What mysteries did the remains of the dinosaur Majungatholus solve?
The discovery of Majungatholus on the island of Madagascar off the southeast coast of Africa cleared up three mysteries that had been puzzling paleontologists for years: 1) What dinosaur left behind numerous fossil teeth on Madagascar? 2) Why were there remains of a Northern Hemisphere pachycephalosaur on the island? 3) How did dinosaurs get from South America to Madagascar?
Paleontologists discovered hundreds of dagger-like fossil teeth throughout Madagascar over a hundred years ago, but no one knew what type of dinosaur had shed the teeth (during a meal, some carnivorous dinosaurs shed a few of their teeth in a manner similar to modern sharks and crocodiles). In 1996, an expedition went to Madagascar to find the dinosaur associated with these teeth. One day, while digging into a hill, a paleontologist found some tail bones. Further digging exposed an upper jaw bone of a large carnivorous dinosaur; the jaw contained the same teeth found scattered throughout Madagascar. The mystery had been solved.
The dinosaur responsible for the fossil teeth was named Majungatholus, a distant relative of Tyrannosaurus rex. It was approximately 20 to 30 feet (6 to 9 meters) long and lived in Madagascar about 70 million years ago. The skull of the dinosaur had a stubby remnant of a horn set between the eyes; some of the skull bones had an unusually rough texture, perhaps echoing patterns in the overlying skin. Paleontologists speculate that the combination of horn and texture on the head may have been used to threaten enemies or attract a mate.
How did the Majungatholus remains explain the pachycephalosaur?
At the turn of the century, fragments of a dinosaur skull were found in Madagascar. One of these fragments had a protrusion, which led some paleontologists to believe these were the remains of a pachycephalosaur, or dome-headed dinosaur. This group of dinosaurs was herbivorous and may have used their thickened skulls as battering rams. Scientists named this dinosaur Majungatholus, but for many years it was only known from a few fossil fragments. The problem was that pachycepthalosaurs have only been found in the Northern Hemisphere. How this dinosaur got to Madagascar was unknown.
With the recent discovery of more complete remains of a Majungatholus, the mystery was finally solved. The older skull fragments matched those of the newly discovered dinosaur. Paleontologists realized that the protrusion on the original bones had been wrongly identified as a dome when in reality it was a horn. There had not been a pachycepthalosaur in Madagascar after all. The, Majungatholus was a large, carnivorous dinosaur with a small horn between its eyes.
How did the Majungatholus remains explain dinosaur migration from South America to Madagascar?
The Majungatholus was very similar to another dinosaur found in Argentina, although this animal had two horns. Other bone fragments found in India were also very similar, indicating these dinosaurs were all from the same group. However, no evidence has been found to date of any of these dinosaurs in Africa.
Approximately 120 million years ago, South America, Africa, Antarctica, Madagascar, Australia, and India were all joined together in one supercontinent called Gondwana, or Gondwanaland. Scientists originally believed a piece of the landmass containing South America and Africa first split away from Gondwanaland, then pulled apart to form the South Atlantic Ocean. As the breakup of Gondwanaland continued, Madagascar ended up as an island to the east of Africa. The discovery of
Majungatholus, and its similarity to dinosaurs in India and South America, made this scenario unlikely. How could this group of dinosaurs get from South America to Madagascar without first going through Africa?
To answer this question, scientists modified the sequence by which Gondwanaland broke up. Now they believe the landmass of Africa broke off from Gondwanaland first, becoming isolated from the rest of the supercontinent. South America, and the Indian subcontinent, which included Madagascar, remained connected to Antarctica as recently as 80 million years ago by means of land bridges. The group of dinosaurs to which Majungatholus belonged, as well as many other dinosaurs, could have migrated freely from South America to India and Madagascar by way of Antarctica. This would account for the remains found in those continents, and also for the lack of them in Africa.
FAMOUS PALEONTOLOGISTS OUTSIDE NORTH AMERICA
Who was Gideon Mantell?
Gideon Mantell (1784-1856), an English country doctor and fossil collector, was the first to recognize certain fossils as giant reptiles. The well known story (but perhaps not completely true) is that Mantells wife, Mary Ann, found some fossilized teeth in rocks along the roadside while accompanying her husband on a house call. (Some people believe that Mantell actually found the fossils.) The rocks had come from the Bestede Quarry in Cuckfield, Sussex, England.
In 1822, Mantells examination of these teeth, and subsequent remains from the same area, led him to the first reconstruction of what is now known as a dinosaur. In 1825, a year after William Bucklands published description of Megalosaurus, Mantell published his own description of this ancient reptile. He named it Iguanodon, or iguana tooth, because the teeth, though much larger, matched those of this modern lizard. Mantell subsequently used a pictorial representation of the Iguanodon on the coat of arms for his residence, Maidstone, in Kent, England. The town of Maidstone also has the Iguanodon embedded on its coat of arms.
Mantell was responsible for other fossil discoveries. And he scientifically described the first known dinosaur skin in 1852. This was from the forelimb of a Pelorosaurus becklesii.
Who is Rinchen Barsbold?
Rinchen Barsbold is a Mongolian paleontologist who has named many recently discovered dinosaurs from China. He has named the Adasaurus (1983), Ansermimus (1988), Conchoraptor (1986), the family Enigmosauridae (1983), Enigmosaurus (1983), Gallimimus (1972), Garudimimus and the family Garudimimidae (1981), Harpymimus and the family Harpymimidae (1984), Ingenia (1981), the family Ingeniidae (1986), the family Oviraptoridae (1976), and the suborder Segnosauria (1980). The duck-billed dinosaur Barsboldia (1981) was named in honor of Barsbold.
Who is Peter M. Galton?
Peter M. Galton is a British paleontologist working in the United States; he is known for naming several dinosaurs, including the Dracopelta and Bugenasaura, and for naming the order Herrerasauria. With Robert Bakker, he championed the cladistic theory to show that birds are modern-day dinosaurs. Galton showed that the Hypsdophodon did not live in trees; that hadrosaurs did not drag their tails (the tail was used as a counterbalance for the head); and that some dinosaurs, such as the pachycephalosaurs, would butt their heads together like modern-day rams.