Hoplitosaurus

Taxobox
name = "Hoplitosaurus"
status = fossil
fossil_range = Early Cretaceous
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Ornithischia
subordo = Thyreophora
infraordo = Ankylosauria
familia = Ankylosauridae
subfamilia = Polacanthinae
genus = "Hoplitosaurus"
genus_authority = Lucas, 1901
species = "H. marshi"
species_authority = Lucas, 1902
binomial = "Hoplitosaurus marshi"
binomial_authority = Lucas, 1902

"Hoplitosaurus" (meaning "Hoplite lizard") was a genus of armored dinosaur related to "Polacanthus". It was named from a partial skeleton found in the ?Barremian-age Lower Cretaceous Lakota Formation of Custer County, South Dakota. It is an obscure genus which has been subject to some misinterpretation of its damaged remains. Although there was a push to synonymize it with "Polacanthus" in the late 1980s-early 1990s, "Hoplitosaurus" has been accepted as a valid albeit poorly-known genus in more recent reviews.

History and Taxonomy

The holotype specimen, USNM 4752, was discovered in 1898 by N. H. Darton, near Buffalo Gap Station, and consisted of ribs, caudal vertebrae, part of a right scapulacoracoid, parts of both humeri, a right femur, and a variety of armor (including tall spines).Lucas, F.A. (1901). A new dinosaur, "Stegosaurus marshi", from the Lower Cretaceous of South Dakota. "Proceedings of the United States National Museum" 23(1224):591-592.] Gilmore, C.W. (1914). Osteology of the armored Dinosauria in the United States National Museum, with special reference to the genus "Stegosaurus". "United States National Museum Bulletin" 89:1-136.] Frederick Lucas described it briefly in 1901 as a new species of "Stegosaurus", but soon gave the material its own genus.Lucas, F.A. (1902). Paleontological notes. The generic name "Omosaurus". A new generic name for "Stegosaurus marshi". "Science", new series 16(402):435.] Charles W. Gilmore fully described the material in 1914.

William T. BlowsBlows, W.T. (1987). The armoured dinosaur "Polacanthus foxi" from the Lower Cretaceous of the Isle of Wight. "Palaeontology" 30(3):557-580.] and Javier Pereda-SuberbiolaPereda-Suberbiola, J. (1991). Nouvelle évidence d'une connexion terrestre entre Europe et Amérique du Nord au Crétacé inférior: "Hoplitosaurus" synonyme de "Polacanthus" (Ornithischia: Ankylosauria). "C.R. Academie Science, Paris" 313:971-976. [French] ] Pereda-Suberbiola, J. (1994). "Polacanthus" (Ornithischia, Ankylosauria), a transatlantic armoured dinosaur from the Early Cretaceous of Europe and North America. "Palaeontographica Abteilung" A 232(4-6):133-159.] both considered the genus to be the same as "Polacanthus", creating the new combination "Polacanthus marshii", but this has since been rejected.Carpenter, K., and Kirkland, J.I. (1998). Review of Lower and middle Cretaceous ankylosaurs from North America. In: Lucas, S.G., Kirkland, J.I., and Estep, J.W. (eds.). "Lower and Middle Cretaceous Terrestrial Ecosystems". "New Mexico Museum of Natural History and Science Bulletin" 14:249-270.] Ken Carpenter and James Kirkland noted that many of the resemblances between the two were more widely distributed among ankylosaurs than previously thought, or were based on damage to the bones, such as some femoral characters.

However, its similarity to "Polacanthus" has been noted since Lucas first published on it in 1901, the two being most similar in armor, although "Hoplitosaurus" lacks the sacral shield of armor found in "Polacanthus". Today, both are considered to be polacanthine or polacanthid ankylosaurs,Carpenter, K. (2001). Phylogenetic analysis of the Ankylosauria. In: Carpenter, K. (ed.). "The Armored Dinosaurs". Indiana University Press:Bloomington, 455-483. ISBN 0-253-33964-2] depending on classification preference (see for example [http://tolweb.org/Polacanthidae/15774 ] ), or ankylosaurians of uncertain relationships.Vickaryous, M.K., Maryańska, T., and Weishampel, D.B. (2004). Ankylosauria. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). "The Dinosauria" (second edition). University of California Press:Berkeley, 363-392. ISBN 0-520-24209-2]

One point of similarity that was found to be spurious was the possession of a tail club. In "Polacanthus", this turned out to be a misinterpretation of caudal vertebrae, ossified tendons, and armor. (It is not clear what the report in "Hoplitosaurus" was based on).

Paleobiology

Gilmore described the animal as being about 1.2 m (4 ft) tall at the hips. It would have been a quadrupedal herbivore, eating low to the ground; armor was its main defense.

Blows (2001) reconsidered the armor in light of new data on polacanthine dinosaurs, and found it to fall into the following categories:Blows, W.T. (2001). Dermal armor of the polacanthine dinosaurs. In: Carpenter, K. (ed.). "The Armored Dinosaurs". Indiana University Press:Bloomington, 363-385. ISBN 0-253-33964-2]
*Pectoral spines
*Presacral spines
*Splates (spine+plate) from the sacral region
*Tall, asymmetric, hollow-based caudal plates
*Small to large solid-based, ridged ossicles (filling spaces)

References

External links

* [http://tolweb.org/Polacanthidae/15774 Polacanthidae at Tree of Life]