April 30, 2012
There’s a lot we don’t know about spinosaurs. Even though a few of these croc-snouted animals are known from mostly complete skeletons—including Baryonyx and Suchomimus—many spinosaurs are known from only sparse bits and pieces. The large spinosaur Oxalaia from the Cretaceous rock of Brazil is known from two skull fragments, and only a few elements have been found from the newly announced Ichthyovenator. We know even less about another recently proposed spinosaur. Called Ostafrikasaurus, this dinosaur is represented by a pair of teeth.
Paleontologist Eric Buffetaut described the dinosaur teeth in the journal Oryctos. They were found a century ago by the German fossil expeditions to Tanzania. During that time, the field team collected more than 230 teeth attributable to Late Jurassic theropod dinosaurs, predators that lived among sauropods and stegosaurs around 150 million years ago. Determining exactly which dinosaurs these dental tidbits belonged to has been a persistent problem. Mammal teeth, with their various cusps and troughs, are often distinctive enough to identify genera and species, but isolated dinosaur teeth are not usually so informative. Many dinosaur species named from teeth alone have turned out to be synonyms of dinosaurs known from better material. Unless you have a detailed knowledge of the dinosaurs that lived in a particular area at a given time, attributing isolated teeth to particular dinosaurs is a risky proposition. Anatomical context is extremely important in these situations.
No surprise, then, that the teeth Buffetaut described have had a complicated history. German paleontologist Werner Janensch, who did much of the initial descriptive work on the Jurassic dinosaurs of Tanzania, thought that the serrated, ridged and slightly curved teeth probably belonged to a dinosaur O.C. Marsh named from the Jurassic of North America, “Labrosaurus.” (“Labrosaurus” is now considered a synonym of Allosaurus.) More recently, in 2000, paleontologists James Madsen and Samuel Welles suggested that the teeth belonged to a form of Ceratosaurus, a highly ornamented theropod typically found in the Late Jurassic rock of western North America. And in 2008, paleontologist Denver Fowler mentioned that these peculiar teeth from Tanzania might hint at a connection between ceratosaurs and spinosaurs. With this in mind, Buffetaut reexamined the strange teeth and concluded that they represent a hitherto unknown form of early spinosaur.
Buffetaut singled out two possible spinosaur teeth—specimens designated MB.R.1084 and MB.R.1091. Both of these teeth have relatively coarse serrations and a number of prominent vertical ridges along both sides of the teeth, with more on the tongue side than the cheek side. Overall, they look similar to the teeth of Baryonyx, and so Buffetaut created a new genus and species of dinosaur for the two teeth: Ostafrikasaurus crassiserratus.
If Ostafrikasaurus is a spinosaur, it would be the earliest known and could help elucidate what these dinosaurs were like before they became fish-catching specialists. But there’s too little material to be sure. The Ostrafrikasaurus teeth look similar to spinosaur teeth, but as previously recognized by other paleontologists, they also resemble ceratosaur teeth. We need a nice skull set with Ostrafrikasaurus-like teeth to determine what this dinosaur actually was. The same is true of a large claw found in the Late Jurassic strata of North America, currently attributed to Torvosaurus, that has been highlighted as possible evidence of a spinosaur. There may have been spinosaurs in North America, and their history might have stretched back 150 million years to the time of Apatosaurus, but definitive proof remains elusive. Until adequate fossil evidence turns up, the idea of Late Jurassic spinosaurs will be left hanging.
Buffetaut, E. 2011. An early spinosaurid dinosaur from the Late Jurassic of Tendaguru (Tanzania) and the evolution of the spinosaurid dentition. Oryctos. 10, 1-8
February 8, 2012
When Roy Chapman Andrews returned from an American Museum of Natural History expedition to the Gobi Desert in 1923, there was only one thing the press wanted to talk to him about—dinosaur eggs. News had spread quickly that the field team had returned with the first dinosaur eggs ever discovered, and newspapers excitedly tried to outbid each other for an exclusive on the fantastic fossil find. Andrews quickly tired of the popular interest. According to Charles Gallenkamp’s biography of the explorer, Andrews became frustrated that all anyone wanted to talk about was dinosaur eggs. “Vainly did I try to tell of the other vastly more important discoveries of the expedition,” Andrews lamented, “No one was interested.”
The fact that the AMNH expedition had found eggs closely associated with dinosaur skeletons was big news. But Andrews and his team were not the first explorers to find dinosaur eggs. That discovery had been made decades before, only no one seemed to remember it. Paleontologists Eric Buffetaut and Jean Le Loeuff set the record straight in a 1994 paper published in the Dinosaur Eggs and Babies volume.
As far as we know, the first naturalist to discover and describe dinosaur eggshells was the Roman Catholic priest Jean-Jacques Pouech. When not acting as head of Pamiers Seminary in southern France, he explored the geology and paleontology of the Late Cretaceous rock preserved in the foothills of the Pyrenees Mountains. He published a report on some of the fossils he found there in 1859, which included this section:
[T]he most remarkable [fossils] are eggshell fragments of very great dimensions. At first, I thought that hey could be integumentary plates of reptiles, but their constant thickness between two perfectly parallel surfaces, their fibrous structure, normal to the surfaces, and especially their regular curvature, definitely suggest that they are enormous eggshells, at least four times the volume of ostrich eggs.
Pouech had discovered dinosaur eggs, although he did not call them that. Buffetaut and Le Loeuff suspect that Pouech might have been unfamiliar with what dinosaurs were—the term “dinosaur” had been coined only in 1842 by British anatomist Richard Owen—and therefore did not connect dinosaurs with the large pieces of eggshell he discovered. Instead, Pouech thought the eggs might have been laid by enormous birds (an conclusion similar to what New England paleontologist Edward Hitchcock proposed for the creatures that left large, three-toed footprints all over the ancient Connecticut Valley.)
The lack of dinosaurian attribution might have played a role in keeping Pouech’s discovery from gaining the attention of other naturalists, but there was another factor which caused his discovery to eventually be overlooked. In 1859, no one had seen dinosaur eggshell before. It’s not altogether surprising that when Pouech showed the fossils to experts at the Muséum National d’Histoire Naturelle in Paris, they did not agree that the shards came from large eggs. Privately, Pouech changed his mind—perhaps the pieces were parts of armadillo shells. It was not until 1989 that Buffetaut and Le Loeuff were able to relocated Pouech’s collection. The amateur paleontologist’s original conclusion had been on the right track. The fragments truly were from huge eggs, only ones laid by dinosaurs rather than birds.
The obscurity of Pouech’s discovery and his subsequent reinterpretation of the fossils prevented the find from gaining much attention. But Pouech wasn’t the only 19th-century naturalist to turn up dinosaur eggs. Only a decade after Pouech wrote about his eggshell pieces, the geologist Philippe Matheron also discovered eggshells in the Cretaceous strata of southern France. Matheron wondered whether the eggs were laid by a giant bird or a “hypselosaur”—a creature Matheron believed to be a giant crocodile on the basis of fossil bones he had previously described, but which ultimately turned out to be a sauropod dinosaur.
Matheron never got around to writing a full description of the eggs, but his countryman and colleague Paul Gervais studied the eggs at a microscopic level in an attempt to figure out what sort of creature had laid them. Although the minute details of the eggs did not exactly match the structure of known bird or reptile eggs, the fossils seemed to roughly resemble eggs laid by turtles. Since it seemed most likely that Matheron’s hypselosaur laid the eggs, Gervais reasoned, the creature may have been more turtle-like than originally thought. Additional analyses of Matheron’s eggshells produced similarly tentative conclusions. The microstructure of the eggs alone was not enough to solve the puzzle, and a dinosaurian connection was impossible to make because no one had found an identifiable dinosaur skeleton associated with the eggs.
But some early 20th century French paleontologists were still aware of what had been found before. In the December 1923 issue of the magazine L’Illustration, Andrews claimed that his discovery was the first to confirm that dinosaurs laid eggs. French paleontologist Louis Joleaud wrote to correct Andrews on this point—Matheron had discovered dinosaur eggs decades earlier, even if he incorrectly presumed that an enormous crocodile had laid the eggs. But it seems that this correction did not gain traction, either. Even though the Gobi finds inspired new analyses of Pouech’s and Matheron’s discoveries—both sets of fragments were reinterpreted as dinosaur eggs—the history behind the discoveries from the south of France were lost. A mix of misinterpretation and lack of communication had hidden the discoveries of dinosaur eggs.
Buffetaut, E., and Le Loeuff, J. 1994. The discovery of dinosaur eggshells in nineteenth-century France. in Carpenter, K., Hirsch, K., and Horner, J. eds. Dinosaur Eggs and Babies. New York: Cambridge University Press. pp. 31-34
Gallenkamp, C. 2001. Dragon Hunter: Roy Champman Andrews and the Central Asiatic Expeditions. New York: Viking. p.181
June 10, 2011
Sometimes people who discovered dinosaurs had no idea what they had found. As recounted by paleontologist and historian Eric Buffetaut, for example, in 1824 the French naturalist Georges Cuvier illustrated what appeared to be a fossil crocodile tooth sent to him by the English paleontologist Gideon Mantell. Further searches of England’s Mesozoic rocks turned up similar teeth—attributed to a prehistoric crocodile Richard Owen named Suchosaurus in 1824—but what the 19th century scientists didn’t know what that the teeth actually represented a dinosaur. The Suchosaurus teeth belonged to one of the spinosaurs, a crocodile-snouted and sometimes sail-backed group of dinosaurs that began to be well understood by paleontologists after the 1986 description of Baryonyx. The European naturalists misidentified the dinosaur teeth because the complete skeletons necessary for them to make the correct, dinosaurian assignment for the teeth had not yet been found.
The changing identity of Suchosaurus is not the only example of mysterious bones later being recognized as belonging to dinosaurs. Othniel Charles Marsh initially mistook the horns of Triceratops for the armaments of a gigantic bison, and the recognition that the weapons belonged to a dinosaur helped establish the archetype of horned dinosaurs in the late 1880s. But even Marsh’s “bison,” found in 1887, was not the first specimen of a horned dinosaur to be discovered. Small pieces of the strikingly ornamented dinosaurs had been found at least three decades earlier.
John Bell Hatcher, one of Marsh’s cadre of paleontologists entrusted to describe the great horned dinosaurs, paid tribute to the earlier discovery of horned dinosaurs in his classic monograph The Ceratopsia. In 1855, Hatcher explained, the geologist and explorer Ferdinand Hayden picked up a variety of fossils from the strata around the mouth of the Judith River in central Montana. Today we know this area as a major center of Late Cretaceous dinosaur sites, but at the time, no one really knew the dinosaurian bounty that lay in the West, and the bits of pieces of the creatures were sent back to Philadelphia to be examined by the polymath Joseph Leidy.
Leidy thought that he could distinguish four different types of dinosaurs among the rather paltry remains, including that of a dinosaur he called Trachodon mirabilis—a name for one of the “duck-billed” dinosaurs that has since fallen out of use because the teeth are not distinctive enough to assign to a particular species. Given the unfamiliar nature of the fossils, though, it is no surprise that Leidy made a mistake in grouping the fossils. Among the lot Leidy attributed to Trachodon were single-rooted and double-rooted teeth. The single-rooted teeth were indicative of hadrosaurs—the type of animal Trachodon was traditionally reconstructed as—but the double-rooted teeth were later confirmed as belonging to horned dinosaurs. They could not have known it from such incomplete material, but Hayden had discovered and Leidy had described some of the first horned dinosaur fossils ever reported. As paleontologists discover more about dinosaurs, they create a richer context by which to compare old discoveries, and old puzzles finally gain solutions.
Buffetaut, E. 2010. Spinosaurs before Stromer: early finds of spinosaurid dinosaurs and their interpretations. In Moody, R.; Buffetaut, E.; Naish, D.; and Martill, D. Dinosaurs and Other Extinct Saurians: A Historical Perspective. Geological Society, London, Special Publications, v. 343, p. 175-188
Hatcher, J.; Marsh, O.; Lull, R. 1907. The Ceratopsia. Washington: Government Printing Office. pp. 3-4