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Ophthalmosaurus

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Ophthalmosaurus (meaning "eye lizard" in Greek) is an ichthyosaur of the Middle to Late Jurassic period (165 to 145 million years ago), named for its large eyes. It has a graceful 6 meter long dolphin-shaped body, and its almost toothless jaw was well adapted to catch squid. Major fossils have been found in Europe and North America.

Description

Ophthalmosaurus had a certain resemblance to the swordfish due to its long snout and end. The head was round with two large eyes adapted to night hunting. It had fins instead of legs, as well as the tail of a fish and a dorsal fin.

Relative to its body size, Ophthalmosaurus had the largest eyes of any vertebrate. Its eyes, 4 inches in width, took up most of the space in the skull. They were protected by bony plates, which most likely helped to keep the shape of the eyeballs against water pressure at depth.[1]

Discovery and species

Apatodontosaurus, Ancanamunia, Baptanodon, Mollesaurus‎, Paraophthalmosaurus‎, Undorosaurus and Yasykovia‎ were all deemed as synonyms of Ophthalmosaurus by Maisch & Matzke, 2000,[2] but newer studies found that Mollesaurus periallus from Argentina is a valid genus of ophthalmosaurid. Ophthalmosaurus natans is likely not a kind of Ophthalmosaurus either, for which the genus name Baptanodon Marsh, 1880 is available. Undorosaurus's is now deemed valid by most authors, even by Maisch (2010) who once thought the synonymy and the two other Russian taxon might be valid too.[3][4][5][6][7][8][9] Ophthalmosaurus chrisorum Russell, 1993 was moved to its own genus Arthropterygius in 2010 by Maxwell.[10]

In Ophthalmosauridae, Ophthalmosaurus was viewed to be most closely related to Aegirosaurus.[11] However, most recent studies found Ophthalmosaurus to nest in a clade with Acamptonectes and Mollesaurus. Aegirosaurus was found to be more closely related to Platypterygius, and thus it doesn't belong to the Ophthalmosaurinae.[12][13]

Classification

List of species

  • Ophthalmosaurus icenicus Seeley, 1874 (type species)
  • Ophthalmosaurus natans
  • Ophthalmosaurus saveljeviensis
  • Ophthalmosaurus yasykovi
  • Ophthalmosaurus gorodischensis
  • Ophthalmosaurus periallus

Paleobiology

Like all ichthyosaurs, Ophthalmosaurus gave birth to its pups tail-first so it won't drown them. Skeletons of unhatched young have been found in more than 50 females on fossil finds, and litter sizes ranged from 2 to 11 pups.

The size of the eyes and the bony plates suggests that Ophthalmosaurus hunted at a depth where there is not much light or that it may have hunted at night when prey was more active.

Estimates suggest that a typical Ophthalmosaurus could stay submerged for about 20 minutes or more.[14] The swimming speed of Ophthalmosaurus has been estimated at 2.5 m/s or greater. Even taking a conservative speed of 1 m/s, an Ophthalmosaurus would be able to dive to 600 meters and back to the surface in 20 minutes.

Ophthalmosaurus in The Land Before Time

Ophthalmosaurus was the only ichthyosaur in the Land Before Time series. This is the type that Mo is who appears in the The Land Before Time IX: Journey to Big Water and the TV episode The Missing Fast-Water Adventure. Mo also made a cameo on The Land Before Time XII: The Great Day of the Flyers and The Land Before Time X: The Great Longneck Migration from songs.

Gallery

References

  1. University of California Museum of Natural History: Motani's ichthyosaur page [1]
  2. Maisch MW, Matzke AT. 2000. The Ichthyosauria. Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 298: 1-159.
  3. Patrick S. Druckenmiller and Erin E. Maxwell (2010). "A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada". Canadian Journal of Earth Sciences 47 (8): 1037–1053. doi:10.1139/E10-028.
  4. Fischer, Valentin; Edwige Masure, Maxim S. Arkhangelsky and Pascal Godefroit (2011). "A new Barremian (Early Cretaceous) ichthyosaur from western Russia". Journal of Vertebrate Paleontology 31 (5): 1010–1025. doi:10.1080/02724634.2011.595464.
  5. Valentin Fischer, Michael W. Maisch, Darren Naish, Ralf Kosma, Jeff Liston, Ulrich Joger, Fritz J. Krüger, Judith Pardo Pérez, Jessica Tainsh and Robert M. Appleby (2012). "New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary". PLoS ONE 7 (1): e29234. doi:10.1371/journal.pone.0029234.
  6. Storrs, Glenn W.; Vladimir M. Efimov and Maxim S. Arkhangelsky (2000). "Mesozoic marine reptiles of Russia and other former Soviet republics". In Benton, M.J.; Shishkin, M.A.; and Unwin, D.M.. The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge University Press. pp. 140–159. ISBN 052154582X, 9780521545822.
  7. McGowan C, Motani R. 2003. Ichthyopterygia. – In: Sues, H.-D. (ed.): Handbook of Paleoherpetology, Part 8, Verlag Dr. Friedrich Pfeil, 175 pp., 101 figs., 19 plts; München
  8. Michael W. Maisch (2010). "Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art". Palaeodiversity 3: 151–214.
  9. Fischer, V.; A. Clement, M. Guiomar and P. Godefroit (2011). "The first definite record of a Valanginian ichthyosaur and its implications on the evolution of post-Liassic Ichthyosauria". Cretaceous Research 32 (2): 155–163. doi:10.1016/j.cretres.2010.11.005.
  10. Maxwell, E.E. (2010). "Generic reassignment of an ichthyosaur from the Queen Elizabeth Islands, Northwest Territories, Canada". Journal of Vertebrate Paleontology 30 (2): 403–415. doi:10.1080/02724631003617944.
  11. Fernández M. 2007. Redescription and phylogenetic position of Caypullisaurus (Ichthyosauria: Ophthalmosauridae). Journal of Paleontology 81 (2): 368-375.
  12. Fischer, Valentin; Edwige Masure, Maxim S. Arkhangelsky and Pascal Godefroit (2011). "A new Barremian (Early Cretaceous) ichthyosaur from western Russia". Journal of Vertebrate Paleontology 31 (5): 1010–1025. doi:10.1080/02724634.2011.595464.
  13. Valentin Fischer, Michael W. Maisch, Darren Naish, Ralf Kosma, Jeff Liston, Ulrich Joger, Fritz J. Krüger, Judith Pardo Pérez, Jessica Tainsh and Robert M. Appleby (2012). "New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary". PLoS ONE 7 (1): e29234. doi:10.1371/journal.pone.0029234.
  14. University of California Museum of Natural History: Motani's ichthyosaur page [2]


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