Bravoceratops
| Bravoceratops Temporal range: Late Cretaceous, 70 Ma | |
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| Restoration | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | †Ornithischia |
| Family: | †Ceratopsidae |
| Subfamily: | †Chasmosaurinae |
| Genus: | †Bravoceratops Wick & Lehman, 2013 |
| Type species | |
| †Bravoceratops polyphemus Wick & Lehman, 2013 | |
Bravoceratops is an extinct genus of large chasmosaurine ceratopsid dinosaur that lived approximately 70 million years ago, and is known from the Late Cretaceous Javelina Formation in what is now Texas, United States. Bravoceratops was a relatively large and heavily built, quadrupedal ground-dwelling herbivore. This discovery is significant paleontologically because ceratopsian dinosaur remains occur only rarely in the Javelina Formation, and Bravoceratops provides useful temporal and paleobiogeographic data to researchers about the proliferation of chasmosaurines from Edmontonian to Lancian time during the Late Cretaceous.
Etymology
The genus name Bravoceratops, means "wild horn-face", and is derived from the Mexican name for the Rio Grande, "Rio Bravo del Norte" (wild river of the north), and the Greek words "keras" (κέρας) meaning "horn" and "ops" (ὤψ) referring to the "face"[1] The specific name polyphemus, refers to the giant cyclops Polyphemus confronted by Odysseus in the Greek epic poem, The Odyssey. Bravoceratops was described and named by Steven L. Wick and Thomas M. Lehman in 2013 and the type species is Bravoceratops polyphemus.
Description
Bravoceratops is known from the holotype specimen TMM 46015-1, which consists of a fragmentary skull in good preservation providing its adequate diagnostic data. Bravoceratops shows a distinctive combination of characters not seen in any previously described chasmosaurine. Two autapomorphies (unique derived traits) were established. Firstly, the median parietal bar, the bone bar between the frill openings, the parietal fenestrae, at mid-length splays out to the rear like a fan and its rear edge is not notched or embayed. Secondly, this rear end of the parietal carries a low epiparietal (a triangular skin ossification) on its midline margin while the upper surface of the bar is at the midline, at the level of the rear bars, hollowed out by a symmetrical depression. It is this hollow in the form of an inverted tear that occasioned the specific name as it resembled the single eye of a cyclops. The authors assumed it formed the base of a horn-like epiparietal. This would imply that a second midline epiparietal, lost in the fossil, would in life have been present on the upper (anterior) frill surface just below the midline marginal epiparietal. This second epiparietal might have been formed as a low boss or spike similar to the pair of epiparietals on the median parietal bar of Anchiceratops or the spike on the midline parietal bar of Pachyrhinosaurus lakustai.
Bravoceratops was among the largest chasmosaurines. The size of its occipital condyle is comparable to that of other very large chasmosaurines such as Torosaurus and Triceratops. It has a distinctive narrow snout, a long frill (squamosal and parietal bone) with large elongated openings, long, robust epijugal "horns", long, brow horns, as well as a bifurcated quadratojugal-squamosal contact.[2] The bones comprising portions of the braincase were also discovered. The skull belonged to an adult individual. This is supported by the observation that the component elements of the skull exhibit complete sutural fusion, the fossils exhibit a pitted bone texture, and are deeply vascularized.
Classification
Bravoceratops was in 2013 assigned to the Chasmosaurinae. It is an "intermediate" form of chasmosaurine as inferred from a combination of primitive and derived morphological traits, its stratigraphic position, and its position in a phylogenetic analysis performed by its describers. The analysis suggested that Bravoceratops may be the sister species of Coahuilaceratops however this relationship is not well supported as there are very few elements available for a direct comparison of these two species. The morphology of the parietal bone distinguishes this genus from the more basal Anchiceratops and Pentaceratops. The presence of a midline epiparietal on the distal margin of the frill, and bifurcated quadratojugal–squamosal joint in the skull, are considered derived features. The latter morphologies suggests that Bravoceratops may be closely related to a clade formed by the most advanced chasmosaurines, Torosaurus and Triceratops.[2][3] The presence of intermediate similar skull characteristics (e.g. midline epiparietals, large fenestrated frill, orientation of horncores, large epijugals) among coeval northern and southern chasmosaurines, according to Wick and Lehman, suggests that chasmosaurine evolution may have progressed in a manner similar to that of a metapopulation and does not support the purported existence of truly isolated, "endemic" populations of chasmosaurines in North America.[2]
The below cladogram follows Longrich (2015), who named a new species of Pentaceratops, and included nearly all species of chasmosaurine.[4]
| Chasmosaurinae |
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Paleoecology
Provenance and occurrence
The type specimen of Bravoceratops polyphemus TMM 46015-1 was recovered at the "Hippiewalk" locality from the lowermost part of the Javelina Formation, in Big Bend National Park, Texas. The specimen was collected in sandy conglomerate sediment that was deposited during the early Maastrichtian stage of the Cretaceous period, approximately 70 million years old.[5] This specimen is housed in the collection of the Texas Memorial Museum, Austin, Texas.
Fauna and habitat
Studies suggest that the paleoenvironment of this section of the Javelina Formation was a fluvial flood-plain which was several hundred kilometers inland from the nearest shoreline.[6]
Taphonomy
The various parts of the holotype skull were completely disarticulated and scattered across an area of approximately ten square meters prior to fossilization. Many of the more robust remains, such as the horns, exhibit weathering and erosion. This circumstance suggests that the skull remained exposed for a time before burial. Although the recovered portions of the skull showed signs of fluvial transport, they were otherwise found in excellent condition.
See also
References
- ↑ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4.
- 1 2 3 Wick, S. L.; Lehman, T. M. (2013). "A new ceratopsian dinosaur from the Javelina Formation (Maastrichtian) of West Texas and implications for chasmosaurine phylogeny". Naturwissenschaften. 100 (7): 667–82. Bibcode:2013NW....100..667W. doi:10.1007/s00114-013-1063-0. PMID 23728202.
- ↑ Farke, A.A. (2007) "Cranial osteology and phylogenetic relationships of the chasmosaurine ceratopsid Torosaurus latus". In: Carpenter, K. (ed) Horns and beaks: Ceratopsian and Ornithopod dinosaurs. Indiana University Press, Bloomington, pp 235–257
- ↑ Longrich, N. R. (2014). "The horned dinosaurs Pentaceratops and Kosmoceratops from the upper Campanian of Alberta and implications for dinosaur biogeography". Cretaceous Research. 51: 292–308. doi:10.1016/j.cretres.2014.06.011.
- ↑ Woodward, H. N. (2005). Bone histology of the sauropod dinosaur Alamosaurus sanjuanensis from the Javelina Formation, Big Bend National Park, Texas.
- ↑ Lehman, T. M., and Busbey, A. B., (2007). Big Bend Field Trip Guidebook. Society of Vertebrate Paleontology, 67th Annual Meeting, Field Trip Guidebook, 69 p.
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