| Thespesius | |
|---|---|
 | |
| The syntype fossils | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Ornithopoda |
| Family: | †Hadrosauridae |
| Subfamily: | †Saurolophinae |
| Genus: | †Thespesius Leidy, 1856 |
| Species: | †T. occidentalis |
| Binomial name | |
| †Thespesius occidentalis Leidy, 1856 | |
| Synonyms | |
| |
Thespesius (meaning "wondrous one") is adubiousgenus ofhadrosauriddinosaur from thelate Maastrichtian-ageUpper CretaceousLance Formation ofSouth Dakota.
In 1855 geologistFerdinand Vandeveer Hayden sent a number of fossils topaleontologistJoseph Leidy inPhiladelphia. Hayden had collected them from the surface of a rock formation then known as the Great Lignite Formation (now recognized as part of the Lance Formation) in theNebraska Territory, near theGrand River (present-daySouth Dakota). Among them were twocaudalvertebrae and aphalanx. In 1856 Leidy named thetype speciesThespesius occidentalis for these three bones.[1][2] The generic name is derived from Greek θεσπεσιος,thespesios, "wondrous", because of the colossal size of the remains. Leidy avoided using the suffix "saurus" in the genus name because Vandeveer Hayden had claimed the bones came from a layer from theMiocene so there was a chance that the animal would turn out to be amammal, though Leidy himself was convinced it was a dinosaurian. Thespecific name means "western" inLatin.
The caudal vertebrae, USNM 219 and USNM 221, and the middle toe phalanx, USNM 220, form the originalsyntype series.
LikeTrachodon, another duckbill genus named byJoseph Leidy,Thespesius is a historically-important genus with a convoluted taxonomy that has been all but abandoned by modern dinosaurpaleontologists. Around 1900 the name was used by some authors to indicate all late Maastrichtian hadrosaurids in North America.[3] In 1875, E.D. Cope stated that he consideredAgathaumas milo, known from partial limb bones and some vertebrae, to be a synonym ofT. occidentalis (which he considered a species ofHadrosaurus at the time).[4] In 1900, a short piece published inScience by F.A. Lucas noted that Leidy's originalThespesius occidentalis fossils were indistinguishable from more complete specimens which had been referred in the late 1800s to the speciesClaosaurus annectens. Therefore, Lucas argued, the nameT. occidentalis should be used for this animal.[5]
Lucas' opinion was supported by Charles W. Gilmore in a 1915 paper forScience re-evaluating the use of the genusTrachodon. A wide variety of hadrosaurid species had been classified asTrachodon or "trachodonts", most notably the large "duck-billed" specimens collected by E.D. Cope and mounted in theAmerican Museum of Natural History. Gilmore noted that the holotype fossils ofT. occidentalis were "inadequate", but that geologic work showed that they undoubtedly came from the same fossil beds asClaosaurus annectens, and that therefore the older name (T. occidentalis) should be used for the Lance-aged "trachodonts."[6] Many later researchers, including L.S. Russell and Charles M. Sternberg, continued to use the namesThespesius occidentalis orThespesius annectens for the Lance hadrosaurids through the 1920s and 1930s.[7][8][9]
However, as early as 1913, paleontologist Lawrence Lambe regarded the type fossils ofThespesius occidentalis as inadequate and that any inferences based on them were too conjectural, as was the case forTrachodon. In an influential 1942 paper on hadrosaurids by Richard S. Lull and Nelda E. Wright, the authors classified most specimens ofThespesius annectens in the new genusAnatosaurus, and referred Cope's giant "duck-billed" specimens toAnatosaurus copei. Though they noted thatT. occidentalis could possibly be distinguished fromAnatosaurus based on its shorter tail vertebrae, they ultimately agreed with Lambe that, despite its historical importance,Thespesius occidentalis was too incomplete for good comparison.[2] It has been generally ignored as anomen dubium ever since.
A referred species ofThespesius,T. saskatchewanensis, was named by Sternberg in 1926,[10] but Nicolás Campione and David Evans found that it was a synonym ofEdmontosaurus annectens in a 2011 study of edmontosaur diversity.[11] Campione and Evans also foundThespesius edmontoni, named by Gilmore in 1924,[12] to be a synonym ofEdmontosaurus regalis.[11]
