26b. What's In a Name: The Trachodon Story


One of the real difficulties in consulting the primary sources on dinosaurs is dealing with changes in nomenclature.  And probably no dinosaur is more confusing than the duck-billed dinosaur.  This dinosaur appears many times in our exhibition, wearing a bewildering variety of names, such as Trachodon, Hadrosaurus, Thespesius, Diclonius, Claosaurus, Anatosaurus, Edmontosaurus, and Anatotitan, The following is a wishful attempt to sort this all out.

In the 1850s, Joseph Leidy created two dinosaur genera, based mainly on teeth.  One was Trachodon, based on a tooth found out West (see item 9), and the other was Hadrosaurus, based on teeth and several limb bones found in New Jersey (see item 10). No skull was found in either location, so it was not yet known that these were duckbills.

In 1882, a nearly complete skeleton of an ornithopod dinosaur was found, complete with duck-billed skull, and it was named Diclonius mirabilis in 1883 by Edward Cope (see item 27b).  Cope never reconstructed the skeleton, and it was sold to the American Museum in 1899.  Charles Knight made a sculpture of it in 1897, and a painting, and it was labeled (on Osborn’s advice) Hadrosaurus mirabilis (see item 30a).

Meanwhile, in 1892, Othniel Marsh described a similar specimen, found in 1891, and he called it Claosaurus annectens (see item 26a).  This was mounted at the Peabody Museum at Yale in 1901, still as Claosaurus (see item 26)Frederick Lucas, however, referred to this specimen in 1901 as Thespesius (see item 27).

In 1906, Barnum Brown excavated a duckbill skeleton in Montana, so now the American Museum had two skeletons (Brown’s, and Cope’s Diclonius, found in 1882).  The Museum decided to mount both of them in 1908, and Brown called them, loosely, Trachodonts (see illustration on this page).

In 1908, Charles Sternberg made the spectacular find of a duckbill mummy, and it was bought by the American Museum and placed on exhibit (see item 28).  Both Sternberg and Osborn call it TrachodonTrachodon is the name nearly all of these duckbills would subsequently wear until 1942.

In 1942, in a review of all the various hadrosaurs, two kinds of uncrested duckbills were recognized.  Both were placed in the genus Anatosaurus.  The Trachodon skeleton pair in the American Museum was renamed Anatosaurus copei, while the Trachodon mummy, and the Yale specimen (which were larger) were renamed Anatosaurus annectens.  Thus matters stood for thirty more years.

In 1978, it was argued that Anatosaurus annectens was really too similar to an Edmontosaurus (discovered and named in 1917), and so it was renamed Edmontosaurus annectens.  That is the current name of the Trachodon mummy and the Yale specimen.

Finally, in 1990, for various taxonomic reasons, Anatosaurus copei was renamed Anatotitan copei.  That is the current name for the pair of Trachodon skeletons in the American Museum.

Does that clear everything up?


Scientific American, July 23, 1910, vol. 103, no. 4, cover.  This work is part of our History of Science Collection, but it was NOT included in the original exhibition.

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