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The head of Coelophysis - a close relative of Camposaurus - as restored by John Conway. Image from Wikipedia.

If you haven’t heard of Camposaurus, you’re not alone. This is one obscure dinosaur (and not to be confused with the better-known and very different Camptosaurus). First described in 1998, this animal may hold a critical place in the evolutionary tree of theropod dinosaurs, although, then again, it might not.

Very little is known about Camposaurus. The only parts that have been found and definitively referred to this dinosaur, recovered from the Late Triassic rock of Arizona, are a few parts of the dinosaur’s lower limb bones. (The original description mentioned bones from other individuals, but it is unclear whether these really belong to Camposaurus.) Still, the anatomy of these parts identified the dinosaur as a neotheropod dinosaur, and its geologic context made it potentially the oldest known representative of the huge, diverse group of dinosaurs which contained genera such as Ceratosaurus, Allosaurus, Tyrannosaurus, Spinosaurus and many, many more. The Camposaurus fossils, as a consequence, could be important for calibrating the early evolutionary history of theropod dinosaurs.

Naturally, the fact that so little is known about Camposaurus has made it a controversial dinosaur. Paleontologists have been trying to figure out where it fits in the theropod family tree—and whether the dinosaur even deserves a distinct name—for over a decade. The known bones are so hard to properly diagnose that they seem more likely to confuse than enlighten. Now paleontologists Martin Ezcurra and Stephen Brusatte have published a reexamination of the paltry Camposaurus bones, and they affirm that the dinosaur will remain important to questions about the early days of theropod dinosaurs.

According to Ezcurra and Brusatte, there are two subtle features which set Camposaurus apart from other early theropods, such as the well-known Coelophysis. The first is a distinctive ridge on one of the lower leg bones—the tibia—where it articulates with the fibula, and the second is the absence of a knob of bone on part of the ankle. Such subtle differences can make all the difference between whether a dinosaur genus or species is kept as distinct, ends up being lumped into another taxon, or remains a problematic mystery.

Ezcurra and Brusatte also attempted to figure out where Camposaurus fit among other theropod dinosaurs. As had been previously suspected, the dinosaur turned out to be most closely related to Coelophysis—so close, in fact, that Camposaurus might turn out to be a species of Coelophysis itself. Additional fossils will be needed to be sure, and, at Chinleana, paleontologist Bill Parker brings up an important point about the significance of the specimen in terms of its age.

Camposaurus has been thought to be the oldest known neotheropod dinosaur based upon the geologic details of the place it was found, known as the Placerias quarry. This site was thought to correspond to a certain part of Triassic rock called the Mesa Redondo Member of the Chinle Formation, but Parker reports that he has found this to be in error. The quarry is actually in slightly younger rock than has been proposed, meaning that Camposaurus is not as old as had been assumed. It’s still a very old theropod, but how old it really is and its relationship to other theropods remains tentative.

The takeaway from all these paleontological jots and tittles is that our knowledge of early dinosaurs is still in a state of flux. Determining the identities, relationships and ages of Triassic dinosaurs is an ongoing task, and our understanding will continue to change as new fossils are found. At the moment, the Camposaurus fossils play an important role in providing some of the only context we have for the early evolution of the neotheropod dinosaurs, and hopefully paleontologists will soon find the fossil clues that will allow us to understand how this great lineage got its start.

References:

EZCURRA, M., & BRUSATTE, S. (2011). Taxonomic and phylogenetic reassessment of the early neotheropod dinosaur Camposaurus arizonensis from the Late Triassic of North America Palaeontology, 54 (4), 763-772 DOI: 10.1111/j.1475-4983.2011.01069.x

The bones of Giraffatitan as discovered in Tanzania. Image from Wikipedia.

In North America, the Morrison Formation is a famous and fossil-rich slice of time; its rock contains the bones of some of the quintessential dinosaurs. Apatosaurus, Allosaurus, Stegosaurus and more—the Morrison represents the heyday of Jurassic dinosaurs. A less similar but less famous site represents the Late Jurassic world. The fossil sites of Tendaguru, in Africa, preserve dinosaurs similar to, yet distinct from, their North American counterparts.

Paleontologists Wolf-Dieter Heinrich, Robert Bussert and Martin Aberhan just reviewed the history and significance of Tendaguru in Geology Today. In 1906, a German mining engineer made the fortuitous discovery of dinosaur bones near Tendaguru Hill in Tanzania. News made it back to Germany, and after an initial expedition in 1907, Berlin’s Museum of Natural History launched a major effort to uncover the area’s dinosaurs between 1909 and 1913. The result? Over 225 tons of dinosaur bones from one of the most productive fossil sites in all of Africa.

The Jurassic dinosaurs of the Tendaguru sites have often been seen as a rough equivalent to those of the Morrison. Big, long-necked sauropods, such as Dicraeosaurus, Tornieria and Giraffatitan (formerly Brachiosaurus), were numerous and a prominent part of the dinosaur fauna. There was also the spiky stegosaur Kentrosaurus, the ornithopod Dysalotosaurus and a host of poorly known predatory dinosaurs, including Elaphrosaurus and an Allosaurus-like theropod.

Frustratingly, no complete, articulated dinosaur skeletons were ever found at Tendaguru, but the sites preserve some intriguing fossil features. For one thing, the early 20th century expeditions found bonebeds of Kentrosaurus and Dysalotosaurus. They were once thought to represent mass deaths when herds of dinosaurs were killed en masse by local flooding, though, as Heinrich and co-authors point out, the bonebeds could have been created by dinosaurs becoming stuck in the mud and dying over a relatively longer period of time. The fact that the articulated feet of big sauropod dinosaurs have been found in an upright position hints that some of these huge dinosaurs also became mired and died—life alongside the Jurassic lagoon could be dangerous.

But one of the most curious aspects of the Tendaguru dinosaurs is that they are so similar to those found in North America’s Morrison Formation. After all, Giraffatitan was previously described as a species of Brachiosaurus—a dinosaur found in Jurassic North America—and problematic big theropod remains from Tendaguru have been attributed to Allosaurus, not to mention the presence of stegosaurs and other dinosaurs on both continents. Whereas the Tendaguru dinosaurs were once thought to be nearly equivalent to those of North America, a different picture has emerged in which the dinosaurs of Tanzania were similar to those found in the Morrison Formation, but actually belonged to different genera. Nevertheless, the close correspondence between the two raises the question of why very similar dinosaur communities independently came to exist on two different continents. Paleontologists will have to dig deeper to find out.

References:

Heinrich, W., Bussert, R., & Aberhan, M. (2011). A blast from the past: the lost world of dinosaurs at Tendaguru, East Africa Geology Today, 27 (3), 101-106 DOI: 10.1111/j.1365-2451.2011.00795.x

A T. rex sighting in South Dakota. Photo by Laura Helmuth

Wall Drug in South Dakota is the ultimate roadside attraction. It’s advertised on goofy billboards all along Interstate 90, features a camel-size jackalope, sells all kinds of trinkets, has a gold-panning operation for kids and is decorated in full high-country kitsch. If you make it past the animatronic cowboy singers and the ice cream parlor and the teepee and the Western wear shop, be sure to stop and admire the T. rex looming out of a patch of palm fronds. Every ten minutes or so, the T. rex comes to life: It shakes its head, snaps its jaws menacingly and roars (or, as commenter Belle put it best, RAWRs) as dry-ice steam spews from the display.

Have you seen a dinosaur or other prehistoric creature in an unusual place? Please send your photo to dinosaursightings@gmail.com.

Barnum Brown, showing off his paleo pick in an August 1932 Popular Science. Image courtesy of Palaeoblog

Barnum Brown was one of the top dinosaur hunters of all time. His nickname was “Mr. Bones,” after all, and according to the paleontological apocrypha surrounding the man, he was so skilled at finding fossils that some joked that he could smell bones. What I didn’t know, though, is that Brown also promoted a pick specially designed for dinosaur hunting.

A good pick is an essential part of the field paleontologist’s arsenal. (Though today Estwing rock hammers are more common.) According to a short Popular Science article published in 1932, Brown found that “no tools on the market quite satisfied [his] needs,” so he created one. The pick had a thin, pointed end and a wider, flatter end on the other side of the head.

But Brown didn’t actually invent the pick, and certainly wasn’t the first to use it. Matthew at The Prep Lounge explains that dinosaur picks had been used by paleontologists for decades, and the tool’s connection to the Yale paleontologist O.C. Marsh led them to be called “Marsh picks.” Brown probably just made a slight modification and the newspaper went with a slightly more hyperbolic presentation. “Paleontologist makes small improvement to traditional tool” isn’t exactly an attention-grabbing headline.

Allosaurus, on display at the CEU Museum in Price, Utah. Photo by author.

Big, predatory dinosaurs were well-adapted to stripping flesh from bone. That’s obvious from the shape and size of their teeth. What has been more difficult to determine, however, is how they behaved as they ate. Studying bones scored with the toothmarks of carnivorous dinosaurs is one of the most direct ways to approach questions about how predatory dinosaurs fed. One such bone—a tail vertebra of the sauropod Pukyongosaurus found on the Korean peninsula—shows that at least two different predators each had their shot at the same carcass.

The damaged bone is described in an in-press Palaeogeography, Palaeoclimatology, Palaeoecology paper by In Sung Paik and colleagues. The paleontologists report that at least five parts of the bone show toothmarks, including gouges, V-shaped scores and divot-shaped lesions. Since the bones of the sauropod dinosaur were otherwise in good condition—they did not exhibit cracks that would indicate that the bones had been lying on the surface for a long time—Paik and co-authors propose that the dinosaur was rapidly buried near the site of death, meaning that all these toothmarks were made in a narrow window between death and burial. Whether or not the sauropod was killed by a predator cannot be determined. All that is clear is that the toothmarks were left after the Pukyongosaurus died.

So what sort of carnivorous dinosaurs left the tooth marks? That is difficult to say. Most of what is known about big predatory dinosaurs on the Korean peninsula comes from teeth attributed to dinosaurs akin to Allosaurus and tyrannosaurs. Big theropods were certainly around in the right area at the right time, but they are almost entirely a mystery.

Nevertheless, the patterns of the toothmarks indicate a few things about how the predatory dinosaurs ate. Some of the marks, for example, are arranged in parallel rows which indicate that the feeding dinosaur was nipping or scraping with teeth at the very front of the jaw, perhaps at a time when the rest of the easily-accessible flesh had been stripped off. Additionally, while three sets of marks appear to have been made by a large animal, there are two that appear to have been left by a smaller carnivorous dinosaur at a time when most of the flesh had been removed. Were the two dinosaurs of different species? Could they have been an adult and a juvenile of the same species? How much time passed between when the big dinosaur fed and the little one tore off the remaining scraps? No one knows, but the traces left on the sauropod bone provide paleontologists with a murky window into an ancient encounter between predator and prey.

References:

Paik, I.; Kim, H.; Lim, J.; Huh, M.; Lee, H. (2011). Diverse tooth marks on an adult sauropod bone from the Early Cretaceous, Korea: implications in feeding behaviour of theropod dinosaurs. Palaeogeography, Palaeoclimatology, Palaeoecology : 10.1016/j.palaeo.2011.07.002