Scientific Findings
The discovery of the Stegosaurus stenops at the Small Quarry of Garden Park was a very significant scientific discovery. As it had the skull, the plates, and the tail still intact; it was an astronomically rare find. One that will probably never be surpassed for the species of Stegosaurus stenops, or stegosaurs in general for that matter. Due to the intact, articulated skeleton of the Small Quarry Stegosaurus stenops, confirmations could be made for the long debated issues about the orientation of the plates and the tail spikes.
The three dimensional perspective of the skeleton showed that the plates were arranged in an upright position, running along either side of the spine in alternating fashion. Another anatomical insight the skeleton provided was the flexibility of the tail. Due to the attachment and the position of the plates, the tail only had a limited amount of movement. This points to Stegosaurus stenops having a very stiff tail and conflicts with the proposed hypothesis of Robert Bakker. His hypothesis was that stegosaurs were able to stand on their hind legs while using their tail as support to allow them to graze from higher vegetation (Bakker, 1986). The spikes on the end of the tail did not point upwards, like previously thought, but to the sides and slightly tilted back. In addition to the plates and spikes was the presence of the throat armor that was arranged in a rosette pattern around the throat. This was the first time that the ossicles were found lumped together (Carpenter, 1997). Othniel Marsh had described finding ossicles (throat armor) with a specimen of Stegosaurus stenops, but they were scattered all across the skeleton. Later, while reviewing Marsh’s notes, Gilmore had suspected that they could have been placed on multiple places on the body (Gilmore, 1914). With the discovery of the Small Stegosaurus Stenops it is now known that the ossicles were only present in the skin around the throat (Carpenter, 1998a).
The display above, from the Denver Museum of Nature and Science, shows the most accurate understanding of Stegosaurus neck armour, alternating plates, and tail spike orientation based on the findings from the Small Quarry.
Aside from the skeleton, the rock that surrounds it also provided some information about the climate of the Garden Park area when the Stegosaurus was alive. The Stegosaurus was found in a lacustrine (lake sediment derived) mudstone that was mixed with pieces of fusain (charcoal), indicating that at least one forest fire had swept through the area at the time of deposition. This is likely evidence that the area was dry enough to be ignited by lightning, much like a drought ridden area in the modern world. Another piece of evidence pointing towards drought conditions is the intact nature of the skeleton. As in areas of severe drought today, scavengers are unable keep pace and pick apart all the bodies of deceased animals due the shear amount of animals affected by the drought. Drought, however, was not the main cause of death for this stegosaur. It had already been weakened by an infection in one of its tail spikes that had been injured. The drought conditions likely deteriorated the animal’s condition further and eventually caused it to perish (Carpenter, 1998a).
Apart from the Stegosaurus stenops, many other taxons were found in the Small Quarry. Other members of Ornithischia include a bone from Dryosaurus altus and ?Mymoorapelta sp. (sp. is used when the genus is known, but the species is undetermined). From saurischia, a theropod bone was also identified from the quarry belonging to the ceratosaur Elaphrosaurus sp. (Carpenter, 1998a) and a few disarticulated vertebrae of Apatosaurus excelsus were also found in the Small Quarry (Carpenter, 1998a; Carpenter, 1998b). Fossils of non-dinosaurian reptiles were also found within the quarry. Shell fragments from the rare turtle Dinochelys whitei and more common Glyptops plicatus, a partial maxillary and dentary of a lizard (Carpenter, 1998b) and the bones of a large pterodactyloid with an estimated 8 foot (2.5 m) wingspan known as Kepodactylus grandis were found. The lizard and the pterodactyl fossils are significant because lizard fossils are very rare in the Morrison and the Kepodactylus fossils indicate the first occurrence of pterodactyloids in the Morrison (Carpenter, 1998b; Harris et al. 1996). Another rare find for the Small Quarry was the inch long jawbone with teeth of the omnivorous mammal Docodon sp. Finally fossils from the boney fish, Ceratodus guentheri and an indeterminate genus and species from the family Actinopterygii were found (Carpenter, 1998b). The assemblage of fossils found at the Small Quarry site represents a diverse fauna and bring life to the lacustrine derived mudstone.
