Name: Saniwa.
Phonetic: San-e-wah.
Named By: Joseph Leidy‭ ‬-‭ ‬1870.
Synonyms: Thinosaurus.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Squamata,‭ ‬Varanoidea,‭ ‬Varanidae.
Species: S.‭ ‬ensidens‭ (‬type‭)‬,‭ ‬T.‭ ‬agilis,‭ ‬T.‭ ‬crassa,‭ ‬S.‭ ‬edura,‭ ‬T.‭ ‬grandis,‭ ‬S.‭ ‬major,‭ ‬S.‭ ‬orsmaelensis‭?‬,‭ ‬T.‭ ‬paucidens.
Diet: Carnivore.
Size: Between‭ ‬1.3‭ ‬and‭ ‬2.15‭ ‬meters long,‭ ‬depending upon the species.
Known locations: Belgium.‭ ‬France.‭ ‬Germany.‭ ‬Krygyzstan.‭ ‬Mexico.‭ ‬USA,‭ ‬California,‭ ‬Colorado,‭ ‬North Dakota,‭ ‬Utah‭ & ‬Wyoming.
Time period: Paleocene‭? ‬through to the end of the Eocene.
Fossil representation: Many individuals,‭ ‬including a complete and articulated juvenile.

       Saniwa is one of the better known genera of prehistoric monitor lizard,‭ ‬and although initially only known from North America,‭ ‬specimens are now known from Europe as well as northern Asia.‭ ‬Like monitor lizards living today,‭ ‬Saniwa was a predator.‭ ‬Juvenile monitor lizards tend to focus upon hunting invertebrates like insects,‭ ‬but as they grow bigger and reach sizes like those Saniwa is known to have attained they switch to a more vertebrate exclusive diet and hunt everything from other lizards to mammals and birds.
       Saniwa was not quite a modern monitor lizard,‭ ‬though it was certainly close.‭ ‬The jugal‭ (‬cheekbone‭) ‬of Saniwa still projected slightly forwards in front of the eye and the suture between the frontal and parietal bones is straight.‭ ‬Additionally,‭ ‬Saniwa still has teeth growing from the palate.‭ ‬Apart from these Saniwa still resembled a modern monitor lizard by scurrying around on all fours.‭ ‬Lizards of the Saniwa genus are also noted for having a tail proportionately much longer than that of the body‭; ‬as much as almost two thirds of the total body length was tail.
       Unlike many fossil genera,‭ ‬the appearance of Saniwa is beyond doubt thanks to some very well preserved specimens.‭ ‬The best of these is a juvenile from the Green River Formation of Wyoming which was found not only complete and fully articulated,‭ ‬but also with some of the internal soft tissues and scales as well.
       Saniwa was also the first extinct lizard to be named from North America.

Further reading
-‭ ‬Descriptions of Emys jaenesi,‭ ‬E.‭ ‬haydeni,‭ ‬Baena arenosa,‭ ‬and Saniwa ensidens,‭ ‬Joseph Leidy‭ ‬-‭ ‬1870.
-‭ ‬The anatomy of the fossil varanid lizard Saniwa ensidens Leidy,‭ ‬1870,‭ ‬based on a newly discovered complete skeleton,‭ ‬O.‭ ‬Rieppel‭ & ‬L.‭ ‬Grande‭ ‬-‭ ‬2007.
-‭ ‬Re-assessment of varanid evolution based on new data from Saniwa ensidens Leidy,‭ ‬1870‭ (‬Squamata,‭ ‬Reptilia‭)‬,‭ ‬J.‭ ‬Conrad,‭ ‬O.‭ ‬Rieppel‭ & ‬L.‭ ‬Grande‭ ‬-‭ ‬2008.
-‭ ‬Holotype snout elements of Saniwa ensidens reassigned to cf.‭ ‬Restes sp.‭ ‬indet.‭ (‬Xenosauridae‭)‬,‭ ‬M.‭ ‬W.‭ ‬Caldwell‭ ‬-‭ ‬2003.
- The Only Known Jawed Vertebrate with Four Eyes and the Bauplan of the Pineal Complex. - Current Biology. 28 (7): 1101–1107. - Krister T. Smith, Bhart-Anjan S. Bhullar, Gunther Köhler & Jörg Habersetzer - 2018.


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