Fish to Tetrapod

An intermediate between limbed-vertebrates and lobe-finned fish helps us to better understand the

evolution of the tetrapod body plan.

http://palaeos.com/paleozoic/devonian/frasnian.htm

Switch From Fish to Tetrapod

During this transition:1. The skull was

remodeled2. The bones

connecting the head to the shoulder were lost

3. The middle ear was modified

4. Robust limbs with digits evolved

5. Shoulder girdle & pelvis were altered

6. Ribs were expanded

7. The bony connections between vertebrae developed

(De Souza, M; 2009)

http://eurwentala.deviantart.com/art/Fish-Fishapod-Tetrapod-185103242

Tiktaalik

http://avonapbiology.wikispaces.com/Nick+Tan+Your+Inner+Fish Daeschler et al. 2006

Tiktaalik Lived in Shallow Waters and Subaerial Habitats

http://evolutionjustatheory.blogspot.ca/2009_09_01_archive.html

In response to this new environment, Tiktaalik developed:1. New mechanisms of

head movement2. New mechanisms of

body support3. New mechanisms of

respiration

New Mechanisms of Head Movement

Loss of opercular,

subopercular and the

extrascapular effectively decoupled the head

from the the pectoral girdle.

These changes are also associated

with new patterns of locomotion and

feeding.

http://www.devoniantimes.org/opportunity/tetrapodsAnswer.html

Daeschler et al. 2006

New Mechanisms of Respiration

http://guardianlv.com/2014/01/extinct-land-walking-fish-tiktaalik-roseae-possessed-robust-hips/

Changes in respiration mechanisms allowed Tiktaalik to exploit both aquatic and terrestrial environments.

New Mechanisms of Body Support

Rib support allowed Tiktaalik to remain supported in shallow water and when on land.

Panderichthys, Elpistostege, and Tiktaalik Form a Paraphyletic

Assemblage of Elpistostegalian Fish

http://en.wikipedia.org/wiki/Eusthenopteron

http://www.richannel.org/finding-tiktaalikDaeschler et al., 2006

Implications for Vertebrate Biology

• Changes in the rear skill preceeded those in the lower jaw and palate.

• Loss of opercular, subopercular, and the extrascapular series series occurs before the loss of the gulars, submandibulars, and the supracleithral series.

Insight Into the Order in Which Derived Characters Evolved

BibliographyDaeschler, Edward B. and Shubin, Neil H. and Jenkins, Farish A. (2006). A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature, 440(7085), 757–763.

De Souza, M. (2009). Just a Theory [Website]. Retrieved January 16th, 2015, from http://evolutionjustatheory.blogspot.ca/2009_09_01_archive.html

Eurwentala (2010). Fish, Fishapod, Tetrapod [Website]. Retrieved January 16th, 2015, from http://eurwentala.deviantart.com/art/Fish-Fishapod-Tetrapod-185103242

James Fenner (2014). Extinct Land-Walking Fish Tiktaalik roseae Possessed Robust Hips [Website]. Retrieved January 18th, 2015, from http://guardianlv.com/2014/01/extinct-land-walking-fish-tiktaalik-roseae-possessed-robust-hips/

Murphy, M.C (2006). Tetrapod Answers [Website]. Retrieved January 18th, 2015, from http://www.devoniantimes.org/opportunity/tetrapodsAnswer.html

Neil Shubin (2015). Your Inner Fish [Website]. Retrieved January 18th, 2015, from http://avonapbiology.wikispaces.com/Nick+Tan+Your+Inner+Fish

Unknown (2013). A Few Selected Transitional Fossils [Websites]. Retrieved January 16th, 2015, from http://www.transitionalfossils.com

Unknown (December 27th, 2014). Eusthenopteron [Website]. Retrieved January 17th, 2015, from http://en.wikipedia.org/wiki/Eusthenopteron

White, T. (2002). The Frasnian [Website]. Retrieved January 16th, 2015, from http://palaeos.com/paleozoic/devonian/frasnian.htm