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 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 the end of the Jurassic period, it also includes members through the end of 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.
|Several macronarian sauropods|
Paleontologist Richard Owen named 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 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 is a subclade, first arose in the late Triassic. Around 230 million years ago, animals such as Eoraptor, the most basal known Sauropodomorph, already displayed certain features of the 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 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 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 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 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, 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 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 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 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 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 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 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 the proximal end are also equal or nearly so in neosauropods, whereas the tranverse 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 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 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 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 thoratic region. Ths skin types are overall more similar to those found in diplodocids and Haestasaurus than in 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 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:
In 1998, Sereno and Wilson published 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 a sister taxon.
From Sereno and Wilson 1998:
Neosauropoda is divided into two major subgroups: Macronaria and Diplodocoidea. These taxa are differentiated on the basis of several morphological features.
From Upchurch et al. 2004:
Macronaria is defined as all neosauropods more closely related to Saltasaurus loricatus than Diplodocus longus. This classification was introduced by Wilson and Sereno in 1998. Macronaria comes from the Latin for “large nose,” referring to the large external naris. The subgroup Titanosauriformes comprises all sauropods descended from the common ancestor of Brachiosaurus and Saltasaurus. Macronaria is an exceedingly diverse clade, with members ranging in size from anywhere between six and thirty-five meters in length and sporting a broad array of body shapes. Some synapomorphies which have been used to characterize macronarians include flared neural spines on the dorsal vertebrae and nearly coplanar ischial distal shafts.
Diplodocoidea is defined as all neosauropods more closely related to Diplodocus longus than Saltasaurus loricatus. The group is named after Diplodocus, its best known member. Other prominent dinosaurs contained in this clade include Apatosaurus, Supersaurus, and Brontosaurus. Diplodocoids are distinguished by a unique head shape, which displays certain highly derived features when compared to other sauropods. The teeth are located entirely anterior to the antorbital fenestra and the snout is especially broad. In some rebbachisaurids, this is taken to such an extreme that the teeth are packed into a row along the transverse portion of the jaw. Several unique features are also noted in the tails of certain diplodocoids. Among the diplodocids, there was a marked increase in the number of caudal vertebrae. Most sauropods have between forty and fifty caudal vertebrae, but in diplodocids this number jumps to eighty or more. In addition, the most distal vertebrae develop a biconvex shape and together form a long, bony rod at the end of the tail, often referred to as a “whiplash tail.” Increased caudal count and a whiplash tail may be features shared by all members of the Diplodocoid group, but, due to a scarcity of evidence, this has yet to be proven.
Bothriospondylus ("excavated vertebra") is a dubious genus of sauropod dinosaur. It lived during the Late Jurassic.Camarasauridae
Camarasauridae (meaning "chambered lizards") is a family of neosauropod dinosaurs within the clade Macronaria, the sister group to Titanosauriformes. Among sauropods, camarasaurids are small to medium-sized, with relatively short necks. They are visually identifiable by a short skull with large nares, and broad, spatulate teeth filling a thick jaw. Based on cervical vertebrae and cervical rib biomechanics, camarasaurids most likely moved their necks in a vertical, rather than horizontal, sweeping motion, in contrast to most diplodocids. Cladistically, they are defined to be all sauropods more closely related to Camarasaurus supremus than to Saltasaurus loricatus.Cetiosauriscus
Cetiosauriscus ( SEE-tee-oh-SOR-iss-kəs) is a genus of sauropod dinosaur that lived between 166 and 164 million years ago during the Callovian (Middle Jurassic Period) in what is now England. A herbivore, Cetiosauriscus had—for sauropod standards—a moderately long tail, and longer forelimbs, making them as long as its hindlimbs. It has been estimated as about 15 m (49 ft) long and between 4 and 10 t (3.9 and 9.8 long tons; 4.4 and 11.0 short tons) in weight.
The only known fossil that was later named Cetiosauriscus includes most of the rear half of a skeleton as well as a hindlimb (NHMUK R3078). Found in Cambridgeshire in the 1890s, it was described by Arthur Smith Woodward in 1905 as a new specimen of the species Cetiosaurus leedsi. This was changed in 1927, when Friedrich von Huene found NHMUK R3078 and the C. leedsi type specimen to be too different from Cetiosaurus, warranting its own genus, which he named Cetiosauriscus, meaning "Cetiosaurus-like". Cetiosauriscus leedsi was referred to the sauropod family Diplodocidae because of similarities in the tail and foot, and had the dubious or intermediate species "Cetiosauriscus" greppini, "C." longus, and "C." glymptonensis assigned to it. In 1980, Alan Charig named a new species of Cetiosauriscus for NHMUK R3078 because of the lack of comparable material to the type of C. leedsi; this species was named Cetiosauriscus stewarti. Because of the poor state of preservation of the Cetiosauriscus leedsi fossil, Charig sent a petition to the International Commission on Zoological Nomenclature to instead make C. stewarti the type species. Cetiosauriscus stewarti became the oldest confirmed diplodocid until a phylogenetic analysis published in 2003 instead found the species to belong to Mamenchisauridae, and followed by studies in 2005 and 2015 that found it outside Neosauropoda, while not a mamenchisaurid proper.
Cetiosauriscus was found in the marine deposits of the Oxford Clay Formation alongside many different invertebrate groups, marine ichthyosaurs, plesiosaurs and crocodylians, a single pterosaur, and various dinosaurs: the ankylosaur Sarcolestes, the stegosaurs Lexovisaurus and Loricatosaurus, the ornithopod Callovosaurus, as well as some unnamed taxa. The theropods Eustreptospondylus, Metriacanthosaurus and Megalosaurus are known from the formation, although probably not from the same level as Cetiosauriscus.Diplodocoidea
Diplodocoidea is a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like Supersaurus, Diplodocus, Apatosaurus, and Amphicoelias. Most had very long necks and long, whip-like tails; however, one family (the dicraeosaurids) are the only known sauropods to have re-evolved a short neck, presumably an adaptation for feeding low to the ground. This adaptation was taken to the extreme in the highly specialized sauropod Brachytrachelopan. A study of snout shape and dental microwear in diplodocoids showed that the square snouts, large proportion of pits, and fine subparallel scratches in Apatosaurus, Diplodocus, Nigersaurus, and Rebbachisaurus suggest ground-height nonselective browsing; the narrow snouts of Dicraeosaurus, Suuwassea, and Tornieria and the coarse scratches and gouges on the teeth of Dicraeosaurus suggest mid-height selective browsing in those taxa. This taxon is also noteworthy because diplodocoid sauropods had the highest tooth replacement rates of any vertebrates, as exemplified by Nigersaurus, which had new teeth erupting every 30 days.Eusauropoda
Eusauropoda (meaning "true sauropods") is a derived clade of sauropod dinosaurs. Eusauropods represent the node-based group that includes all descendant sauropods starting with the basal eusauropods of Shunosaurus, and possibly Barapasaurus, and Amygdalodon, but excluding Vulcanodon and Rhoetosaurus. The Eusauropoda was coined in 1995 by Paul Upchurch to create a monophyletic new taxonomic group that would include all sauropods, except for the vulcanodontids.Eusauropoda are herbivorous, quadrupedal, and have long necks. They have been found in South America, Europe, North America, Asia, Australia, and Africa. The temporal range of Eusauropoda ranges from the early Jurassic to the Latest Cretaceous periods. The most basal forms of eusauropods are not well known and because the cranial material for the Vulcanodon is not available, and the distribution of some of these shared derived traits that distinguish Eusauropoda is still completely clear.Flagellicaudata
Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.Gravisauria
Gravisauria is a clade of sauropod dinosaurs consisting of some genera, Vulcanodontidae and Eusauropoda.Haestasaurus
Haestasaurus is a genus of herbivorous sauropod dinosaur, belonging to the Macronaria, that during the Early Cretaceous lived in the area of present-day England. The only species is Haestasaurus becklesii.Huangshanlong
Huangshanlong is a genus of mamenchisaurid dinosaurs native to the Anhui province of China. It contains a single species, Huangshanlong anhuiensis. H. anhuiensis represents, along with Anhuilong and Wannanosaurus, one of three dinosaurs fround in Anhui province.Macronaria
Macronaria is a clade of the "suborder" (more likely an unranked clade than a suborder) Sauropodomorpha. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (hence macro- meaning large, and –naria meaning nose). Fossil evidence suggests that macronarian dinosaurs lived from the Late Jurassic (Kimmeridgian) through the Late Cretaceous (Maastrichtian). Macronarians have been found globally, including discoveries in Argentina, the United States, Portugal, China, and Tanzania. Like other sauropods, they are known to have inhabited primarily terrestrial areas, and little evidence exists to suggest that they spent much time in coastal environments. Macronarians are diagnosed through their distinct characters on their skulls, as well as appendicular and vertebral characters. Macronaria is composed of several subclades and families notably including Camarasauridae and Titanosauriformes, among several others. Titanosauriforms are particularly well known for being some of the largest terrestrial animals to ever exist.
Macronaria was described by Wilson and Sereno who proposed the new subdivisions among the clade Neosauropoda. Previously, this clade was thought to have Brachiosaurus and Camarasauridae forming one sister group, and Titanosauroidea and Diplodocoidea forming another. This proposed shift with Macronaria placed Diplodocoidea as an outgroup to the new clade Macronaria, under which all other neosauropods would fall.Ohmdenosaurus
Ohmdenosaurus (meaning "Ohmden lizard") is the name given to a genus of herbivorous dinosaur from the Early Jurassic. It was a very small (4 m (13 ft) long) perhaps vulcanodontid sauropod which lived in Germany. Only a couple of fragmentary leg bones were found.Qinlingosaurus
Qinlingosaurus is a genus of herbivorous sauropod dinosaur from the Late Cretaceous of Asia.
The type species, Qinlingosaurus luonanensis, was named by Xue Xiangxu, Zhang Yunxiang and Bi Xianwu in 1996. The generic name comes from the Qinling mountain range of Shaanxi Province in China, where the first fossils were recovered at Hongtuling. The specific name refers to the provenance near Luonang.The holotype, NWUV 1112, was found in a layer of the Hongtuling Formation, perhaps dating from the Maastrichtian. It consists of an ilium, ischium and three vertebrae. The ilium has a length of seventy-seven centimetres and is elongated with a convex upper profile. Its anterior process is relatively long. The pubic process is long, the ischial process short.
In view of the limited fossil evidence, it is classified as Sauropoda incertae sedis. It probably represents a member of the Neosauropoda. Given its temporal range it may be a titanosaur.Rayososaurus
Rayososaurus is a genus of plant-eating sauropod dinosaur of the superfamily Diplodocoidea. It was found in the Candeleros Formation, but was named Rayososaurus after the Rayoso Member, which later has been elevated to the older Rayoso Formation. The formations are located in the Neuquén Basin of northern Patagonia, Argentina. Rayososaurus lived during the Cenomanian epoch of the Late Cretaceous, about 99 to 96 million years ago. The type species is R. agrioensis, named by Argentinian paleontologist José Bonaparte in 1996. The species epithet agrioensis refers to the Agrio del Medio locality.Rhoetosaurus
Rhoetosaurus (meaning "Rhoetos lizard"), named after Rhoetus, a titan in Greek Mythology, is a genus of sauropod dinosaur from the Jurassic Hutton Sandstone of what is now eastern Australia. Rhoetosaurus is estimated to have been about 15 metres (49 ft) long, weighing about 9 tonnes (8.9 long tons; 9.9 short tons). Subsequent authors have sometimes misspelled the name: Rhaetosaurus (de Lapparent & Laverat, 1955); Rheteosaurus (Yadagiri, Prasad & Satsangi, 1979).Sauropoda
Sauropoda ( or ), or the sauropods (; sauro- + -pod, "lizard-footed"), are a clade of saurischian ("lizard-hipped") dinosaurs. They had very long necks, long tails, small heads (relative to the rest of their body), and four thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land. Well-known genera include Brachiosaurus, Diplodocus, Apatosaurus, Brontosaurus, and Mamenchisaurus.Sauropods first appeared in the late Triassic Period, where they somewhat resembled the closely related (and possibly ancestral) group "Prosauropoda". By the Late Jurassic (150 million years ago), sauropods had become widespread (especially the diplodocids and brachiosaurids). By the Late Cretaceous, those groups had mainly been replaced by the titanosaurs, which had a near-global distribution. However, as with all other non-avian dinosaurs alive at the time, the titanosaurs died out in the Cretaceous–Paleogene extinction event. Fossilised remains of sauropods have been found on every continent, including Antarctica.The name Sauropoda was coined by O.C. Marsh in 1878, and is derived from Greek, meaning "lizard foot". Sauropods are one of the most recognizable groups of dinosaurs, and have become a fixture in popular culture due to their impressive size.
Complete sauropod fossil finds are rare. Many species, especially the largest, are known only from isolated and disarticulated bones. Many near-complete specimens lack heads, tail tips and limbs.Shunosaurus
Shunosaurus, meaning "shu lizard", is a genus of sauropod dinosaur from Early Jurassic (Oxfordian) beds in Sichuan Province in China, approximately 159±2 million years ago. The name derives from "Shu", an ancient name for the Sichuan province.Turiasauria
Turiasauria is an unranked clade of basal sauropod dinosaurs known from Middle Jurassic to Early Cretaceous deposits in Europe, North America, and Africa.Turiasaurus
Turiasaurus (meaning "Turia lizard"; Turia is the Latin name of Teruel) is a genus of sauropod dinosaurs. It is known from a single fossil specimen representing the species Turiasaurus riodevensis, found in the Kimmeridgian Villar del Arzobispo Formation of Teruel, Spain.Yuanmousaurus
Yuanmousaurus ("Yuanmou lizard") was a sauropod dinosaur from the Middle Jurassic period of China. It is known from incomplete remains, recovered in 2000 from the Zhanghe Formation in Yuanmou County in Yunnan Province. Yuanmousaurus was a relatively large sauropod and may have reached about 17 meters (56 ft) in length. It was a basal member of the Sauropoda, but its exact systematic position is unclear. A recent study placed Yuanmousaurus within the family Mamenchisauridae. The only and type species was Yuanmousaurus jiangyiensis.