Information: - Hydrozoa (hydrozoans, from ancient Greek , "hydra", "sea serpent" and , "zoon", "animal") are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most living in salt water. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony. A few genera within this class live in fresh water. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria. - Heterastridium is a genus of fossil marine Hydrozoan from the Upper Triassic . They are mostly discoid or spherical and some forms found in the Karakorum mountains are called Karakorum stones . They vary in diameter from 1 to 35 cm and appear to follow Cope 's rule for the prehistoric climate . - Cope's rule, named after American paleontologist Edward Drinker Cope, postulates that population lineages tend to increase in body size over evolutionary time. It was never actually stated by Cope, although he tended to hypothesize the occurrence of linear evolutionary trends. It is sometimes also known as the Cope-Deperet rule, because Charles Deperet explicitly advocated the idea. Theodor Eimer had also done so earlier. The term "Cope's rule" was apparently coined by Bernhard Rensch, based on the fact that Deperet had "lionized Cope" in his book. While the rule has been demonstrated in many instances, it does not hold true at all taxonomic levels, or in all clades. Larger body size is associated with increased fitness for a number of reasons, although there are also some disadvantages both on an individual and on a clade level: clades comprising larger individuals are more prone to extinction, which may act to limit the maximum size of organisms. - Mongolia (Mongolian: ["Monggol Ulus"] in Mongolian script; ["Mongol Uls"] in Mongolian Cyrillic) is a landlocked unitary sovereign state in East Asia. Its area is roughly equivalent with the historical territory of Outer Mongolia, and that term is sometimes used to refer to the current state. It is sandwiched between China to the south and Russia to the north. While it does not share a border with Kazakhstan, Mongolia is separated from it by only . - 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. - Jellyfish or jellies are softbodied, free-swimming aquatic animals with a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate to acquire propulsion and locomotion. The tentacles may be utilized to capture prey or defend against predators by emitting toxins in a painful sting. Jellyfish species are classified in the subphylum Medusozoa which makes up a major part of the phylum Cnidaria, although not all Medusozoa species are considered to be jellyfish. - 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. - The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era; the following Triassic Period belongs to the Mesozoic Era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. - 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. - Bernhard Rensch (21 January 1900 4 April 1990) was a German evolutionary biologist and ornithologist who did field work in Indonesia and India. He is probably best known as one of the architects of the modern evolutionary synthesis, which he popularised in Germany. Besides his work on how environmental factors influenced the evolution of geographically isolated populations and on evolution above the species level, which contributed to the modern synthesis, he also worked extensively in the area of animal behavior (ethology). His education and scientific work were interrupted by service in the German military during both World War I and World War II. - Karakorum (Classical Mongolian: "Qara Qorum", Khalkha Mongolian: "Kharkhorum") was the capital of the Mongol Empire between 1235 and 1260, and of the Northern Yuan in the 1415th centuries. Its ruins lie in the northwestern corner of the Ovorkhangai Province of Mongolia, near today's town of Kharkhorin, and adjacent to the Erdene Zuu monastery. They are part of the upper part of the World Heritage Site Orkhon Valley Cultural Landscape. - 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". - Germany, officially the Federal Republic of Germany, is a federal parliamentary republic in central-western Europe. It includes 16 constituent states, covers an area of , and has a largely temperate seasonal climate. With about 82 million inhabitants, Germany is the most populous member state of the European Union. After the United States, it is the second most popular immigration destination in the world. Germany's capital and largest metropolis is Berlin. Other major cities include Hamburg, Munich, Cologne, Frankfurt, Stuttgart and Dusseldorf. - Kharkhorin is a town and sum (district) center in Ovorkhangai Province in Mongolia. The sum population was 13,828 (1994), 13,964 (2000), and 13,496 (2003). The population of Kharkhorin town itself was 8,977 in 2003 and covered an area of 20.5 km. - The Jurassic (from Jura Mountains) is a geologic period and system that spans 56.3 million years from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period is marked by the major TriassicJurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian/Toarcian event in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions. After reading the paragraphs above, choose the best answer for the entity that related to 'heterastridium' with the relationship of 'parent taxon'. Choices: - animal - area - homo - idea - medusozoa - mya
A:
medusozoa