Dysganus

''Dysganus'' (dis-GANN-us) (meaning "rough enamel") is a dubious genus of ceratopsian dinosaur from the Campanian stage of the Late Cretaceous. The fossil teeth referred to ''Dysganus'' were first collected by Charles Sternberg from the Cretaceous Judith River Formation of Montana and later described by Edward Drinker Cope.E. D. Cope. 1876. Descriptions of some vertebrate remains from the Fort Union Beds of Montana. Proceedings of the Academy of Natural Sciences of Philadelphia 28:248-261. All of the species are now seen as dubious Ceratopsians, though referred material from tyrannosaurids and hadrosaurids were found in New Mexico.Cope, E. D. (1885). The relations of the Puerco and Laramie deposits. ''American Naturalist'', ''19'', 985-986.Carr, T. D., & Williamson, T. E. (2000). A review of Tyrannosauridae (Dinosauria, Coelurosauria) from New Mexico. ''New Mexico Museum of Natural History and Science Bulletin'', ''17'', 113-145.

Etymology

The generic name ''Dysganus'' is derived from the Greek roots ''dys-'' meaning “bad” and ''-ganos'' for tooth enamel, the full name meaning “rough enamel”. The specific name for the type species, ''D. encaustus,'' means “burnt in” based on the concave tooth tip. The other species named by Cope have several meanings. ''D. bicarinatus'' means “two keels” after the 2 keels running down the length of the type teeth. ''D. haydenianus'' was named after American paleontologist and biologist Ferdinand V. Hayden. Lastly, ''D. peiganus'' was named after the Peigan Native Americans of Montana, where the type was found.

History and species

''Dysganus'' was first described by American Paleontologist Edward Drinker Cope in 1876 with ''Dysganus encaustus'' as the type species based on several fragmentary teeth, believing it was a small herbivorous dinosaur related to ''Cionodon'' and ''Hadrosaurus.'' Cope also named the species ''D. haydenianus, D. bicarinatus,'' and ''D. peiganus'' based on solely fragmentary teeth. The fossils had been collected from the Campanian strata of the Judith River Formation east of the Judith River in Montana by Charles Sternberg and company. The type specimens of each species consist of one to eight teeth, all being detached and likely from different indiviudals. Cope named ''Dysganus'' during the Bone Wars, his competition with Yale paleontologist Othniel Charles Marsh, to collect and describe as many fossil taxa as possible. This competition caused the two to publish small papers on finds that hadn't been properly named or analyzed, contributing to taxonomic issues later on. All of the specimens described by Cope were later sold to the American Museum of Natural History in New York after Cope's death where they remain today. Some of the teeth like those of ''D. peiganus'' were said by Cope to be more similar to those of ''Palaeoscincus'', while others more akin to ''Cionodon'' and ''Trachodon.'' Cope also referred teeth collected by David Baldwin from the Upper Cretaceous of the San Juan Basin in northwestern New Mexico, stating they were similar to those of ''D. encaustus''. These likely were the teeth of hadrosaurids and even tyrannosaurids.In 1907, John Bell Hatcher redescribed the teeth of ''Dysganus'', and found that the genus' teeth were composed of those from Hadrosaurs and Ceratopsids making it a chimera and ''nomen dubium''. William Matthew at the AMNH later designated holotype teeth due to their chimeric and composite nature.

Type:

* ''Dysganus encaustus'' Cope, 1876; Single maxillary tooth, though originally included 5 additional teeth. Dubious at the Ceratopsia level.

Species previously referred to ''Dysganus'':

* ''D. bicarinatus'' Cope, 1876; Single maxillary tooth, originally included 7 others from various areas of the skull. Dubious at the Ceratopsia level.
* ''D. haydenianus'' Cope, 1876; Single maxillary tooth, originally included 2 others and bone shards. Dubious at the Ceratopsia level.
* ''D. peiganus'' Cope, 1876; Single tooth from the anterior dentary. Hypothesized to be ankylosaurian, stegosaurid,Hatcher, J. B. (1907). ''The ceratopsia'' (No. 310). US Government Printing Office. or hypsilophodontid, but it is actually an unworn Ceratopsian tooth.

Classification

Cope originally classified ''Dysganus'' in Trachodontidae, a family of hadrosauroids now considered a junior synonym of the family Hadrosauridae. In 1901, Franz Nopcsa von Felső-Szilvás assigned ''Dysganus'' to the Ceratopsia, either by reading Cope's original descriptions of the genus or by Cope in 1890 indirectly suggesting that ''Dysganus'' was a ceratopsian rather than a "trachodontid". Later in 1907, Hatcher ''et al''. republished Cope's original descriptions of ''Dysganus'' in their entirety and deduced that the holotype of ''D. encaustus'' included teeth of hadrosaurids (then trachodontids), and the teeth of ceratopsids.Coombs Jr, W. P., & Galton, P. M. (1988)
Dysganus, an indeterminate ceratopsian dinosaur.
''Journal of Paleontology'', 818-821. The teeth of ''D. peiganus'' were thought to be from a stegosaurian by Lull and Wright in 1942. However, later analysis by Walter Coombs and Peter Galton demonstrated that all of the teeth were of ceratopsian nature, just from different parts of the mouth and at different stages of erosion.

Paleoecology

All 4 named species are known from the Judith River Formation, the site of expeditions first by Edward Drinker Cope's crews during the early stages of the Bone Wars, including the discoveries of many taxa that he named, though all are now seen as dubious. These include fossils of large, carnivorous tyrannosaurid theropods like ''Aublysodon'' and ''Deinodon'' and the small Dromaeosaur ''Zapsalis.'' As for the herbivorous Ornithischians, like the beaked hadrosaurids ''Trachodon'' and ''Cionodon'' were named. The most common fossils are those of the horned Ceratopsians like ''Monoclonius, Ceratops,'' and ''Pteropelyx.'' Lastly, the armored ankylosaur ''Palaeoscincus'' is known from scattered teeth.

References

{{Taxonbar, from=Q311507

Ceratopsids
Late Cretaceous dinosaurs of North America
Campanian genus first appearances
Campanian genus extinctions
Nomina dubia
Paleontology in Montana
Fossil taxa described in 1876
Taxa named by Edward Drinker Cope
Ornithischian genera