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  • Erismatopterus levatus (COPE, 1870)


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    • Erismatopterus is only known from Lake Gosiute and Lake Uinta deposits. It is one of the rarer Green River fish fossils, except in some mass mortality zones.  Erismatopterus belongs together with its close relative Amphiplaga to the family Percopsidae within the order Percopsiformes.  

       

      Amphiplaga is best distinguished from Erismatopterus  by its dorsal fin, which has three hard spines (the first one is very small) followed by 9 or 10 soft rays. Erismatopterus usually has two hard spines followed by 6 or 7 soft spines. Amphiplaga can reach up to 15cm with an average length of about 10cm while Erismatopterus does not exceed 12cm with an average length of about 5cm.

       

      The Order Percopsiformes is a small order of North American freshwater fishes that includes three families: Amblyopsidae (cavefishes); Aphredoderidae (pirate perches); and Percopsidae (trout-perches).  Closely related to neither trout nor perch, trout-perches have characteristics of both the trout and perch families. They exhibit characters of the salmonids, such as an adipose fin, cycloid scales, and soft fin rays, as well as characters of the percids, such as dorsal and anal fin spines, and ctenoid scales.    

      Trout-perch are generally silvery in appearance, often with a partially transparent appearance, and relatively large heads and eyes. They are small fish with weak fin spines, and an adipose fin similar to those of trouts.  They feed on insects and small crustaceans.
       

      Fossil percopsids are only known from North America, the current home of the extant genus Percopsis

       

      Lit.:

      E. D. Cope. 1877. A contribution to the knowledge of the ichthyological fauna of the Green River shales. Bulletin of the United States Geological and Geographical Survey 3(4):807-819

       

      Grande, L. (1984): PALEONTOLOGY OF THE GREEN RIVER FORMATION, WITH A REVIEW OF THE FISH FAUNA. THE GEOLOGICAL SURVEY OF WYOMING, BULLETIN 63

    Taxonomy

    Trout-perch

    Kingdom: Animalia
    Phylum: Cordata
    Class: Actinopterygia
    Order: Percopsiformes
    Family: Percopsidae
    Genus: Erismatopterus
    Species: E. levatus
    Author Citation (COPE, 1870)

    Geological Time Scale

    Eon: Phanerozoic
    Era: Cenozoic
    Period: Paleogene
    Epoch: Eocene
    International Age: Ypresian

    Stratigraphy

    Green River Formation
    Lake Gosiute

    Provenance

    Acquired by: Purchase/Trade

    Location

    Lincoln County
    Wyoming
    United States

    Comments

    Erismatopterus is only known from Lake Gosiute and Lake Uinta deposits. It is one of the rarer Green River fish fossils, except in some mass mortality zones.  Erismatopterus belongs together with its close relative Amphiplaga to the family Percopsidae within the order Percopsiformes.  

     

    Amphiplaga is best distinguished from Erismatopterus  by its dorsal fin, which has three hard spines (the first one is very small) followed by 9 or 10 soft rays. Erismatopterus usually has two hard spines followed by 6 or 7 soft spines. Amphiplaga can reach up to 15cm with an average length of about 10cm while Erismatopterus does not exceed 12cm with an average length of about 5cm.

     

    The Order Percopsiformes is a small order of North American freshwater fishes that includes three families: Amblyopsidae (cavefishes); Aphredoderidae (pirate perches); and Percopsidae (trout-perches).  Closely related to neither trout nor perch, trout-perches have characteristics of both the trout and perch families. They exhibit characters of the salmonids, such as an adipose fin, cycloid scales, and soft fin rays, as well as characters of the percids, such as dorsal and anal fin spines, and ctenoid scales.    

    Trout-perch are generally silvery in appearance, often with a partially transparent appearance, and relatively large heads and eyes. They are small fish with weak fin spines, and an adipose fin similar to those of trouts.  They feed on insects and small crustaceans.
     

    Fossil percopsids are only known from North America, the current home of the extant genus Percopsis

     

    Lit.:

    E. D. Cope. 1877. A contribution to the knowledge of the ichthyological fauna of the Green River shales. Bulletin of the United States Geological and Geographical Survey 3(4):807-819

     

    Grande, L. (1984): PALEONTOLOGY OF THE GREEN RIVER FORMATION, WITH A REVIEW OF THE FISH FAUNA. THE GEOLOGICAL SURVEY OF WYOMING, BULLETIN 63



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