. 1994. Aug 2013 < http://web.ebscohost.com/ehost/detail?vid=1&hid=3&sid=72aafebc-31f7-40ce-b541-44f44dbb72cb%40sessionmgr2&bdata=jmxvz2lucgfnzt1mb2dpbi5hc3amc2l0zt1lag9zdc1saxzl#db=aph&an=9404017813>. 2) Gingerich, Philip D., and D.E. Russel. "Pakicetus inachus, A New Archaeocete (Mammalia, Cetacea) from the Early-Middle Eocene Kuldana Formation of Kohat (Pakistan)." Paleontology, Museum of - Publications 25 (1981): 236-45. Aug 2013 3) Gingerich, Philip D. "Research on the Origin and Early Evolution of Whales (Cetacea)." Personal Pages. 5 Nov. 08. University of Michigan Aug 2013 <http://www-personal.umich.edu/~gingeric/pdgwhales/whales.htm>. 4) Myers, P. Z. "Evolution of Whale Ear." Pharyngula. 12 Aug. 2004. University of Minnesota, Morris. Aug 2013<http://pharyngula.org/index/weblog/comments/evolution_of_the_whale_ear/>. 5) "Researchers Discover Clues to Whale Evolution." Science Daily. 10 May 2002. Aug 2013<http://www.sciencedaily.com/releases/2002/05/020509073449.htm>. 6) Sutera, Raymond. "The Origin of Whales and the Power of Independent Evidence." Talk Origins. 10 Aug. 2001. Aug 2013 <http://www.talkorigins.org/features/whales/>. 7) Thewissen, J.G.M. "Whale Origins!" Northeastern Ohio Universities Colleges of Medicine and Pharmacy. Aug 2013<http://darla.neoucom.edu/depts/anat/whaleorigins.htm>. 8) "Whales Descended From Tiny Deer-like Ancestors." Science Daily. 21 Dec. 2007. Aug 2013<http://www.sciencedaily.com/releases/2007/12/071220220241.htm>.