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53-414: Callorhinchus , the plough-nosed chimaeras or elephantfish , are the only living genus in the family Callorhinchidae (sometimes spelled Callorhynchidae ). A few extinct genera only known from fossil remains are recognized. Callorhinchus spp. are similar in form and habits to other chimaeras , but are distinguished by the presence of an elongated, flexible, fleshy snout, with a vague resemblance to

106-557: A species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in the nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

159-403: A zygote that develops into a new diploid organism. It is generally accepted that isogamy is the ancestral state from which anisogamy and oogamy evolved, although its evolution has left no fossil records. There are almost invariably only two gamete types, all analyses showing that intermediate gamete sizes are eliminated due to selection. Since intermediate sized gametes do not have

212-399: A haploid ovum . Spermatogenesis , the process of male gamete formation in animals, involves meiosis in a diploid primary spermatocyte to produce haploid spermatozoa . In animals, ova are produced in the ovaries of females and sperm develop in the testes of males. During fertilization, a spermatozoon and an ovum, each carrying half of the genetic information of an individual, unite to form

265-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

318-401: A life cycle involving alternation of diploid and haploid generations some differences from animal life cycles exist. Plants use meiosis to produce spores that develop into multicellular haploid gametophytes which produce gametes by mitosis. In animals there is no corresponding multicellular haploid phase. The sperm of plants that reproduce using spores are formed by mitosis in an organ of

371-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

424-596: A ploughshare. They are only found in the oceans of the Southern Hemisphere along the ocean bottom on muddy and sandy substrates. They filter feed, with small shellfish making up the bulk of their diet. The plough-nosed chimaera lays eggs on the ocean floor that hatch at around 8 months. They are currently not a target of conservation efforts; however, they may be susceptible to overfishing and trawling. Plough-nose chimaeras range from about 70 to 125 cm (2.30 to 4.10 ft) in total length. Their usual color

477-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

530-527: A reproductive technique for same-sex male couples, although a surrogate mother would still be required for the gestation period. Women who have passed menopause may be able to produce eggs and bear genetically related children with artificial gametes. Robert Sparrow wrote, in the Journal of Medical Ethics , that embryos derived from artificial gametes could be used to derive new gametes and this process could be repeated to create multiple human generations in

583-407: A single human sperm cell. The type of gamete an organism produces determines its sex and sets the basis for the sexual roles and sexual selection . In humans and other species that produce two morphologically distinct types of gametes, and in which each individual produces only one type , a female is any individual that produces the larger type of gamete called an ovum , and a male produces

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636-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

689-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

742-403: Is 8 months, and the embryo uses the yolk for all nourishment. Once hatched, the young instinctively move to deeper water. The egg cases are long and flat, and resemble pieces of seaweed. The family contains three extant species, all in the same genus: A number of fossil species are also known, extending back into the mid- Cretaceous ( Albian ). Currently, no effort is being made to conserve

795-423: Is black or brown, and, often a mixture between the two. While the club-like snout makes elephantfish easy to recognize, they have several other distinctive features. They possess large pectoral fins, believed to aid in moving swiftly through the water. They also have two dorsal fins spaced widely apart, which help identify the species in the open ocean. In front of each pectoral fin is one single gill opening. Between

848-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

901-464: Is just under this snout and the eyes are located high on top of the head. They have broad, flat teeth that have adapted for this eating habit, two pairs that reside in the upper jaw and one pair in the lower jaw. In addition to its use for feeding, the "trunks" of the Callorhinchus fish can sense movement and electric fields, allowing them to locate their prey. Phylogenetically , they are

954-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

1007-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

1060-722: The IUCN , the three extant species of Callorhinchidae are all listed as least concern , as they remain common. While fishing quotas are in place in Australia and New Zealand, this is the furthest that the conservation effort spans. Rarely, they are caught to be placed in aquaria, but this is much less common than fishery for food. Genus The composition of a genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including

1113-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

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1166-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

1219-402: The gametes . They migrate to more shallow waters to spawn. Also, a club-like protrusion from the head is used to hold onto the female during mating. The keratinous eggs are released onto the muddy sediment of the ocean bottom, usually in shallower water. At first, the egg is a golden yellow color, but this transforms into brown, and finally, black right before hatching. The average time in the egg

1272-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

1325-551: The Callorhinchidae as a chimeric species due to their shared characteristics of both the sharks and rays. Members of this genus are all found in subtropical and temperate waters in the Southern Hemisphere: The encephalization quotient is 1.1, compared to 6 in humans. Compared to humans, it has a larger cerebellum than forebrain . Its vision is very poor and the electrical sensing capabilities of

1378-438: The Callorhinchidae have been shown to also feed on invertebrates such as jellyfish or small octopuses. They are considered to be incapable of eating bony fish, in that they cannot keep up with the teleosts ' speed. The Callorhinchidae are oviparous . Mating and spawning happen during the spring and early summer. Males possess the characteristic claspers near the pelvic fin that are seen in sharks, and these are used to transport

1431-473: The French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or the scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of

1484-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

1537-445: The cartilaginous fish class. They are considered to resemble a cross between a shark and a ray or skate, but can be distinguished from sharks because they possess an operculum over their gill slits. Additionally, their skin is smooth, not covered in tough scales, characteristic of the shark. While the shark's jaw is loosely attached to the skull, the family Callorhinchidae differ in that their jaws are fused to their skulls. Many classify

1590-464: The family Callorhinchidae, but the species are heavily fished for food in South America. Because of this, they are extremely susceptible to being overfished. The greatest risk to this species is trawling or net fishing. Using this method, large numbers are caught quickly. Once caught, the fish are sold as whitefish or silver trumpeter fillets. The most common location of export is Australia. Under

1643-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

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1696-402: The gametophyte known as the antheridium and the egg cells by mitosis in a flask-shaped organ called the archegonium . Plant sperm cells are their only motile cells, often described as flagellate, but more correctly as ciliate. Bryophytes have 2 flagella, horsetails have up to 200 and the mature spermatozoa of the cycad Zamia pumila has up to 50,000 flagella. Cycads and Ginkgo biloba are

1749-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

1802-506: The genes during meiosis ensures that the chromosomes of gametes are not exact duplicates of either of the sets of chromosomes carried in the parental diploid chromosomes but a mixture of the two. Artificial gametes, also known as in vitro derived gametes (IVD), stem cell-derived gametes (SCDGs), and in vitro generated gametes (IVG), are gametes derived from stem cells . The use of such artificial gametes would "necessarily require IVF techniques". Research shows that artificial gametes may be

1855-432: The idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but

1908-444: The laboratory. This technique could be used to create cell lines for medical applications and for studying the heredity of genetic disorders . Additionally, this technique could be used for human enhancement by selectively breeding for a desired genome or by using recombinant DNA technology to create enhancements that have not arisen in nature. Plants that reproduce sexually also produce gametes. However, since plants have

1961-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

2014-606: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Gametes A gamete ( / ˈ ɡ æ m iː t / ; from Ancient Greek γαμετή ( gametḗ )  'wife', ultimately from Ancient Greek γάμος ( gámos )  'marriage') is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually . Gametes are an organism's reproductive cells , also referred to as sex cells . The name gamete

2067-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

2120-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

2173-553: The oldest group of living jawed Chondrichthyes . They possess the same cartilaginous skeleton seen in sharks, but are considered holocephali to distinguish them from the shark and ray categorization. Because of this, they provide a useful research organism for studying the early development of the jawed characteristic. Among the Chondrichthyes, Callorhinchus has the smallest genome . Because of this, it has been proposed to be used for entire genome sequencing to represent

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2226-410: The only gymnosperms with motile sperm. In the flowering plants , the female gametophyte is produced inside the ovule within the ovary of the flower. When mature, the haploid gametophyte produces female gametes which are ready for fertilization. The male gametophyte is produced inside a pollen grain within the anther and is non-motile, but can be distributed by wind, water or animal vectors. When

2279-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

2332-406: The same advantages as small or large ones, they do worse than small ones in mobility and numbers, and worse than large ones in supply. In contrast to a gamete, which has only one set of chromosomes, a diploid somatic cell has two sets of homologous chromosomes , one of which is a copy of the chromosome set from the sperm and one a copy of the chromosome set from the egg cell. Recombination of

2385-415: The smaller type, called a sperm cell or spermatozoon. Sperm cells are small and motile due to the presence of a tail-shaped structure, the flagellum , that provides propulsion. In contrast, each egg cell or ovum is relatively large and non-motile. Oogenesis , the process of female gamete formation in animals, involves meiosis (including meiotic recombination ) of a diploid primary oocyte to produce

2438-496: The snout are predominantly used to find food. Both its circulatory and endocrine systems are similar to similar vertebrates, likely due to the early homologous structures the Callorhinchidae possess relative to the other Chondrichthyes. The Callorhinchidae are predominantly filter feeders, feeding on the sandy sediment of the ocean bottoms or continental shelves. The large protrusion of the snout aids in this task. Their diet consists of molluscs, more specifically, clams. Besides this,

2491-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

2544-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

2597-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

2650-437: The two dorsal fins is a spine, and the second dorsal fin is significantly smaller than the more anterior one. The caudal fin is divided into two lobes, the top one being larger. The eyes, set high on the head, are often green in color. The snout is used to probe the sea bottom in search of the invertebrates and small fishes on which it preys. The remainder of the body is flat and compressed, often described as elongated. The mouth

2703-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

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2756-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

2809-454: Was introduced by the German cytologist Eduard Strasburger in 1878. Gametes of both mating individuals can be the same size and shape, a condition known as isogamy . By contrast, in the majority of species, the gametes are of different sizes, a condition known as anisogamy or heterogamy that applies to humans and other mammals. The human ovum has approximately 100,000 times the volume of

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