Nasutoceratops
| Nasutoceratops | ||||||||||||
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Reconstruction of the skull of Nasutoceratops titusi at the Utah Museum of Natural History (UMNH) in Salt Lake City. |
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| Upper campanium | ||||||||||||
| 75.5 to 76.0 million years | ||||||||||||
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| Nasutoceratops | ||||||||||||
| Sampson et al., 2013 | ||||||||||||
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Nasutoceratops is a genus of ceratopsid dinosaurs from the Centrosaurinae group . The only known species of the so far monotypical genus is Nasutoceratops titusi from the upper Campanium (approx. 75.5 to 76 million years ago) of Utah (USA).
Etymology and history of research
The generic name is made up of the Latin " nasutus " "big-nosed" and the ending " -ceratops ", which is often used by representatives of the Ceratopsidae , from ancient Greek κέρας kéras "horn" and ὤψ ōps "eye", "face". The additional species " titusi " honors Alan Titus , paleontologist at the Grand Staircase-Escalante National Monument , for his support during the field work. The species name can roughly be translated as "Titus' bigenose horn face".
The fossil remains of Nasutoceratops titusi were discovered in 2006 during an excavation campaign as part of the “Kaiparowits Basin Project” in the Kaiparowits Formation within the Grand Staircase-Escalante National Monument in southern Utah.
The genus and type species were already described by Lund in 2010 as part of his master's thesis at the University of Utah . However, since Lund's master's thesis was not published, it was not considered an official first description according to the rules of the ICZN (“Nomen ex dissertatione”).
The first valid description based on the cranial skeleton was not until 2013 by Sampson et al. with Lund as co-author. A new description of the type species, which also included features of the postcranial skeleton, was published in 2016 by Lund et al. subsequently delivered.
In the same year 2016, Nasutoceratops was discovered by Ryan et al. together with Avaceratops in the clade of Nasutoceratopsini asked.
Fossil record
The holotype UMNH VP 16800 comprises an almost complete, approx. 1.5 m long skull, the first cervical vertebrae fused to form the "syncervical" , as with all representatives of the coronosauria , three fragmentarily preserved vertebrae, both front legs including shoulder blades and the left coracoid of a sub adult individual. In addition to the holotype, there is further fossil evidence:
- UMNH VP 19466: Parts of the cranial skeleton of an adult animal
- UMNH VP 19469: A single, isolated scale leg
Taken together, about 80% of the diagnostically significant facial skull are known, and about 10% of the postcranial skeleton.
All known remains of Nasutoceratops come from the middle unit of the Kaiparowits Formation . The holotype and the reference material come from different sites and from slightly different stratigraphic levels within the middle Kaiparowits Formation. Nasutoceratops is the second representative of the Centrosaurinae from the area of the Grand Staircase-Escalante National Monument after Diabloceratops ( Wahweap Formation , Lower to Middle Campanium) .
Characteristics of the genus
(Abbreviations used in the description refer to the illustration on the right)
Nasutoceratops differs from all other representatives of the Centrosaurinae in particular in the shape of the skull. Characteristics typical of the genus ( autapomorphies ) are:
- The nasal region is greatly enlarged and takes up about 75% of the pre-orbital (in front of the eye sockets) facial skull.
- The nasal bone (n) has clearly formed cavities (np) internally, behind the attachment (nh) of the nasal horn.
- The contact area between the premaxilla (pm) and maxilla (m) is unusually elongated.
- The inside of the maxilla (m) has a forward-facing, flange-like extension with two socket-like indentations that match corresponding counterparts on the premaxilla (pm); the extension is involved in the construction of the palatum durum .
- The long over-eye horns (poh) are directed laterally forward and twisted with the tips inwards and upwards.
In addition, Nasutoceratops shows a number of characteristics that, taken individually, are already known from other representatives of the Centrosaurinae, but are so far unique in combination:
- The bone attachment of the nasal horn (nh) is narrow, elongated and relatively low.
- The scaly bone ( sq) has a clearly pronounced bone back (sqr) dorsolaterally
- The shape of the neck shield, made up of the parietal (p) and scaled bones (sq), can be described as approximately circular or approximately rectangular.
- The epiparietals (p 0 - p 7 ) and episquamosalia are simple and crescent-shaped.
- There is an epiparietal (p 0 ) located centrally on the outside of the neck shield .
All other established skeletal features correspond to those of a typical representative of the Centrosaurinae and prove that they belong to this group. Nasutoceratops titusi probably reached a length of 4.5 m with a body mass of about 1.5 tons.
Integument
In connection with the left foreleg of the holotype (UMNH VP 16800), the imprints of 3 pieces of skin ("A", "B" and "C") were discovered when the find was uncovered:
Imprint "A" consists of a collection of dense, irregularly arranged, oval to approximately circular tubercles with diameters between 2 mm and 8 mm. Imprint “A” was found close to and posterior to the humeral head .
Imprint “B” shows a similar structure, but with slightly larger tubercles with diameters between 5 mm and 11 mm. Imprint “B” was also related to the left humerus, but was closer to the scapula .
Imprint "C" differs significantly from the other two skin impressions and shows a regular pattern of raised hexagons with a diameter between 8 mm and 11 mm, each surrounded by smaller, triangular notches. This imprint was also found in the vicinity of the left humeral head, but somewhat further away from the bone as imprint “A”.
The imprints "A" and "B" resemble skin imprints that are already known from other representatives of the Ceratopsia , such as Psittacosaurus , Chasmosaurus or Centrosaurus , although the large, circular scales that are embedded in Chasmosaurus and Centrosaurus between the irregularly arranged, smaller tubercles , could not yet be detected in Nasutoceratops . However, the regular patterns of type "C" do not resemble anything that would have been known before.
Age classification of the finds
The clastic sediments of the Kaiparowits Formation in Utah are interspersed with several bentonite horizons of volcanic origin. The Sanidines, some of which are still preserved in these bentonite horizons, are ideally suited for geochronological dating using the Ar-Ar method .
An age of 75.97 ± 0.18 Ma could thus be assigned to a bentonite horizon (KP-07) lying in the layers of the find . Two other bentonite horizons (KBC-109 and KBC-144) in the hanging wall, however, show identical ages of 75.51 ± 0.15 Ma. The Nasutoceratops fossils accordingly have an age between these two time stamps, which corresponds to a relatively short period of time within the Upper Campanian .
The sediments of the Kaiparowits Formation were therefore approximately at the same time as z. B. the upper Judith River Formation (not to be confused with the parent Judith River Group ) or the Two Medicine Formation in Montana and the Dinosaur Park Formation in Alberta , all of which have also provided rich dinosaur finds.
Systematics and phylogeny
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| Systematic position of Nasutoceratops according to Evans & Ryan, 2015; expanded from Ryan et al., 2016 |
Nasutoceratops is a basic representative of the Centrosaurinae .
Phylogenetic analyzes indicate that Nasutoceratops is more closely related to Avaceratops , a representative of the Centrosaurinae from the Judith River Formation in the north-west of the USA, which lives almost at the same time , than to the somewhat older, but in the same region, Diabloceratops .
Nasutoceratops , Avaceratops , a cranial skeleton (CMN 8804) from the Oldman Formation of Alberta that cannot be precisely determined and only partially preserved, as well as a still undescribed find from Malta (Montana) ("New Malta Taxon"; GPDM 63) were included in the clade of the Nasutoceratopsini summarized. The Nasutoceratopsini are defined as all taxa that are more closely related to Nasutoceratops titusi than to Centrosaurus apertus and are compared to the Centrosaurini or the Pachyrhinosaurini .
Paleecology
Nasutoceratops was, like all representatives of the Ceratopsidae, a pure herbivore. The biological function of the cavities within the nasal bone is unclear. Theoretically conceivable are connections with the moisture exchange through the breath, a function for shock absorption, an organ for vocal expression, simple weight reduction of the oversized nasal region or a combination of several of these reasons.
The North American continent was partially covered by a shallow epicontinental sea during the Middle and Upper Cretaceous Period . This Western Interior Seaway divided the continent into two land masses; the western Laramidia and the eastern Appalachia . The latter was temporarily split into a northern and a southern part by another inlet (Hudson Seaway). The sediments of the Kaiparowits Formation were deposited as erosion material of the young Rocky Mountains on the east coast of Laramidia, i.e. in the direction of the Western Interior Seaway.
The Kaiparowits Formation was deposited in the area of anastomosing or meandering rivers or in the area of their alluvial plains . Indications of a tidal influence in the deposit area, for example in the vicinity of an estuary ("Utah Embayment"), at least partially overlap with the temporal appearance of Nasutoceratops .
The numerous plant fossils from the Kaiparowits Formation provide indications of the paleoclimatological conditions in the habitat of Nasutoceratops . The reference "DMNH Loc. 3642 “is only a few kilometers away from the Nasutoceratops discovery sites in an analogous stratigraphic position within the Kaiparowits Formation and can be considered to coincide with the known occurrence of Nasutoceratops . The extremely species-rich palaeoflora (87 proven morphotypes ) is dominated by dicotyledons (~ 70% of all morphotypes and ~ 83% of all plant fossils in total). In addition, there are also monocots (including at least two representatives of the palm-like species ), conifers from the cypress family , cycads , ferns and horsetails . The flora of the Kaiparowits Formation indicates a subtropical, humid climate with an annual mean temperature of around 20 ° C and an average rainfall of around 1800 mm per year.
Nasutoceratops shared this habitat, among others, with two other Ceratopsiden , utahceratops and Kosmoceratops , both, unlike Nasutoceratops , representatives of Chasmosaurinae , and with the Hadrosauriern gryposaurus monumentensis and Parasaurolophus cyrtocristatus , in addition there are unnamed representative of ankylosauria , the tyrannosaur teratophoneus , Coelurosaurier of the genus Ornithomimus and also unspecified representatives of the Caenagnathidae within the group of Oviraptosauria . Numerous finds of amphibians, scaly reptiles, crocodiles and turtles and at least one bird from the group of enantiornithes as well as mammals from the groups of Multituberculata , Marsupialia and Insectivora complete the picture of the terrestrial vertebrate fauna.
Individual evidence
- ↑ a b c d e f g h i j k l m S. D. Sampson, EK Lund, MA Loewen, AA Farke & KE Clayton: A remarkable short-snouted horned dinosaur from the Late Cretaceous (late Campanian) of southern Laramidia In: Proceedings of the Royal Society B , 280: 20131186 doi: 10.1098 / rspb.2013.1186
- ↑ a b c d e f g h i j k l m n E. K. Lund, SD Sampson & MA Loewen: Nasutoceratops titusi (Ornithischia, Ceratopsidae), a basal centrosaurine ceratopsid from the Kaiparowits Formation, southern Utah . In: Journal of Vertebrate Paleontology , 2016. doi: 10.1080 / 02724634.2015.1071265
- ^ A b c E.K. Lund: Nasutoceratops titusi, a new Basal Centrosaurine Dinosaur (Ornithischia: Ceratopsidae) from the Upper Cretaceous Kaiparowits Formation, Southern Utah. unpubl. Master thesis, 161 pages, University of Utah, 2010 (pdf)
- ↑ a b c M. J. Ryan, R. Holmes, J. Mallon, M. Loewen & DC Evans: A basal ceratopsid (Centrosaurinae: Nasutoceratopsini) from the Oldman Formation (Campanian) of Alberta, Canada In: Canadian Journal of Earth Sciences , Vol . 54, pp. 1–14, 2017. doi: 10.1139 / cjes-2016-0110
- ↑ GS Paul : The Princeton Field Guide to Dinosaurs: 2nd Edition , 360 pp., Princeton University Press, 2016. ISBN 978-0-691-16766-4 (reading sample)
- ^ A b E. M. Roberts, SD Sampson, AL Deino, SA Bowring & R. Buchwaldt: The Kaiparowits Formation: A Remarkable Record of Late Cretaceous Terrestrial Environments, Ecosystems, and Evolution in Western North America. In: AL Titus & MA Loewen (Eds.): At the Top of the Grand Staircase: The Late Cretaceous of Southern Utah. Pp. 85–106, Indiana University Press, Bloomington, Indiana, 2013. (digitized)
- ↑ DC Evans & MJ Ryan: Cranial Anatomy of Wendiceratops pinhornensis gen. Et sp. nov., a Centrosaurine Ceratopsid (Dinosauria: Ornithischia) from the Oldman Formation (Campanian), Alberta, Canada, and the Evolution of Ceratopsid Nasal Ornamentation. PLOS ONE 10 (7): e0130007. doi: 10.1371 / journal.pone.0130007
- ^ EM Roberts, L. Tapanila & B. Mijal: Taphonomy and Sedimentology of Storm-Generated Continental Shell Beds: A Case Example from the Cretaceous Western Interior Basin. In: The Journal of Geology , Vol. 116, pp. 462–479, 2008 (available)
- ^ A b I. M. Miller, KR Johnson, DE Kline, DJ Nichols & RS Barclay: A Late Campanian Flora from the Kaiparowits Formation, Southern Utah, and a Brief Overview of the Widely Sampled but Little-Known Campanian Vegetation of the Western Interior of North America . In: AL Titus & MA Loewen (Eds.): At the Top of the Grand Staircase: The Late Cretaceous of Southern Utah. Pp. 107-131, Indiana University Press, Bloomington, Indiana, 2013. (digitized version)
- ↑ DW Fowler: Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America. In: PLOS ONE , 12, (11): e0188426. doi: 10.1371 / journal.pone.0188426
- ↑ AL Titus, JG Eaton & J. Sertich: Late Cretaceous Stratigraphy and Vertebrate Faunas of the Markagunt, Paunsaugunt, and Kaiparowits Plateaus, Southern Utah. In: Geology of the Intermountain West , Vol. 3, pp. 229–291, 2016. (pdf) ( Memento of the original from 23 August 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
