41-571: Neosauropoda is a clade within Dinosauria , coined in 1986 by Argentine paleontologist José Bonaparte and currently described as Saltasaurus loricatus , Diplodocus longus , and all animals directly descended from their most recent common ancestor. The group is composed of two subgroups: Diplodocoidea and Macronaria . Arising in the early Jurassic and persisting until the Cretaceous–Paleogene extinction event , Neosauropoda contains
82-686: A dicraeosaurid from the late Early Jurassic or early Middle Jurassic of China. Diplodocid and brachiosaurid members of the group composed the greater portion of neosauropods during the Jurassic, but they began to be replaced by titanosaurs in most regions through the Cretaceous period . By the late Cretaceous, titanosaurs were the dominant group of neosauropods, especially on the southern continents. In North America and Asia, much of their role as large herbivores had been supplanted by hadrosaurs and ceratopsians , although they remained in smaller numbers all
123-588: 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 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
164-479: 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
205-446: 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"
246-623: 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
287-594: A cladistic analysis of the sauropod family which proposed Macronaria as a new taxon containing Camarasaurus , Haplocanthosaurus , and Titanosauriformes. Titanosauriformes was considered to include Brachiosaurus , Saltasaurus , and all descendants of their most recent common ancestor. This represented a significant deviation from Upchurch's 1995 phylogeny as well as much of the traditional understanding of neosauropod taxonomy. Conventional cladistics had long considered titanosaurs and diplodocoids to be more closely related, with brachiosaurids and camarasaurids together forming
328-461: A digitigrade posture with the manus raised up off the ground. Prosauropods and basal sauropods have metacarpals which are articulated at the base, but this is further developed in neosauropods such that the articulation continues down the shafts. The ends of the metacarpals also form a tight arch with wedge-shaped shafts fitting closely together. The tibia of neosauropods has a subcircular proximal end. The transverse and anteroposterior dimensions of
369-475: A facultatively bipedal to a quadrupedal posture. The limbs also rotated directly under the body, in order to better support the weight of the steadily increasing body size. During the Middle Jurassic, sauropods began to display increased neck length and more specialized dentition. They also developed a digitigrade posture in the hindlimbs, in which the heel and proximal metatarsals were raised completely off
410-424: A large opening in the skull located ventral to the antorbital fenestra, known as the preantorbital fenestra. This opening is differentially shaped among various species of neosauropods, and it has been proposed that the preanorbital fenestra is reduced or closes up completely in adult Camarasaurus , but is otherwise ubiquitous among neosauropods. The ventral process of the postorbital bone is broader when viewed from
451-422: 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
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#1732891473784492-414: A sister taxon. From Sereno and Wilson 1998: Vulcanodon Shunosaurus Barapasaurus Omeisaurus Diplodocoidea Haplocanthosaurus Camarasaurus Brachiosauridae Euhelopus Titanosauria Clade In biological phylogenetics , a clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group ,
533-429: 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 ,
574-537: 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 the fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual,
615-629: Is a subclade, first arose in the late Triassic . Around 230 million years ago, animals such as Eoraptor , the most basal known member of Dinosauria and also Saurischia , already displayed certain features of the Sauropod group. These derived characters began to distinguish them from Theropoda . There were several major trends in the evolution of sauropodomorphs, most notably increased size and elongated necks, both of which would reach their culmination in neosauropods. Basal members of Sauropodomorpha are often collectively termed prosauropods , although this
656-471: 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
697-457: Is likely a paraphyletic group, the exact phylogeny of which has not been conclusively determined. True sauropods appear to have developed in the Upper Triassic, with trackways from a basal member known as the ichnogenus Tetrasauropus being dated to 210 million years ago. At this point, the forelimbs had lengthened to at least 70% of the length of the hindlimbs and the animals moved from
738-515: 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
779-489: 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
820-421: The limb anatomy of plantigrades, unguligrades, and digitigrades. Digitigrade and unguligrade animals have relatively long carpals and tarsals , and the bones which correspond to the human ankle are thus set much higher in the limb than in a human. In a digitigrade animal, this effectively lengthens the foot, so much so that what are often thought of as a digitigrade animal's "hands" and "feet" correspond to only
861-490: The anterior when compared to the width when viewed from the lateral side. Neosauropods lack a point of contact between the jugal bone and the ectopterygoid arch. Instead, the ecterpteryoid arch abuts the maxilla, anterior to the jugal. The external mandibular fenestra, present in prosauropods and some basal sauropods, is entirely closed. Neosauropods lack denticles on the majority of their teeth. In some species, including Camarasaurus and Brachiosaurus , they are retained on
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#1732891473784902-587: The astragalus. The astragalus is also wedge shaped when viewed from the anterior side due to a reduction in the medial portion. Among macronarians, fossilized skin impressions are only known from Haestasaurus , Tehuelchesaurus and Saltasaurus . Haestasaurus , the first dinosaur known from skin impressions, preserved integument over a portion of the arm around the elbow joint approximately 19.5 by 21.5 cm (7.7 by 8.5 in) in area. Small, hexagonal scales are preserved, ranging from 1–2.5 cm (0.39–0.98 in) in diameter. It has been suggested that
943-484: The convex surface of the scales was from the internal size of the integument, facing the bones, but this has been rejected as the convex surfaces are preserved on the outside of Saltasaurus and titanosaur embryos. Dermal impressions are more widespread in the material of Tehuelchesaurus , where they are known from the areas of the forelimb, scapula and torso. There are no bony plates or nodules, to indicate armour, but there are several types of scales. Skin associated with
984-988: The current definition for Diplodocoidea, which was then classified as a subgroup of Titanosauridae. Cetiosaurus was linked to Neosauropoda by a trichotomy, as the genus’ fragmentary and often dubious description meant that it could be placed as a sister taxon to the Titanosauridae-Diplodocoidae clade, the Brachiosauridae-Camarasauridae clade, or Neosauropoda as a whole. From Upchurch 1995: Vulcanodon Barapasaurus Shunosaurus Omeisaurus Mamenchisaurus Euhelopus Cetiosaurus Brachiosaurus Haplocanthosaurus Camarasaurus Opisthocoelicaudia Malawisaurus Alamosaurus Saltasaurus Nemegtosaurus Quaesitosaurus Dicraeosaurus Amargasaurus Apatosaurus Diplodocus Barosaurus lentus In 1998, Sereno and Wilson published
1025-544: The end of the Jurassic period, it also includes members throughout the Cretaceous . Neosauropoda is currently delineated by specific shared, derived characteristics rather than the time period in which its members lived. The group was further refined by Upchurch, Sereno , and Wilson , who have identified thirteen synapomorphies shared among neosauropods. As Neosauropoda is a subgroup of Sauropoda, all members also display basic sauropod traits such as large size, long necks, and columnar legs. Paleontologist Richard Owen named
1066-447: The evolutionary record. Early dinosaurs such as Eoraptor tend to have four distal carpals. In prosauropods, this is reduced to three and the proximal carpals are usually lost or shrink in size. Basal sauropods also tend to have three carpal bones, but they are more block-like than in earlier forms. Neosauropods further reduce this number to two, and in some cases even fewer. The metacarpals of neosauropods are bound together, allowing
1107-687: The first sauropod, Cetiosaurus , in 1841. Due to the fragmentary evidence, he originally believed it to be a type of massive crocodile. Cetiosaurus has at times been classified as a basal member of Neosauropoda, which would make it the first member of this group discovered. Most current research, however, places Cetiosaurus outside Neosauropoda as a sister taxon. The first dinosaurs discovered which are conclusively known to fall within Neosauropoda were Apatosaurus and Camarasaurus , both found in North America in 1877, and Titanosaurus discovered
1148-463: The ground. The foot also became more spread out, with the ends of the metatarsals no longer in contact with each other. These developments have been used to distinguish a new clade among sauropods, termed Eusauropoda . Neosauropoda diverged from the rest of Eusauropoda in the Early Jurassic and quickly became the dominant group of large herbivores. The earliest known neosauropod is Lingwulong ,
1189-409: The human fingers or toes. Digitigrade locomotion is responsible for the distinctive hooked shape of dog legs. Plantigrade animals, such as humans, normally walk with the soles of their feet on the ground. Unguligrade animals, such as horses and cattle, walk only on the distal-most tips of their digits. Digitigrade animals walk on their distal and intermediate phalanges ; more than one segment of
1230-518: 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
1271-451: The majority of sauropod genera, including genera such as Apatosaurus , Brachiosaurus , and Diplodocus . It also includes giants such as Argentinosaurus , Patagotitan and Sauroposeidon , and its members remain the largest land animals ever to have lived. When Bonaparte first coined the term Neosauropoda in 1986, he described the clade as comprising “end-Jurassic” sauropods. While Neosauropoda does appear to have originated at
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1312-408: The most posterior teeth, but most advanced forms have lost them entirely. Certain members of the subgroup Titanosauria have ridges along their posterior teeth, but these are not large enough to be considered denticles of a form similar to those found in more basal sauropods. The number of carpal bones in neosauropods is reduced to two or fewer. This continues a trend of successive carpal loss seen in
1353-401: The proximal end are also equal or nearly so in neosauropods, whereas the transverse dimension of the tibia is always shorter than the anteroposterior dimension in prosauropods, theropods, and those basal sauropods for which evidence is available. The astragalus displays two unique features in neosauropods. When viewed from the proximal side, the ascending process extends to the posterior end of
1394-482: 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" 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"
1435-561: The same year in India . There were other sauropods besides Cetiosaurus which were described before the 1870s, but most were known from only very fragmentary material and none were described in sufficient detail that they may conclusively be classified as neosauropods. A great number of neosauropod skeletons were unearthed in western North America during the late nineteenth and early twentieth centuries, primarily Apatosaurus , Camarasaurus , and Diplodocus . Sauropodomorpha , of which Neosauropoda
1476-522: The scapular blade is the largest, arranged in rosettes (spiral formations) with a smooth, hexagonal shape. These largest tubercles are 2.5–3 cm (0.98–1.18 in), surrounded by smaller 1.5–2 cm (0.59–0.79 in) scales. The other type of scales are very small, only between 1 and 4 mm (0.039 and 0.157 in) in diameter, and are preserved in small fragments from the forelimb and thoracic region. These skin types are overall more similar to those found in diplodocids and Haestasaurus than in
1517-508: 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. Digitigrade In terrestrial vertebrates , digitigrade ( / ˈ d ɪ dʒ ɪ t ɪ ˌ ɡ r eɪ d / ) locomotion is walking or running on
1558-550: The titanosaur embryos of Auca Mahuevo . As the shape and articulation of the preserved tubercles in these basal macronarians are similar in other taxa where skin is preserved, including specimens of Brontosaurus excelsus and intermediate diplodocoids, such dermal structures are probably widespread throughout Neosauropoda. José Bonaparte originally described Neosauropoda as comprising members of four sauropod groups: Dicraeosauridae, Diplodocidae, Camarasauridae, and Brachiosauridae. Upchurch's 1995 paper on sauropod phylogeny proposed
1599-540: The toes (from the Latin digitus , 'finger', and gradior , 'walk'). A digitigrade animal is one that stands or walks with its toes (phalanges) on the ground, and the rest of its foot lifted. Digitigrades include birds (what many see as bird's knees are actually ankles ), cats, dogs, and many other mammals , but not plantigrades (such as humans) or unguligrades (such as horses). Digitigrades generally move more quickly than other animals. There are structural differences between
1640-485: The way until the Cretaceous-Paleogene extinction. In addition to the basic features of sauropods in general and eusauropods in particular, neosauropods share certain derived features, which have been used to distinguish them as a cohesive group. In their 1998 paper, Sereno and Wilson identified thirteen characteristics that distinguish neosauropods from more basal sauropods (described below). Neosauropods display
1681-423: 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, the group consists of a common ancestor with all its descendant branches. Rodents, for example, are