Name: Omphalosaurus ‭(‬button lizard‭)‬.
Phonetic: Om-phal-o-sore-us.
Named By: J.‭ ‬C.‭ ‬Merriam‭ ‬-‭ ‬1906.
Classification: Chordata,‭ ‬Reptolia,‭ ‬Ichthyopterygia,‭ ‬Ichthyosauria.
Species: O.‭ ‬nevadanus‭ (‬type‭)‬,‭ ‬O.‭ ‬merriami,‭ ‬O.‭ ‬nettarhynchus,‭ ‬O.‭ ‬peyeri,‭ ‬O.‭ ‬wolfi.
Diet: Durophagus carnivore‭ (‬shellfish eater‭)‬.
Size: Roughly about‭ ‬2‭ ‬meters long.
Known locations: Germany‭ ‬-‭ ‬Lercheck Limestone Formation,‭ ‬Oberer Hauptmuschelkalk Formation.‭ ‬Norway,‭ ‬Svalbard.‭ ‬USA,‭ ‬Nevada‭ ‬-‭ ‬Prida Formation.
Time period: Anisian to Ladnian of the Triassic.
Fossil representation: Several individuals by partial skull and post cranial remains.

       Since the genus was first named from fossils in Nevada,‭ ‬USA,‭ ‬Omphalosaurus was usually perceived as a small and primitive ichthyosaur that lived during the early Triassic.‭ ‬Towards the end of the twentieth and early twenty-first centuries however questions were raised about the genus being an ichthyosaur with notes about how the known fossils of Omphalosaurus don’t show any feature that are exclusive just to the ichthyosaurs.‭ ‬Most of this doubt was highlighted in a paper by Motani and published in‭ ‬2000,‭ ‬however since this papers by Sander and Faber in‭ ‬2003,‭ ‬and Maisch in‭ ‬2010,‭ ‬both describing new specimens of Omphalosaurus,‭ ‬have concluded that Omphalosaurus is a primitive ichthyosaur.
       One thing that we can be a little more certain about Omphalosaurus is the diet.‭ ‬The teeth of Omphalosaurus are blunt and rounded,‭ ‬and usually these kinds of teeth are seen in animals that eat hard bodied items.‭ ‬In reference to Omphalosaurus specifically this would be shellfish which would have had their hard outer shells broken up by the teeth so that the soft inside could then be swallowed by the feeding‭ ‬Omphalosaurus.

Further reading
-‭ ‬Preliminary note on a new marine reptile from the Middle Triassic of Nevada.‭ ‬University of California Publications in Geological Sciences‭ ‬5‭(‬5‭)‬:71-79.‭ ‬-‭ ‬J.‭ ‬C.‭ ‬Merriam‭ ‬-‭ ‬1906.
-‭ ‬New finds of Omphalosaurus and a review of Triassic ichthyosaur paleobiogeography.‭ ‬-‭ ‬Palaeontologische Zeitschrift‭ ‬72‭(‬1/2‭)‬:149-162.‭ ‬-‭ ‬P.‭ ‬M.‭ ‬Sander‭ & ‬C.‭ ‬Faber‭ ‬-‭ ‬1998.
-‭ ‬Is Omphalosaurus ichthyopterygian‭? ‬-‭ ‬A phylogenetic perspective.‭ ‬Journal of Vertebrate Paleontology‭ ‬20‭(‬2‭)‬:‭ ‬295-301.‭ ‬-‭ ‬Ryosuke Motani‭ ‬-‭ ‬2000.
-‭ ‬The Triassic marine reptile Omphalosaurus:‭ ‬osteology,‭ ‬jaw anatomy,‭ ‬and evidence for ichthyosaurian affinities.‭ ‬-‭ ‬Journal of Vertebrate Paleontology Volume‭ ‬23,‭ ‬Issue‭ ‬4.‭ ‬-‭ ‬P.‭ ‬Martin Sander‭ & ‬Christiane Faber‭ ‬-‭ ‬2003.
-‭ ‬Phylogeny,‭ ‬systematics,‭ ‬and origin of the Ichthyosauria‭ ‬-‭ ‬the state of the art.‭ ‬-‭ ‬Palaeodiversiry‭ ‬3:‭ ‬151-214.‭ ‬-‭ ‬M.‭ ‬Maisch‭ ‬-‭ ‬2010.
- Two Records of Omphalosaurus from the Muschelkalk - The Reconstruction of Triassic Marine Ecosystems Based on Teeth. - International Symposium on Paleohistology. - Tanja Wintrich & Martin Sander - 2015.
- Preliminary report on ichthyopterygian elements from the Early Triassic (Spathian) of Spitsbergen. - Norwegian Journal of Geology. - Christina Ekeheien, Lene Delsett, Aubrey Roberts & Hurum Jørn - 2018.


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