''Brachydegma'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of prehistoric freshwater ray-finned fish that lived during the Leonardian age (

Cisuralian The Cisuralian is the first Series (stratigraphy), series/Epoch (geology), epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian (geology), Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the w ...

/lower Permian) in what is now Texas, United States. It is known from two fossils, which were recovered from the Clear Fork Formation. A potential record is also known from the concurrent Hennessey Formation of

Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

. It is one of the only fossil ray-finned fish from the Permian that preserves the skull bones in three dimensions.

Classification

''Brachydegma'' was first considered a " palaeoniscid". A later study rather suggested that ''Brachydegma'' could be one of the earliest crown neopterygians ( Halecomorphi) known from the fossil record. However, this view relied on misinterpretations of cranial features. A more recent study yielded conflicting placements of ''Brachydegma'' on the actinopterygian tree of life, rendering its placement in an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

or family difficult. It appears to be closely related or possibly a member of the

crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

of Actinopterygii, though a closer relationship with either Neopterygii or Polypteriformes appears plausible.

References

Monotypic prehistoric ray-finned fish genera Permian fish of North America Permian bony fish Kungurian genera Fossils of Texas Fossil taxa described in 1939 {{paleo-rayfinned-fish-stub

Classification

See also

References