The holotype was discovered in 1995 at the Bone Cabin Quarry West locality, in Albany County, Wyoming in exposures of the Upper Jurassic (Kimmeridgian to Tithonian stages) Morrison Formation.

A mounted skeletal reconstruction of Gargoyleosaurus parkpinorum can be seen at the Denver Museum of Nature and Science and, alongside a couple skeletons of baby Stegosaurus, has been on display there since around 2002.

[3][4][5] Much of the skull and skeleton has been recovered, and the taxon displays cranial sculpturing, including pronounced deltoid quadratojugal and squamosal bosses.

The taxon is further characterized by a narrow rostrum (in dorsal view), the presence of seven conical teeth in each premaxilla, an incomplete osseous nasal septum, a linearly arranged nasal cavity, the absence of an osseus secondary palate, and, as regards osteoderms, two sets of co-ossified cervical plates and a number of elongate conical spines.

Below is a reproduced phylogenetic analysis from Soto-Acuña et al. (2021):[6] Scelidosaurus Stegosauria Kunbarrasaurus Antarctopelta Stegouros Cedarpelta Dongyangopelta Gargoyleosaurus Gastonia Hylaeosaurus Mymoorapelta Panoplosaurus Peloroplites Polacanthus Hoplitosaurus Sauroplites Taohelong Nodosaurinae Aletopelta Chuanqilong Liaoningosaurus Gobisaurus Shamosaurus Ankylosaurinae