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51-594: Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the group Megalosauroidea . Appearing in the Middle Jurassic , megalosaurids were among the first major radiation of large theropod dinosaurs. They were a relatively primitive group of basal tetanurans containing two main subfamilies, Megalosaurinae and Afrovenatorinae, along with the basal genus Eustreptospondylus , an unresolved taxon which differs from both subfamilies. The defining megalosaurid, Megalosaurus bucklandii ,

102-506: A binary tree ), and an unrooted bifurcating tree takes the form of an unrooted binary tree , a free tree with exactly three neighbors at each internal node. In contrast, a rooted multifurcating tree may have more than two children at some nodes and an unrooted multifurcating tree may have more than three neighbors at some nodes. Both rooted and unrooted trees can be either labeled or unlabeled. A labeled tree has specific values assigned to its leaves, while an unlabeled tree, sometimes called

153-480: A rooted phylogenetic tree, each node with descendants represents the inferred most recent common ancestor of those descendants, and the edge lengths in some trees may be interpreted as time estimates. Each node is called a taxonomic unit. Internal nodes are generally called hypothetical taxonomic units, as they cannot be directly observed. Trees are useful in fields of biology such as bioinformatics , systematics , and phylogenetics . Unrooted trees illustrate only

204-568: A European group of dinosaurs, based on fossils found in France and the UK, but fossils show that the group is also found in North America, Africa, South America and possibly Asia. The family Megalosauridae was first defined by Thomas Huxley in 1869, yet it has been contested throughout history due to its role as a " waste-basket " for many partially described dinosaurs or unidentified remains. In

255-496: 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 . This would render Megalosauridae a family of carnosaurs. Monolophosaurus [REDACTED] Spinosauridae [REDACTED] Monophyletic In biological cladistics for

306-452: A certain subgroup. The cladogram presented here follows Benson (2010) and Benson et al. (2010). Eustreptospondylus [REDACTED] Magnosaurus [REDACTED] Streptospondylus Duriavenator [REDACTED] Afrovenator [REDACTED] Dubreuillosaurus [REDACTED] Megalosaurus [REDACTED] Torvosaurus [REDACTED] Wiehenvenator Then, in 2012, Carrano, Benson, and Sampson did

357-409: A clear outgroup. Another method is midpoint rooting, or a tree can also be rooted by using a non-stationary substitution model . Unrooted trees illustrate the relatedness of the leaf nodes without making assumptions about ancestry. They do not require the ancestral root to be known or inferred. Unrooted trees can always be generated from rooted ones by simply omitting the root. By contrast, inferring

408-814: A combination of genes that come from different genomic sources (e.g., from mitochondrial or plastid vs. nuclear genomes), or genes that would be expected to evolve under different selective regimes, so that homoplasy (false homology ) would be unlikely to result from natural selection. When extinct species are included as terminal nodes in an analysis (rather than, for example, to constrain internal nodes), they are considered not to represent direct ancestors of any extant species. Extinct species do not typically contain high-quality DNA . The range of useful DNA materials has expanded with advances in extraction and sequencing technologies. Development of technologies able to infer sequences from smaller fragments, or from spatial patterns of DNA degradation products, would further expand

459-427: A function of the number of tips. For 10 tips, there are more than 34 × 10 6 {\displaystyle 34\times 10^{6}} possible bifurcating trees, and the number of multifurcating trees rises faster, with ca. 7 times as many of the latter as of the former. A dendrogram is a general name for a tree, whether phylogenetic or not, and hence also for the diagrammatic representation of

510-416: A group of basal tetanurans, due to the fact that they have more derived taxa than ceratosaurs and that the name Megalosauridae should represent this group. Megalosauridae also has priority over Torvosauridae under ICZN rules governing family names. Megalosauridae was first phylogenetically defined in 1869 by Thomas Huxley, yet was used as a ‘waste-basket’ clade for many years. In 2002, Ronan Allain redefined

561-506: A length to height ratio of 3:1. In addition, the typical skull roof tends to be much less ornamented than that of other tetanurans, and crests or horns are either very small or absent entirely. Megalosaurids also have femoral heads with an orientation 45 degrees between anteromedial and fully medial. Megalosauridae are also defined by the following unique unambiguous synapomorphies: Megalosaurinae (all megalosaurids more closely related to Megalosaurus than Afrovenator ) are characterized by

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612-883: A moderate (0.5–2.0) height/length ratio of the premaxilla below the level of the nares, compared to other megalosaurids which have a lower ratio and thus less tall snout tip. Afrovenatorinae (all megalosaurids more closely related to Afrovenator than Megalosaurus) are characterized by a squared anterior margin of the antorbital fossa and the puboischiadic plate being broadly open along the midline. Dental findings are frequently used to differentiate between various theropods and to further inform cladistic phylogeny . Tooth morphology and dental evolutionary markers are prone to homoplasy and disappear or reappear throughout history. However, megalosaurids have several specific denture conditions that differentiate them from other basal theropods. One dental condition present in Megalosauridae

663-609: A more suitable metaphor than the tree . Indeed, phylogenetic corals are useful for portraying past and present life, and they have some advantages over trees ( anastomoses allowed, etc.). Phylogenetic trees composed with a nontrivial number of input sequences are constructed using computational phylogenetics methods. Distance-matrix methods such as neighbor-joining or UPGMA , which calculate genetic distance from multiple sequence alignments , are simplest to implement, but do not invoke an evolutionary model. Many sequence alignment methods such as ClustalW also create trees by using

714-1304: A much larger analysis of tetanurans and defined Megalosauria more broadly as the clade containing Megalosaurus , Spinosaurus , and all its descendants. In other words, Megalosauria is the group that contains the two families Megalosauridae and its close relative Spinosauridae. Within this new cladogram, Megalosauridae was given a new subfamily Afrovenatorinae, which included all megalosaurids more closely related to Afrovenator than Megalosaurus . Carrano, Benson, and Sampson also included various megalosaurids that had previously been excluded from cladograms in their 2012 study, such as Duriavenator and Wiehenvenator in Megalosaurinae and Magnosaurus , Leshansaurus , and Piveteausaurus in Afrovenatorinae. Piatnitzkysauridae [REDACTED] Streptospondylus Spinosauridae [REDACTED] Eustreptospondylus [REDACTED] Duriavenator [REDACTED] Megalosaurus [REDACTED] Torvosaurus [REDACTED] Afrovenator [REDACTED] Dubreuillosaurus [REDACTED] Magnosaurus [REDACTED] Leshansaurus Piveteausaurus Scuirumimus albersodoerferi ,

765-536: A number of different formats, all of which must represent the nested structure of a tree. They may or may not encode branch lengths and other features. Standardized formats are critical for distributing and sharing trees without relying on graphics output that is hard to import into existing software. Commonly used formats are Although phylogenetic trees produced on the basis of sequenced genes or genomic data in different species can provide evolutionary insight, these analyses have important limitations. Most importantly,

816-441: A phylogenetic tree. A cladogram only represents a branching pattern; i.e., its branch lengths do not represent time or relative amount of character change, and its internal nodes do not represent ancestors. A phylogram is a phylogenetic tree that has branch lengths proportional to the amount of character change. A chronogram is a phylogenetic tree that explicitly represents time through its branch lengths. A Dahlgrenogram

867-461: A polyphyletic grouping are not inherited from a common ancestor, but evolved independently. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies ), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly . The word "mono-phyly" means "one-tribe" in Greek. These definitions have taken some time to be accepted. When

918-417: A small theropod described in 2012 which preserved protofeathers , was initially believed to be a juvenile megalosauroid. This led to the belief that megalosaurids may have had feathers. However, subsequent analyses have placed Sciurumimus as a basal coelurosaur , and several supposed megalosauroid synapomorphies reported in the original description are shared with basal coelurosaurs. In 2016, Wiehenvenator

969-445: A tree shape, defines a topology only. Some sequence-based trees built from a small genomic locus, such as Phylotree, feature internal nodes labeled with inferred ancestral haplotypes. The number of possible trees for a given number of leaf nodes depends on the specific type of tree, but there are always more labeled than unlabeled trees, more multifurcating than bifurcating trees, and more rooted than unrooted trees. The last distinction

1020-609: Is a diagram representing a cross section of a phylogenetic tree. A phylogenetic network is not strictly speaking a tree, but rather a more general graph , or a directed acyclic graph in the case of rooted networks. They are used to overcome some of the limitations inherent to trees. A spindle diagram, or bubble diagram, is often called a romerogram, after its popularisation by the American palaeontologist Alfred Romer . It represents taxonomic diversity (horizontal width) against geological time (vertical axis) in order to reflect

1071-506: Is most true of genetic material that is subject to lateral gene transfer and recombination , where different haplotype blocks can have different histories. In these types of analysis, the output tree of a phylogenetic analysis of a single gene is an estimate of the gene's phylogeny (i.e. a gene tree) and not the phylogeny of the taxa (i.e. species tree) from which these characters were sampled, though ideally, both should be very close. For this reason, serious phylogenetic studies generally use

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1122-429: Is multiple enamel wrinkles near the carinae, the sharp edge or serration row of the tooth. Ornamented teeth and a well-marked enamel surface also characterize basal megalosaurids. The ornamentation and well-marked surface appears in early megalosaurids but disappears in derived megalosaurids, suggesting that the condition was lost over time as megalosaurids grew in size. From the family's inception, many specimens found in

1173-539: Is the most biologically relevant; it arises because there are many places on an unrooted tree to put the root. For bifurcating labeled trees, the total number of rooted trees is: For bifurcating labeled trees, the total number of unrooted trees is: Among labeled bifurcating trees, the number of unrooted trees with n {\displaystyle n} leaves is equal to the number of rooted trees with n − 1 {\displaystyle n-1} leaves. The number of rooted trees grows quickly as

1224-533: The book Elementary Geology , by Edward Hitchcock (first edition: 1840). Charles Darwin featured a diagrammatic evolutionary "tree" in his 1859 book On the Origin of Species . Over a century later, evolutionary biologists still use tree diagrams to depict evolution because such diagrams effectively convey the concept that speciation occurs through the adaptive and semirandom splitting of lineages. The term phylogenetic , or phylogeny , derives from

1275-504: The clade after he discovered a complete megalosaurid skull in northwestern France of species Poekilopleuron . Using the characters described in this study, Allain defined Megalosauridae as dinosaurs including Poekilopleuron valesdunesis , now known as Dubreuillosaurus , Torvosaurus , Afrovenator , and all descendants of their common ancestor. Allain also defined two taxa within Megalosauridae: Torvosaurinae

1326-404: The cladistics school of thought became mainstream in the 1960s, several alternative definitions were in use. Indeed, taxonomists sometimes used terms without defining them, leading to confusion in the early literature, a confusion which persists. The first diagram shows a phylogenetic tree with two monophyletic groups. The several groups and subgroups are particularly situated as branches of

1377-689: The classification of organisms , monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of taxa which meets these criteria: Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A paraphyletic grouping meets 1. but not 2., thus consisting of the descendants of a common ancestor, excepting one or more monophyletic subgroups. A polyphyletic grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of

1428-453: The early years of paleontology , most large theropods were grouped together and up to 48 species were included in the clade Megalosauria , the basal clade of Megalosauridae. Over time, most of these taxa were placed in other clades and the parameters of Megalosauridae were narrowed significantly. However, some controversy remains over whether Megalosauridae should be considered its own distinct group, and dinosaurs in this family remain some of

1479-413: The fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a unique common ancestor. Conversely, the term polyphyly , or polyphyletic , builds on the ancient Greek prefix πολύς ( polús ), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. By comparison,

1530-481: The family Spinosauridae . Like other tetanurans, megalosaurids are carnivorous theropods characterized by large size and bipedalism . Specifically, megalosaurids exhibit especially giant size, with some members of the family weighing more than one tonne . Over time, there is evidence of size increase within the family. Basal megalosaurids from the Early Jurassic had smaller body size than those appearing in

1581-417: The field have been wrongly classified as megalosaurids. For example, most large carnivores found for about a century after the naming of Megalosaurus bucklandii were placed in Megalosauridae. Megalosaurus was the first paleontological finding of its kind when William Buckland discovered a giant femur and named it in 1824, predating even the term Dinosauria. When initially defined, the species M. bucklandii

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1632-399: The late Middle Jurassic. Due to this size increase over time, Megalosauridae appear to follow a size increase pattern similar to that of other giant sized theropods like Spinosauridae . This pattern follows Cope's rule , the postulation by paleontologist Edward Cope about evolutionary increase in body size. One unambiguous synapomorphy of Megalosauridae is a lower and longer skull with

1683-426: The meat-eaters in a new group Carnosauria . As more information was uncovered about basal theropods and phylogenetic characteristics, modern paleontologists began to question the proper naming for this group. In 2005 paleontologist Paul Sereno rejected the use of the clade Megalosauridae due to its ambiguous early history in favor of the name Torvosauridae. Today, it is accepted that megalosaurids existed at least as

1734-402: The most problematic taxa in all Dinosauria. Some paleontologists, such as Paul Sereno in 2005, have disregarded the group due to its shaky foundation and lack of clarified phylogeny. However, recent research by Carrano, Benson, and Sampson has systematically analyzed all basal tetanurans and determined that Megalosauridae should exist as its own family. They have been generally closely related to

1785-439: The optimal tree using many of these techniques is NP-hard , so heuristic search and optimization methods are used in combination with tree-scoring functions to identify a reasonably good tree that fits the data. Tree-building methods can be assessed on the basis of several criteria: Tree-building techniques have also gained the attention of mathematicians. Trees can also be built using T-theory . Trees can be encoded in

1836-403: The parent of all other nodes in the tree. The root is therefore a node of degree 2, while other internal nodes have a minimum degree of 3 (where "degree" here refers to the total number of incoming and outgoing edges). The most common method for rooting trees is the use of an uncontroversial outgroup —close enough to allow inference from trait data or molecular sequencing, but far enough to be

1887-405: The range of DNA considered useful. Phylogenetic trees can also be inferred from a range of other data types, including morphology, the presence or absence of particular types of genes, insertion and deletion events – and any other observation thought to contain an evolutionary signal. Phylogenetic networks are used when bifurcating trees are not suitable, due to these complications which suggest

1938-479: The relatedness of the leaf nodes and do not require the ancestral root to be known or inferred. The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being ). Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in

1989-574: The root of an unrooted tree requires some means of identifying ancestry. This is normally done by including an outgroup in the input data so that the root is necessarily between the outgroup and the rest of the taxa in the tree, or by introducing additional assumptions about the relative rates of evolution on each branch, such as an application of the molecular clock hypothesis . Both rooted and unrooted trees can be either bifurcating or multifurcating. A rooted bifurcating tree has exactly two descendants arising from each interior node (that is, it forms

2040-417: The simpler algorithms (i.e. those based on distance) of tree construction. Maximum parsimony is another simple method of estimating phylogenetic trees, but implies an implicit model of evolution (i.e. parsimony). More advanced methods use the optimality criterion of maximum likelihood , often within a Bayesian framework , and apply an explicit model of evolution to phylogenetic tree estimation. Identifying

2091-709: The species was initially described and classified by a mass of possibly unrelated characteristics. Modern paleontology first began to approach the problematic cladistic separation of Megalosauridae during the early 20th century. Fredrich von Huene separated carnivorous theropods, which had all been grouped into the broad category of megalosaurids, into two distinct families of larger, more giant sized and smaller, more lightly built theropods. These two groups were named Coelurosauria and Pachypodosauria respectively. Later on, Huene distinguished between carnivorous and herbivorous dinosaurs in Pachypodosauria, placing

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2142-622: The term paraphyly , or paraphyletic , uses the ancient Greek prefix παρά ( pará ), meaning "beside, near", and refers to the situation in which one or several monophyletic subgroups are left apart from all other descendants of a unique common ancestor. That is, a paraphyletic group is nearly monophyletic, hence the prefix pará . On the broadest scale, definitions fall into two groups. The concepts of monophyly, paraphyly , and polyphyly have been used in deducing key genes for barcoding of diverse group of species. Phylogeny Phylogenetic trees may be rooted or unrooted. In

2193-411: The tree before hybridisation takes place, and conserved sequences . Also, there are problems in basing an analysis on a single type of character, such as a single gene or protein or only on morphological analysis, because such trees constructed from another unrelated data source often differ from the first, and therefore great care is needed in inferring phylogenetic relationships among species. This

2244-493: The tree to indicate ordered lineal relationships between all the organisms shown. Further, any group may (or may not) be considered a taxon by modern systematics , depending upon the selection of its members in relation to their common ancestor(s); see second and third diagrams. The term monophyly , or monophyletic , derives from the two Ancient Greek words μόνος ( mónos ), meaning "alone, only, unique", and φῦλον ( phûlon ), meaning "genus, species", and refers to

2295-529: The trees that they generate are not necessarily correct – they do not necessarily accurately represent the evolutionary history of the included taxa. As with any scientific result, they are subject to falsification by further study (e.g., gathering of additional data, analyzing the existing data with improved methods). The data on which they are based may be noisy ; the analysis can be confounded by genetic recombination , horizontal gene transfer , hybridisation between species that were not nearest neighbors on

2346-422: The two ancient greek words φῦλον ( phûlon ), meaning "race, lineage", and γένεσις ( génesis ), meaning "origin, source". A rooted phylogenetic tree (see two graphics at top) is a directed tree with a unique node — the root — corresponding to the (usually imputed ) most recent common ancestor of all the entities at the leaves of the tree. The root node does not have a parent node, but serves as

2397-404: The variation of abundance of various taxa through time. A spindle diagram is not an evolutionary tree: the taxonomic spindles obscure the actual relationships of the parent taxon to the daughter taxon and have the disadvantage of involving the paraphyly of the parental group. This type of diagram is no longer used in the form originally proposed. Darwin also mentioned that the coral may be

2448-467: Was anatomically based on various dissociated bones found in quarries around the village of Stonesfield, UK. Some of these early findings included a right dentary with a well-preserved tooth, ribs , pelvic bones , and sacral vertebrae . As early paleontologists and researchers found more dinosaur bones in the surrounding area, they attributed them all to M. bucklandii since it was the only named and described dinosaur at this point in history. Therefore,

2499-604: Was defined as all Megalosauridae more closely related to Torvosaurus than to Poekilopleuron and Afrovenator , and Megalosaurinae was defined as all those that are more closely related to Poekilopleuron . Megalosauridae also falls under the basal clade Megalosauroidea, which also contains Spinosauridae . However, many taxa are still quite unstable and cannot be placed in one clade with absolute certainty. For example, Eustreptospondylus and Streptospondylus , while they are both defined as Megalosauridae, are often excluded to make more stable cladograms since they are not defined to

2550-514: Was first named and described in 1824 by William Buckland after multiple finds in Stonesfield, Oxfordshire , UK. Megalosaurus was the first formally described dinosaur and was the basis for the establishment of the clade Dinosauria. It is also one of the largest known Middle Jurassic carnivorous dinosaurs, with the best-preserved femur at 805 mm and a proposed body mass of around 943 kg. Megalosauridae has mainly been recognized as

2601-623: Was found by phylogenetic analysis to be in the Megalosauridae as a sister taxon to Torvosaurus . The following is a cladogram based on the phylogenetic analysis conducted by Rauhut et al., showing the relationships of Wiehenvenator . Eustreptospondylus [REDACTED] Dubreuillosaurus [REDACTED] Magnosaurus [REDACTED] Afrovenator [REDACTED] Piveteausaurus Duriavenator [REDACTED] Megalosaurus [REDACTED] Wiehenvenator [REDACTED] Torvosaurus [REDACTED] In 2019, Rauhut and Pol described Asfaltovenator vialidadi ,

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