Exquisitely-Preserved Discoserra Bear Gulch Fish Fossil

Discoserra pectinodon

Class Actinoptergyii, Order Guildayichthyformes, Family Guildayichthyidae

Geological Time: Mississippian (~320 m.y.a.)

Size: Fish fossil is 60 mm long

Fossil Site: Bear Gulch Limestone, Heath Shale Formation, Fergus County, Montana

DiscoserraDescription: The Bear Gulch Limestone is a deposit of some 70 square km in extent and 30 m in depth that has been a source of one of the most diverse assemblages of fossil fish with some 110 species having been described over the past 30 years. Most were new to science, and provided a unique view of the marine environment of Mississippian times. Fine preservation of both fish and invertebrates is a hallmark of these deposits, presumably due to an anoxic depositional environment. This fine specimen is a rare example of Gulidayichthyformes. The order and family was erected in 2000 to accommodate this unusual taxon which possesses an unusual mixture of primitive and modern characters in the skull bones. Note the detailed rhombic ganoid type scales and comb-like teeth. The species derives its name from the long teeth which presumably aided it in feeding, possibly on sponges. The 2 tone matrix color for the one side is because of a fracture (repaired with little impact to the specimen) in the upper piece which caused differential weathering of the piece below.

Overall, this is an exceptional example of the type, one that is sure to become a keystone of any Carboniferous fossil fish collection rendered all the more desirable by the fact that both the part and counterpart examples are preserved.

click to enlarge

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