Discoveries of the (Dinosaur) Incisivosaurus Gauthier, and (Hominid) Sahelanthropus Tchadensis
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In the year 2002 a bizarre looking theropod dinosaur fossil was found in China (Xu). It challenges the way researchers have been thinking of theropods and other dinosaurs for a long time. In the Sahara desert, the oldest hominid skull in the world was found that same year. These are just two of many discoveries that have challenged the way we perceive the ancient world.
Incisivosaurus Gauthier was what is believed to be a primitive Oviraptorosaurian that was recently discovered in China. The Theropod and its highly specialized skull is described as a bizarre creature that lived 128 million years ago (Gee). The characteristic that “sticks out” the most are it’s rodent-like teeth. Harry Gee has described the dinosaur as “a [cross between] Roadrunner [and] Bugs Bunny” (Ibid.) and Hillary Mayell calls it a “’Weird’ Bucktoothed Dino.” (Mayell)
Oviraptorosaurians are known for their specialized skulls and for being egg thieves, which is where they get their name. It was later discovered that they were more than likely near the nests not to eat the eggs but hatch them. In Mongolia there was a discovery of a fossil of a female Oviraptor shielding her nest from a sandstorm (Mayell). They are thought to have evolved in the early Cretaceous (Xu). The Cretaceous period, is the interval of time that came just after the most well known of periods in the earth’s history, the Jurassic. Xing Xu, the man who with his team found Incisivosaurus, works for Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China. Xu and his team believe that this find proves that not all theropods ate meat (Ibid). In an article for the National Geographic, Phillip Currie of the Royal Tyrell Museum of Paleontology in Canada says, "These teeth are totally inappropriate for eating meat. Even with the beak, we had always assumed that oviraptorosuars were still carnivorous—hawks and eagles do it quite well.
But these teeth are teeth you expect to see in an herbivore” (Mayell).
Researchers believe that Incisivosaurus shows a link between typical theropods and the more rare or at least bizarre Oviraptorosaurians which are more birdlike (Gee). Xu also believes that this may show a link between the Oviraptorosaurians and an herbivorous group of dinosaurs, the Therizinosaurs. Which shows that not all of them were carnivores (Mayell).
So why is it being called primitive? Well, first of all, most Oviraptorosaurians had toothless jaws that then became beaks (Ibid).
Incisivosaurus has what appears to be the formation of a beak for the lower jaw, but the upper jaw is characterized by it’s rodent like buckteeth.
Secondly, its body is less birdlike than most of its relatives (Gee). This questions whether or not Oviraptorosaurians actually did give rise to the birds of today. A paleontologist at the Field Museum of Chicago, Peter Makovicky states, “It doesn’t have a true beak. It has a beak at the edge of the lower jaw, but the upper jaw has two enormous beaver-like incisors.
Behind them are small pointy teeth. The cheek teeth, if you can call them that, are leaf-shaped. It’s a very complex and weird dentition” (Mayell).
For awhile it was considered that Oviraptorosaurians were the dinosaurs that gave rise to birds, but Incisivosaurus was already evolved by the time birds had emerged. Incisivosaurus had a skull that was four inches long (Ibid). The later Oviraptosaurians had higher and shorter skulls. The skull resembles more of the traditional theropod skulls and therefore gives scientists a link between theropods and the strange Oviraptosaurians (Gee).
So while Incisivosaurus was busy changing preconceptions about theropods and Oviraptosaurians, Toumai, the name of the hominid skull found in the Sahara desert is doing the exact same thing to the thinking of human evolution. Michel Brunet spent a decade searching the Sahara desert trying to find some evidence of ancient human life. What he found was the oldest hominid skull currently known of. It is between six and seven million years old and has some surprising characteristics.
Sahelanthropus tchadensis is its scientific name, partly named after the country it was found in, Chad (Whitfield). It was found about 1500 miles from the East African Rift Valley by Brunet and his team. The fact that it is so far away from the Rift Valley and given the years it was thought to have lived, Brunet says this lends a different idea of the distribution of early hominids. From 1925-1995 many of the early hominid fossils were being found in Southern and Eastern Africa. The findings of hominid fossils in Eastern Africa led many researchers to believe that perhaps the hominid family began in this area (Brunet). Hominid refers to any member of a group that is more closely related to humans than to apes (Ibid).
Bernard Wood, an anthropologist at George Washington University in Washington D.C. says, “There must have been a group of apes knocking around between 5 and 8 million years ago for which there's a very poor fossil record…Anybody who thinks this isn't going to get more complex isn't learning from history…” (Ibid). He then goes on to explain how the theory of evolution has changed so much already in one lifetime. Early on, human evolution was thought to have occurred as a ladder. One species would slowly and steadily evolve into the next, eventually giving rise to Homo sapiens. However, as hominid fossils accumulated, it became clear that certain species were living at the same time as others, giving a diagram or picture of evolution more of a bush-like shape. Certain species would give rise to others which would branch off and perhaps die out, or carry on and continue to evolve. In any case, the picture of human evolution is far from a ladder.
So what is so special about this hominid apart from the fact that it’s so old? Well, according to Whitfield, the skull has many characteristics that are very hominid-like. This includes the teeth, which are usually better preserved than other parts of the body. The teeth have thicker enamel that apes do, and the canines are significantly smaller. (Whitfield). What is really puzzling is that Toumai has certain characteristics that later hominid Australopithecus is lacking but then come back in later hominids (Ibid). With this new information, Wood says that people may need to reconsider what exactly is categorized as a hominid. He also states that this is a good example of how using appearances to determine different species is a bad idea (Ibid). The skull was originally thought to be an ape because of the size of the brain capacity. But other features, such as the teeth for example, pointed toward hominid. Harvard University anthropologist Daniel Lieberman is among the many people who thought Toumai was an ape. Now, he says he’s willing to bet that it’s a hominid and not an of the ape family. He says, “It's got a massive brow ridge, the size of a large male gorilla, and yet it's just a little hominid…”(Ibid). Tim White, a Palaeoanthropologist at the University of California, Berkeley, has quite a different view. “My guess is that it's neither a chimp nor a human ancestor - it's a creature that was living at the same time” (Ibid).
While still more needs to be found out about both Incisivosaurus, and Sahelanthropus tchadensis, it is interesting that even now, in this age of knowledge and technology there is still so much we don’t know. Hopefully more fossils with more revealing and boat-rocking information will be found. Until then, the debates and speculations will continue to escalate and create new ideas for us all.
1. Brunet, M. et al. A new hominid from the Upper Miocene of Chad, Central Africa. Nature 418, 145 - 151 (2002).
2. Gee, Henry. Dinosaur like chicken-rabbit cross. Nature, September 19, 2002. http://www.nature.com/nsu/020916/020916-13.html#b1
2. Mayell, Hillary. “Weird” Bucktoothed Dino Found in China. National Geographic. September 18, 2002
3. Whitfield, John. Oldest Member of Human Family Found. Nature, July 11, 2002. http://www.nature.com/nsu/020708/020708-12.html
4. Xu, X., Cheng, Y.-N., Wang, X.-L., Chang, C.-H. An unusual oviraptorosaurian dinosaur from China.. Nature, 419, 291 - 293, (2002).