| VOL. 23, NO. 22||APRIL 24, 1998 |
200-Million-Year-Old Reptile Skull Discovery Adds to Scarce Fossil Record
|Drawing of a reptile skull.|
BY HANNAH FAIRFIELD
our skulls of reptiles that lived before dinosaursabout 200-million years agohave been discovered in two Pennsylvania sites, a Columbia scientist announced Apr. 18.
The skulls were among about 150 ancient bones found in Exeter Township, Pa., said Paul Olsen, a paleontologist at Columbias Lamont-Doherty Earth Observatory, who identified the fossils. They represent a sizeable addition to the scarce fossil record of the Triassic-Jurassic boundary 202 million years ago, when an as-yet unknown event wiped out more than half the Earths land animals and set the stage for dinosaurs to dominate the planet.
Olsen, who is the Arthur D. Storke Memorial Professor at Columbia, presented the findings at a symposium in Philadelphia that is part of Dinofest, a month-long worlds fair of dinosaurs hosted by the Academy of Natural Sciences. The event continues until Apr. 26.
Two of the three partial yet well-preserved skulls were found in Exeter Township, and another one found in Pennsburg, Pa., belong to the Hypsognathus genus, a barrel-shaped herbivorous reptile that was about one foot long and proportioned like a modern-day groundhog. It has very distinctive horns on the sides of the skull, which make it easily identifiable. The third skull from Exeter is very recently discovered and has not yet been identified.
The findings are important because so little is known about the latest part of the Triassic period. Skeletal remains were thought by most scientists to be very rare, said Olsen. He had a hunch the problem wasnt a scarcity of bones but rather poor conditions for actually finding them.
We were looking at rocks at a construction site, and there was so much new, clean rock exposed after a rain, he said. I thought there might be a lot more bones there than we had originally thoughtand low and behold, once I really paid attention, there were.
|Paul Olsen. Photo by Sally Savage.|
The Exeter rock that encases the bones is a hard, slightly-baked mudstone. It is purple-brown, and so the bright white of the bones stands out dramatically after rainfall. The site was also good for preserving footprints; paleontologists and amateurs had been collecting prints from the area for ten years. Two amateur paleontologists, Brian Hartline and Mike Szajna, both of Reading, Pa., found the skulls after Olsen told them he had begun to find bones at the site.
Ninety percent of the first skull was covered in dirt, Szajna said. The only parts showing were two bony prongs. We knew the Triassic reptile Hypsognathus had prongs on its skull. We called Paul and had him clean and identify it for us.
The skull from Pennsburg, Pa., was found by Joe Siske and Bob Hoffman, two more amateur paleontologists who asked Peter Dodson of the University of Pennsylvania to look at it. Both Dodson and Olsen identify the fossil as most likely a Hypsognathus.
The three skulls from Exeter are being prepared for further study by Hans-Dieter Sues, the curator of vertebrate paleontology at the Royal Ontario Museum in Toronto. The greatest thing about this find is that it is in well-dated rock near the Triassic-Jurassic boundary, Sues said. Now we have evidence that these animals lived right up to the boundary, which supports our ideas about a large-scale extinction there.
The fossils are critical pieces in the unsolved mystery of the mass extinction that occurred at the end of the Triassic period. The extinction changed the course of evolution and allowed dinosaurs to dominate the Earth. The Exeter site is especially important because the fossils can be precisely dated from about 500,000 years before the mass extinction, said Olsen.
Because the sites are so newly discovered, little of the bone material has been prepared. Olsen suspects that the most important material remains to be identified.
Olsen has been a leading scientist in Triassic period fossil discoveries in the East Coast region for several decades. He has previously found Triassic fossil sites in the Bay of Fundy, Connecticut, Virginia and North and South Carolina.