August 20, 2012
Last fall, fossil tracker Ray Stanford and paleontologists David Weishampel and Valerie Deleon announced something wonderful–a rare impression of a baby ankylosaur. The delicate specimen, officially named Propanoplosaurus marylandicus and on display at the Smithsonian National Museum of Natural History, is an Early Cretaceous snapshot from Maryland that gives us a fleeting picture of how these armored dinosaurs started life. And the fossil is even more spectacular given the rarity of dinosaur bones found in the area. Paleontologists have discovered teeth and bone fragments over the years–including bones from “Capitalsaurus” in Washington, D.C.–but even partially complete skeletons remain elusive. Dinosaur tracks are far more common, and, according to the Washington Post, Stanford may have discovered a footprint of an adult ankylosaur in an unexpected place.
As reported by Brian Vastag, the print sits on the property of a NASA‘s Goddard Space Flight Center in Greenbelt, Maryland. Stanford stumbled across the lone track earlier this summer and recently led NASA scientists out to the site to show them the fossil depression. Though the track has started to erode, and may have been damaged by a lawnmower, the roughly 112-million-year-old track still shows four toe imprints. According to David Weishampel, the track could have been made by a nodosaur–a member of the heavily-armored ankylosaur subgroup that lacked tail clubs but often sported prominent spikes along their sides.
Officials at the NASA campus are already moving to protect the fossil, and they plan to bring in paleontologists to look for other dinosaur tracks. The NASA scientists want to keep the site a secret, Vastag reports, but ultimately want the public to be able to see the track. What happens next will depend on the laws that regulate how fossils can be removed and curated. But it seems that there is more than just a lone track at the spaceflight facility. When Stanford took the NASA scientists out to the site, he and other researchers found several more possible dinosaur tracks. The high-tech NASA facility may have been founded on a Cretaceous dinosaur stomping ground.
June 28, 2012
Compared to mounted dinosaur skeletons, fossil footprints might seem like mundane objects. They only record one small part of a fantastic creature, and it is harder to envision a whole dinosaur from the ground up than the wrap flesh around a skeletal frame. But we should not forget that dinosaur footprints are fossilized behavior—stone snapshots of an animal’s life. And sometimes, trackways record dramatic moments in dinosaur lives.
In 1938, American Museum of Natural History paleontologist Roland T. Bird traveled to Glen Rose, Texas to investigate rumors of huge dinosaur tracks found in the vicinity of the Paluxy River. Bird found them in abundance, but one site was especially intriguing. Set in 113-million-year-old rock were the footprints of a huge sauropod dinosaur—and it seemed that the long-necked giant was followed. The large, three-toed footprints of a predatory dinosaur, probably the ridge-backed Acrocanthosaurus or a similar theropod, paralleled and eventually converged on the footsteps of the sauropod. And at the point of overlap, the predator seemed to skip a step—a little hop that Bird took to mean that the carnivore had sunk its teeth into the herbivore and was lifted out of its tracks a short distance.
Bird excavated the trackway in 1940. About half of the long trail went to the AMNH and can now be seen stretching out behind the museum’s Apatosaurus mount, despite the fact that Apatosaurus lived millions of years before the tracks were made. The other portion is housed at the Texas Memorial Museum in Austin. Bird’s hypothesis about how the tracks were made has inspired exhibits at other museums, such as the Maryland Science Center and the North Carolina Museum of Natural Sciences. Yet not everyone agrees about what the tracks represent. Do they record an Acrocanthosaurus attack as it happened? Or could the trackway simply be a fortuitous association of tracks from dinosaurs that walked the same ground at different times?
Artist David Thomas and paleontologist James Farlow went back to Bird’s notes and the trackway evidence to reconstruct what might have transpired. The association between the sauropod and theropod tracks seemed too tight to just be coincidence. The predatory dinosaur very closely followed the pathway of the larger herbivore, both moving along a broad left curve. Near the end of the excavated area, both the theropod and sauropod turned abruptly to the right. If the two dinosaurs had passed at different times, then we’d expect that the sauropod or theropod would have continued on in the same trajectory and crossed another set of tracks preserved nearby. Based on the fully reconstructed image, the sauropod and theropod were interacting with each other.
And there’s something else. Just before the enigmatic double-right-footprints made by the theropod, there is a drag mark made by the sauropod’s right hind foot. This might be where the titan was attacked and faltered, or maybe the sauropod threw its weight to avoid being bitten. Frustratingly, we can’t know for sure. And the missing left theropod footprint isn’t a clear sign of an attack, either—all we know is that there’s a missing track right where the animals were in close proximity.
Whether or not the Paluxy River Trackway records a successful Acrocanthosaurus assault is uncertain. But the tight connection between the theropod and sauropod tracks suggests that the carnivore at least stalked the herbivore, and perhaps even took a swipe at it. Specimens like this test our ability to draw brief moments in time from stone. The task is made all the more complicated by the gradual loss of information contained within the rock. While they look sturdy, trackways are actually fragile fossils, and the half of the trackway at the Texas Memorial Museum has significantly deteriorated since it was put on display. The museum is trying to raise a million dollars to properly conserve and house this historically and scientifically significant fossil. If you wish to learn more about their campaign, you can find more information here.
March 12, 2012
In the American Museum of Natural History’s Hall of Saurischian Dinosaurs, there is a great fossil mismatch. You can find the deceptive pairing in the Apatosaurus exhibit. Set in the floor behind the enormous dinosaur is a set of trackways—the Apatosaurus is posed as if the skeletal sauropod has just left the tracks behind. But there is no way that Apatosaurus left those tracks. The footprints and the long-necked dinosaur on display were separated by tens of millions of years.
Apatosaurus is an iconic Morrison Formation dinosaur. The hefty sauropod trod across prehistoric floodplains of America’s Jurassic West around 150 million years ago. But the footprints on display at the AMNH comes from a different time. The slab is part of a roughly 113-million-year-old trackway found along the Paluxy River near Glen Rose, Texas. Apatosaurus was long gone by the time the Texas tracks were created, and the shape of the footprints indicate that a very different kind of sauropod, probably belonging to the subgroup called titanosaurs, actually created the tracks.
Regardless of the inappropriate juxtaposition, though, getting those tracks out of the ground and set up at the AMNH was a massive paleontological undertaking. A YouTube video—posted above—shows actual footage of the 1938 excavation.
Although dinosaur tracks were known to local people since at least the beginning of the 20th century, it wasn’t until the late 1930s that the footprints garnered broad attention from paleontologists. Roland T. Bird, a fossil collector working with the AMNH, was roving the Southwest in 1937 when he got word of dinosaur tracks in the vicinity of the Paluxy River. When he got there, he found that the tracks supported a small local industry—everyone seemed to know about them, and many people had quarried tracks to sell for rock gardens. Fortunately for Bird, there were still plenty of tracks in the ground, including impressive trackways of multiple dinosaurs moving together.
The slab at the AMNH is one section of a large trackway that Bird had divided into three pieces. (The other two parts are at the University of Texas and the Smithsonian Institution.) Getting the tracks out was arduous, destructive work, made all the more complicated by the fact that at least some of the trackway went under the river. Bird and members of the local Works Progress Administration crew diverted the river to access and remove the tracks.
Bird’s tracks didn’t immediately go up on display. The broken pieces of excavated trackway just sat in the museum’s yard, and Bird’s health rapidly declined due to unknown causes and he was forced into an early retirement. When the AMNH decided to renovate its dinosaur halls in the 1940s, however, paleontologist Edwin Colbert asked Bird to come back to oversee the reconstruction of the trackway behind the museum’s “Brontosaurus” mount. Without Bird, the project would have been impossible—the broken trackway pieces were becoming exposed to the elements in the museum’s storage yard, and many of the fossil pieces were not labeled. The project was scheduled to take six weeks. Bird took six months, but, nonetheless, Bird and his collaborators were able to restore the steps of a Cretaceous giant.
January 4, 2012
Even before we knew what they really were, dinosaurs inspired our imagination. Unidentifiable bones and tracks formed the basis of legend–they were the evidence of great battles, fearsome monsters and times when the world was new and hostile to human existence. Indeed, contrary to what John Noble Wilford wrote in The Riddle of the Dinosaur, fossilized bones were not just ignored or ground up for “dragon-bone medicine” in the centuries prior to the scientific discovery of dinosaurs. People have puzzled over dinosaurian fossils for centuries. Some of that folklore still persists today.
In a paper recently published in Ichnos, researchers Lida Xing, Adrienne Mayor, Yu Chen, Jerald Harris and Michael Burns focus on one particular source of dinosaur-inspired myths–trackways found in China. Just as dinosaur tracks in New England generated tales about primeval monsters, huge turkeys and ostrich-like birds, the tracks in China motivated the creation of different stories to explain just what left such imposing footprints.
According to the new study, Chinese folklore about dinosaur tracks can be divided into four categories–mythical birds, mammals, plants, and gods or heroes. In the case of three-toed theropod tracks discovered in Chabu, Inner Mongolia, for example, the footprints had been known to local farmers since the 1950s and were believed to be footprints of a “divine bird.” As explained by Xing and co-authors, “The herders believed that the tracks represented beautiful wishes for human happiness left by the sacred bird Shen Niao.” This is a common theme across sites where theropod tracks are found. Three-toed dinosaur footprints have often been interpreted as the steps of birds, and other sites in Heibei, Yunnan, Guizhou and Liaoning provinces have been attributed to other mythical birds, such as the golden and heavenly chickens.
Not all the dinosaur tracks are associated with supernatural avians. The fossil footprints of a sauropod dinosaur near Zigong City have traditionally been cast as the footprints of a rhinoceros–”The tradition of counting the footprints to pray for good fortune is popular,” the authors note–and hadrosaur tracks at Qijang County may have been interpreted as impressions of lotus flowers on stone. The size of the impressions and the fact that they were made on stone were often taken to mean that some supernatural agency was involved. What else could leave such detailed markings on rock?
One such powerful figure, according to myths about footprints found in Changdu County, Tibet, was the Mountain Deity. During the construction of a highway through the area in 1999, construction crews found several large footprints. Local villagers believed that all the noise had disturbed a god who dwelt in the mountains, and when the deity fled, it left the footprints in stone. Though not everyone agrees. Others think that the footprints represent King Gesar, a warrior featured in an epic poem about Tibet’s history. In reality, the tracks are the fore- and hindfoot impressions of a sauropod dinosaur. The shape of the tracks and their arrangement roughly resemble a large human footprint, and so the legendary explanation was born. Indeed, not all myths about dinosaur remains are ancient. In places where people don’t know about dinosaurs or paleontology, fantastic stories are still employed to explain the origin of fossils.
The nature of tracksites themselves may explain why they often find their way into folklore. Fossilized bone is often fragile and visible on the surface for a short time before eroding away. Exposed tracks, on the other hand, often remain in place for generations before fully succumbing to the wear of wind and water. The persistence of the tracks may allow them to become more readily established in cultural tradition–the stone footprints are visible for years and act as evidence of the stories.
And these legends have practical applications for paleontologists. By using rumors of “dragon bones” and stories about stone footprints, researchers can use local folklore to locate previously-unknown fossil localities. Folklore may tell tales too fantastic to believe, but they may be based on very real traces of prehistoric life.
Xing, L., Mayor, A., Chen, Y., Harris, J., & Burns, M. (2011). The Folklore of Dinosaur Trackways in China: Impact on Paleontology Ichnos, 18 (4), 213-220 DOI: 10.1080/10420940.2011.634038
November 21, 2011
Earlier this month, paleontologists from around the world convened in Las Vegas for the 71st annual Society of Vertebrate Paleontology conference. Preliminary findings were shared, new discoveries were presented, and researchers caught up with friends and colleagues, but not all the news came from the meeting halls. Various field trips held just before the conference introduced paleontologists to the geology and paleontology in the vicinity of Las Vegas, Arizona, and southern Utah. One of them confirmed the traces of a dinosaur not far from the bright lights of the Las Vegas strip.
An article in the Las Vegas Review Journal has the details. About twenty minutes outside of Las Vegas, within the Red Rock Canyon National Conservation Area, lie the tracks of a relatively small theropod dinosaur in the red, roughly 190-million-year-old Early Jurassic rock. Our knowledge of dinosaurs in North America from this time is relatively sparse. Very few skeletons have been found from this period, and much of what we know about the dinosaurs of the Early Jurassic Southwest comes from tracksites. For the moment, these three claw-tipped toe impressions indicate that the Red Rock Canyon dinosaur was a small theropod. Details of the dinosaur’s behavior, such as how fast it might have been walking, have not yet been studied.
The interpretation of the Red Rock Canton site will emerge as research is conducted. According to the LVRJ story, Bureau of Land Management officials are planning to create casts of the tracks to let visitors learn about the site without risking damage to the ancient footprints. If you’re in the area and are really itching to see some dinosaur tracks, though, there are other opportunities within a few hours drive: the Dinosaur Discovery Site in St. George, Utah is packed with similar Early Jurassic dinosaur footprints.