Claim CC216.1:
There are gaps between land mammals and whales.
Source:
Response:
- The transitional sequence from a land mammal to whales is quite robust.
See Babinski (2003) or Zimmer (1998) for pictures of some of these.
- Pakicetus inachus: latest Early Eocene (Gingerich et al. 1983;
Thewissen and Hussain 1993).
- Ambulocetus natans: Early to Middle Eocene, above Pakicetus. It
had short front limbs and hind legs adapted for swimming; undulating
its spine up and down helped its swimming. It apparently could walk
on land as well as swim (Thewissen et al. 1994).
- Indocetus ramani: earliest Middle Eocene (Gingerich et al. 1993).
- Dorudon: the dominant cetacean of the late Eocene. Their tiny
hind limbs were not involved in locomotion.
- Basilosaurus: middle Eocene and younger. A fully aquatic whale
with structurally complete legs (Gingerich et al. 1990).
- an early baleen whale with its blowhole far forward and some
structural features found in land animals but not later
whales (Stricherz 1998).
The whale's closest living relative is the hippopotamus. A fossil
group known as anthracotheres links hippos with whales (Boisserie et
al. 2005). The common ancestor of whales and hippos likely was a
primitive artiodactyl (cloven-hoofed mammal); ankle bones from the
primitive whales Artiocetus and Rodhocetus show distinctive
artiodactyl traits (Gingerich et al. 2001).
Links:
Babinski, E. T., 2003. Cetacean evolution (whales, dolphins,
porpoises)
http://www.edwardtbabinski.us/babinski/whale_evolution.html
Sutera, Raymond, 2001. The origin of whales and the power of independent
evidence. Reports of the National Center for Science Education 20(5):
33-41.
http://www.talkorigins.org/features/whales/
References:
- Boisserie, Jean-Renaud, Fabrice Lihoreau and Michel Brunet. 2005. The
position of Hippopotamidae within Cetartiodactyla. Proceedings of the
National Academy of Science USA 102(5):
1537-1541.
- Gingerich, P. D. et al., 1983. Origin of whales in epicontinental
remnant seas: New evidence from the Early Eocene of Pakistan.
Science 220: 403-406.
- Gingerich, P. D., B. H. Smith, and E. L. Simons, 1990. Hind limb of
Eocene Basilosaurus: Evidence of feet in whales. Science
249:
154-157.
- Gingerich, P. D. et al., 1993. Partial skeletons of Indocetus ramani
[Mammalia, Cetacea] from the Lower Middle Eocene Domanda Shale in the
Sulaiman Range of Punjab [Pakistan]. Contributions from the Museum of
Paleontology of the University of Michigan 28: 393-416.
- Gingerich, P. D. et al., 1994. New whale from the Eocene of Pakistan
and the origin of cetacean swimming. Nature 368: 844-847.
- Gingerich, P. D. et al. 2001. Origin of whales from early
artiodactyls: Hands and feet of Eocene Protocetidae from Pakistan.
Science 293: 2239-2242. See also: Rose, K. D. 2001. The ancestry
of
whales. Science 293: 2216-2217.
- Thewissen, J. G. M. and S. T. Hussain, 1993. Origin of underwater
hearing in whales. Nature 361: 444-445.
- Thewissen, J. G. M., S. T. Hussain and M. Arif, 1994. Fossil evidence
for the origin of aquatic locomotion in archaeocete whales. Science
263: 210-212. See also Berta, A., 1994. What is a whale? Science
263: 180-181.
- Stricherz, Vince, 1998 (10 Oct.). Burke displays fossil of toothless
whale.
http://depts.washington.edu/uweek/archives/1998.10.OCT_29/_article2.html
See also
http://more.abcnews.go.com/sections/science/DailyNews/baleen980916.html
Further Reading:
Gould, S. J. 1995. Hooking leviathan by its past. In: Dinosaur in a
Haystack. New York: Harmony Books, pp. 359-376.
Pojeta, John Jr. and Dale A. Springer. 2001. Evolution and the Fossil
Record, American Geological Institute, Alexandria, VA.
http://www.agiweb.org/news/spot_06apr01_evolutionbk.htm
,
http://www.agiweb.org/news/evolution.pdf
.
Thewissen, J. G. M. (ed.). 1998. The Emergence of Whales: evolutionary
patterns in the origin of Cetacea. New York: Plenum. (technical)
Thewissen, J. G. M., S. I. Madar, and S. T. Hussain. 1998. Whale ankles
and evolutionary relationships. Nature 395: 452. See also Wong, K.,
1999 (Jan.). Cetacean creation. Scientific American 280(1): 26,30.
Thewissen, J. G. M. and E. M. Williams. 2002. The early radiations of
Cetacea (Mammalia): Evolutionary pattern and developmental correlations.
Annual Review of Ecology and Systematics 33: 73-90. (technical)
Zimmer, Carl. 1995. Back to the sea. Discover 16(1) (Jan.): 82-84.
Zimmer, Carl. 1998. At the Water's Edge. New York: Touchstone,
ch. 6-10.
created 2001-4-29, modified 2006-2-25