Name: Stenopterygius ‭(‬Narrow wing‭)‬.
Phonetic: Sten-op-teh-re-ge-us.
Named By: Otto Jaekel‭ ‬-‭ ‬1904.
Synonyms: ‭ ‬Ichthyosaurus quadriscissus,‭ ‬I.‭ ‬triscissus,‭ ‬Stenopterygius eos,‭ ‬S.‭ ‬incessus,‭ ‬S.‭ ‬hauffianus,‭ ‬S.‭ ‬longifrons,‭ ‬S.‭ ‬megacephalus,‭ ‬S.‭ ‬megalorhinus.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Ichthyosauria,‭ ‬Stenopterygiidae.
Species: S.‭ ‬quadriscissus‭ (‬type‭)‬,‭ ‬S.‭ ‬triscissus,‭ ‬S.‭ ‬uniter,‭ ‬S.‭ ‬aaleniensis.
Diet: Piscivore/carnivore.
Size: Average around‭ ‬3‭ ‬to‭ ‬4‭ ‬meters long,‭ ‬depending upon the species.
Known locations: England,‭ ‬France,‭ ‬Germany,‭ ‬Luxembourg and Switzerland.
Time period: Toarcian to Aalenian of the Jurassic.
Fossil representation: Over‭ ‬100‭ ‬specimens.

       Stenopterygius is yet another example of a genus that once had a large number of species assigned to it only for most of these to now be regarded as synonyms to other previously named species.‭ ‬In addition while some of the remains of one species,‭ ‬S.‭ ‬hauffianus were reassigned to the type species S.‭ ‬quadriscissus,‭ ‬some of the former remains of this species were used to establish the genus Hauffiopteryx.‭ ‬Also like with many other ichthyosaurs,‭ ‬Stenopterygius was initially described as a species of Ichthyosaurus by Stenopterygius in‭ ‬1856,‭ ‬until Otto Jaekel discovered the remains to actually belong to a distinct genus.
       At least one well preserved specimen of Stenopterygius shows a large embryo inside the body of a female.‭ ‬Combined with other specimens showing the actual birth of baby ichthyosaurs,‭ ‬this‭ ‬helps prove without doubt that ichthyosaurs were viviparous reptiles,‭ ‬which in laymens terms means that they gave birth to live young instead of laying eggs.‭ ‬Although this might seem strange,‭ ‬live birth is actually well documented in some species of reptiles,‭ ‬including some modern species of snake and lizard alive today.‭ ‬Baby ichthyosaurs are also known to be born tail first so that they didn’t drown while being passed out of the birth canal.
       Like with the majority of other icthyosaurs,‭ ‬Stenopterygius was a pelagic‭ (‬open seas‭) ‬hunter of fish and cephalopods like squid.‭ ‬In this environment its streamlined body would have afforded Stenopterygius with a high degree of speed and mobility,‭ ‬allowing it to hunt in a similar manner to a dolphin.‭ ‬Possible predators of Jurassic era ichthyosaurs like Stenopterygius may have included large pliosaurs similar to Simolestes and Pliosaurus‭ (‬although these two genera lived a little later than Stenopterygius‭)‬.‭ ‬Although while in the water Stenopterygius would have been very difficult to catch,‭ ‬they like other marine reptiles would still need to surface to breathe in fresh air,‭ ‬and it would be then that they would be at their most vulnerable.

Further reading
- Revision der Gattung Stenopterygius Jaekel, 1904 emend. von Huene, 1922 (Reptilia: Ichthyosauria) aus dem unteren Jura Westeuropas - Palaeodiversity 1: 227–271. - Michael W. Maisch - 2008.
- First diagnostic marine reptile remains from the Aalenian (Middle Jurassic): a new ichthyosaur from southwestern Germany - PLoS ONE 7(8):e41692 - E. E. Maxwell, M. S. Fernández & R. R. Schoch - 2012.


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