Claim CC212:
There are no transitional fossils between fish and tetrapods.
Source:
Morris, Henry M., 1974. Scientific Creationism, Green Forest, AR: Master
Books, pp.
82-83.
Watchtower Bible and Tract Society, 1985. Life--How Did It Get
Here? Brooklyn, NY, p. 72.
Response:
- There are several good transitional fossils:
- Most fish have anterior and posterior external nostrils. In
tetrapods, the posterior nostril is replaced by the choana, an
internal nostril opening into the roof of the mouth.
Kenichthys,
a 395-million-year-old fossil from China, is exactly intermediate
between the two, having nostrils at the margin of the upper jaw
(Zhu and Ahlberg 2004).
- A fossil shows eight bony fingers in the front fin of a lobed fish,
offering evidence that fingers developed before land-going
tetrapods (Daeschler and Shubin 1998).
- A Devonian humerus has features showing that it belonged to an
aquatic tetrapod that could push itself up with its forelimbs but
could not move it limbs back and forth to walk (Shubin et
al. 2004).
- Acanthostega, a Devonian fossil, about 60 cm long, probably
lived in rivers (Coates 1996). It had polydactyl limbs with no
wrists or ankles (Coates and Clack 1990). It was predominantly, if
not exclusively, aquatic: It had fishlike internal gills (Coates and
Clack 1991), and its limbs and spine could not support much weight.
It also had a stapes and a lateral sensory system like a fish.
- Ichthyostega, a tetrapod from Devonian streams, was about 1.5 m
long and probably amphibious. It had seven digits on its rear legs
(its hands are unknown). Its limbs and spine were more robust than
those of Acanthostega, and its rib cage was massive. It had
fishlike spines on its tail, but these were fewer and smaller than
Acanthostega's. Its skull had several primitive fishlike
features, but it probably did not have internal gills (Murphy
2002).
- Tulerpeton, from estuarine deposits roughly the same age as
Acanthostega and Ichthyostega, had six digits on its
front
limbs and seven on its rear limbs. Its shoulders were more robust
than Acanthostega, suggesting it was somewhat less aquatic, and
its skull appears to be closer to later Carboniferous amphibians
than to Acanthostega or Ichthyostega.
Links:
Morton, Glenn R., 1997. Fish to amphibian transition.
http://home.entouch.net/dmd/transit.htm
References:
- Coates, M. I. 1996. The Devonian tetrapod Acanthostega gunnari Jarvik:
postcranial anatomy, basal tetrapod interrelationships and patterns of
skeletal evolution. Transactions of the Royal Society of Edinburgh:
Earth Sciences 87: 363-421.
- Coates, M. I. and J. A. Clack, 1990. Polydactyly in the earliest
known tetrapod limbs. Nature 347: 66-69.
- Coates, M. I. and J. A. Clack, 1991. Fish-like gills and breathing
in the earliest known tetrapod. Nature
352: 234-236.
- Daeschler, Edward B. and Neil Shubin, 1998. Fish with fingers?
Nature 391: 133.
- Murphy, Dennis C., 2002. Devonian times: Ichthyostega stensioei.
http://www.mdgekko.com/devonian/Order/re-ichthyostega.html
- Shubin, N. H., E. B. Daeschler and M. I. Coates, 2004. The early
evolution of the tetrapod humerus. Science 304: 90-93. See also:
Clack, J. A., 2004. From fins to fingers. Science 304: 57-58.
- Zhu, Min and Per E. Ahlberg, 2004. The origin of the internal nostril
of tetrapods. Nature 432: 94-97. See also: Janvier, Philippe,
2004. Wandering nostrils. Nature 432: 23-24.
Further Reading:
Clack, J. A., 2002. Gaining Ground: The origin and early evolution of
tetrapods. Bloomington, IN: Indiana Univ. Press.
Murphy, Dennis C., 2002. Devonian times.
http://www.devoniantimes.org/
Pojeta, John Jr. and Springer, Dale A., 2001. Evolution and the fossil
record, Alexandria, VA: American Geological Institute,
http://www.agiweb.org/news/spot_06apr01_evolutionbk.htm
,
http://www.agiweb.org/news/evolution.pdf
.
Zimmer, Carl, 1998. At the Water's Edge. New York: Touchstone,
ch. 1-4.
created 2001-4-29, modified 2004-11-19