See text Birgeria is a genus of carnivorous marine ray-finned fish from the Triassic period.

[3] Birgeria had a global distribution, with fossil known from Madagascar, Spitsbergen, Germany, Switzerland, Italy, Slovenia, China, Russia, Canada and Nevada, United States.

The oldest fossils are from Griesbachian aged beds of the Wordie Creek Formation of East Greenland.

He thus erected a new genus, which he named after his colleague Birger Sjöström, who had joined him on an expedition to the Arctic island of Spitsbergen (Svalbard) in 1915.

[3][6] The genera Psilichthys, Ohmdenia and Brazilichthys have been previously referred to Birgeriidae, but they were shown to be only distantly related to Birgeria.

[9] Together, they are also often recovered as stem chondrosteans, closely related to sturgeons and paddlefish (Acipenseriformes), with their exact relationship to each other and to sturgeons/paddlefish varying depending on the study.

[15] A jaw fragment from the Late Triassic of California, described as Xenestes velox by David Starr Jordan, was tentatively synonymized with Birgeria.

The axial skeleton consists of ossified neural and haemal arches, both of which may show spines, and additional supraneurals.

[1] A specimen of Birgeria nielseni from Madagascar was described as supposedly carrying embryos whose bodies are covered with rhombic scales.

[18] It is more likely that these "embryos" were actually preyed ray-fins, which would indicate that the diet of Birgeria included small actinopterygians.

Based on its anatomical features, Birgeria is interpreted as a pelagic, swift swimmer.