Gargoyleosaurus
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| Gargoyleosaurus parkpinorum Carpenter et al. 1998 |
Gargoyleosaurus parkpinorum ("gargoyle lizard") is both the smallest and the earliest well-known ankylosaur. Its skull measures only 29 cm in length, and its total body length is an estimated three to four meters. It may have weighed as much as a tonne. The holotype was discovered at the Bone Cabin Quarry West locality, in Albany County, Wyoming in exposures of the Upper Jurassic (Kimmeridgian to Tithonian stages) Morrison Formation.
The next earliest known ankylosaur is Minmi paravertebrata from the Aptian stage in Queensland, Australia. A mounted skeletal reconstruction of Gargoyleosaurus parkpinorum can be seen at the Denver Museum of Nature and Science.
[edit] Holotype
The holotype specimen of Gargoyleosaurus parkpinorum was collected by Western Paleontology Labs in 1996 and is currently held in the collections of the Denver Museum of Nature and Science, Denver, Colorado. Besides the holotype, two other partial skeletons are known (although not yet desribed) The holoype consists of most of the skull and a partial postcranial skeleton. The specimen was originally described as Gargoyleosaurus parkpini by Carpenter et al. (1998), then renamed G. parkpinorum by Carpenter et al. 2001, in accordance with ICZN art. 31.1.2A.
[edit] Classification
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 linerarly 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.
Vickaryous et al. (2004) place Gargoyleosaurus parkpinorum within the Family Ankylosauridae of the Ankylosauria and are in agreement with most previous phylogenetic hypotheses, which place the genus as the sister group to all other ankylosaurids (i.e., members of the Ankylosauridae). These studies however, only utilized the skull, whereas many of the distinctive features of the family Polacanthidae are in the postcranial skeleton.
[edit] References
- Carpenter, K., Miles, C. and Cloward, K.. 1998. Skull of a Jurassic ankylosaur (Dinosauria). Nature 393: 782-783.
- Carpenter, K. (ed.) The Armored Dinosaurs. pp. 454-483. Indiana University Press, Bloomington.
- Vickaryous, Maryanska, and Weishampel 2004. Chapter Seventeen: Ankylosauria. in The Dinosauria (2nd edition), Weishampel, D. B., Dodson, P., and Osmólska, H., editors. University of California Press.
