42-457: Ornithopoda ( / ˌ ɔːr n ə ˈ θ ɒ p ə d ə / ) is a clade of ornithischian dinosaurs , called ornithopods ( / ˈ ɔːr n ə θ ə ˌ p ɒ d z , ɔːr ˈ n ɪ θ -/ ). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous . The most primitive members of the group were bipedal and relatively small-sized, while advanced members of
84-534: A clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group , is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi ) is used rather than the English form. Clades are
126-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
168-434: A 2013 paper, which separated the specimen number MPM–10001 into MPM–10001A, for the adult specimen, and MPM–10001B, for the neonate. The specimen is one of only very few embryonic or hatchling ornithopod specimen, and was the very first discovered from the southern hemisphere. Wear on the tiny, 1.7mm wide tooth crowns indicate the individual had fed, meaning it was not an embryo and had hatched, but only recently before death. It
210-598: A 2024 analysis of Fonseca et al. Thescelosauridae Kulindadromeus Marginocephalia [REDACTED] Gideonmantellia Hypsilophodon [REDACTED] Tenontosauridae Rhabdodontoidea Anabisetia Diluvicursor Gasparinisaura Notohypsilophodon Elasmaria [REDACTED] Iyuku Dryosauridae CM 1949 Oblitosaurus Ankylopollexia [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Clade In biological phylogenetics ,
252-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
294-497: A distinct Southern Hemisphere ornithopod group, but at the time the authors cautioned that such an interpretation was not entirely justified. In 2015, the describers of Morrosaurus found that such a clade did indeed exist. Talenkauen is most noted for a set of smooth, ovoid plates found along the side of the rib cage . These plates can be long (180 millimeters, or 7.1 in), but are very thin (only 3 millimeters thick [0.1 in]). They were present with at least
336-558: A higher estimate of 4.7 m (15 ft) in length and 300 kg (660 lb) in body mass. Unlike more derived iguanodontians, it still had teeth in the tip of the beak ( premaxillary teeth), and a first toe . More derived iguanodonts lose this toe, retaining only the three middle toes. The humerus has reduced areas for muscle attachment, a featured shared with other South American ornithopods like Notohypsilophodon and Anabisetia . This and other similarities to South American ornithopods suggests that there may have been
378-649: A horny beak , having an elongated pubis (that eventually extended past the ilium ), and having a missing hole in the lower jaw (a Mandibular fenestra ). A variety of ornithopods, and related ornithischians , had thin cartilaginous plates along the outside of the ribs; in some cases, these plates mineralized and were fossilized. The function of these intercostal plates is unknown. They have been found with Hypsilophodon , Nanosaurus , Parksosaurus , Talenkauen , Thescelosaurus , and Macrogryphosaurus to date. The early ornithopods were only about 1 metre (3 feet) long, but probably very fast. They had
420-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
462-445: A similar function for the plates of Talenkauen . This homology was rejected in a more recent study by Richard Butler and Peter Galton because of the plates' form . The plates were too thin and limited in location to have been very useful as defensive devices. Through cladistic analysis, it was found to be more basal than Dryosaurus and Anabisetia , but more derived than Tenontosaurus and Gasparinisaura . More recently,
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#1732791896759504-525: A stiff tail, like the theropods , to help them balance as they ran on their hind legs. Later ornithopods became more adapted to grazing on all fours; their spines curved, and came to resemble the spines of modern ground-feeders, such as the bison . As they became more adapted to eating while bent over, they became facultative quadrupeds; still running on two legs, and comfortable reaching up into trees, but spending most of their time walking or grazing on all fours. The taxonomy of dinosaurs previously ascribed to
546-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
588-499: Is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case,
630-461: Is derived from the words " Talenk , meaning small, and kauen , meaning skull, both from the Aonikenk language. The specific name santacrucensis refers to the province of Argentina where it was found. Following its original, preliminary description, the taxon was described more thoroughly described in an unpublished PhD dissertation in 2007 by Andrea V. Cambiaso. In 2020 an extensive description
672-476: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
714-494: Is often listed as an infraorder within a suborder Ornithopoda, though Benton (2004) lists Ornithopoda as an infraorder and does not rank Iguanodontia. Traditionally, iguanodontians were grouped into the superfamily Iguanodontoidea and family Iguanodontidae . However, phylogenetic studies show that the traditional "iguanodontids" are a paraphyletic grade leading up to the hadrosaurs (duck-billed dinosaurs). Groups like Iguanodontoidea are sometimes still used as unranked clades in
756-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
798-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
840-511: Is usually given the rank of Suborder, within the order Ornithischia. While ranked taxonomy has largely fallen out of favour among dinosaur paleontologists, some researchers have continued to employ such a classification, though sources have differed on what its rank should be. Benton (2004) placed it as an infraorder within the suborder Cerapoda (originally named as an unranked clade ), while others, such as Ibiricu et al. 2010, have retained it at its traditional ranking of suborder. Iguanodontia
882-533: The Cretaceous–Paleogene extinction event along with all other non- avian dinosaurs . Members are known worldwide. In 1870, Thomas Henry Huxley listed Iguanodontidae (coined by Cope a year earlier) as one of his three families of dinosaurs (alongside Megalosauridae and Scelidosauridae ), including within it the genera Iguanodon , Hypsilophodon , and Hadrosaurus , in addition to Cetiosaurus and tentatively Stenopelix . The term Ornithopoda
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#1732791896759924-829: The Hypsilophodontidae is problematic. The group previously consisted of all non- iguanodontian bipedal ornithischians, but a phylogenetic reappraisal has shown such species to be paraphyletic . As such, the hypsilophodont family is currently represented only by Hypsilophodon . Later ornithopods became larger, but never rivalled the incredible size of the long-necked, long-tailed sauropods that they partially supplanted. The very largest, such as Shantungosaurus , were as heavy as medium-sized sauropods (up to 23 metric tons /25 short tons ), but never grew much beyond 15 metres (50 feet). Historically, most indeterminate ornithischian bipeds were lumped in as ornithopods. Most have since been reclassified. Ornithopoda
966-622: The Pari Aike Formation of Patagonian Lake Viedma , in the Austral Basin of Santa Cruz , Argentina . It is based on MPM -10001A, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands. The type and only species is Talenkauen santacrucensis . One among a string of discoveries of ornithopods in South America, following taxa such as Gasparinisaura and Anabisetia ,
1008-591: The associated family followed suit, becoming Camptosauridae. In Iguanodontidae, only found in Europe, he included Iguanodon and Vectisaurus . In Hadrosauridae, he included Hadrosaurus , Cionodon , and tentatively Agathaumas . Ornithopoda means "bird feet", from the Greek ornithos , ornis ("bird") and pous , podos ("feet"); this is in reference to members’ characteristic birdlike feet. They were also characterized as lacking in body armour, not developing
1050-653: The describers of Macrogryphosaurus found their genus and Talenkauen to be related, and coined the clade Elasmaria for the two genera. In 2015, several other Patagonian and Antarctic ornithopods were also found to be related. The simplified cladogram below results from analysis by Rozadilla et al. , 2019, showing all members of Elasmaria forming a polytomy . Hypsilophodon Fulgurotherium Trinisaura Gasparinisaura Qantassaurus Notohypsilophodon Morrosaurus Kangnasaurus Anabisetia Atlascopcosaurus Macrogryphosaurus Talenkauen Dryomorpha Talenkauen , as
1092-441: The first eight ribs , attaching along the middle portion of a rib and lying flat. Several other dinosaurs are known to have had similar plates, including Hypsilophodon , Nanosaurus , Parksosaurus , Thescelosaurus , and Macrogryphosaurus (also from Argentina, but from somewhat older rocks), which may have been related. Because of the fragility of the plates, and the fact that they may not have always turned to bone in
1134-543: The former was a new name, whereas the latter two were carried over from the nomenclatures of Huxley and Edward Drinker Cope respectively. Within Camptonotidae he included the European Hypsilophodon and three American taxa he named himself, Camptonotus , Laosaurus , and Nanosaurus . Camptonotus was in 1885 renamed to Camptosaurus , as the original name was pre-occupied by a cricket ;
1176-451: The fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over
1218-546: The group consists of a common ancestor with all its descendant branches. Rodents, for example, are a branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
1260-590: The last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of the relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade"
1302-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
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1344-454: The living animal, they may have been more widespread than currently known. Novas and colleagues suggested that the plates may be homologous to uncinate processes , strip-like bony projections found on the ribs of a variety of animals including the tuatara , crocodiles , birds , and some maniraptoran theropod dinosaurs. In birds, uncinate processes help to ventilate the lungs, working with rib cage muscles, and Novas and colleagues proposed
1386-535: The paraphyletic nature of Hypsilophodontidae . A 2017 study which named and described Burianosaurus noted that the type species Iguanodon bernissartensis must be part of the definition, and that the 2005 definition would, in their analysis, include a far larger group than intended (including Marginocephalia ). They proposed an entirely new, node-based definition: the last common ancestor of Iguanodon bernissartensis , Dryosaurus altus , Rhabdodon priscus , and Tenontosaurus tilletti . In 2021, Iguanodontia
1428-469: The scientific literature, though many traditional "iguanodontids" are now included in the more inclusive group Hadrosauroidea . Iguanodontia was originally phylogenetically defined, by Paul Sereno , in 1998, as the most inclusive group containing Parasaurolophus walkeri but not Hypsilophodon foxii . Later, in 2005, he amended the definition to include Thescelosaurus neglectus as a secondary external specifier, alongside Hypsilophodon , accounting for
1470-670: The specimen that would become Talenkauen was collected in February 2000 and would later be described and named in a short 2004 paper by Fernando E. Novas and colleagues. It was discovered on Los Hornos Hill on the coast of Viedma Lake , in the Santa Cruz Province region of Argentina . Geologically, it hails from the Cerro Fortaleza Formation . The holotype specimen is MPM–10001A, a relatively complete and articulated skeleton. The name Talenkauen
1512-667: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Talenkauen Talenkauen is a genus of basal iguanodont dinosaur from the Campanian or Maastrichtian age of the Late Cretaceous Cerro Fortaleza Formation , formerly known as
1554-458: The subgroup Iguanodontia became quadrupedal and developed large body size. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a non-avian dinosaur, rivaling that of modern mammals such as the domestic cow . They reached their apex of diversity and ecological dominance in the hadrosaurids (colloquially known as 'duck-bills'), before they were wiped out by
1596-406: Was erected by Othniel Charles Marsh in 1881 as part of his then still ongoing investigation of the classification of Dinosauria. It was considered one of the four definite orders of dinosaurs, the others being Theropoda , Sauropoda , and Stegosauria ( Hallopoda was considered a possible fifth). He subdivided the order into three families: Camptonotidae , Iguanodontidae , and Hadrosauridae ;
1638-589: Was given a formal definition under the PhyloCode : "The smallest clade containing Dryosaurus altus , Iguanodon bernissartensis , Rhabdodon priscus , and Tenontosaurus tilletti , provided that it does not include Hypsilophodon foxii ." Under this revised definition, Iguanodontia is limited to its traditionally included species, and if it were found to include hypsilophodonts, which were not traditionally considered iguanodontians, it would become an invalid grouping. The slightly less inclusive clade Dryomorpha
1680-610: Was named by Paul Sereno in 1986 and given a formal definition in the PhyloCode as "the smallest clade containing Dryosaurus altus and Iguanodon bernissartensis ". This group includes basal members such as Hesperonyx , members of the family Dryosauridae , and the derived clade Ankylopollexia . In 2021, Ornithopoda was given a formal definition under the PhyloCode : "The largest clade containing Iguanodon bernissartensis but not Pachycephalosaurus wyomingensis and Triceratops horridus ." The cladogram below follows
1722-416: Was noted as possible that the adult had been practicing parental care due to the individuals being found together, but that more concrete evidence would be needed to confidently make such an assertion. Talenkauen was rather like Dryosaurus in shape and build, but with a proportionally longer neck. The full length of the body is estimated at no more than 4 meters (13 feet). However, Gregory S. Paul gave
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1764-403: Was published by Sebastián Rozadilla and colleagues. It has been recognized that, nestled amongst the rock matrix of the holotype specimen, are a collection of minuscule bone fragments and teeth. Identifiable as the teeth of some degree of ornithopod, and associated with the adult specimen, this is considered to be a neonatal, or recently hatched, baby specimen of Talenkauen . It was described in
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