Name: Tyrannoneustes ‭(‬Tyrant swimmer‭)‬.
Phonetic: Tie-ran-no-new-steez.
Named By: M.‭ ‬T.‭ ‬Young,‭ ‬M.‭ ‬B.‭ ‬d.‭ ‬Andrade,‭ ‬S.‭ ‬L.‭ ‬Brusatte,‭ ‬M.‭ ‬Sakamoto‭ & ‬J.‭ ‬Liston‭ ‬-‭ ‬2013.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Crocodylomorpha, Thalattosuchia.
Species: T.‭ ‬lythrodectikos‭ (‬type‭)‬.
Diet: Carnivore/Piscivore.
Size: Lower jaw about‭ ‬66‭ ‬centimetres long.‭
Known locations: England‭ ‬-‭ ‬Oxford Clay Formation. Germany.
Time period: Mid Callovian to Early Oxfordian of the Jurassic.
Fossil representation: Lower jaw and partial post cranial remains including vertebrae,‭ ‬ribs and limbs. Partial skull material also known.

       The metriorhynchids are the best known of the thalattosuchians,‭ ‬a group of crocodiles that had adapted themselves to life at sea.‭ ‬Out of these,‭ ‬Tyrannoneustes is considered to be a geosaurine metriorhynchid,‭ (‬more closely related to genera like Geosaurus‭)‬.‭ ‬It took quite some time for Tyrannoneustes to be named though,‭ ‬as the fossils were first recovered in‭ ‬1906‭ ‬and‭ ‬1907‭ ‬by a fossil hunter named Albert Leeds.‭ ‬Not considered to be anything special,‭ ‬the remains were left in museum storage for over a century until it was realised that they represented a new genus.
       Studies of the jaw of Tyrannoneustes have revealed that these metriorhynchids had a notably wide gape when they opened their mouths to the maximum extent.‭ ‬In addition to this wide gape,‭ ‬the teeth were large and blade like,‭ ‬perfect for‭ ‬slicing into the bodies of prey.‭ ‬These two observations together strongly suggest that Tyrannoneustes would attack large prey animals ranging to be anything from plesiosaurs,‭ ‬to possibly even biting chunks out of large filter feeding fish such as Leedsichthys‭ (‬which coincidentally was named after Albert Leeds,‭ ‬the person who discovered the Tyrannoneustes holotype fossils‭)‬.
       The holotype remains of Tyrannoneustes include a jaw that was roughly about sixty-six centimetres long,‭ ‬though the rest of the post cranial skeleton is only partially represented.‭ ‬In the absence of other specimens it seems that Tyrannoneustes was actually fairly small or at least within the lower average of its other geosaurine brethren.‭ ‬Indeed,‭ ‬a relative and similar named genus called Torvoneustes is thought to have grown just a little short of five meters.‭ ‬Another genus named Plesiosuchus that lived after Tyrannoneustes during the late Jurassic is known to have grown to just short of seven meters long,‭ ‬at least roughly double the size of the Tyrannoneustes holotype.
       Although a predator in its own right,‭ ‬Tyrannoneustes would have needed to watch out for other larger oceanic predators,‭ ‬These may have included large sharks and ichthysaurs,‭ ‬but of a principal threat to Tyrannoneustes and other smaller thalattosuchians,‭ ‬would have been the pliosaurs,‭ ‬with genera such as Simolestes and Liopleurodon known to have likely been swimming in the same waters at the same time as Tyrannoneustes.

Further reading
-‭ ‬The oldest known metriorhynchid super-predator:‭ ‬a new genus and species from the Middle Jurassic of England,‭ ‬with implications for serration and mandibular evolution in predacious clades‭ ‬-‭ ‬Journal of Systematic Palaeontology‭ ‬-‭ ‬M.‭ ‬T.‭ ‬Young,‭ ‬M.‭ ‬B.‭ ‬d.‭ ‬Andrade,‭ ‬S.‭ ‬L.‭ ‬Brusatte,‭ ‬M.‭ ‬Sakamoto‭ & ‬J.‭ ‬Liston‭ ‬-‭ ‬2013.
- The first record of Tyrannoneustes (Thalattosuchia: Metriorhynchidae): a complete skull from the Callovian (late Middle Jurassic) of Germany. - PalZ 92, 457–480. - K. Waskow, D. Grzegorczyk & P. M. Sander - 2018.


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