Henodus

Name: Henodus ‭(‬Single tooth‭)‬.
Phonetic: Hen-oh-dus.
Named By: Friedrich von Huene‭ ‬-‭ ‬1936.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Sauropterygia,‭ ‬Placodontia,‭ ‬Henondontidae.
Species: H.‭ ‬chelyops‭ (‬type‭)‬.
Diet: Shellfish.
Size: 1‭ ‬meter long.
Known locations: Europe,‭ ‬Germany.
Time period: Carnian of the Triassic.
Fossil representation: Well preserved specimen.

       Although many of the placodonts had shells only a few like Henodus and Placochelys had single shells that covered the entire body,‭ ‬while others like Cyamodus had two shells.‭ ‬Henodus has one of the most well developed single shells of all placodonts made up by a fusion of a large number of scutes with a covering‭ ‬of‭ ‬horn,‭ ‬and is almost as wide as it is long.‭ ‬Aside from being very tough this made the shell was so large that most marine predators of the Triassic couldn’t get the shell of a full grown adult between their jaws.‭ ‬This shell however would have been a great hindrance when Henodus was on land and it may be that as a result Henodus spent most of its life in the water except for‭ ‬laying eggs‭ (‬assuming that placodonts laid eggs‭)‬.‭ ‬This is especially the case when you consider that Henodus had a plastron‭ (‬lower shell‭) ‬like a turtle,‭ ‬while the carapace‭ (‬upper shell‭) ‬was actually fused to the spine.
       Henodus differed from most other placodonts in that the mouth was broad and squared off instead of pointed.‭ ‬Henodus probably used this mouth to shovel through sediment to find shellfish that were buried just below the surface,‭ ‬while other placodonts with pointed mouths were better able to get shell fish wedged between rocks.‭ ‬Such feeding behaviour would also make Henodus a niche specialist that allowed it to share ecosystems with other placodonts without competition with them.

Further reading
- Henodus chelyops, ein neuer placodontier. - Sonder-Abduck aus Palaeontographica Beiträge zur Naturgeschichte der Vorzeit, Abteilung A 84:99-148. - F. von Huene - 1936.
- Der Dritte Henodus ergänzungen zur Kenntnis des Placodontiers Henodus chelyops Huene. - Sonder-Abdruck aus Palaeontographica Beiträge zur Naturgeschichte der Vorzeit, Abteilung A 89:105-114. - F. von Huene - 1938.



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