Aublysodon

Aublysodon (uncertain derivation; perhaps "backwards-flowing tooth"?) is a carnivorous dinosaur taxon named by Joseph Leidy in 1868. It is a dubious name, since the type specimen consists only of an isolated premaxillary tooth, found in strata from the Late Cretaceous Period. This specimen is now lost. Identical teeth have been found in many US states, western Canada, and Asia.[1]. These teeth almost certainly belong to a juvenile tyrannosaurine tyrannosaurid, but cannot be identified with any more specificity. {| class="toc" id="toc"

Contents
[hide]*1 Discovery
 * 2 Later findings
 * 3 Current status
 * 4 Species
 * 5 References
 * 6 External links
 * }

[edit] Discovery
In the mid and late 1800s (19th century) many dinosaur taxa were named for isolated teeth; such genera include Trachodon, Palaeoscincus, and Troodon. Even before the badlands of North America started revealing the bones of Tyrannosaurus, teeth turning up in many localities in the Western United States revealed the presence of large predatory dinosaurs.

Leidy named nonserrated premaxillary teeth Aublysodon in 1868. These specimens had been collected from the Judith River Badlands of Montana.[1] This tooth-based taxon was a mystery for a long time since no further skeletal elements were found that could be assigned with certainty to the teeth.

[edit] Later findings
The first skeletal material referred to Aublysodon was a partial skull unearthed in Montana[1] in the 1980s. The skull bore pointed teeth attached to a long narrow skull the length of an average human arm. First thought to be a juvenile Tyrannosaurus, then interpreted as a large dromaeosaurid, this "Jordan theropod" was later (2004) reinterpreted to be a juvenile tyrannosaurine by Thomas Carr and Tom Williamson.[2]

Another partial skeleton from New Mexico was considered to represent Aublysodon, but later research by Thomas Carr and Tom Williamson (2004) has shown that it is probably referable to Daspletosaurus.[2]

Most recently, in 2006, a near complete skeleton of a 5-6 meter long tyrannosaurid was collected by private collectors in the Judith River Formation of eastern Montana. Due to the lack of serrations on its premaxillary teeth, and the similarity of the low, long skull to the "Jordan theropod," this specimen has been referred to Aublysodon. The similarity of this specimen to the "Jordan theropod" and immature tyrannosaurines from Asia strongly indicates that this specimen is in fact a juvenile of Daspletosaurus or a related taxon.

Now that the type specimen of Aublysodon is missing, the name is invalid, and coupled with the presence of Aublysodon teeth in juvenile tyrannosaurines, the name is no longer considered to represent a real biological taxon.[2]

[edit] Current status
Most paleontologists no longer recognize Aublysodon as a valid genus. It is now widely considered to be just a juvenile tyrannosaurine. The apparently unique morphological traits of a long, low snout, nonserrated teeth, and upturned dentary tip are characteristic of younger tyrannosaurines in general.

[edit] Species
Type: Other Species:
 * Aublysodon mirandus Leidy, 1868 (including Ornithomimus mirandus and Deinodon horridus, in part); teeth only
 * A. amplus (Marsh, 1892) and
 * A. cristatus (Marsh, 1892) were at one stage included with A. mirandus, but have now been referred to the corresponding Stygivenator (=Tyrannosaurus rex) species.
 * A. explanatus (Cope, 1876/Hatcher, 1903); nomen dubium included with Paronychodon explanatus.
 * A. (= Deinodon) grandis (Marsh, 1890/von Huene, 1932); nomen dubium
 * A. (= Deinodon) horridus (Leidy, 1856/Cope, 1868); nomen dubium
 * A. (= Deinodon) lateralis (Cope, 1876); nomen dubium
 * A. huoyanshanensis (Dong, 1977/Paul, 1988); from Shanshanosaurus, now believed to be a juvenile Tarbosaurus bataar.
 * A. lancensis (Gilmore, 1946/Charig, 1967); included with Nanotyrannus lancensis.
 * A. lancinator (Maleev, 1955/Charig, 1967); = Tarbosaurus bataar.
 * The "Jordan theropod", from Montana, originally A. molnari (Paul, 1988), was made the type species for Stygivenator by Olshevsky in 1992, but appears to be a juvenile Tyrannosaurus rex.
 * A. novojilovi (Maleev, 1955/Charig, 1967) is considered to be a juvenile Tarbosaurus bataar.