Name: Diplomystus ‭(‬Double whiskers‭)‬.
Phonetic: Dip-low-my-stus.
Named By: Edward Drinker Cope‭ ‬-‭ ‬1877.‭
Synonyms: Clupea humilis, Clupea theta, Clupea vectensis, Copeichthys, Diplomystus analis, Diplomystus pectorosus, Diplomystus theta.
Classification: Chordata,‭ ‬Actinopterygii,‭ ‬Clupeiformes,‭ ‬Ellimmichthyidae.
Species: D.‭ ‬dentatus‭ (‬type‭)‬,‭ D. altisomus, ‬D.‭ ‬birdii,‭ ‬D. dartevellei, D. dentatus, D. dubretreiti, D. humilis, D. kokuraensis, D. primotinus, D. shengliensis, D. vectensis.
Diet: Small invertebrates and small fish.
Size: Up to‭ ‬65‭ ‬centimetres long.
Known locations: USA,‭ ‬Wyoming‭ ‬-‭ ‬Green River Formation. Also Japan - Third Formation, Italy and Morocco - Akfabou Formation.
Time period: Lower Eocene.
Fossil representation: So numerous no one knows for certain how many specimens have been recovered.

       Diplomystus are thought to be related to modern day herring,‭ ‬and like them their strongly upturned mouths suggest that they fed in open water rather than feeding off the bottom.‭ ‬Although Diplomystus are known to have grown up to sixty-five centimetres long,‭ ‬fossils of Diplomystus are usually smaller with fossils even revealing the presence of Diplomystus fry.
       Diplomystus are often found in association with other Eocene fish from the Green River Formation,‭ ‬particularly the genus Knightia.‭ ‬In fact fossil evidence suggests that Diplomystus preyed upon Knightia.‭ ‬Like Knightia,‭ ‬Diplomystus are quite common and are often found for sale on the fossil market.

Further reading
- Early Cretaceous freshwater fishes from Northern Kyushu, Japan I. Description of two new species of the clupeid genus Diplomystus - T. Uyeno - 1979.
- Early Cretaceous Freshwater Fishes From Japan and Korea - Yoshitaka Yabumoto, Seong-Young Yang & Tae-Wan Kim - 2006.


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