So after watching Spielberg’s masterpiece, I decided to look up some cool shark photos on the web and tape them all around the windows for a nice weekend theme. Works well with the Friday Bloody Mary special.
Anyways—while looking for pictures, I came across an article in American Scientist from 2005. According to some paleontologists, shark evolution is still evolving. The piece itself is a little science-y… so I’ll just summarize the cool parts.
It seems that there is a missing link between the development of fish into shark and boney fish. Since shark fossils are rarely intact, paleontologists have a hard time finding the missing few links that takes the species from fish to a creature befitting of a blockbuster film (Turner/Miller 244). However, scientists recently (well, recently as in circa 2005) discovered a well intact early shark fossil and began researching to see what part of the puzzle it fit into.
As it turned out, early sharks were more developed and diverse than paleontologists had originally thought (244). A pectoral spine was found in the fossil, which makes it relatable to boney fish. Worldwide discoveries began popping up, and paleontologists were working to close the evolutionary gap.
After a few mutations, evolutionists believe that fish split into jawed fish and another species that developed into a land dweller. The jawed fish are the species which paleontologists believe morphed into our presently know sharks (244).
Miller, one of the article’s contributors, found a nicely intact shark fossil in Canada in 1997. By examining the teeth (which is the most common way to identify sharks and their timeline), Miller and his team found that a shark going back 400 million years had already developed the kind of teeth that made JAWS! famous (245).
Problems with shark classification and too many hands in the taxonomy pot causes for confusion. However, this article’s other contributor, Turner, was able to recognize that the teeth they were looking at in fact did belong to a shark.
What a team!
Next, the Turner and Miler found the oldest known, most complete shark fossil yet to be discovered—on the shores of Canada! The geographical location is of interest because this is not a place where sharks or boney fish were typical. This must mean that the species was more widespread than originally thought (246).
Though naming the exact date of when fish morphed into sharks is difficult to pinpoint, the first definite evidence of sharks is around 440 million years ago (also written mya) (247).
Prompted by the research of Gary Nelson, Turner began to make a connection between a species named thelodonts and sharks. Nelson’s research showed that sharks had a certain type of scale in their throats. Turner found that the scales that cover the bodies of modern sharks are similar to the brachial scales discovered by Nelson (250).
Turner’s connection proved to be a very important piece to the puzzle. “The accepted model is that teeth evolved from the modification of specialized skin scales that became attached to the jaw cartilages (parts of the gill branches that are believed to have evolved into the lower and upper jaws), and the structures evolved” (251).
Another theory argues that teeth developed from within the throat, not the jaw cartilage as in the above theory. Either way—paleontologists generally have come to accept the fact of the teeth evolving at a particular time due to Turner’s observations.
Turner and Miller concluded that 50 million years ago, it seems as if there was experimentation with different types of fish. Even the modern sharks of today seem to have been swimming around that time (251).
Currently, paleontologists are working backwards. Playing connect the dots, modern sharks are being related to early sharks. This leaves a gap that scientists continually try to close.
Interesting bits of information, eh? I thought so… I hope you did too.
Perhaps I’ll make a special rule this Friday night… just for everyone who has read this post: if you walk into my bar on Friday between 9 p.m. and 2 a.m. and say, “I can connect the dots between thelodonts and modern day sharks through bronchial scales,” I just may have to give you a Friday night special on the house.
Turner, Susan and Randall F. Miller. “New Ideas About Old Sharks.” American Scientist. Volume 93.Issue 3 (May/June 2005): pages 244-252. EBSCO Host Research Databases. UNC- Chapel Hill. 31 January 2007.
1 comment:
Carly, as always your tone is spot on and this was a fascinating post to read. Your hook was excellent and you interspersed the jokes tastefully throughout, never compromising Desmond's credibility. My only real problem with the post is that Scientific American isn't a real academic journal, but more of a magazine for people with a general interest in science. This made your task much easier. In the future if you or any of your groupmates express skepticism about whether an article comes from an academic source be sure to ask me.
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