Atlantochelys mortoni bones
March 25, 2014

Two Parts Of Same Sea Turtle Fossil Found 160 Years Apart

[ Watch the Video: Two Turtle Bones Reunited After 160 Years ]

Brett Smith for - Your Universe Online

Against insurmountable odds and after more than 160 years, an ancient sea turtle has finally been reunited – with itself.

Fossil evidence of the massive turtle Atlantochelys mortoni was first discovered in 1849 in the form of one-half of an upper arm bone – called the humerus. The other half of that bone would lie in a New Jersey streambed until it was stumbled upon by amateur paleontologist Gregory Harpel in 2012.

"I picked it up and thought it was a rock at first – it was heavy," Harpel said.

The newer specimen was found in a fossil-hunting hotspot in Monmouth County, N.J., where Harpel often goes to look for fossilized shark teeth as a weekend hobby. After realizing that he had indeed found a fossil, Harpel brought the specimen to experts at the New Jersey State Museum, who joked that the amateur paleontologist had found the other half of a partial turtle limb being stored at the Academy of Natural Sciences of Drexel University in Philadelphia.

In a video released by Drexel University, researchers Ted Daeschler and Jason Schien described how – sure enough – the two fossils fit together, like puzzle pieces: Both were from the same turtle!

"I didn't think there was any chance in the world they would actually fit," said Schien, assistant curator of natural history at the New Jersey State Museum.

Schien doubted the two would be a match because paleontologists assume that fossils present in exposed strata will disintegrate due to contact with the elements if they aren't found and conserved, certainly within a few years – decades at the most. There wasn't any reason to believe a lost 50 percent the same old bone would make it through in one piece, sitting in a streambed from at least the time of the first bone's first scientific description in 1849. Since its discovery and description by renowned 19th-century naturalist Louis Agassiz, the sample of A. mortoni was the only known specimen from that genus and species.

The New Jersey scientists said they were stunned to discover that the two fossils fit so perfectly together.

"Sure enough, you have two halves of the same bone, the same individual of this giant sea turtle," said Daeschler, associate curator of vertebrate zoology and vice president for collections at the Academy of Natural Sciences of Drexel University. "One half was collected at least 162 years before the other half."

The paleontologists said the discovery should spark a reexamination of the conventional wisdom that says exposed fossils cannot survive for long periods. They added that a report on the find will be published in an upcoming edition of the Proceedings of the Academy of Natural Sciences of Philadelphia. The find is also featured in the April 2014 issue of National Geographic magazine, on newsstands now.

"The astounding confluence of events that had to have happened for this to be true is just unbelievable, and probably completely unprecedented in paleontology," Schein said.

In addition to shaking a long-held scientific belief, the newly discovered fossil also provides more information about the ancient sea turtle. The New Jersey team said A. mortoni would have been about 10 feet from end to end, making it one of the largest seas turtles or record. The species may have resembled modern day loggerhead turtles, but was much larger than any seas turtles alive today.

The researchers added that original bone was embedded 70 to 75 million years ago, when the turtle lived and died. Erosion caused the bone to fracture millions of years later, eventually becoming embedded in sediments and protected from further deterioration for a few thousand more years.

Image 2 (below): Now that paleontologists have assembled a complete humerus bone from the sea turtle Atlantochelys mortoni, they have more information about the species and its overall size. Prior to the discovery of the bone's missing half, the partial limb in the collections of the Academy of Natural Sciences of Drexel University was the only known fossil specimen of its genus and species. Based on the complete limb, they calculated the animal's overall size to be about 10 feet from tip to tail, making it one of the largest sea turtles ever known. It may have resembled modern loggerhead turtles. In this illustration, it is depicted with the outline of a human diver to indicate scale. The turtle lived 70 to 75 million years ago. Credit: Jason Poole, Academy of Natural Sciences of Drexel University