Order Guildayichthyformes, Family Guildayichthyidae
Time: Mississippian (~320 m.y.a.)
fossil is 60 mm long
Site: Bear Gulch Limestone, Heath Shale Formation, Fergus County,
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.
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
counterpart examples are preserved.