Information:  - Acipenser is a genus of sturgeons. With 17 species, many of which are threatened, it is the largest genus in the order Acipenseriformes.  - The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period million years ago (Mya), to the beginning of the Jurassic Period Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers ("tri" meaning "three") that are found throughout Germany and northwestern Europered beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstonescalled the "Trias".  - Huso is a genus of large sturgeons from Eurasia. It contains two species, which both are critically endangered:  - Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. Their evolution dates back to the Triassic some 245 to 208 million years ago. The family is grouped into four genera: "Acipenser", "Huso", "Scaphirhynchus" and "Pseudoscaphirhynchus". Four species may now be extinct. Two closely related species, "Polyodon spathula" (paddlefish) and "Psephurus gladius" (Chinese paddlefish, possibly extinct) are of the same order, Acipenseriformes, but are in the family Polyodontidae and are not considered to be "true" sturgeons. Both sturgeons and paddlefish have been referred to as "primitive fishes" because their morphological characteristics have remained relatively unchanged since the earliest fossil record. Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America.  Sturgeons are long-lived, late-maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to that of sharks, and an elongated spindle-like body that is smooth-skinned, scaleless and armored with 5 lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging 712 feet (2-3 m) in length. The largest sturgeon on record was a Beluga female captured in the Volga estuary in 1827, weighing and long. Most sturgeons are anadromous bottom-feeders which migrate upstream to spawn but spend most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean.  - Scaphirhynchinae is a subfamily of sturgeon which includes two genera comprising a total of six species . Genus Scaphirhynchus Heckel , 1835 ( native to North America ) Scaphirhynchus albus ( Forbes & R. E. Richardson , 1905 ) ( Pallid sturgeon ) Scaphirhynchus platorynchus ( Rafinesque , 1820 ) ( Shovelnose sturgeon ) Scaphirhynchus suttkusi J. D. Williams & Clemmer , 1991 ( Alabama sturgeon ) Genus Pseudoscaphirhynchus Nikolskii , 1900 ( native to Central Asia ) Pseudoscaphirhynchus fedtschenkoi ( Kessler , 1872 ) ( Syr Darya sturgeon ) Pseudoscaphirhynchus hermanni ( Kessler , 1877 ) ( Dwarf sturgeon ) Pseudoscaphirhynchus kaufmanni ( Kessler , 1877 ) ( Amu Darya sturgeon  - Scaphirhynchus is a genus of sturgeons native to the United States of America. All species in this genus are considered to be threatened. The pallid sturgeon is Endangered and the Alabama sturgeon is Critically Endangered.  - Acipenseriformes is an order of basal ray-finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families.  - Pseudoscaphirhynchus is a genus of fishes in the Acipenseridae family. The three species, all of which are threatened, are restricted to Central Asia.    What is the relationship between 'scaphirhynchinae' and 'acipenseridae'?
parent taxon