Discovery and history
editBison alticornis and Ceratops horridus
edit
The first fossil discoveries of Triceratops were not recognized to belong to dinosaurs when they were first described by American paleontologist Othniel Charles Marsh in 1889. Discoveries throughout the late 1860s to 1880s included partial horns, teeth, or fragments that were sent to Marsh at the Yale Peabody Museum from the Denver Formation in and around what would become the city of Denver, Colorado, including a partial skull showing two horns found in the spring of 1887 by teacher and geologist George L. Cannon Jr. This partial skull was collected in multiple pieces over several years by Cannon, and Whitman Cross and George Eldridge of the United States Geological Survey before being repaired and accessioned at the YPM as specimen 1871E, with other bones collected alongside it accessioned as YPM 1871A-D.[1] Marsh believed that YPM 1871E had come from Pliocene-aged deposits along the banks of Green Mountain Creek near Denver, and so when he described it in 1887 he noted the similarities to American bovines and named it as the new species Bison alticornis, one of the largest bison known at the time.[2]
Surveying of the Laramie Formation of Dakota Territory and Montana in 1887 led to additional collection of large horns and other elements, this time from definitively Cretaceous beds. Marsh described the fossils in 1888 as the new genus Ceratops of the new stegosaur family Ceratopsidae, and designating the horns, found by John Bell Hatcher in Montana, as the type.[3] The following year he described further specimens from the "Laramie" of Wyoming as the new species Ceratops horridus, and noted that the horns are nearly indistinguishable from those of Bovidae with the possibility that Bison alticornis may later prove to belong to Ceratops.[4] Such a reclassification was finalized by Marsh later in 1889 with the reidentification of the provenance of the new combination Ceratops alticornis as the Cretaceous Denver Formation rather than the Pliocene beds as he had initially believed. At the same time, he elevated Ceratops horridus to its own new genus Triceratops, and described the new species' T. flabellatus and T. galeus.[5] C. alticornis would be moved into the genus Triceratops as T. alticornis in 1907 by Hatcher based on the length and form of the horns,[6] and the horns themselves later became part of the collection of the National Museum of Natural History as specimen USNM 4739.[1]
The holotype of Triceratops, YPM 1820, was collected by Hatcher from a canyon 50 km (31 mi) north of Lusk, Wyoming, after it was brought to his attention by the rancher Charles Guernsey. Ranch foreman Edmund Wilson had come across a large head partially exposed halfway up the side of the dry gulch during a cattle roundup, and tried to remove it with a lasso looped around a horn. This failed, with the horn breaking off and the remainder of the skull rolling to the bottom of the gulch, but the horn was collected and given to Guernsey, who sent it to Marsh after it was viewed by Hatcher. Marsh immediately sent Hatcher back to collect the skull for the YPM, which was in a sandstone concretion weighing nearly 500 kg (1,100 lb). Hatcher continued to collect fossils from this area in the "Ceratops beds", now known as the Lance Formation, until 1892. After further preparation of YPM 1820 showed that it had two horns over the eyes and one on the snout, Marsh moved it to the new genus as Triceratops horridus for its "three-horned face, projecting or standing up".[7]
Additional Triceratops species
editTriceratops galeus, named in the same study that founded the genus, was described by Marsh on the basis of a nasal horn and several other remains from the Laramie Formation of Colorado.[5] The specimen, USNM 2410, was collected by G. H. Eldridge of the USGS from near Brighton, Colorado, as a collection of numerous fragments from across over a 1.6 km (1 mi) of the Denver beds in the region. This lack of association of elements means T. galeus has to be restricted to just the nasal horn, which could not be distinguished from other Triceratops or Torosaurus by Hatcher or palaeontologist Richard Swann Lull in 1907, who recommended abandoning the name.[6]
References
edit- 1 2 Carpenter, K. (2006). "Bison" alticornis and O.C. Marsh's early views on ceratopsians". In Carpenter, K. (ed.). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington: Indiana University Press. pp. 349–364. ISBN 978-0-253-34817-3.
- ↑ Marsh, O.C. (1887). "Notice of new fossil mammals". American Journal of Science, Third Series. 34 (202): 323–331. doi:10.2475/ajs.s3-34.202.323.
- ↑ Marsh, O.C. (1888). "A New Family of Homed Dinosauria, from the Cretaceous". American Journal of Science, Third Series. 36 (216): 477–478. doi:10.2475/ajs.s3-36.216.477.
- ↑ Marsh, O.C. (1889). "Notice of New American Dinosauria". American Journal of Science, Third Series. 37 (220): 331–336. doi:10.2475/ajs.s3-37.220.331.
- 1 2 Marsh, O.C. (1889). "Notice of Gigantic Homed Dinosauria from the Cretaceous". American Journal of Science, Third Series. 38 (224): 173–175. doi:10.2475/ajs.s3-38.224.173.
- 1 2 Hatcher, J.B.; Marsh, O.C.; Lull, R.S. (1907). "The Ceratopsia". Monographs of the United States Geological Survey. 49 (310): 1–300.
- ↑ Dodson, P. (1996). "Three-Horned Face". The Horned Dinosaurs: A Natural History. Princeton: Princeton University Press. pp. 56–88. ISBN 0-691-02882-6.