Produced by the Population Genetics and Evolution class, Furman University

The Devonian: Tiktaalik roseae
Tiktaalik roseae is a 375 million year old tetrapod-like fish fossil discovered in 2004 in the Canadian Arctic (UCMP 2009). Since it lived 12 million years before the rise of tetrapods, Tiktaalik represents the earliest evidence for fish moving onto land (University of Chicago 2006). Moreover, its special mix of sarcopterygian (lobe-finned fish) and tetrapod morphological traits provides insight into the evolution of the early tetrapods. For example, Tiktaalik has gills, body scales, fin rays, and a lower jaw and palate consistent with those of primitive sarcopterygians. However, it also has a shortened skull roof, a modified ear region, a mobile neck, and a functional wrist joint, all of which are characteristics of early tetrapods (Daeschler et al. 2006). Moreover, it has a flat head and body with eyes on top of its skull, making it look like more like a crocodile than a fish. Its ribs also resemble those of the earliest tetrapods because they appear to provide the body with support and assist in breathing. Yet another sign that Tiktaalik is a key transitional form comes from an analysis of its frontal fin structure, which shows that it could actually prop its body up in addition to swimming (University of Chicago 2006). After considering both its morphology and presumed geological environment, researchers concluded that Tiktaalik most likely lived in shallow-water habitats where it preyed on small fish while trying to stay away from its own predators (Daeschler et al 2006).

Page by Robert Mazgaj

Tiktaalik roseae
Photo Credit: Ted Daeschler

Daeschler EB, Shubin NH, Jenkins, FA. 2006. A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature 440: 757-763.

University of California Museum of Paleontology (UCMP). 2009. Understanding Evolution. 2009. What has the head of a crocodile and the gills of a fish? Accessed 24 Feb. 2010.

University of Chicago. 2006. Tiktaalik roseae. Accessed 24 Feb. 2010.