Peloroplites
| Peloroplites Temporal range: Early Cretaceous-Late Cretaceous,
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| Peloroplites skeletal reconstruction on display at the USU Eastern Prehistoric Museum, Price, Utah. | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Thyreophora |
| Clade: | †Ankylosauria |
| Family: | †Nodosauridae |
| Subfamily: | †Polacanthinae |
| Genus: | †Peloroplites Carpenter et al., 2008 |
| Species: | †P. cedrimontanus
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| Binomial name | |
| †Peloroplites cedrimontanus Carpenter et al., 2008
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Peloroplites (meaning “monstrous heavy one”) is a monospecific genus of nodosaurid dinosaur from Utah that lived during the Late Cretaceous (Cenomanian to lower Turonian stage, 98.2 to 93 Ma) in what is now the Mussentuchit Member of the Cedar Mountain Formation.[1] The type and only species, Peloroplites cedrimontanus, is known from a partial skull and postcranial skeleton.[1] It was named in 2008 by Kenneth Carpenter and colleagues.[1] Peloroplites was 6 metres (20 feet) long and weighed 2 tonnes (4,410 lbs), making it one of the largest known nodosaurids, and came from a time when ankylosaurids and nodosaurids were attaining large sizes.[2][1]
Discovery and Naming
In 2001, a skeleton of a large nodosaurid from the Cedar Mountain Formation in Emery County, Utah was mentioned by Burge and Bird in a publication about the faunal composition of the Price River II quarry. More material was obtained and was subsequently described in 2008 by by Kenneth Carpenter, Jeff Bartlett, John Bird and Reese Barrick. The Price River II quarry was previously reported as occurring in the Ruby Ranch Member by Burge and Bird (2001) but was later reported as occurring in the base of the Mussentuchit Member due to the dark, carbonaceous nature of mudstones of the strata. The Price River II quarry has also produced specimens pertaining to four individuals of a new brachiosaurid, an iguanodontid, associated cranial and postcranial material of Cedarpelta, a turtle and a pterosaur. The holotype specimen, CEUM 26331, consists of a partial skull. Additional specimens were assigned to Peloroplites that consist of cervical vertebrae, dorsal vertebrae, synsacrums, caudal vertebrae, chevron, scapula-coracoids, humeri, radii, ulnae, ilia, pubis, ischium, femora, tibiae, fibulae, metacarpals, metatarsal, metapodials, phalanges, unguals, osteoderms and various bone fragments. The holotype and assigned specimens are currently housed at the College of Eastern Utah, Prehistoric Museum, Utah.[1]
The generic name, Peloroplites, is derived from the Greek words “peloros” (monstrous, gigantic) and “hoplites” (heavily armed), and as a subjunctive, a heavily armed soldier. The specific name, cedrimontanus, is derived from the Latin words “cedrus” (Cedar) and “mont-“ (mountain), in reference to the Cedar Mountain Formation.[1]
Description
Size and distinguishing traits
Carpenter et al. (2008) originally gave Peloroplites an estimated length of 5-5.5 metres (16-18 feet).[1] However, Gregory S. Paul in 2016 gave a higher estimate of 6 metres (20 feet) and a weight of 2 tonnes (4,410 lbs).[2]
Carpenter et al. (2008) diagnosed Peloroplites based on the lack of premaxillary teeth, occiput sloping forwards and towards the back, the absence of a prominent lateral temporal notch towards the back as in Sauropelta, small and blunt squamosal horns, paroccipital process projecting from the sides, a vertical quadrate that isn’t anteriorly bowed or sloped on the underside of the front, a very short odontoid, a short axis centrum which is as long as it is tall, and similar coracoid to scapula proportions to Animantarx and Edmontonia.[1]
Cranium
The skull was about 56 centimeters (22 inches) long, and 35.5 centimeters (14.0 inches) wide between the eyes. It lacked beak teeth, and had only modest horn-like projections. The top of the skull was only slightly domed, and the only preserved upper cheek tooth was large and similar to teeth assigned to Priconodon, another large nodosaurid from about the same time. The lower jaws are represented by their rear halves, and were heavily built.[1]
Postcrania
Of the postcranial skeleton, bones from all areas of the body are represented, except the hind foot. Six fused vertebrae supported the hip, as in Silvisaurus. The ilia, the largest bones of the hip, appear to have been flared out unusually, at 55° compared to the ~30° or ~40° degrees of other nodosaurids, but this could be a preservational accident. Unlike most other nodosaurids, the ulna was long and straight, and the major ankle bone (the astragalus) was not fused to the shin.[1]
Classification
Carpenter et al. (2008) originally placed Peloroplites within Nodosauridae but did not conduct a phylogenetic analysis to determine its exact relationships within the clade.[1] Thompson et al. (2012) recovered Peloroplites as sister taxon to Polacanthus, a position also recovered by Chen et al. (2013).[3][4] However, Yang et al. (2013) found Peloroplites to be sister taxon to both Taohelong and Polacanthus, while Zheng et al. (2018) found it to be sister taxon to Taohelong and a large clade containing more nested taxa such as Nodosaurus, Edmontonia, Struthiosaurus and Europelta.[5] Rivera-Sylva et al. (2018) placed Peloroplites as sister taxon to Sauropelta, Taohelong and a clade containg more nested taxa.[6]
A phylogenetic analysis conducted by Rivera-Sylva et al. (2018) and modified by Madzia et al. (2021) is reproduced below.[6][7]
The results of an earlier analysis by Thompson et al. (2012) are reproduced below.[3]
Paleobiology and paleoecology
Peloroplites was found in mudstone, in a quarry that also produced fossils of a turtle, a pterosaur, four individuals of a new brachiosaurid sauropod, the basal ankylosaurid Cedarpelta, and an iguanodont ornithopod. Ankylosaurians attained large sizes at the Aptian-Albian boundary; both Peloroplites and Cedarpelta are comparable in size to Sauropelta, a nodosaurid from about the same time but known from the Cloverly Formation of Wyoming and Montana. In fact, isolated bones from older levels of the Cedar Mountain Formation, assigned to Sauropelta, may actually pertain to Peloroplites.[1]
Ankylosaurians are usually interpreted as low-browsing quadrupedal herbivores.[8] The large teeth and robust jaws of Peloroplites suggest that it was consuming tougher forage than other ankylosaurians.[1]
References
- ^ a b c d e f g h i j k l m Carpenter, Kenneth; Bartlett, Jeff; Bird, John; Barrick, Reese (2008). "Ankylosaurs from the Price River Quarries, Cedar Mountain Formation (Lower Cretaceous), east-central Utah". Journal of Vertebrate Paleontology. 28 (4): 1089–1101. doi:10.1671/0272-4634-28.4.1089.
- ^ a b Paul, G.S., 2016, The Princeton Field Guide to Dinosaurs 2nd Edition, Princeton University Press
- ^ a b Richard S. Thompson, Jolyon C. Parish, Susannah C. R. Maidment and Paul M. Barrett, 2012, "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)", Journal of Systematic Palaeontology 10(2): 301–312
- ^ Rongjun Chen; Wenjie Zheng; Yoichi Azuma; Masateru Shibata; Tianliang Lou; Qiang Jin; Xingsheng Jin (2013). "A New Nodosaurid Ankylosaur from the Chaochuan Formation of Dongyang, Zhejiang Province, China". Acta Geologica Sinica (English Edition). 87 (3): 658–671. doi:10.1111/1755-6724.12077.
- ^ Yang J.-T.; You H.-L.; Li D.-Q.; Kong D.-L. (2013). "First discovery of polacanthine ankylosaur dinosaur in Asia" (PDF). Vertebrata PalAsiatica (in Chinese and English). 51 (4): 265–277.
- ^ a b Rivera-Sylva, H.E.; Frey, E.; Stinnesbeck, W.; Carbot-Chanona, G.; Sanchez-Uribe, I.E.; Guzmán-Gutiérrez, J.R. (2018). "Paleodiversity of Late Cretaceous Ankylosauria from Mexico and their phylogenetic significance". Swiss Journal of Palaeontology. 137 (1): 83–93. doi:10.1007/s13358-018-0153-1. ISSN 1664-2376. S2CID 134924657.
- ^ Madzia, D.; Arbour, V.M.; Boyd, C.A.; Farke, A.A.; CruzadoCaballero, P.; Evans, D.C. (2021). "The phylogenetic nomenclature of ornithischian dinosaurs". PeerJ. 9: e12362. doi:10.7717/peerj.12362. S2CID 245111393.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Vickaryous, Matthew K.; Maryańska, Teresa; Weishampel, David B. (2004). "Ankylosauria". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (Second ed.). Berkeley: University of California Press. pp. 363–392.
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