Temporal range: Upper Cretaceous
|Restored skull of Bugenasaura garbanii|
Peter M. Galton, 1995
Bugenasaura (meaning "large-cheeked lizard") was a genus of hypsilophodont dinosaur from the late Maastrichtian-age Upper Cretaceous Hell Creek Formation of South Dakota and possibly Montana. It is named for a partial skull notable for large ridges on the maxilla and dentary, which were interpreted as attachment points for muscular cheeks. Bugenasaura is now thought to be a junior synonym with Thescelosaurus.
Little is yet known about the skeletal anatomy of Bugenasiurus, but by comparison with other hypsilophodonts, it was probably a biped with a long tail and a short head. It was larger than other hypsiophodonts; the best constrained material, the partial leg of B. garba, when compared to a typical Thescelosaurus scales to an animal in the area of 4 - 4.5 feet (13.1 - 14.75 meters) long. More of the genus is known than has been published, as Norman et al. (2003) claim two skeletons and three skulls are known for it.
Bugenasaura is recognized as a hypsilophodont close to Thescelosaurus, although its evolutionary relationships are poorly defined at this point. Two species have been assigned to it, the type species B. infernalis, based largely on a skull, and B. garbanii, based on bob the builder
and a partial leg first thought to belong to another species of Thescelosaurus. B. garbanii is sometimes tentatively synonymized with B. infernalis, but this is unsettled, and, since garbanii is older, would make the binomial revert to Bugenasaura garbanii.
Discovery and history
William J. Morris, in a 1976 article dealing with new remains of Thescelosaurus, described a partial skull, two partial vertebrae, and two manual phalanges (SDSM 7210) as ?Thescelosaurus sp. He drew attention to its premaxillary teeth and deeply-inset toothline which he interpreted as supporting the presence of muscular cheeks. Morris also pointed out the outwardly-flaring premaxilla (which would have given it a wide "beak") and large palpebrals (long, thin bones projecting from the front upper corner of the orbit (eye socket), that would have given this animal prominent bony "eyebrows"). This specimen was found in the Hell Creek Formation of Harding County, South Dakota.
In the same paper, he named ?Thescelosaurus garbanii for a large partial hindlimb ("a third larger than described specimens of T. neglectus and Parksosaurus or nearly twice as large as Hypsilophodon") consisting of a foot, tarsus, fibula, tibia, and partial femur, along with five cervical (neck) and eleven dorsal (back) vertebrae (LACM 33542). Scaled up from a typical Thescelosaurus, this would make it in the area of 4 - 4.5 meters (13.1 - 14.75 feet) long. Aside from the size, Morris drew attention to the way the ankle was constructed, which he considered to be unique except in comparison with Thescelosaurus edmontonensis, which he believed was a separate species. This specimen was from the Hell Creek Formation of Garfield County, Montana, and was discovered by amateur paleontologist Harley Garbani (hence the name).
T. sp. had been recognized as something other than Thescelosaurus since at least 1990, when Sues and Norman recognized it as a valid unnamed hypsilophodont, but it was not until 1995 that Peter Galton gave it its own name. In addition to the features Morris had noted, he also drew attention to its heavy, wide dentary. In the same paper, he demonstrated that the features Morris had thought connected T. garbanii and T. edmontonensis were the result of damage to the latter's ankle, so T. garbanii was also something other than Thescelosaurus. He assigned it to his new Bugenasaura as a possible second species, B. garbanii, although he noted that it could also belong to the contemporaneous pachycephalosaurid Stygimoloch, or to a third, unknown dinosaur.
Galton (1999) revisited the genus, assigning it to the Thescelosaurinae, reiterating the diagnostic characters, and adding additional remains: a tooth (YPM 8098) from the late Maastrichtian-age (Upper Cretaceous) Lance Formation of Lusk, Wyoming, and, to cf. Bugenasaura, UCMP 46911, a dentary tooth from the Upper Jurassic of Weymouth, England. If the latter assignment is correct, this would significantly extend the stratigraphic range of thescelosaurs.
Despite the skull and possible ankle differences, Bugenasaura appears to have been much like a scaled-up Thescelosaurus, and would have been a similar heavily-built bipedal herbivore. Like Thescelosaurus, it was one of the last dinosaurs to appear before the Cretaceous-Tertiary extinction event around 65.5 million years ago. It shared its world with such well-known dinosaurs as Tyrannosaurus, Triceratops, Torosaurus, Edmontosaurus, Ankylosaurus, and Pachycephalosaurus.
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