Missing link between fish and land animals discovered
By Morgan Erickson-Davis, special to mongabay.com
November 7, 2008
New fossil brings more insight into vertebrates’ transition to life on land
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A study published in the October 16 issue of Nature details research
into and implications of a fossil fish, Tiktaalik roseae, discovered
last year at Ellesmere Island in Canada. The Devonian fossil shows an
array of features found in both terrestrial and aquatic animals,
providing the best glimpse so far into the transitory period during
which vertebrates were able to adapt to life out of water. The find
provides some of the first osteological evidence of neck development,
a crucial adaptation to terrestrial life because it allows an animal’s
body to remain stationary while it surveys its environment. Other
adaptations include a flattened head, elongated snout, and reduction
of the hyomandibula, a bone that in fish corridinates movement between
the braincase, pallete, and gills. The hyomandibula later evolved into
a structure associated with hearing in mammals.
 The photo is from The Academy of Natural Sciences.. |
A team led by The Academy of Natural Sciences’ Dr. Ted Daeschler
discovered the 375-million-year-old T. roseae in benthic deposits,
suggesting that the animal was a bottom-dweller in shallow water. Its
structural similarities to terrestrial vertebrates imply that it may
have lived out of the water for short periods of time. The shift
towards terrestrial life was probably driven by a variety of factors
including predator evasion, food acquisition, and to escape the
evaporation and deoxygentaion of seasonal water sources.