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8. Mutant Gar Is Missing Link
- University of Arkansas Press
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8 Mutant Gar Is Missing Link IN MAY OF 2006 the JPEGs began pouring in. Since family and friends knew that I had a bad case of Gar Fever, and since it was obvious that the recently discovered fossil remains of Tiktaalik roseae in the Arctic looked like a freaky gar, the newspaper clippings soon followed. And as all this information came in, I did some research of my own, and even contacted Dr. Neil H. Shubin of the University of Chicago Department of Organismal Biology and Anatomy, who was in on the discovery. The result is the following proclamation: Hear Ye, Hear Ye! I Hereby Officially Establish That The Existence Of Tiktaalik Proves That Humans Evolved From Gar! As Darwin predicted in his P.S. to C. Lyell in his letter of 1860, “Our ancestor was an animal which breathed water, had a swim bladder, a great swimming tail, [and] an imperfect skull.” The proof is in the scree. Right at the top of North America, in the Nunavut region of Canada (which used to be part of Euramerica back in the Devonian days), there were four- to-nine-foot crocodile-headed fish with wrist-like bones in their front fins for crawling out of the muck. Because 375 million years ago, this area had a subtropical, fluvial geography , much like that of the Mississippi Delta today—which, of course, is an ideal habitat for gar. Not only that, but Tiktaalik (which is Inuit for big fish living in the shallows) shares other characteristics with its gar-descendants from the Cretaceous. Both gar and Tiktaalik have diamond-shaped scale patterns common to the Crossopterygii class (represented by coelacanths and rhipidistians ), from which lungfish, bowfin and gar evolved. According to Edward Daeschler et al. (who announced their findings in the April 6, 2006, issue of Nature), “The dorsal surface of Tiktaalik is covered with rhombic, overlapping, tuberculated scales.” And according to Dr. Shubin, 65 Tiktaalik’s scales are similar to those of the Lepisosteids (the gar family)— which, in Greek, means bony scales. Dr. Shubin informs me that Tiktaalik’s teeth are “a combination of fangs and denticles; fangs on the coronoids, vomer, etc., and denticles on the dentary.” These predator teeth are structured in two rows (similar to the alligator gar), and are handy for chomping down on all sorts of swampy prey—just like gar. Dr. Shubin also notes that Tiktaalik has nostrils, “both internal and external”—just like gar. As for Tiktaalik’s “imperfect skull,” Daeschler uses the term “elpistostegalian ” to indicate its paraphyletic grade of flat-headedness among the “finned sarcopterygians that lie along the tetrapod stem lineage.” Tiktaalik’s body, however, is tubular and streamlined—just like gar. Plus, both species “lack the anterior dorsal fins and possess broad, dorsoventrally compressed skulls with dorsally placed eyes, paired frontal bones, marginal nares and a subterminal mouth”—just like gar. Tiktaalik’s curving ribcage indicates that it had the same type of lunglike organs that gar have, which are convenient when it comes to “specializations for spiracular breathing across the aquatic-terrestrial interface” —an accessory that made it possible for Tiktaalik to pull itself up on the 66 Mutant Gar Is Missing Link Tiktaalik Roseae, Arctic. Photo by Beth Rooney for the University of Chicago. [3.236.101.52] Project MUSE (2024-03-29 14:10 GMT) mud front-wheel-drive style and breathe oxygen for a spell. The refrain continues. But the most complicated feature of this fishapod (a creature filling the gap between tetrapod and fish), which makes it the morphological bridge between Panderichthys (the fish it once was) and Acanthostega (the gatorlike creature it became), are the endochondral bones in the pectoral fins which suggest a fingerlike functionality found in primates. And this, of course, is wigging out the fundamentalists. A month after the announcement of the breakthrough discovery of Tiktaalik, the Internet is buzzing with controversy. Whereas scientists are saying that Tiktaalik is just one of many intermediates between species, the non-believers are basically saying that Tiktaalik does not fill a gap, because it creates two more. But as John Noble Wilford states in The New York Times article “Fossil Called Missing Link from Sea to Land Animals,” these fossils are “a powerful rebuttal to religious creationists, who have long argued that the absence of such transitional creatures are a serious weakness in Darwin’s theory.” And as Dr. Michael J. Novacek, a paleontologist for the American Geographic Society, adds, “We’ve...