50-661: Megalosauroidea (meaning 'great/big lizard forms') is a superfamily (or clade ) of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period. The group is defined as Megalosaurus bucklandii and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus . Members of the group include Spinosaurus , Megalosaurus , and Torvosaurus . They are possibly paraphyletic in nature with respect to Allosauroidea . The name Spinosauroidea
100-492: A BioCode that would regulate all taxon names, but this attempt has so far failed because of firmly entrenched traditions in each community. Consider a particular species, the red fox , Vulpes vulpes : in the context of the Zoological Code , the specific epithet vulpes (small v ) identifies a particular species in the genus Vulpes (capital V ) which comprises all the "true" foxes. Their close relatives are all in
150-420: A "hybrid formula" that specifies the parentage, or may be given a name. For hybrids receiving a hybrid name , the same ranks apply, prefixed with notho (Greek: 'bastard'), with nothogenus as the highest permitted rank. If a different term for the rank was used in an old publication, but the intention is clear, botanical nomenclature specifies certain substitutions: Classifications of five species follow:
200-424: A 'sigmoidal' humerus. It has been proposed that they are basal Allosaurs or Non Megalosaurian Megalosauroids. If Piatnitzkysaurids are Megalosauroids, they can be distinguished from other megalosauroids and placed into their own category due to the following synapomorphies (distinguishing features): In addition, this family shows several reversals to basal Tetanuran traits. These include: Piatnitzkysauridae
250-472: A basal allosauroid displaying a mosaic of primitive and derived features seen within Tetanurae . Their phylogenetic analysis found traditional Megalosauroidea to represent a basal grade of carnosaurs, paraphyletic with respect to Allosauroidea . Monolophosaurus [REDACTED] Taxonomic rank In biology , taxonomic rank (which some authors prefer to call nomenclatural rank because ranking
300-410: A branch clade with the same name containing all species closer to Spinosaurus than to Passer domesticus . The ICZN holds that even clade names (which do not yet have any governing body) should be replaced if having a traditional taxon suffix and being synonyms of ranked taxa at or below the superfamily level. The seniority of Megalosauroidea was not followed in most paleontological literature during
350-470: A clade containing the megalosaurids (such as Megalosaurus and Torvosaurus ) and the spinosaurids (such as Spinosaurus and Baryonyx ). Condorraptor and Piatnitzkysaurus are generally grouped together within this family in a clade excluding Marshosaurus . This is not only due to Condorraptor and Piatnitzkysaurus being from the same locality and time period, but also due to them having flat anterior faces of presacral vertebrae as well as
400-560: A fast evolutionary radiation that occurred long ago, such as the main taxa of placental mammals . In his landmark publications, such as the Systema Naturae , Carl Linnaeus used a ranking scale limited to kingdom, class, order, genus, species, and one rank below species. Today, the nomenclature is regulated by the nomenclature codes . There are seven main taxonomic ranks: kingdom, phylum or division, class, order, family, genus, and species. In addition, domain (proposed by Carl Woese )
450-638: A lower level may be denoted by adding the prefix " infra ", meaning lower , to the rank. For example, infra order (below suborder) or infra family (below subfamily). Botanical ranks categorize organisms based (often) on their relationships ( monophyly is not required by that clade, which does not even mention this word, nor that of " clade "). They start with Kingdom, then move to Division (or Phylum), Class, Order, Family, Genus, and Species. Taxa at each rank generally possess shared characteristics and evolutionary history. Understanding these ranks aids in taxonomy and studying biodiversity. There are definitions of
500-399: A new rank at will, at any time, if they feel this is necessary. In doing so, there are some restrictions, which will vary with the nomenclature code that applies. The following is an artificial synthesis, solely for purposes of demonstration of absolute rank (but see notes), from most general to most specific: Ranks are assigned based on subjective dissimilarity, and do not fully reflect
550-453: A new subfamily was named, Afrovenatorinae , to include all megalosaurids more closely related to Afrovenator than to Megalosaurus . Unlike Benson et al. , 2010, they recovered Poekilopleuron as an afrovenatorine, while Xuanhanosaurus was recovered as the basalmost metriacanthosaurid . However, the position of these taxa is very unstable, and their exclusion from the analysis gave more resolved and stable cladogram. Streptospondylus
SECTION 10
#1732848493226600-459: A particular organism, it is usually not necessary to specify names at ranks other than these first two, within a set of taxa covered by a given rank-based code. However, this is not true globally because most rank-based codes are independent from each other, so there are many inter-code homonyms (the same name used for different organisms, often for an animal and for a taxon covered by the botanical code). For this reason, attempts were made at creating
650-421: A pronounced ventral keel on the anterior dorsal vertebrae. Due to the strong resemblance to Piatnitzkysaurus , it has been suggested that the sister taxa Condorraptor could be better interpreted as the result of individual variation within the species, and not as separate taxa. The main noted differences between the two dinosaurs include both a less well developed enemial crest and a first sacral vertebra with
700-454: A shallower fossa in Condorraptor . Xuanhanosaurus , a problematic tetanuran with uncertain affinities, was placed as the sister taxon of these three genera when their relation was first observed in 2010. However, due to the incompleteness of Xuanhanosaurus's remains, this placement is considered uncertain. Other studies have considered Xuanhanosaurus a basal tetanuran. Xuanhanosaurus
750-576: A taxon in a category above the species level). It should be a natural group (that is, non-artificial, non- polyphyletic ), as judged by a biologist, using all the information available to them. Equally ranked higher taxa in different phyla are not necessarily equivalent in terms of time of origin, phenotypic distinctiveness or number of lower-ranking included taxa (e.g., it is incorrect to assume that families of insects are in some way evolutionarily comparable to families of mollusks). Of all criteria that have been advocated to rank taxa, age of origin has been
800-564: Is also called a binomial , that is, a two-term name. For example, the zoological name for the human species is Homo sapiens . This is usually italicized in print or underlined when italics are not available. In this case, Homo is the generic name and it is capitalized; sapiens indicates the species and it is not capitalized. While not always used, some species include a subspecific epithet. For instance, modern humans are Homo sapiens sapiens , or H. sapiens sapiens . In zoological nomenclature, higher taxon names are normally not italicized, but
850-476: Is an extinct family of megalosauroid or basal allosauroid dinosaurs . It only consists of three to four known dinosaur genera: Condorraptor , Marshosaurus , Piatnitzkysaurus and possibly Xuanhanosaurus . The most complete and well known member of this family is Piatnitzkysaurus , which also gives the family its name. So far all known piatnitzkysaurids have only been found in Jurassic deposits of
900-425: Is defined as all members of Megalosauroidea more closely related to Piatnitzkysaurus than to either Spinosaurus or Megalosaurus . Condorraptor, Marshosaurus, and Piatnitzkysaurus were all placed in a clade by Benson in 2010 during a redescription of Megalosaurus . This clade was defined as a family by Carrano et al in 2012 . Piatnitzkysauridae has been recovered as the sister taxa to Megalosauria ,
950-462: Is not a requirement of the zoological and botanical codes. A classification in which all taxa have formal ranks cannot adequately reflect knowledge about phylogeny. Since taxon names are dependent on ranks in rank-based (Linnaean) nomenclature, taxa without ranks cannot be given names. Alternative approaches, such as phylogenetic nomenclature , as implemented under the PhyloCode and supported by
1000-435: Is now widely used as a fundamental rank, although it is not mentioned in any of the nomenclature codes, and is a synonym for dominion ( Latin : dominium ), introduced by Moore in 1974. A taxon is usually assigned a rank when it is given its formal name. The basic ranks are species and genus. When an organism is given a species name it is assigned to a genus, and the genus name is part of the species name. The species name
1050-406: Is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of organisms (a taxon ) in a hierarchy that reflects evolutionary relationships. Thus, the most inclusive clades (such as Eukarya and Opisthokonta ) have the highest ranks, whereas the least inclusive ones (such as Homo sapiens or Bufo bufo ) have
SECTION 20
#17328484932261100-428: Is sometimes used in place of Megalosauroidea. The superfamily Spinosauroidea was named in 1915 by Ernst Stromer . It is a synonym of Megalosauroidea in almost all modern phylogenetic analyses, and it is therefore redundant. Spinosauroidea was defined as a clade in 1998 by Paul Sereno as the node clade containing the common ancestor of Spinosaurus and Torvosaurus and all its descendants. Thomas Holtz in 2004 defined
1150-557: Is still sometimes found as a Piatnitzkysauridae. In 2019, Rauhut and Pol described Asfaltovenator vialidadi , a basal allosauroid displaying a mosaic of primitive and derived features seen within Tetanurae . Their phylogenetic analysis found traditional Megalosauroidea to represent a basal grade of carnosaurs, paraphyletic with respect to Allosauroidea . Because the authors amended the definition of Allosauroidea to include all theropods that are closer to Allosaurus fragilis than to either Megalosaurus bucklandii or Neornithes ,
1200-439: Is usually associated with a certain body plan , which is also, however, an arbitrary criterion. Enigmatic taxa are taxonomic groups whose broader relationships are unknown or undefined. (See Incertae sedis .) There are several acronyms intended to help memorise the taxonomic hierarchy, such as "King Phillip came over for great spaghetti". (See taxonomy mnemonic .) Piatnitzkysauridae Piatnitzkysauridae
1250-762: The Botanical Code , the Prokaryotic Code , the Code for Viruses , the draft BioCode and the PhyloCode all recommend italicizing all taxon names (of all ranks). There are rules applying to the following taxonomic ranks in the International Code of Zoological Nomenclature : superfamily, family, subfamily, tribe, subtribe, genus, subgenus, species, subspecies. The International Code of Zoological Nomenclature divides names into "family-group names", "genus-group names" and "species-group names". The Code explicitly mentions
1300-474: The International Society for Phylogenetic Nomenclature , or using circumscriptional names , avoid this problem. The theoretical difficulty with superimposing taxonomic ranks over evolutionary trees is manifested as the boundary paradox which may be illustrated by Darwinian evolutionary models. There are no rules for how many species should make a genus, a family, or any other higher taxon (that is,
1350-689: The Morrison Formation of the United States , which was dated to the Kimmeridgian epoch of the Late Jurassic . Piatnitzkysaurids were among the first large theropods present in South America, and are evidence for a radiation of basal tetanurans in the middle Jurassic. Although there is support for basal megalosauroid affinities, piatnitzkysaurids also share some traits with allosaurids , such as
1400-727: The Prokaryotic Code , and the Code for Viruses ) require them. However, absolute ranks are not required in all nomenclatural systems for taxonomists; for instance, the PhyloCode , the code of phylogenetic nomenclature , does not require absolute ranks. Taxa are hierarchical groups of organisms, and their ranks describes their position in this hierarchy. High-ranking taxa (e.g. those considered to be domains or kingdoms, for instance) include more sub-taxa than low-ranking taxa (e.g. those considered genera, species or subspecies). The rank of these taxa reflects inheritance of traits or molecular features from common ancestors. The name of any species and genus are basic ; which means that to identify
1450-516: The Tetanurae that includes more taxa. They used the clade name Megalosauria (Bonaparte, 1850) in their analysis and defined it as the node comprising Megalosaurus , Spinosaurus , their most recent common ancestor, and all its descendants. Furthermore, a new megalosauroid family Piatnitzkysauridae was named to include all megalosauroids more closely related to Piatnitzkysaurus than to either Spinosaurus or Megalosaurus . Within Megalosauridae
1500-427: The fruit fly familiar in genetics laboratories ( Drosophila melanogaster ), humans ( Homo sapiens ), the peas used by Gregor Mendel in his discovery of genetics ( Pisum sativum ), the "fly agaric" mushroom Amanita muscaria , and the bacterium Escherichia coli . The eight major ranks are given in bold; a selection of minor ranks are given as well. Taxa above the genus level are often given names based on
1550-418: The type genus , with a standard termination. The terminations used in forming these names depend on the kingdom (and sometimes the phylum and class) as set out in the table below. Pronunciations given are the most Anglicized . More Latinate pronunciations are also common, particularly / ɑː / rather than / eɪ / for stressed a . There is an indeterminate number of ranks, as a taxonomist may invent
Megalosauroidea - Misplaced Pages Continue
1600-627: The western hemisphere / New world (however, if Xuanhanosaurus is included than this may expand their range). Piatnitzkysaurus and Condorraptor hail from the Cañadón Asfalto Formation of Argentina , which has been dated from the Toarcian epoch of the Early Jurassic to the Bathonian epoch of the Middle Jurassic (approximately 179 to 168 million years ago). Marshosaurus was found in
1650-449: The 1990s and early 2000s. A series of papers supporting the validity of Megalosaurus as a genus, the relationships of megalosauroids, and the placement of "spinosauroids" among them, published between 2008 and 2010 argued that Megalosauroidea was in fact the valid name for the group. The classification of megalosauroids follows a study by Benson in 2010. Note that several "wildcard" taxa that are probably megalosauroids were excluded from
1700-612: The American Ornithologists' Union published in 1886 states "No one appears to have suspected, in 1842 [when the Strickland code was drafted], that the Linnaean system was not the permanent heritage of science, or that in a few years a theory of evolution was to sap its very foundations, by radically changing men's conceptions of those things to which names were to be furnished." Such ranks are used simply because they are required by
1750-432: The family Canidae , which includes dogs, wolves, jackals, and all foxes; the next higher major taxon, Carnivora (considered an order), includes caniforms (bears, seals, weasels, skunks, raccoons and all those mentioned above), and feliforms (cats, civets, hyenas, mongooses). Carnivorans are one group of the hairy, warm-blooded, nursing members of the class Mammalia , which are classified among animals with notochords in
1800-987: The final tree, including Magnosaurus , Piveteausaurus and Streptospondylus . Later, Magnosaurus and Streptospondylus were added in the final tree. These are known from remains too fragmentary to be reliably classified. Some of these 'wildcard' taxa, such as Poekilopleuron and Megaraptor , have been considered possible megalosauroids in the past, but the analysis found that they are more likely allosauroids . Xuanhanosaurus Marshosaurus Condorraptor Piatnitzkysaurus Chuandongocoelurus Monolophosaurus [REDACTED] Baryonyx Suchomimus [REDACTED] Irritator [REDACTED] Spinosaurus [REDACTED] Eustreptospondylus Magnosaurus Streptospondylus Duriavenator Afrovenator [REDACTED] Dubreuillosaurus Megalosaurus Torvosaurus [REDACTED] Carrano, Benson & Sampson (2012) performed much larger phylogenetic analysis of
1850-595: The following ranks for these categories: The rules in the Code apply to the ranks of superfamily to subspecies, and only to some extent to those above the rank of superfamily. Among "genus-group names" and "species-group names" no further ranks are officially allowed, which creates problems when naming taxa in these groups in speciose clades, such as Rana . Zoologists sometimes use additional terms such as species group , species subgroup , species complex and superspecies for convenience as extra, but unofficial, ranks between
1900-461: The following taxonomic categories in the International Code of Nomenclature for Cultivated Plants : cultivar group , cultivar , grex . The rules in the ICN apply primarily to the ranks of family and below, and only to some extent to those above the rank of family. (See also descriptive botanical name .) Taxa at the rank of genus and above have a botanical name in one part (unitary name); those at
1950-480: The gradational nature of variation within nature. These problems were already identified by Willi Hennig , who advocated dropping them in 1969, and this position gathered support from Graham C. D. Griffiths only a few years later. In fact, these ranks were proposed in a fixist context and the advent of evolution sapped the foundations of this system, as was recognised long ago; the introduction of The Code of Nomenclature and Check-list of North American Birds Adopted by
2000-434: The hierarchy of taxa (hence, their ranks) does not necessarily reflect the hierarchy of clades . While older approaches to taxonomic classification were phenomenological, forming groups on the basis of similarities in appearance, organic structure and behavior, two important new methods developed in the second half of the 20th century changed drastically taxonomic practice. One is the advent of cladistics , which stemmed from
2050-422: The lowest ranks. Ranks can be either relative and be denoted by an indented taxonomy in which the level of indentation reflects the rank, or absolute, in which various terms, such as species , genus , family , order , class , phylum , kingdom , and domain designate rank. This page emphasizes absolute ranks and the rank-based codes (the Zoological Code , the Botanical Code , the Code for Cultivated Plants ,
Megalosauroidea - Misplaced Pages Continue
2100-405: The most basic (or important) is the species, but this opinion is not universally shared. Thus, species are not necessarily more sharply defined than taxa at any other rank, and in fact, given the phenotypic gaps created by extinction, in practice, the reverse is often the case. Ideally, a taxon is intended to represent a clade , that is, the phylogeny of the organisms under discussion, but this
2150-409: The most frequently advocated. Willi Hennig proposed it in 1966, but he concluded in 1969 that this system was unworkable and suggested dropping absolute ranks. However, the idea of ranking taxa using the age of origin (either as the sole criterion, or as one of the main ones) persists under the name of time banding, and is still advocated by several authors. For animals, at least the phylum rank
2200-474: The phylum Chordata , and with them among all animals in the kingdom Animalia . Finally, at the highest rank all of these are grouped together with all other organisms possessing cell nuclei in the domain Eukarya . The International Code of Zoological Nomenclature defines rank as: "The level, for nomenclatural purposes, of a taxon in a taxonomic hierarchy (e.g. all families are for nomenclatural purposes at
2250-455: The rank of species and above (but below genus) have a botanical name in two parts ( binary name ); all taxa below the rank of species have a botanical name in three parts (an infraspecific name ). To indicate the rank of the infraspecific name, a "connecting term" is needed. Thus Poa secunda subsp. juncifolia , where "subsp". is an abbreviation for "subspecies", is the name of a subspecies of Poa secunda . Hybrids can be specified either by
2300-653: The rank-based codes; because of this, some systematists prefer to call them nomenclatural ranks . In most cases, higher taxonomic groupings arise further back in time, simply because the most inclusive taxa necessarily appeared first. Furthermore, the diversity in some major taxa (such as vertebrates and angiosperms ) is better known that that of others (such as fungi , arthropods and nematodes ) not because they are more diverse than other taxa, but because they are more easily sampled and studied than other taxa, or because they attract more interest and funding for research. Of these many ranks, many systematists consider that
2350-460: The same rank, which lies between superfamily and subfamily)." Note that the discussions on this page generally assume that taxa are clades ( monophyletic groups of organisms), but this is required neither by the International Code of Zoological Nomenclature nor by the Botanical Code , and some experts on biological nomenclature do not think that this should be required, and in that case,
2400-481: The subgenus and species levels in taxa with many species, e.g. the genus Drosophila . (Note the potentially confusing use of "species group" as both a category of ranks as well as an unofficial rank itself. For this reason, Alain Dubois has been using the alternative expressions "nominal-series", "family-series", "genus-series" and "species-series" (among others) at least since 2000. ) At higher ranks (family and above)
2450-723: The works of the German entomologist Willi Hennig . Cladistics is a method of classification of life forms according to the proportion of characteristics that they have in common (called synapomorphies ). It is assumed that the higher the proportion of characteristics that two organisms share, the more recently they both came from a common ancestor. The second one is molecular systematics, based on genetic analysis , which can provide much additional data that prove especially useful when few phenotypic characters can resolve relationships, as, for instance, in many viruses , bacteria and archaea , or to resolve relationships between taxa that arose in
2500-1112: Was also excluded to get more resolved Megalosauridae and Afrovenatorinae. The Chinese tetanuran Leshansaurus was included for the first time in a phylogenetic analysis, and was recovered as an afrovenatorine. Both Chuandongocoelurus and Monolophosaurus were found to be just outside Orionides . The cladogram presented here follows that study. Cryolophosaurus [REDACTED] "Dilophosaurus" sinensis [REDACTED] Chuandongocoelurus Monolophosaurus [REDACTED] Allosauroidea [REDACTED] Lourinhanosaurus Other coelurosaurians [REDACTED] Marshosaurus Condorraptor Piatnitzkysaurus Streptospondylus Baryonyx Suchomimus [REDACTED] Angaturama Irritator [REDACTED] Spinosaurus [REDACTED] Eustreptospondylus Duriavenator Megalosaurus Torvosaurus [REDACTED] Afrovenator [REDACTED] Dubreuillosaurus Magnosaurus Leshansaurus Piveteausaurus In 2019, Rauhut and Pol described Asfaltovenator vialidadi ,
#225774