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A Spinosaurus sculpture near an ice cream shop in California. Image from Flickr user larry&flo.

Spinosaurus may not be as popular as Tyrannosaurus, but sculptures and models of the sail-backed predatory dinosaur are fairly common along America’s roadsides. This one, photographed by Larry Miller, was spotted outside the Garlic Ice Cream Stand near Gilroy, California. It makes me wonder what sort of ice cream a Spinosaurus would have preferred. Would the crocodile-snouted dinosaur have liked a cone of rocky road, or would it have preferred something a little more attuned to its natural tastes, like a scoop based on its possible fishy prey Lepidotes? I guess we’ll never know.

Have you seen a prehistoric creature in an unusual place? Submissions of dinosaurs—and other ancient beasts—should be sent to dinosaursightings@gmail.com.

A restoration of Apatosaurus. Image from Wikipedia.

Though not nearly as common as the bone fragments and bits of tooth found at dinosaur fossil sites, remnants and impressions of dinosaur skin are not as rare as you might think. Paleontologists have been finding them for more than a century. The delicate fossil traces are often easy to miss—fossil hunters may even unintentionally destroy them in the process of excavating a skeleton or bone—but paleontologists have slowly been accumulating a collection of dinosaur skin traces. The newest specimens, reported by scientists John Foster and Rebecca Hunt-Foster in the new issue of the Journal of Vertebrate Paleontology, come from the Jurassic rock of Colorado’s Morrison Formation.

Foster and Hunt-Foster describe three distinct skin specimens. Two of them are thin, carbonized patches of fossilized skin that appear to have come from sauropod dinosaurs. Both were found near sauropod bones. The third specimen, however, is not attributed to any particular dinosaur. The pebbly texture of the fossil skin identifies it as coming from a dinosaur, but the paleontologists leave its assignment as “indeterminate.”

Determining exactly what species of dinosaur the skin impressions represent is extremely difficult. There were a number of possibly candidates at the approximately 153-million-year-old site. Called the Mygatt-Moore Quarry, the locality has yielded the remains of the sauropods Apatosaurus, Camarasaurus and Diplodocus; the predatory dinosaurs Allosaurus and Ceratosaurus; the ankylosaur Mymoorapelta; and the small herbivore Othnielosaurus. The putative sauropod skin patches were found near Apatosaurus bones, making this famous dinosaur a good candidate for the pair of specimens.

Curiously, though, the Mygatt-Moore Quarry is not the only site of its kind to preserve thin, carbonized films of dinosaur skin. Two other Jurassic localities—the Howe Quarry in Wyoming and the Mother’s Day Quarry in Montana—have yielded similar specimens. Exactly why this is so is a mystery. Perhaps, Foster and Hunt-Foster hypothesize, the skin fossils were preserved due to a combination of factors including the thickness of dinosaur skin and the characteristics of the local environment. The details of the plant fossils at the site and the fact that the specimens are embedded in mudstone are consistent with a wet environment in which the skin of dead dinosaurs may have become naturally tanned due to the action of bacteria and acidic conditions. Dinosaur skin may have been more likely to be preserved under such a scenario, although, frustratingly, paleontologists are typically left with only scraps.

References:

Foster, J., & Hunt-Foster, R. (2011). New occurrences of dinosaur skin of two types (Sauropoda? and Dinosauria indet.) from the Late Jurassic of North America (Mygatt-Moore Quarry, Morrison Formation) Journal of Vertebrate Paleontology, 31 (3), 717-721 DOI: 10.1080/02724634.2011.557419

Paleontologist Philip Currie poses with a tyrannosaur skull. Photo courtesy Atlantic Productions.

Tarbosaurus, the great tyrannosaur of Cretaceous Mongolia, hunted in packs. That is the exceptional claim made by University of Alberta paleontologist Philip Currie in a press release, and news outlets all over the world have picked up the story. Just imagine rapacious tyrannosaur families tearing over the prehistoric countryside; it is a terrifying notion that the press release heralds as a “groundbreaking” discovery that will forever change paleontology.

But does the actual evidence live up to all the hype? Unfortunately, the answer is no. The proposal of pack-hunting dinosaurs is old news in paleontological circles, and the hard evidence to support the claims about Tarbosaurus has not yet been released.

Packaged under the theme “Dino Gangs,” the media release, book, and cable-network documentary arranged by Atlantic Productions hinge on a Tarbosaurus bonebed found in Mongolia’s Gobi Desert. The site was one of 90 Tarbosaurus localities surveyed by Currie and the Korea-Mongolia International Dinosaur Project, but it is unique in that it preserves the remains of six individual animals of different life stages. How the animals died and became buried is unknown. Even so, the press claims that these dinosaurs were a single family group that hunted together.

There was no scientific paper attached to the release, and I received no reply from Atlantic Productions when I inquired whether a technical description of the site will soon be published. The media release–reporting conclusions without providing evidence–was presented on its own.

This is not the first time tyrannosaurs have been reconstructed as living in packs. In 1997 Currie relocated a rich dinosaur bonebed in Alberta, Canada that had been discovered by the fossil hunter Barnum Brown in 1905. The site was dominated by remains of the tyrannosaur Albertosaurus—at least a dozen individuals of this species were found in this one place. Why one site should contain so many tyrannosaurs was difficult to explain, but in a 1998 paper published in Gaia, Currie proposed that the Albertosaurus were living in a social group and that the site was evidence of gregarious behavior among the dinosaurs. More than that, Currie proposed that there was a “division of labor” within the Albertosaurus packs. Compared with the adults, juvenile Albertosaurus would have been much faster runners thanks to their different leg proportions, and so Currie suggested: “The faster, more agile juveniles may have been responsible for driving potential prey towards the larger, more powerful adult tyrannosaurids.” Currie has suggested the same thing for Tarbosaurus in the “Dino Gangs” press release.

But the idea that young and old tyrannosaurs worked together to tackle prey rests upon the inference that the bonebeds contain social groups. This is not necessarily so. There are many ways to make a bonebed, and the fine geological details of such fossil-rich sites contain essential information about how the bodies of the different individuals became preserved together. Proximity does not always indicate sociality, as Currie himself noted in a paper published with David Eberth last year about the Albertosaurus quarry.

Although the idea that the Albertosaurus quarry indicates complex social interactions among pack-hunting dinosaurs is a sexy hypothesis, Currie and Eberth noted that the animals could have been brought into close association by some kind of environmental catastrophe. “[T]he evidence for a significant storm and associated flooding event at the [Albertosaurus] site and in the surrounding area is well documented,” the scientists wrote, and they suggested that solitary Albertosaurus might have been driven together into a small area by the floodwaters. Pack behavior among the animals could not be taken as a given. The Albertosaurus were together when they died, but exactly how they died and why they were so close to each other remains unclear.

In the 2005 book Carnivorous Dinosaurs, Currie and several co-authors reported on a bonebed found in Montana that contained several hadrosaurs and remains of three tyrannosaurs identified as Daspletosaurus. Though the scientists suggested that the tyrannosaurs might have been interacting socially before they died, how the animals died and became buried was unknown. The same was true of a site in Argentina described by Currie and colleague Rodolfo Coria. The bonebed contained seven individuals of a large predatory dinosaur unrelated to tyrannosaurs named Mapusaurus. Although the site could have represented a social group, Currie and Coria concluded that “It is conceivable that this bonebed represents a long term or coincidental accumulation of carcasses.”

There is no slam-dunk evidence that tyrannosaurs or other large predatory dinosaurs hunted in packs. Even in the case of Deinonychus—a small, sickle-clawed “raptor” traditionally thought to be a cooperative hunter—evidence of multiple individuals in association with prey species has recently been questioned. In the end, trackways that record the footsteps of multiple raptors moving together has provided better evidence that these dinosaurs were sometimes social. No such evidence exists for tyrannosaurs yet. (Only one footprint attributed to a tyrannosaur has been found so far.)

Various processes can bring bones together into a single fossil deposit. A bonebed might represent a social group killed and buried by a flood, scattered bodies or bones that were washed together by water currents, or a natural trap where multiple individual animals died over a long period of time, among other possibilities. How the animals died, how long it took for the fossil deposit to accumulate, and other questions must be answered before hypotheses about behavior can be drawn out. As for the Tarbosaurus bonebed, no technical details of the site have yet been released. There is no science to talk about at this point. The site might record the death of a dinosaur pack, but that is just one of many possibilities that have yet to be ruled out.

The hubbub over the “Dino Gangs” press release is intensely frustrating. No scientific information is available, and the supposedly jaw-dropping findings are almost exactly the same as those proposed on the basis of a different site in 1998. The press release is full of bombastic language about how it is now time to rewrite the dinosaur books and how this discovery will forever change our understanding of dinosaur behavior. None of the information provided so far will do any such thing. The new find is one more discovery that will add to our understanding of dinosaurs, but is not wildly different from what has been discovered or proposed before. If there is something truly exceptional about the Tarbosaurus bonebed, it has yet to be revealed.

A discovery isn’t important simply because a press release says it is. Scientific findings should not be judged by how glitzy a documentary is or how well a book sells. By the sound of it, Currie and his colleagues have found a spectacular fossil site that is brimming with information about prehistoric life. None of the details have been published yet, and, consequently, they have not been submitted to the process of scientific debate, so no one can definitively say how the Tarbosaurus bonebed will affect our understanding of these dinosaurs. The discovery of the fossil site is just one part of the story. The rest, including how the Tarbosaurus lived and died, will take time to draw out.

References:

Coria, R., and Currie, P. (2006). A new carcharodontosaurid (Dinosauria, Theropoda) from the Upper Cretaceous of Argentina Geodiversitas, 28 (1), 71-118

Currie, P. (1998). POSSIBLE EVIDENCE OF GREGARIOUS BEHAVIOR IN TYRANNOSAURIDS Gaia, 271-277

Currie, P., & Eberth, D. (2010). On gregarious behavior in Albertosaurus Canadian Journal of Earth Sciences, 47 (9), 1277-1289 DOI: 10.1139/E10-072

Currie, P.; Trexler, D.; Koppelhus, E.; Wicks, K.; Murphy, N. (2005) An unusual multi-individual, tyrannosaurid bonebed in the Two Medicine Formation (Late Cretaceous, Campanian) of Montana (USA), in Carpenter, K. (ed.), The Carnivorous Dinosaurs. Indiana University Press, Bloomington; Indianapolis: 313-324.

Boneheads by Richard Polsky

The way a mid-life crisis manifests itself differs from person to person. Some people might suddenly decide to take up sky diving, others are driven to purchase a shiny car they can’t afford. A rare few, as in Richard Polsky’s case, may feel an overwhelming urge to find a Tyrannosaurus rex. With his career as an art dealer in stasis, Polsky writes in the introduction to his travelogue memoir Boneheads, it was time “to experience life all over again,” and a search for the most famous predator of all time seemed like just the thing.

Finding a Tyrannosaurus is no easy task. Even though more than 43 specimens have been found to date and the dinosaur is one of the most completely known of all dinosaurs, you can’t simply walk out into the field and expect to find a complete tyrant skull smiling back at you. Polsky seems to understand this, and so he fashioned himself as a fossil gadfly—buzzing around fossil dealers and commercial fossil hunters in the hope that one of them will lead him to his quarry. His quest was not to discover a Tyrannosaurus for a museum or to understand something about the animal’s biology—Boneheads is almost devoid of any scientific content—but instead merely to find a tyrant to call his own.

Polsky’s journey to secure a Tyrannosaurus winds through hotel rooms, rural bars, greasy spoons and ranches. After getting a little help with initial introductions from his friend Henry Galiano—founder of the New York City natural history store Maxilla & Mandible—Polsky eventually meets up with some of the fossil hunters associated with recent Tyrannosaurus finds in the hope that one of them will take him out into the field. Peter Larson, one of the fossil hunters who excavated the famous Tyrannosaurus known as “Sue,” declines, as do several other fossil hunters, but Polsky does have a measured degree of success. Along the way Polsky meets Maurice Williams—the owner of the ranch where Sue was found—and somehow the wannabe fossil hunter convinces Williams to let him search the ranch for other Tyrannosaurus fossils. The search doesn’t yield much, but soon Polsky latches onto the self-proclaimed “Fossil King” Bob Detrich and his crew. Given to hyperbole and stretching the evidence further than it will go, Dietrich is a man after Polsky’s own heart in that he is seemingly convinced that there is a Tyrannosaurus in almost every fossil deposit, even when more experienced dinosaur hunters say it just isn’t so.

Polsky’s attempts to locate a Tyrannosaurus are about more than the simple thrill of hunting down a prehistoric monster. The Tyrannosaurus acts as a kind of totem of a road left untraveled. Long before he became an author and an art dealer, Polsky confides, he wanted to be a paleontologist. He met with a few paleontologists, went on a fossil-hunting trip at Dinosaur National Monument, and even volunteered prepping fossils at the Cleveland Museum of Natural History. Polsky saw himself as a brilliant budding paleontologist, but college was a cold bath. “I never realized that majoring in geology was actually majoring in science,” Polsky writes, and after two weeks of studying geology he realized that the field was not for him. Still, the compulsion to collect fossils came back to him later in life, and Polsky believed that finding a Tyrannosaurus would act as an unmistakable confirmation that he was truly meant to be a paleontologist.

Paleontology doesn’t work that way. Simply finding a fossil—even a Tyrannosaurus—does not automatically make you a paleontologist. Anyone can become a paleontologist with effort and dedicated study—a Ph.D. in the field is not a prerequisite—but the passion to learn about the life of the past in a scientific and responsible way must be there. Polsky clearly lacks that. He spends no time educating himself on the science behind the dinosaur he is hunting, and he spends only a few short hours in the field. Boneheads is clearly the memoir of an art dealer after another rare object, not of someone who cares a whit about what fossils actually mean.

Nevertheless, Polsky’s book is a worthwhile read for dinosaur fans because it records the mania that surrounds Tyrannosaurus rex. Discovering one of these famous dinosaurs can be more of a nightmare than a blessing—especially with the complicated nature of land ownership in the West—and Polsky’s story features expert fossil hunters that are well known to those in the field but will be unfamiliar to casual dinosaur fans. The commercial fossil world is a strange place—one of petrified wonders, forgeries, and odd personalities—and Boneheads offers a brief glimpse of this unique world in which every fossil has its price.

A skeletal reconstruction depicting the old, tail-dragging image of Diplodocus. Image from Wikipedia.

One century ago, when paleontologists were still just becoming acquainted with the great dinosaurs of the American West, the skilled paleo-illustrator Charles R. Knight created a curious vision of the long-necked dinosaur Diplodocus. The consensus at the time was that the giant dinosaurs were amphibious—spending much of their time wallowing in swamps and straining soft water plants through their peg-like teeth—but in a scene that also contained this typical image, Knight presented one Diplodocus rearing back onto its tail. This seemed like a very active pose for the sauropod, one that would not become popular until decades later when dinosaurs got a major overhaul in the 1970s and 80s. What compelled Knight to give the Diplodocus a more dynamic position?

The answer can be found in an 1899 paper on Diplodocus by the American Museum of Natural History’s Henry Fairfield Osborn. In studying the dinosaur, Osborn was especially struck by the length of the animal’s tail. Clearly the tapering tail of Diplodocus must have been “of immense service as a propeller in enabling it to swim rapidly through the water,” and the naturalist even speculated that the dinosaur may have been equipped with a “vertical fin” near the tail tip to help move it along. But that wasn’t all. On land, the tail would have served a different purpose:

The tail, secondly, functioned as a lever to balance the weight of the dorsals, anterior limbs, neck and head, and to raise the entire forward portion of the body upwards. This power was certainly exerted while the animal was in the water, and possibly also while upon land. Thus the quadrupedal Dinosaurs occasionally assumed the position characteristic of the bipedal Dinosaurs—namely, a tripodal position, the body supported upon the hind feet and the tail.

Osborn based this supposition on what he thought was a change in tailbone anatomy about halfway down the organ’s length. To him, the posterior half of the tail looked well-suited to supporting the weight of Diplodocus when it reared up on its hind legs. That Diplodocus was capable of such activities was made clear by the relatively lightness of its skeleton compared to the more hefty “Brontosaurus.” “There is a traditional view that these animals were ponderous and sluggish,” Osborn wrote. “ In the case of Diplodocus [this view] is certainly unsupported by facts.” If the dinosaur had a relatively light skeleton and looked as if it should have been agile, then why shouldn’t it have been? This sentiment was clearly passed along to Knight, who created many dinosaur paintings for the AMNH and other museums, though Osborn’s idea that some sauropods were graceful was lost in the slew of museum displays and illustrations that showed them as big, slow reptiles. Sauropods remained relegated to the swamp, though it is too bad that Knight never illustrated Osborn’s idea that Diplodocus propelled itself about the Jurassic lakes with a tail fin!