Tiktaalik

Tiktaalik
	Tiktaalik roseae , replica of the holotype
Temporal occurrence
	Upper Devonian
	383.7 to 376.1 million years
Locations
	North America ( Ellesmere Island , ; Nunavut Territory, Canada);
Systematics
Trunk :	Chordates (chordata)
Sub-stem :	Vertebrates (vertebrata)
Superclass :	Jaw mouths (Gnathostomata)
Class :	Meat finisher (Sarcopterygii)
Subclass :	Elpistostegalia
Genre :	Tiktaalik
Scientific name
	Tiktaalik
	Daeschler et al. , 2006
Art
	Tiktaalik roseae;

Tiktaalik ( Inuktitut for " burbot ", a large freshwater and brackish water fish) was a genus of amphibian-like meat- floss (Sarcopterygii), the fossils of which were discovered in sedimentary rocks of the Upper Devonian of Ellesmere Island (Ellesmere Island) in northern Canada . So far only the species Tiktaalik roseae is known.

As a mosaic shape , Tiktaalik is evidence of the order in which bony fish developed characteristics of land vertebrates (tetrapods) before the first primeval amphibians such as Acanthostega and Ichthyostega emerged from them. As ancestors of Tiktaalik have Shubin and colleagues Panderichthys from -like fish.

features

Tiktaalik resembles other meat fins such as the coelacanth and lungfish in the scaling , in the structure of the fins , lower jaw and palate . The shortened top of the skull and the ear region, the movable neck and the forelegs are amphibian : Equipped with elbow and wrist joints , the pectoral fins of Tiktaalik are reminiscent of arms, but they ended in rays , not fingers. The pelvic girdle and hind limbs show a mosaic of primitive and inferred features . The pelvic bones of Tiktaalik are large and strong compared to those of other flooded tetrapodomorphs. However, they are not connected to the sacral ribs and there is no ischium . The flat, elongated snout of the up to 20 cm long skull gives the animal a crocodile-like appearance. A detailed analysis of the skull bones showed that Tiktaalik roseae "is morphologically intermediate between the conditions in more pristine fish and those known from tetrapods."

According to Daeschler et al. a. and Shubin et al. a. was Tiktaalik a resident of the shallow coastal water; its remains were found in the sediments of a river delta . He used the pectoral fins to move on the bottom of the water. Among other things, he was able to support himself from the ground by stretching his shoulders and elbows as if on forelegs.

Life picture of Tiktaalik roseae
Skull from the front
Front limb (front) with shoulder girdle (back)
Shoulder girdle and forelimbs

Naming

When assigning the scientific name, the discoverers of the fossils on Ellesmere Island , Farish A. Jenkins Jr., Neil Shubin and Ted Daeschler, wanted to take into account the site and the Inuit resident there who had given the excavation permission. They sent a request to the Nunavut Council of Elders , the Inuit Qaujimajatuqangit Katimajiit, to suggest names . From the two suggestions, "Siksagiaq" and "Tiktaalik", the paleontologists selected the latter, which in Inuktitut means " burbot " or "large freshwater fish".

literature

Per Erik Ahlberg, Jennifer A. Clack: A firm step from water to land. in: Nature . London 440. 2006, pp. 747-749. ISSN 0028-0836 , doi : 10.1038 / 440747a
Jason P. Downs, Edward B. Daeschler, Farish A. Jenkins, Neil H. Shubin: The cranial endoskeleton of Tiktaalik roseae. in: Nature . London 455.2008, pp. 925-929. ISSN 0028-0836 , doi : 10.1038 / nature07189

Web links

Commons : Tiktaalik - collection of images, videos and audio files

Tiktaalik's virtual home (University of Chicago)

Tiktaalik roseae and the criticism of the opponents of evolution (AG Evolutionary Biology of the VdBiol)

Information about Tiktaalik (University of Berkeley)

“It is inevitable that we will die out.” Interview with paleontologist Neil Shubin about Tiktaalik, published in the NZZ on Sunday , August 3, 2008

Video: Tiktaalik roseae Fossils Reveals Key Link in Evolution of Hind Limbs. eurekalert.org of January 13, 2014.

Individual evidence

↑ Entry "tiktaalik" (= "burbot") in the Nunavut Living Dictionary

^ ^A ^b Edward B. Daeschler, Neil H. Shubin and Farish A. Jenkins, Jr: A Devonian tetrapod-like fish and the evolution of the tetrapod body plan . In: Nature . 440, April 6, 2006, pp. 757-763. doi : 10.1038 / nature04639 .

↑ ^a ^b ^c Neil H. Shubin, Edward B. Daeschler and Farish A. Jenkins, Jr: The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb . In: Nature . 440, April 6, 2006, pp. 764-771. doi : 10.1038 / nature04637 .

↑ Neil H. Shubin, Edward B. Daeschler & Farish A. Jenkins, Jr. Pelvic girdle and fin of Tiktaalik roseae. PNAS , January 13, 2014 DOI: 10.1073 / pnas.1322559111

↑ JP Downs, EB Daeschler, FA Jenkins, Jr and NH Shubin: The cranial endoskeleton of Tiktaalik roseae . In: Nature . 455, October 16, 2008, pp. 925-929. doi : 10.1038 / nature04639 .

↑ Neil Shubin: The Fish Within Us: A Journey Through the 3.5 billion year history of our body . Fischer, Frankfurt 2008, ISBN 3-10-072004-0 .

[1] Entry "tiktaalik" (= "burbot") in the Nunavut Living Dictionary

[Daeschler-2] A ^b Edward B. Daeschler, Neil H. Shubin and Farish A. Jenkins, Jr: A Devonian tetrapod-like fish and the evolution of the tetrapod body plan . In: Nature . 440, April 6, 2006, pp. 757-763. doi : 10.1038 / nature04639 .

[Shubin-3] Neil H. Shubin, Edward B. Daeschler and Farish A. Jenkins, Jr: The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb . In: Nature . 440, April 6, 2006, pp. 764-771. doi : 10.1038 / nature04637 .

[4] Neil H. Shubin, Edward B. Daeschler & Farish A. Jenkins, Jr. Pelvic girdle and fin of Tiktaalik roseae. PNAS , January 13, 2014 DOI: 10.1073 / pnas.1322559111

[Downs-5] JP Downs, EB Daeschler, FA Jenkins, Jr and NH Shubin: The cranial endoskeleton of Tiktaalik roseae . In: Nature . 455, October 16, 2008, pp. 925-929. doi : 10.1038 / nature04639 .