Гастония: раннемеловой анкилозавр Северной Америки

Ankylosaurian dinosaur genus from the Early Cretaceous period

Gastonia is a genus of herbivorous ankylosaurian dinosaur from the Early Cretaceous of North America, around 139 to 134.6 million years ago. It is often considered a nodosaurid closely related to Polacanthus. Gastonia has a sacral shield and large shoulder spikes.

The type specimen of Gastonia burgei (CEUM 1307) was discovered in a bonebed from the limestone strata of the lower Cedar Mountain Formation in Yellow Cat Quarry, Grand County, eastern Utah, the type specimen consisting of a single skull. In 2004, the number of skulls was reported as four, in 2014 this had risen to ten. Gastonia was formally named and described by James Kirkland in 1998, from the holotype specimen and other fossil material recovered beginning in 1989. A second species, G. lorriemcwhinneyae, was described from the Ruby Ranch Member in 2016 based on a large bonebed that had been found by Lorrie McWhinney in 1999, probably formed when a group died of drought or drowning. The type specimen and its paratypes were collected by the Denver Museum of Nature and Science from Lorrie's Site in Grand County, Utah and belonged to the Ruby Ranch Member of the Cedar Mountain Formation. A wealth of disarticulated material from a bonebed presents problems as it can be hard to tell how many spikes a particular Gastonia actually had.

Gastonia was a medium sized ankylosaur. In 1998, Kirkland estimated its length at 6 metres. The skeleton mount is 459 centimetres long with a hip height of 112 centimetres. A phylogenetic analysis conducted by Rivera Sylva et al. (2018) and modified by Madzia et al. (2021) is reproduced below.

Gastonia lived in a partly wooded habitat, with riverine forests being separated by open areas. The climate was rather dry with a short wet season. Other dinosaurs of the Yellow Cat include the ornithopods Hippodraco and Cedrorestes, the sauropods Cedarosaurus and Moabosaurus, and the theropods Martharaptor, Nedcolbertia, and Utahraptor. Gastonia was the only ankylosaurian present and one of the most common species of its fauna. Kirkland suggested that Gastonia could have been so abundant because its armour effectively protected it against the apex predator of its habitat, the giant dromaeosaurid Utahraptor, remains of which have been found in the original Gastonia quarry. Gastonia would have shown a typical polacanthine defence, which Kirkland understood to have consisted of a combination of passive protection offered by the vertical spikes and active protection by hitting a predator with the horizontal spikes of the flexible tail. The armour would also have served intraspecific antagonistic behaviour, i. e. fighting between males. The vertical spikes could have intimidated rivals and animals could have determined who was the strongest by ramming their heads together. Kirkland proposed that the typical ankylosaurid down turned head, made possible by a more ventrally directed occipital condyle compared to nodosaurids, and an increased loosening of the rear skull elements to absorb shocks, were adaptations to this kind of behaviour. Ankylosaurs are often assumed to have been solitary living animals because their short legs seem poorly adapted to the trekking behaviour of herds, but the concentration of Gastonia fossils seems to contradict this.