Context: Asia is Earth's largest and most populous continent, located primarily in the eastern and northern hemispheres and sharing the continental landmass of Eurasia with the continent of Europe. Asia covers an area of , about 30% of Earth's total land area and 8.7% of the Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilizations. Asia is notable for not only its overall large size and population, but also dense and large settlements as well as vast barely populated regions within the continent of 4.4 billion people., In biology, an organism is any contiguous living system, such as an animal, plant, fungus, archaeon, or bacterium. All known types of organisms are capable of some degree of response to stimuli, reproduction, growth and development and homeostasis. An organism consists of one or more cells; when it has one cell it is known as a unicellular organism; and when it has more than one it is known as a multicellular organism. Most unicellular organisms are of microscopic scale and are thus loosely described as microorganisms. Humans are multicellular organisms composed of many trillions of cells grouped into specialized tissues and organs., The Atlantic Ocean is the second largest of the world's oceans with a total area of about . It covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. It separates the "Old World" from the "New World"., Binomial nomenclature (also called binominal nomenclature or binary nomenclature) is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just "binomial"), a binomen or a scientific name; more informally it is also called a Latin name. The first part of the name identifies the genus to which the species belongs; the second part identifies the species within the genus. For example, humans belong to the genus "Homo" and within this genus to the species "Homo sapiens". The "formal" introduction of this system of naming species is credited to Carl Linnaeus, effectively beginning with his work "Species Plantarum" in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book "Pinax theatri botanici" (English, "Illustrated exposition of plants") many names of genera that were later adopted by Linnaeus., 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., A genus ( genera) is a taxonomic rank used in the biological classification of living and fossil organisms in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus., Eurasia is the combined continental landmass of Europe and Asia. The term is a portmanteau of its constituent continents. Located primarily in the Northern and Eastern Hemispheres, it is bordered by the Atlantic Ocean to the west, the Pacific Ocean to the east, the Arctic Ocean to the north, and by Africa, the Mediterranean Sea, and the Indian Ocean to the south. The division between Europe and Asia as two different continents is a historical and cultural construct, with no clear physical separation between them; thus, in some parts of the world, Eurasia is recognized as the largest of five or six continents. In geology, Eurasia is often considered as a single rigid megablock. However, the rigidity of Eurasia is debated based on the paleomagnet data., Africa is the world's second-largest and second-most-populous continent. At about 30.3 million km² (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area and 20.4 % of its total land area. With 1.1 billion people as of 2013, it accounts for about 15% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, both the Suez Canal and the Red Sea along the Sinai Peninsula to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognized sovereign states (countries), nine territories and two "de facto" independent states with limited or no recognition., Huso is a genus of large sturgeons from Eurasia . It contains two species , which both are critically endangered : Huso dauricus ( Georgi , 1775 ) ( kaluga ) Huso huso ( Linnaeus , 1758 ) ( beluga ) Recent data indicate a polyphyletic origin of the genus Huso , and it is suggested that the two Huso species should be included in the genus Acipenser ., Subject: huso, Relation: parent_taxon, Options: (A) acipenseridae (B) animal (C) area (D) homo
Output: acipenseridae