Tiktaalik - the fishapod
Model by Tyler Keillor and this particular set up on display at the Harvard Museum of Natural History
When: Late Devonian (~375 million years ago)
Where: Found on Ellesmere Island in Nunavut, Canada
What: Tiktaalik is a very critical specimen on the line of tetrapod evolution. In the tetrapod family tree it falls between sarcopterygians (‘lobed fin’ fish) that looked much like the living Coelacanth and more advanced tetrapods, such as Acanthostega.The discovery and announcement of Tiktaalik was very exciting, as fossils on both side of transitional period were known for a long time, but nothing really in the middle. Of course as with the discovery of any ‘missing link’ now we have two more ‘links missing’: one on either side of Tiktaalik ;). The most important part of the specimen is the anatomy of its forelimb - there was a well developed wrist inside the fin of Tiktaalik! Not only that, but it possibly has the first ‘fingers’ seen in the tetrapod lineage. Unfortunately the back end of Tiktaalik is unknown… for now!
In life Tiktaalik would have been an aquatic animal, as its limbs could not support its weight on land - but they would have been very helpful for maneuvering the creature around the shallow waters of prehistoric Canada. Based on the spiracles - openings behind the eyes- of the skull it has been preposed Tiktaalik could have had a form of primitive lung.
If you want to know more about Tiktaalik - check out its website at: http://tiktaalik.uchicago.edu/. And for more in depth reading, I cannot recommend the book ‘Your Inner Fish’, written by the discover of Tiktaalik - Neil Shubin, enough! It is a really great explanation of how Tiktaalik fits into the evolution of tetrapods and explaining homology in general! Shubin has done a fantastic job of promoting public science education using this great Tiktaalik specimen as a starting point.
Just look at all of these models getting ready to go out to museums. Maybe one is near you!