May 27, 2011
Triceratops—the giant with a “three-horned face”—is one of the great ambassadors for dinosaurs. Everyone knows this well-ornamented Cretaceous herbivore today, but the dinosaur was originally mistaken for a very different creature. For a short time, the horns of Triceratops were thought to belong to a giant bison.
Near the close of the 19th century, relatively little was known about the dinosaurs of North America (or, in fact, dinosaurs in general). The word “dinosaur” had been coined by the English anatomist Richard Owen in 1842, and the entire group was only represented by a handful of species known from specimens of varying completeness. The extraordinary fossil-rich formations of the American West had just begun to be examined, meaning each discovery had the potential to significantly change the image of prehistoric life. The early Triceratops fossil was one such discovery.
The story of the fossil—including its changing attribution—was retold by paleontologist Ken Carpenter in a 2007 paper in the book Horns and Beaks. The tale of the specimen began in the rock around Denver, Colorado. This area was peppered with fossils from the last days of the dinosaurs and the earliest days of the post-dinosaur world, and the fossils were so accessible that many were picked up by local collectors and those in want of natural curiosities to display at home.
But the Triceratops fossil had a different fate. In the spring of 1887, a local high school teacher and geologist by the name of George Cannon found two large horns and part of a skull roof. The specimen was sent to Othniel Charles Marsh at Yale University, and after urging his contacts in the field that he wanted more of the skull, a few more fragments of the horns soon followed. Altogether, the fossil consisted of a pair of long horns attached to part of the skull roof, and it had clearly belonged to some prehistoric animal much larger than anything that roamed the West in modern times.
Anatomically speaking, the horns most closely resembled those of herbivorous, horn-bearing mammals like bison. In fact, the horns looked as if they had come from some gigantic predecessor of that iconic Western symbol, and therefore Marsh named this new creature “Bison alticornis” that same year. Those who know the rocks from which the bones came were not so sure. Cannon, who had found other dinosaur fossils in the same rock layers, found it strange that the remains of a giant bison should be found mixed in with those of dinosaurs, and he wrote to Marsh that he would devote every spare second to figuring out why such disparate organisms should be found in the same strata.
Marsh eventually recognized the Denver horns as belonging to a horned dinosaur, but his path to this conclusion was circuitous. For example, in 1888 Marsh named the dinosaur Ceratops on the basis of similar, smaller horns that had been sent to him, but the Yale paleontologist initially thought the horns were spikes akin to those anchored in the tail of Stegosaurus. (Another dinosaur that Marsh changed his mind about multiple times.) Marsh changed his stance again after receiving the partial skull of the dinosaur that he would name Triceratops horridus in 1889 —the long, pointed structures were horns peculiar to this previously unrecognized group of dinosaurs, and further discoveries of horned dinosaurs reinforced this view. (Marsh’s nemesis, Edward Drinker Cope, had studied a number of horned dinosaur specimens during the 1870s, but he was also left puzzled by the horn cores and other incomplete remains from the ceratopsians.) Still, to cover his mistake, Marsh affirmed that the structure of the Denver horns truly was similar to that of a bison. This isn’t so far-fetched. The horn structures of Triceratops and bison are somewhat similar, and paleontologist Tobin Hieronymus and colleagues recently used the horn anatomy of buffalo and musk oxen to reconstruct the facial structures of the horned dinosaur Pachyrhinosaurus.
As Carpenter cautions, though, we should not ridicule Marsh for his mistakes. No one in the late 1880s knew what a ceratopsian really looked like, especially since many of the dinosaurs that Marsh had previously studied were Jurassic creatures that lived many millions of years before. With nothing else for comparison, the Triceratops horns did show some features in common with both bison horns and Stegosaurus spikes, which led Marsh to incorrect conclusions until more complete specimens finally solved the mystery. Marsh’s mistakes are a prime example of how new dinosaurs are sometimes identified—parts of unknown creatures are compared to what is already known in an attempt to narrow down a range of possibilities for identification. Triceratops was so different from other dinosaurs Marsh studied that it is little wonder that he erred in his conclusions. Who could have imagined an animal as magnificent as Triceratops on the basis of the horns alone?
Carpenter, K. 2007. “Bison” alticornis and O.C. Marsh’s early views on ceratopsians. In K. Carpenter ed., Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. pp. 349-364. Bloomington: Indiana University Press.
Hieronymus, T., Witmer, L., Tanke, D., & Currie, P. (2009). The Facial Integument of Centrosaurine Ceratopsids: Morphological and Histological Correlates of Novel Skin Structures The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 292 (9), 1370-1396 DOI: 10.1002/ar.20985
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