Othnielosaurus

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Othnielosaurus
Othnielosaurus consors

Othnielosaurus consors

Temporal occurrence
Upper Jurassic
155 to 148 million years
Locations
Systematics
Dinosauriformes
Dinosaur (dinosauria)
Pelvic dinosaur (Ornithischia)
Genosauria
Neornithischia
Othnielosaurus
Scientific name
Othnielosaurus
Galton , 2007
Art
  • O. consors ( Marsh , 1878)

Othnielosaurus is a genus of avian dinosaur known from the Upper Jurassic of the Morrison Formation in the western United States . The genus name honors the famous paleontologist Othniel Charles Marsh , whooriginallyassignedthe fossil to the Laosaurus genus. The genus Othnielosaurus was created to include fossils that were formerlyassigned tothe genus Othnielia , but which is based on sparse material. It is therefore part of decades of workto unravel the taxonomy left behindby Marsh and his rival Edward Drinker Cope from the Bone Wars . Othnielosaurus is commonlyclassifiedas a hypsilophodont , a group of small bipedal herbivorous or omnivorous dinosaurs, but the existence of a valid taxon has recently been questioned by some scientists.

description

Othnielosaurus is known of material encompassing all parts of the body, including two well-preserved skeletons. However, the skull is poorly documented (in the older literature a large number of names are used for this material, but most publications after 1977 use the name Othnielia rex ). Othnielosaurus was a small animal, no more than two meters long and weighed 10 kilograms. It walked on two legs and therefore had short front limbs and long rear limbs with pronounced apophyses for the muscle attachments. Othnielosaurus' hands were short and wide with short fingers. Examination of the partially preserved skull of the holotype and the skull of the possible specimen Barbara revealed that the head was small. The animal had small, leaf-shaped molars and premaxillary teeth with less ornamentation. How many ornithopods from the groups of Hypsilophodonten or iguanodons as Hypsilophodon , Thescelosaurus and Talenkauen had othnielosaurus thin plates, which were at its ribs. These intercostal platelets consisted of cartilage tissue.

classification

Othnielosaurus (formerly Laosaurus , Nanosaurus , and Othnielia ) have long been considered a hypsilophodontic ornithoped , an unclear and poorly defined group of small herbivorous dinosaurs. This view was adopted in 1990 by Robert Bakker et al. questioned. In their description of the new taxon Drinker nisti they divided Othnielia into two species ( O. rex and O. consors ) and established the "Othnielids" as a more basal variant than the Hypsilophodontids. Recent research suggests that the Hypsilophodontidae were paraphyletic , so that the general idea of ​​the "Othnielids" as basal in comparison to other representatives of the Hypsilophodontidae received support, although Drinker remains controversial as nothing new has been published about the taxon since it was first described . Other basal ornithopods have at times been associated with Othnielosaurus , particularly Hexinlusaurus , which at least one author considered a new species of the genus Othniela ( O. multidens ).

Recent studies agree with the hypothesis of Othnielosaurus as the basal representative of the Hypsilophodonts, but go even further and take the genus out of the Ornithopoda and the larger group of Cerapoda , which also includes the Ceratopsia and the Pachycephalosauria .

History of discovery and taxonomy

Skeletal reconstruction of Laosaurus consors ( Othnielosaurus ) by Othniel Charles Marsh from 1896

Othniel Charles Marsh named numerous species and genera in the late 19th century that were considered hypsilophodonts, or hypshilophodont-like dinosaurs. These included Nanosaurus agilis (possibly), Nanosaurus rex , Laosaurus celer , Laosaurus consors , and Laosaurus gracilis . This taxonomy has become more and more complicated over the years and there have been various attempts at revision since then.

In 1877 Marsh named two species of Nanosaurus in separate publications based on incomplete remains from the Morrison Formation in Garden Park , Colorado . One article described N. agilis using a specimen from the Peabody Museum of Natural History , YPM 1913, the remains of which included impressions of the jaw and postcranial parts of the skeleton including the iliac , femur, and fibula . The other publication described with Nanosaurus rex another species that Marsh founded on the specimen YPM 1915, which is only preserved with a complete femur. He regarded both species as small ("fox-sized") animals and placed them in the now abandoned family of the Nanosauridae.

A year later, Marsh described the new genus Laosaurus based on material excavated by Samuel Wendell Williston in Como Bluff , Wyoming . Two species were introduced: the type species Laosaurus celer , based on eleven vertebrae (YPM 1875); and the smaller Laosaurus gracilis , whose description was originally based on parts of a dorsal and caudal vertebra and a cubit .

Othnielosaurus consors , fossil in the Paleontological Museum of the University of Zurich

A third species, Laosaurus consors , was described by Marsh in 1894 for the specimen YPM 1882, which consisted of large parts of a skeleton in an anatomical association and parts of at least one other individual. The skull was only partially preserved and the fact that only the vertebral bodies of the vertebrae were preserved suggests that the individual was not fully grown.

These species received little professional attention well into the 1970s and 1980s when Peter Galton reviewed many of the hypsilophodonts in a series of publications. In 1973 he and Jim Jensen described an incomplete skeleton ( BYU ESM 163 ) without a head, hands and tail as a Nanosaurus rex . This specimen had been damaged before it was described. In 1977 he determined that Nanosaurus agilis was different from Nanosaurus rex and the new skeleton and coined the name Othnielia for Nanosaurus rex . That 1977 note, which got somewhat lost in an article on the transcontinental species Dryosaurus , assigned Laosaurus consors and Laosaurus gracilis to the new genus without giving any specifics, and considered Laosaurus celer a nomen nudum . The introduction of Drinker further complicated things.

Galton recently re-evaluated the ornithischia of the Morrison Formation and concluded that the femur , on the basis of which Nanosaurus rex (and later Othniela ) had been described, was not meaningful. He therefore assigned the BYU skeleton to the species Laosaurus consors , which is based on significant material. Since the genus Laosaurus is also based on inconclusive material, he gave the species Laosaurus consors its own genus, Othnielosaurus . As a result, Othniela fossils are now classified as Othnielosaurus consors . Othnielia is not a synonym for Othnielosaurus because both are based on different specimens. The fossils that were used to describe Othniela were assigned to the genus Othnielosaurus, so that only the original thigh bone of the holotype is classified under the older name . The current status of the various species is as follows: Nanosaurus agilis is possibly a basal ornithopod, Nanosaurus rex ( Othnielia ) is a dubious basal ornithopod, Drinker nisti keeps its own provisional taxon, Laosaurus consors is a type of Othnielosaurus , and Laosaurus celer as well as Laosaurus gracilis are still considered dubious.

Paleobiology and paleoecology

Othnielosaurus was one of the smaller members of the highly diversified dinosaur fauna of the Morrison Formation and appears tiny compared to the giant sauropods . The Morrison Formation is viewed as a semi-arid ecosystem with pronounced rainy and dry seasons and flat floodplains . The vegetation varied between gallery forests that lined the river banks and consisted of conifers , tree ferns and ferns , and savannas with ferns and scattered trees. The Morrison Formation is extremely rich in fossils. Among other things, the remains of chlorophytes , mushrooms , mosses , horsetail , ferns, cycads , ginkgos and various families of conifers were found. Other finds included mussels , snails , fish from the class of ray-finned fishes , frogs , salamanders , turtles , Sphenodontia , Lacertilia , terrestrial and aquatic Crocodylomorpha , various types of pterosaurs , numerous species of dinosaurs and early mammals such. B. Representatives of the Docodonta , Multituberculata , Symmetrodonta and the Triconodonta . The dinosaur species in the ecosystem included theropods such as Ceratosaurus , Allosaurus , Ornitholestes , and Torvosaurus . The sauropods were represented by Apatosaurus , Brachiosaurus , Camarasaurus , and Diplodocus , while the Ornithischia Camptosaurus , Dryosaurus , and Stegosaurus are also known from the Morrison formation.

Othnielosaurus occurs in stratigraphic zones 2 to 5.

Usually Othnielosaurus, like other hypsilophodonts, is interpreted as a small, nimble herbivore, although Bakker interpreted the possibly related Nanosaurus as an omnivore in 1986 . However, this idea found little support in the scientific literature, since a better and as completely preserved skull is essential to verify this thesis.

Individual evidence

  1. ↑ a b c d e David B. Norman , Hans-Dieter Sues , Lawrence M. Witmer , Rodolfo A. Coria : Basal Ornithopoda. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 393-412, digitized version (PDF; 2.66 MB) .
  2. ^ A b John R. Foster: Paleoecological analysis of the vertebrate fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain region, USA (= New Mexico Museum of Natural History and Science. Bulletin. 23, ISSN  1524-4156 ). New Mexico Museum of Natural History, Albuquerque NM 2003, p. 29, digitized .
  3. ↑ Scott Hartman: Othnielia . Retrieved September 18, 2014.
  4. ↑ a b c d Peter M. Galton : Teeth of ornithischian dinosaurs (mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the western United States. In: Kenneth Carpenter (Ed.): Horns and Beaks. Ceratopsian and Ornithopod Dinosaurs. Indiana University Press, Bloomington IN 2007, ISBN 978-0-253-34817-3 , pp. 17-47.
  5. ^ Richard J. Butler, Peter M. Galton: The 'dermal armor' of the ornithopod dinosaur Hypsilophodon from the Wealden (Early Cretaceous: Barremian) of the Isle of Wight: a reappraisal. In: Cretaceous Research. Vol. 29, No. 4, 2008, ISSN  0195-6671 , pp. 636-642, doi : 10.1016 / j.cretres.2008.02.002 .
  6. ^ Hans-Dieter Sues, David B. Norman: Hypsilophodontidae, Tenontosaurus, Dryosauridae. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . University of California Press, Berkeley CA et al. 1990, ISBN 0-520-06726-6 , pp. 498-509.
  7. ^ A b Robert T. Bakker , Peter M. Galton, James Siegwarth, James Filla: A new latest Jurassic vertebrate fauna, from the highest levels of the Morrison Formation at Como Bluff, Wyoming. Part IV. The dinosaurs: A new Othnielia-like hypsilophodontoid. In: Hunteria. Vol. 2, No. 6, 1990, ZDB -ID 1251702-1 , pp. 8-14.
  8. ↑ David B. Weishampel, Coralia-Maria Jianu, Zoltan Csiki, David B. Norman: Osteology and phylogeny of Zalmoxes (ng), an unusual euornithopod dinosaur from the latest Cretaceous of Romania. In: Journal of Systematic Palaeontology. Vol. 1, No. 2, 2003, ISSN  1477-2019 , pp. 65-123, doi : 10.1017 / S1477201903001032 .
  9. ^ A b David J. Varricchio, Anthony J. Martin, Yoshihiro Katsura: First trace and body fossil evidence of a burrowing, denning dinosaur. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 274, No. 1616, 2007, ISSN  0950-1193 , pp. 1361–1368, doi : 10.1098 / rspb.2006.0443 , PMID 17374596 , PMC 2176205 (free full text, PDF).
  10. ^ Peter W. Buchholz: The Mesozoic in Wyoming, Tate 2002. The Geological Museum - Casper College, Casper WY 2002, pp. 18-34: Phylogeny and biogeography of basal Ornithischia.
  11. ↑ Gregory S. Paul : The Complete Illustrated Guide to Dinosaur Skeletons. Gakken Mook, Tokyo 1996, ISBN 4-05-400656-6 , pp. 98 f.
  12. ^ Richard J. Butler, Roger MH Smith, David B. Norman: A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 274, No. 1621, 2007, pp. 2041-2046, doi : 10.1098 / rspb.2007.0367 , PMID 17567562 , PMC 2275175 (free full text, PDF).
  13. ^ Richard J. Butler, Paul Upchurch , David B. Norman: The phylogeny of the ornithischian dinosaurs. In: Journal of Systematic Palaeontology. Vol. 6, No. 1, 2008, pp. 1-40, doi : 10.1017 / S1477201907002271 .
  14. ^ Othniel C. Marsh : Notice of some new vertebrate fossils. In: American Journal of Science and Arts. Series 3, Vol. 14 = Vol. 114, No. 81, Article 33, 1877, ISSN  0002-9599 , pp. 249-256, digitized .
  15. ^ A b Othniel C. Marsh: Notice of new dinosaurian reptiles from the Jurassic formations. In: American Journal of Science and Arts. Series 3, Vol. 14 = Vol. 114, No. 84, Article 53, 1877, pp. 514-516, digitized .
  16. ^ A b Othniel C. Marsh: Notice of new dinosaurian reptiles. In: American Journal of Science and Arts. Series 3, Vol. 15 = Vol. 115, No. 87, Article 33, 1878, pp. 241-244, digitized .
  17. ^ Peter Galton, The cranial anatomy of Dryosaurus, a hypsilophodontid dinosaur from the Upper Jurassic of North America and East Africa, with a review of hypsilophodontids from the Upper Jurassic of North America. In: Geologica et Palaeontologica. Vol. 17, 1983, ISSN  0072-1018 , pp. 207-243.
  18. ^ Othniel C. Marsh: The typical Ornithopoda of the American Jurassic. In: American Journal of Science. Series 3, Vol. 48 = Vol. 148, No. 283, Article 11, 1894, pp. 85-90, digitized .
  19. ↑ Peter M. Galton, James A. Jensen: Skeleton of a hypsilophodontid dinosaur (Nanosaurus (?) Rex) from the Upper Jurassic of Utah. In: Brigham Young University, Department of Geology. Geology Studies. Vol. 20, No. 4, 1973, ISSN  0068-1016 , pp. 137-157.
  20. ^ A b Peter M. Galton: The ornithopod dinosaur Dryosaurus and a Laurasia-Gondwanaland connection in the Upper Jurassic. In: Nature . Vol. 268, No. 5617, 1977, pp. 230-232, doi : 10.1038 / 268230a0 .
  21. ^ Dale A. Russell : An Odyssey in Time. Dinosaurs of North America. NorthWord Press, Minocqua WI 1989, ISBN 1-559-71038-1 , pp. 64-70.
  22. ↑ Kenneth Carpenter: Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus Cope, 1878. In: John R. Foster, Spencer G. Lucas (eds.): Paleontology and Geology of the Upper Jurassic Morrison Formation (= New Mexico Museum of Natural History & Science. Bulletin. 36). New Mexico Museum of Natural History & Science, Albuquerque NM 2006, pp. 131-138, online .
  23. ^ Daniel J. Chure, Ron Litwin, Stephen T. Hasiotis, Emmett Evanoff, Kenneth Carpenter: The fauna and flora of the Morrison Formation: 2006. In: John R. Foster, Spencer G. Lucas (Eds.): Paleontology and Geology of the Upper Jurassic Morrison Formation (= New Mexico Museum of Natural History & Science. Bulletin. 36). New Mexico Museum of Natural History & Science, Albuquerque NM 2006, pp. 233-248, online .
  24. ↑ John Foster: Jurassic West. The Dinosaurs of the Morrison Formation and their World. Indiana University Press, Bloomington IN 2007, ISBN 978-0-253-34870-8 , pp. 327-329: Appendix.
  25. ^ Robert Bakker: The Dinosaur Heresies. New Theories unlocking the Mystery of the Dinosaurs and their Extinction. William Morrow, New York NY 1986, ISBN 0-688-04287-2 , p. 180.

Web links

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