March 19, 2008
Great Steps in the History of Life: Discovering Arctic Fossils that Link Ancient Fishes and the Earliest Limbed Vertebrates
Ted Daeschler
Chairman, Department of Paleontology Academy of Natural Sciences, Philadelphia
Minutes of the 24th Meeting of the 66th Year
At 10:30 AM, President Joe Giordmaine opened the first spring meeting of the Old Guard at the Carl Fields Center. Nick Wilson read the minutes of the prior week’s meeting, featuring Professor Stanley Katz speaking on the Constitution, Constitution Day, and the rising study of American history today.
Joe thanked the members of the Program Committee for securing so many outstanding speakers this Spring, mentioned them by name and asked them to stand please in recognition.
John Schmidt, former Chair of the Academy of Natural Sciences in Philadelphia, introduced Dr. Ted Daeschler, Chair of the Paleontology Department at the Academy. Ted earned his bachelor’s degree at Franklin and Marshall in geology, his master’s at Berkley and doctorate at Penn in paleontology and has been at the Academy of Natural Sciences since 1987.
n addressing the topic of “Great Steps in the History of Life: Discovering a Link between Ancient Fish and Limbed animals,” Daeschler reviewed briefly the history of vertebrate paleontology over the past 600 million years. He said his focus was on a “slice of time” rather than the evolution of a particular group of animals.
The slice he has focused on over the past 20 years has been the Devonian period from about 380 to 365 million years ago beginning in eastern Pennsylvania, Lycoming County, particularly in the cuts for roads that expose fossils and reaching to Eastern Greenland a well studied zone. But he hit the jackpot with explorations in the Canadian Arctic, the Nunavut Territory, specifically southern Ellesmere Island, over a span of six years.
Such expeditions, 600 miles inside the Arctic Circle, are not undertaken lightly since the team has to fly to Resolute Bay, take a twin otter plane, and then a helicopter to get into position to examine valleys of rough terrain for fossils of interest. The tip off is broken pieces or fragments on the surface that may suggest layered deposits in former streambeds of perhaps fairly intact specimens.
Well known and well described are the fishes prior to the Devonian era and later the limbed animals called tetrapods. You have all seen the evolutionary progression in museums or in New Yorker cartoons. What is remarkable about the discovery by Daeschler and his co-collaborators Dr. Neil Shubin of the University of Chicago and Dr. Farish Jenkins of Harvard is a new species of an ancient fish, a key marker in the evolutionary transition of fish to limbed animals. Their results When Fins became Limbs were published in a cover paper of the journal Nature on April 6, 2006.
(Hold up paper inscribed with best wishes to the Old Guard of Princeton.)
For about a century, scientists have been able to trace the broad outline of the millions-of-years-long transition of lobe-finned fish to limbed animals (or tetrapods). What is exciting about the new find, which we saw in images on a large screen as it was dug out with meticulous care and then put into “plaster jackets” to secure it intact, is compelling evidence that it was an animal on the verge of the transition from water to land. Only back in the laboratory in Philadelphia was the fine detail scraping and careful cleaning done.
This creature was named Tiktaalik, an Inuktikuk word for large, freshwater fish, seen in the shallows, according to the people in Nunavut, who gave the permission for prospecting on their land every other year.
Tiktaalik, as members noted when scrutinizing the image on the screen, has a flattened, triangle-shaped skull reminiscent of the earliest tetrapods. Although the lower jaws and snout have fish-like features, the rear portion of the skull looks more like a limbed animal. Several members noted that the skull is significantly shortened behind the eye sockets and has deep notches in its rear margin. The bones that connect the skull to the shoulders in fishes are not found in Tiktaalik, also hinting at its tetrapod-like nature even though it still had scales.
It was only after walking the entire area that the critical site called NV2K17 was discovered, explored, exploited, and returned to over the years – and probably again this coming summer.
Daeschler said these expeditions were expensive, and he acknowledged some of the donors including the National Science Foundation, the National Geographic Society, and a person whose name is eternally affixed to the name Tiktaalik rosae, an anonymous supporter.
From among some 80 members present, a dozen penetrating questions were asked from the size of the specimens (about four feet) to how the lung systems evolved (the rib cage was important later was on land) to how the fossils were dated (chemically by radio-active decay, carbon 14 dating, and by organic material such as pollen spores).
(Not mentioned but worth noting is the fact that Ted Daeschler was on the Stephen Colbert Report on May 18, 2006. You can google this interview at home if you like.)
Joe Giordmaine concluded the meeting at 11:29 AM.
Respectfully submitted,
Scott McVay
Joe thanked the members of the Program Committee for securing so many outstanding speakers this Spring, mentioned them by name and asked them to stand please in recognition.
John Schmidt, former Chair of the Academy of Natural Sciences in Philadelphia, introduced Dr. Ted Daeschler, Chair of the Paleontology Department at the Academy. Ted earned his bachelor’s degree at Franklin and Marshall in geology, his master’s at Berkley and doctorate at Penn in paleontology and has been at the Academy of Natural Sciences since 1987.
n addressing the topic of “Great Steps in the History of Life: Discovering a Link between Ancient Fish and Limbed animals,” Daeschler reviewed briefly the history of vertebrate paleontology over the past 600 million years. He said his focus was on a “slice of time” rather than the evolution of a particular group of animals.
The slice he has focused on over the past 20 years has been the Devonian period from about 380 to 365 million years ago beginning in eastern Pennsylvania, Lycoming County, particularly in the cuts for roads that expose fossils and reaching to Eastern Greenland a well studied zone. But he hit the jackpot with explorations in the Canadian Arctic, the Nunavut Territory, specifically southern Ellesmere Island, over a span of six years.
Such expeditions, 600 miles inside the Arctic Circle, are not undertaken lightly since the team has to fly to Resolute Bay, take a twin otter plane, and then a helicopter to get into position to examine valleys of rough terrain for fossils of interest. The tip off is broken pieces or fragments on the surface that may suggest layered deposits in former streambeds of perhaps fairly intact specimens.
Well known and well described are the fishes prior to the Devonian era and later the limbed animals called tetrapods. You have all seen the evolutionary progression in museums or in New Yorker cartoons. What is remarkable about the discovery by Daeschler and his co-collaborators Dr. Neil Shubin of the University of Chicago and Dr. Farish Jenkins of Harvard is a new species of an ancient fish, a key marker in the evolutionary transition of fish to limbed animals. Their results When Fins became Limbs were published in a cover paper of the journal Nature on April 6, 2006.
(Hold up paper inscribed with best wishes to the Old Guard of Princeton.)
For about a century, scientists have been able to trace the broad outline of the millions-of-years-long transition of lobe-finned fish to limbed animals (or tetrapods). What is exciting about the new find, which we saw in images on a large screen as it was dug out with meticulous care and then put into “plaster jackets” to secure it intact, is compelling evidence that it was an animal on the verge of the transition from water to land. Only back in the laboratory in Philadelphia was the fine detail scraping and careful cleaning done.
This creature was named Tiktaalik, an Inuktikuk word for large, freshwater fish, seen in the shallows, according to the people in Nunavut, who gave the permission for prospecting on their land every other year.
Tiktaalik, as members noted when scrutinizing the image on the screen, has a flattened, triangle-shaped skull reminiscent of the earliest tetrapods. Although the lower jaws and snout have fish-like features, the rear portion of the skull looks more like a limbed animal. Several members noted that the skull is significantly shortened behind the eye sockets and has deep notches in its rear margin. The bones that connect the skull to the shoulders in fishes are not found in Tiktaalik, also hinting at its tetrapod-like nature even though it still had scales.
It was only after walking the entire area that the critical site called NV2K17 was discovered, explored, exploited, and returned to over the years – and probably again this coming summer.
Daeschler said these expeditions were expensive, and he acknowledged some of the donors including the National Science Foundation, the National Geographic Society, and a person whose name is eternally affixed to the name Tiktaalik rosae, an anonymous supporter.
From among some 80 members present, a dozen penetrating questions were asked from the size of the specimens (about four feet) to how the lung systems evolved (the rib cage was important later was on land) to how the fossils were dated (chemically by radio-active decay, carbon 14 dating, and by organic material such as pollen spores).
(Not mentioned but worth noting is the fact that Ted Daeschler was on the Stephen Colbert Report on May 18, 2006. You can google this interview at home if you like.)
Joe Giordmaine concluded the meeting at 11:29 AM.
Respectfully submitted,
Scott McVay