A new study, published in the open access journal PeerJ, attempts to clear up confusion about several types of the long-necked dinosaurs, particularly whether the famous Brontosaurus was a unique creature or simply confused for a pre-existing species, the Apatosaurus.
The study found enough differences in the samples previously described as belonging to the Brontosaurus to consider it a separate genus from the Apatosaurus, instead of classifying the two as synonymous.
Apatosaurus can be roughly translated as "deceptive lizard," while Brontosaurus translates into "thunder lizard." The latter's evocative name might explain why its title continued to appear in school text books and children's science books for years.
"We were very surprised when we got these results that Brontosaurus was valid again," Emanuel Tschopp, co-author of the study, told Wired. "It was a number of small differences that were important, but probably the most obvious features that would help distinguish the two is that the Apatosaurus has an extremely wide neck, where Brontosaurus' is more high than wide."
Both lived 150 million years ago during the Jurassic period. They were herbivorous, but the Brontosaurus is estimated to have weighed about 31 tonnes, comparatively less than the Apatosaurus's 41 tonnes.
The 'Bone Wars'
Problems of identification began as far back as the 1870s and 1880s, when scientists first discovered the fossils of several types of long-necked dinosaurs, or sauropods. This was during the so-called Bone Wars, when a flurry of new dinosaur genera were identified by paleontologists in a race for fame and fortune.
Paleontologist Othiel C. March named two types of Apatosaurus (Apatosaurus ajax and Apatosaurus laticollis), along with two types of Brontosaurus (Brontosaurus excelsus and Brontosaurus amplus), after their bones were discovered in Colorado and Wyoming.
Questionable tactics were rife during the Bone Wars. Marsh never found a complete skull of either the Brontosaurus or Apatosaurus, and so used a "hypothetical skull," as the PeerJ study describes, based on the Camarasaurus instead, to present what would at the time be recognized as the first complete skeleton of a long-necked dinosaur.
His findings came under fire soon after, however. In 1903, another paleontologist named Elmer Riggs made the case that there weren't enough identifiable differences between the Apatosaurus and Brontosaurus. The Apatosaurus genus, which was named first, took precedence, and so the Brontosaurus was retired.
Thunder lizard revived
As more fossils have been unearthed over the years, and electronic databases and tools made it easier to compile and compare fossils found around the world, more dinosaur genera have been classified in the years since the Bone Wars. The PeerJ study compared 81 fossils, 49 of which belonged to Diplodocidae, the family which includes Apatosaurus, Diplodocus and others.
The newest data now recommends five separate species of the dinosaurs: Apatosaurus ajax, Apatosaurus louisae, Brontosaurus excelsus, Brontosaurus yahnahpin, and Brontosaurus parvus. The complete study identified a total of 15 to 18 "valid diplodocid species," including 12 that originated in what is now the western United States.
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