Life › Seas, forests & the move to land › Vertebrates move onto land (tetrapods)
Tiktaalik
c. 375 million years ago (found 2004)· Fossil or site· Animals
Well establishedStrong fossil, genetic or geological evidence.
A 375-million-year-old 'fishapod' from Arctic Canada: a fish with a neck, lungs and wrist-like fin bones.
See it on the Life map →What happened
Neil Shubin, Ted Daeschler and Farish Jenkins searched Ellesmere Island, Nunavut, for years because its rocks were the right age and type: river-delta sediments laid down about 375 million years ago. In 2004 they found Tiktaalik roseae, named in Inuktitut ('large freshwater fish') with local elders. It had scales, fins and gills, but also a flat, crocodile-like head, a mobile neck, lungs, sturdy ribs, and fin bones forming shoulder, elbow and wrist.
Why it matters
It is a textbook transitional fossil showing how fish anatomy was reshaped toward tetrapods, and it was found by a successful prediction of where to look.
The evidence (fossils, genes, rocks)
Several partial skeletons, published in Nature in 2006, with the pelvis and hind fins described in 2014; dated by the age of the Fram Formation rocks.
Still debated
It is probably a close cousin rather than a direct ancestor of tetrapods; older footprints from Poland suggest tetrapods already existed by its time.
Connections (3)
▸Lobe-finned fish include the tetrapod-like TiktaalikWell established
The connection
Within the lobe-finned fish, one branch (the tetrapodomorphs) lived in shallow, often oxygen-poor waters. Over some 30 million years their fins grew sturdier, their heads flatter and their lungs more important. Eusthenopteron and Panderichthys show the trend; Tiktaalik is one of the most limb-like forms that is still technically a fish.
When and how
Devonian rivers and deltas, about 400–375 million years ago, on the old continent of Euramerica; Tiktaalik was found in Arctic Canada in 2004.
The evidence
A series of fossils in dated rocks shows stepwise changes in fins, skulls and shoulders, matching predictions from comparative anatomy.
Debates and open questions
Which environments drove these changes, whether rivers, swamps or tidal flats, is debated.
▸Tiktaalik is a transitional step toward Vertebrates move onto land (tetrapods)Well established
The connection
Tiktaalik combined fish features (scales, fins, gills) with traits of four-legged animals: a neck, sturdy ribs, lungs and fin bones forming shoulder, elbow and wrist. It could probably prop itself up in shallow water. It shows the tetrapod body being assembled in stages, before true legs with toes.
When and how
Ellesmere Island, Nunavut, Canada, about 375 million years ago; found in 2004 by Neil Shubin, Ted Daeschler and Farish Jenkins.
The evidence
Its mix of features fits between fish like Panderichthys and early tetrapods like Acanthostega, both in anatomy and in age.
Debates and open questions
Whether Tiktaalik ever left the water, even briefly, or only propped itself up in the shallows is still argued from its bones.
▸Tiktaalik confirmed a prediction of Common descent & the tree of lifeWell established
The connection
If tetrapods descend from fish, intermediate creatures should appear in rocks between the last fish-only and first tetrapod-bearing layers. Neil Shubin's team chose about 375-million-year-old river deposits in Arctic Canada for that reason and found Tiktaalik, a fish with a neck and wrists. A successful prediction is strong evidence for common descent.
When and how
Ellesmere Island, Nunavut, Canada; found in 2004 by Neil Shubin, Ted Daeschler and Farish Jenkins, published in Nature in 2006.
The evidence
The fossil's age and mixed fish-tetrapod anatomy match what was predicted; Shubin's book Your Inner Fish (2008) tells how the search worked.
Debates and open questions
Tetrapod-like footprints in Poland, about 395 million years old (published 2010), are older than Tiktaalik, so it is a late-surviving cousin showing the transition, not a direct ancestor.