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Shonisaurus

From Wikipedia, the free encyclopedia
Not to be confused withShinisaurusorShinosaur.

Shonisaurus
Temporal range:Norian
Restored skull in a Japanese museum
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: †Ichthyosauria
Family: †Shastasauridae
Genus: †Shonisaurus
Camp, 1976
Type species
†Shonisaurus popularis
Camp, 1976
Species[1][2]
  • †S. popularisCamp, 1976
  • †S.? sikanniensisNicholls and Manabe, 2004

Shonisaurusis a genus of very largeichthyosaurs.At least 37 incomplete fossil specimens of thetype species,Shonisaurus popularis,have been found in theLuning FormationofNevada,USA. This formation dates to the lateCarnian-earlyNorianage of theLate Triassic,around 227 million years ago.[3]Other possible species ofShonisaurushave been discovered from the middleNoriandeposits ofCanadaandAlaska.[2][4]

Description

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Size ofS. popularis(green) andShastasaurussikanniensis(red) compared with a human (blue)
Shonisaurusskeleton, Nevada State Museum

Shonisauruslived during the lateCarniantoNorianstages of theLate Triassic.With a large skull about 2.75 m (9.0 ft) long,S. popularisand measured around 13.5–15 metres (44–49 ft) in length and 21.6–29.7 metric tons (23.8–32.7 short tons) in body mass.[5][6]S. sikanniensiswas one of the largest marine reptiles of all time, measuring 21 metres (69 ft) and weighing 81.5 metric tons (89.8 short tons).[5]

Shonisaurushad a long snout, and its flippers were much longer and narrower than in other ichthyosaurs. WhileShonisauruswas initially reported to have had socketed teeth (rather than teeth set in a groove as in more advanced forms), these were present only at the jaw tips, and only in the very smallest, juvenile specimens. All of these features suggest thatShonisaurusmay be a relatively specialised offshoot of the main ichthyosaur evolutionary line.[7]More recent finds however indicate thatShonisauruspossessed teeth in all ontogenetic stages.[8]Robust sectorial teeth and gut contents indicate thatShonisauruswas a macrophagous raptorial predator which fed on vertebrates and shelled mollusks like cephalopods, possibly even large-bodied prey.[9][10]Additionally,Shonisauruswas historically depicted with a rather rotund body, but studies of its body shape since the early 1990s have shown that the body was much more slender than traditionally thought,[11]and had a relatively deep body compared with related marine reptiles.[2]

History of discovery

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Restoration

FossilsofShonisauruswere first found in a large deposit inNevadain 1920. Thirty years later, they were excavated, uncovering the remains of 37 very large ichthyosaurs. These were namedShonisaurus,which means "lizard from theShoshone Mountains",after the formation where the fossils were found.

S. popularis,was adopted as thestate fossilof Nevada in 1984. Excavations, begun in 1954 under the direction ofCharles CampandSamuel Wellesof theUniversity of California, Berkeley,were continued by Camp throughout the 1960s. It was named by Charles Camp in 1976.[12]The Nevada fossil sites can currently be viewed at theBerlin-Ichthyosaur State Park.

A second species from thePardonet FormationofBritish Columbiawas namedShonisaurus sikanniensisin 2004.[2]However, aphylogeneticstudy by Sander and colleagues in 2011 later showedS. sikanniensisto be a species ofShastasaurusrather thanShonisaurus.[13] A subsequent study by Ji and colleagues published in 2013 reasserted the original classification, finding it more closely related toShonisaurusthan toShastasaurus.[14]Support for both hypotheses has been found in later studies, with some authors classifying the species inShonisaurusand others inShastasaurus.[15][16]

Specimens belonging toS. sikanniensishave been found in thePardonet FormationBritish Columbia,dating to the middleNorianage.[2]An isolated humerus from a smaller individual (TMP 94.381.4) and a postorbital region (TMP 98.75.9) from a juvenile were also reported from the same formation and were referred to asShonisaurussp.[2]Other fossils from this formation include the ichthyosaursMacgowaniaandCallawayia,coelacanthsWhiteia banffensisand possiblyGarnbergia,and various genera of molluscs including ammonites and bivalves.[2][17]Large ichthyosaur remains found in Alaska have also been identified asShonisaurussp.[4]

See also

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Notes

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  1. ^McGowan, C.; Motani, R. (1999). "A Reinterpretation Of the Upper Triassic IchthyosaurShonisaurus".Journal of Vertebrate Paleontology.19(1): 42–49.Bibcode:1999JVPal..19...42M.doi:10.1080/02724634.1999.10011121.
  2. ^abcdefgNicholls, Elizabeth L.; Manabe, Makoto (2004). "Giant Ichthyosaurs of the Triassic—A New Species ofShonisaurusfrom the Pardonet Formation (Norian: Late Triassic) of British Columbia ".Journal of Vertebrate Paleontology.24(4): 838–849.doi:10.1671/0272-4634(2004)024[0838:GIOTTN]2.0.CO;2.ISSN0272-4634.
  3. ^Balini, M.; Jenks, James F.; Martin, R.; McRoberts, Christopher A.; Orchard, Michael J.; Silberling, Norman J. (2015). "The Carnian/Norian boundary succession at Berlin-Ichthyosaur State Park (Upper Triassic, central Nevada, USA)".Paläontologische Zeitschrift.89(3): 399–433.Bibcode:2015PalZ...89..399B.doi:10.1007/s12542-014-0244-2.
  4. ^abAdams, Thomas L. (2009). "Deposition and taphonomy of the Hound Island Late Triassic vertebrate fauna: Fossil preservation within subaqueous gravity flows".PALAIOS.24(9): 603–615.Bibcode:2009Palai..24..603A.doi:10.2110/palo.2009.p09-010r.
  5. ^abSander, P.M.; Griebeler, E.M.; Klein, N.; Juarbe, J.V.; Wintrich, T.; Revell, L.J.; Schmitz, L. (2021)."Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans"(PDF).Science.374(6575): eabf5787.doi:10.1126/science.abf5787.PMID34941418.S2CID245444783.
  6. ^Sander, P.M.; Romero Pérez de Villar, P.; Furrer, H.; Wintrich, T. (2022)."Giant Late Triassic Ichthyosaurs from the Kössen Formation of the Swiss Alps and Their Paleobiological Implications"(PDF).Journal of Vertebrate Paleontology.41(6): e2046017.doi:10.1080/02724634.2021.2046017.
  7. ^Palmer, D., ed. (1999).The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals.London: Marshall Editions. pp. 78–79.ISBN1-84028-152-9.
  8. ^Kelley, Neil P.; Irmis, Randall; Rasmussen, Cornelia; Depolo, Paige E.;Pyenson, Nicholas(2016)."Beyond theShonisaurusDeath Cult: New Insights into the Ecology and Life History of the Earliest Gigantic Marine Tetrapod ".76th Annual Meeting of the Society of Vertebrate Paleontology, Salt Lake City:587.Retrieved27 September2021.
  9. ^Kelley, Neil P.; Irmis, Randall B.; dePolo, Paige E.; Noble, Paula J.; Montague-Judd, Danielle; Little, Holly; Blundell, Jon; Rasmussen, Cornelia; Percival, Lawrence M.E.; Mather, Tamsin A.; Pyenson, Nicholas D. (December 2022)."Grouping behavior in a Triassic marine apex predator".Current Biology.32(24): 5398–5405.e3.Bibcode:2022CBio...32E5398K.doi:10.1016/j.cub.2022.11.005.ISSN0960-9822.PMID36538877.S2CID254874088.
  10. ^Druckenmiller, Patrick S.; Kelley, Neil; Whalen, Michael T.; Mcroberts, Christopher; Carter, Joseph G. (2014-09-19)."An Upper Triassic (Norian) ichthyosaur (Reptilia, Ichthyopterygia) from northern Alaska and dietary insight based on gut contents".Journal of Vertebrate Paleontology.34(6): 1460–1465.Bibcode:2014JVPal..34.1460D.doi:10.1080/02724634.2014.866573.ISSN0272-4634.S2CID129908740.
  11. ^Kosch, Bradley F. (1990). "A revision of the skeletal reconstruction ofShonisaurus popularis(Reptilia: Ichthyosauria) ".Journal of Vertebrate Paleontology.10(4): 512–514.Bibcode:1990JVPal..10..512K.doi:10.1080/02724634.1990.10011833.
  12. ^Hilton, Richard P. (2003).Dinosaurs and Other Mesozoic Animals of California.University of California Press, Berkeley. pp. 90–91.ISBN0-520-23315-8.
  13. ^Sander, P. Martin; Chen, Xiaohong; Cheng, Long; Wang, Xiaofeng (2011). Claessens, Leon (ed.)."Short-Snouted Toothless Ichthyosaur from China Suggests Late Triassic Diversification of Suction Feeding Ichthyosaurs".PLOS ONE.6(5): e19480.Bibcode:2011PLoSO...619480S.doi:10.1371/journal.pone.0019480.PMC3100301.PMID21625429.
  14. ^Ji, C.; Jiang, D. Y.; Motani, R.; Hao, W. C.; Sun, Z. Y.; Cai, T. (2013). "A new juvenile specimen ofGuanlingsaurus(Ichthyosauria, Shastasauridae) from the Upper Triassic of southwestern China ".Journal of Vertebrate Paleontology.33(2): 340.Bibcode:2013JVPal..33..340J.doi:10.1080/02724634.2013.723082.S2CID83784699.
  15. ^Moon, B. (2019)."A new phylogeny of ichthyosaurs (Reptilia: Diapsida)".Journal of Systematic Palaeontology.17(2): 1–27.Bibcode:2019JSPal..17..129M.doi:10.1080/14772019.2017.1394922.
  16. ^Bindellini G; Wolniewicz AS; Miedema F; Scheyer TM (2021)."Cranial anatomy ofBesanosaurus leptorhynchusDal Sasso & Pinna, 1996 (Reptilia: Ichthyosauria) from the Middle Triassic Besano Formation of Monte San Giorgio, Italy/Switzerland: taxonomic and palaeobiological implications ".PeerJ.9(e11179): e11179.doi:10.7717/peerj.11179.hdl:11573/1682932.PMC8106916.PMID33996277.
  17. ^Yabumoto, Y.; Neuman, A. (2004)."A Coelacanth Scale from the Upper Triassic Pardonet Formation, British Columbia, Canada".Paleontological Research.8(4): 337–340.doi:10.2517/prpsj.8.337.

References

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  • Dixon, Dougal. "The Complete Book of Dinosaurs." Hermes House, 2006.
  • Camp, C. L. (1980). "Large ichthyosaurs from the Upper Triassic of Nevada".Palaeontographica, Abteilung A.170:139–200.
  • Camp, C.L. 1981. Child of the rocks, the story of Berlin-Ichthyosaur State Park. Nevada Bureau of Mines and Geology special publication 5.
  • Cowen, R. 1995. History of life. Cambridge, Massachusetts: Blackwell Scientific.
  • Hogler, J. A. (1992). "Taphonomy and Paleoecology of Shonisaurus popularis (Reptilia: Ichthyosauria)".PALAIOS.7(1): 108–117.Bibcode:1992Palai...7..108H.doi:10.2307/3514800.JSTOR3514800.
  • McGowan, Chris; Motani, Ryosuke (1999). "A reinterpretation of the Upper Triassic ichthyosaurShonisaurus".Journal of Vertebrate Paleontology.19:42–49.Bibcode:1999JVPal..19...42M.doi:10.1080/02724634.1999.10011121.
  • Motani, Ryosuke; Minoura, Nachio; Ando, Tatsuro (1998). "Ichthyosaurian relationships illuminated by new primitive skeletons from Japan".Nature.393(6682): 255–257.Bibcode:1998Natur.393..255M.doi:10.1038/30473.S2CID4416186.
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