Eusauropoda

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Eusauropods
Temporal range: Early JurassicLate Cretaceous, 184.5–66  Ma
Jobaria head.jpg
Skull of Jobaria
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Sauropodomorpha
Clade: Sauropoda
Clade: Gravisauria
Clade: Eusauropoda
Upchurch, 1995
Subgroups

Eusauropoda (meaning "True Lizard Foot") 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 . [1] 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. [2]

Contents

Eusauropoda are herbivorous, quadrupedal, and have long necks. They have been found in South America, Europe, North America, Asia, Australia, and Africa. [3] The temporal range of Eusauropoda ranges from the early Jurassic to the Latest Cretaceous periods. [1] 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. [1] [4] However the discovery of the vulcanodont, Tazoudasaurus, which does preserve cranial material did help refine some of the characteristics. [5]

Description

Eusauropods are long-necked, strictly herbivorous, obligate quadrupedals. [6] They have a highly specialized set of skeletal adaptions due to their large size, and are graviportal. [7]

Teeth and mouth

Yates and Upchurch described eusauropod evolution as moving towards a “bulk-browsing mode of feeding”. They describe the development of lateral plates on the alveolar margins of tooth-bearing bones. These plates can be used to strip foliage, the eusauropod's “U-shaped” jaws create a wide bite, and their loss of “fleshy cheeks” increased the gape. [7] The crowns of eusauropod teeth also have “wrinkled enamel textures”, but it is unclear what this meant for their feeding habits. [1]

Head and neck

Reconstruction of selected sauropod necks, showing posture and length Sauropod neck reconstructions.png
Reconstruction of selected sauropod necks, showing posture and length

The skull length of the basal eusauropod, Patagosaurus is about 60 centimetres (24 in). [8] One of the most basal eusauropods, Shunosaurus , has two characteristic features of the eusauropod elongated neck: the incorporation of the equivalent of the first dorsal vertebra into the cervical region of the spine, and the addition of two cervical vertebra in the middle of the cervical vertebrae. [4]

Other synapomorphies of Eusauropoda includes a retracted position of the external nares. Unlike prosauropods and theropods, which have a snout with smooth, unprotruding alveolar and subnarial regions, eusauropods have snouts with “stepped anterior margins”. Further distinguishing features of eusauropods include the absence of the contact between the squamosal and the quadratojugal, the absence of the anterior process of the prefrontal, and a distally elongated anterior ramus of the quadratojugal. Separating the anteroventral process of the nasal from the posterolateral process of the premaxilla, eusauropods also have a long maxilla that forms the posteroventral margin of the external naris. [1]

Feet and limbs

Eusauporoda are also hypothesized to have a semi-digitigrade foot posturem demonstrated by footprint evidence. [4] Paleontologist Jeffrey Wilson explains that eusauropods differ from theropods and prosauropods that have digitigrade pes where their heel and metatarsals are lifted off the ground. Eusauropods show asymmetry in their metatarsal shaft diameters where metatarsal I is broader than the others, suggesting that their weight was mostly assumed by their inner feet. [1] According to Steven Salisbury and Jay Nair, basal eusauropods retain four pedal unguals but reduce their phalangeal number in their fourth digit to three units. [9] The metatarsus in eusauropods is less than a quarter of their tibial length, unlike sauropod outgroups that have long hindlimbs and metatarsus that are almost half of their tibial length. [4]

Distribution

Eusauropods are found on all major continents, with diplocodoids being widespread in the Northern Hemisphere, and titanosaurs being found in Southern Hemisphere. However, basal eusauropods that do not fall into either group are fairly well represented. [10]

Early eusauropods such as Volkeimeria and Amygdalodon, and more derived eusauropods such as Patagosaurus have been found in South America. [8] Volkeimeria is classified as a basal eusauropod, though in 2004 Paul Upchurch was suspicious of its placement, because of its “opisthoceolous cervical centra, the absence of a femoral anterior trochanter, and laterally projecting cnemial crest of the tibia”, and instead thought it may be a generic sauropod. [10]

African eusauropods may include Spinophorosaurus , from Niger, although that taxon may instead be closer to Vulcanodon and outside Eusauropoda. [3] [9] Also, Atlasaurus was found in Morocco, and Jobaria was found in Niger. However, both genera have been found as possible Macronarians, but Atlasaurus was found to be a turiasaurian, and Jobaria a eusauropod, by a phylogenetic analysis of Xing in 2012. [3] [10]

In Europe, the clade Turiasauria has been found in France, Spain, and possibly England, with multiple genera from the same locality in Spain. [10] [11] Cetiosaurus skeletons have also been found in England, along with the possibly eusauropod genera Cardiodon and Oplosaurus , known only from teeth. [10]

The family Mamenchisauridae is found widespread throughout Asia. A majority of the genera are found in China, although a possible specimen of Mamenchisaurus has been found in Thailand. [3] [10] Also in China, the basal eusauropod Nebulasaurus taito was found to be a sister taxon to Spinophorosaurus, and more derived than Mamenchisauridae, but less derived than Patagosaurus, and the genus Shunosaurus is likely one of the most basal eusauropods. [3] [10] The genus Barapasaurus has been found in India, and may represent a cetiosaurid, a basal eusauropod, or a genus outside Eusauropoda. [3] [9] [10]

Paleobiology

The data around sauropods evolution, as Novas points out, is largely based on a few formations mostly in the Northern Hemisphere. However, other beds in places such as Tanzania, specifically the Canadon Asfalto and Canadon Calcereo formations reveal a more diverse and widespread peleobiology of eusauropods in the Late Jurassic period. [8]

Classification

The following cladogram demonstrates hypothesized relationships within the Eusauropoda. [12] The basal eusauropods include the Turiasauria ( Turiasaurus , Zby and others). [13]

Eusauropoda

Related Research Articles

<i>Barapasaurus</i> Sauropod dinosaur genus from Early Jurassic India

Barapasaurus is a genus of basal sauropod dinosaur from Jurassic rocks of India. The only species is B. tagorei. Barapasaurus comes from the lower part of the Kota Formation, which is of Early to Middle Jurassic age. It is therefore one of the earliest known sauropods. Barapasaurus is known from approximately 300 bones from at least six individuals, so that the skeleton is almost completely known except for the anterior cervical vertebrae and the skull. This makes Barapasaurus one of the most completely known sauropods from the early Jurassic.

<i>Amygdalodon</i> Extinct genus of reptiles

Amygdalodon was a genus of basal sauropod from the Middle Jurassic of Argentina. The type species is Amygdalodon patagonicus. Fossils of Amygdalodon have been found in the Toarcian Cerro Carnerero Formation of the Jurassic. Very little is known about it, but it is one of the few Jurassic dinosaurs from South America found thus far.

<i>Vulcanodon</i> Extinct genus of dinosaurs

Vulcanodon is an extinct genus of sauropod dinosaur from the Early Jurassic Uppermost Forest Sandstone of southern Africa. The only known species is V. karibaensis. Discovered in 1969 in Zimbabwe, it was regarded as the earliest-known sauropod for decades, and is still one of the most primitive sauropods that has been discovered. As a quadrupedal, ground-dwelling herbivore, Vulcanodon already showed the typical sauropod body plan with column-like legs and a long neck and tail. It was smaller than most other sauropods, measuring approximately eleven metres (36 ft) in length. Vulcanodon is known from a fragmentary skeleton including much of the pelvic girdle, hindlimbs, forearms, and tail, but lacking the trunk and neck vertebrae as well as the skull.

<i>Shunosaurus</i> Extinct genus of dinosaurs

Shunosaurus, meaning "Lizard from Sichuan", is a genus of sauropod dinosaur from Late Jurassic (Oxfordian) beds in Sichuan Province in China, from 161 to 157 Million years ago. The name derives from "Shu", an ancient name for the Sichuan province.

<i>Tazoudasaurus</i> Extinct genus of dinosaurs

Tazoudasaurus is a genus of gravisaurian, probably a vulcanodontid sauropod dinosaurs hailing from the late Early Jurassic (Toarcian), that was recovered in the "Toundoute Continental Series" located in the High Atlas Mountains of Morocco in North Africa. Along with Patagosaurus, Volkheimeria, Bagualia and Perijasaurus represents one of the few sauropods named from this stage on Gondwana, as well as the only one from Africa.

Volkheimeria is an extinct genus of sauropod dinosaurs that lived in what is now Argentina during the Early Jurassic, 178–179 million years ago. Its type and only species is Volkheimeria chubutensis.

<i>Atlasaurus</i> Extinct genus of dinosaurs

Atlasaurus is a genus of sauropod dinosaurs from Middle Jurassic beds in North Africa.

<i>Rhoetosaurus</i> Extinct genus of dinosaurs

Rhoetosaurus, named after Rhoetus, a titan in Greek mythology, is a genus of sauropod dinosaur from the Jurassic (Oxfordian) Walloon Coal Measures of what is now eastern Australia. Rhoetosaurus is estimated to have been about 15 metres (49 ft) long, weighing about 9 tonnes. Subsequent authors have sometimes misspelled the name: Rhaetosaurus ; Rheteosaurus.

<i>Hudiesaurus</i> Extinct genus of dinosaurs

Hudiesaurus is a herbivorous sauropod genus of dinosaur from China. Its fossil remains were found in 1993 by a Chinese-Japanese expedition near Qiketai in Shanshan, Xinjiang province. The genus contains a single species, Hudiesaurus sinojapanorum, was named and described by Dong Zhiming in 1997. The generic name is derived from Mandarin hudie, meaning "butterfly," and refers to a flat butterfly-shaped process on the front base of the vertebral spine. The specific name refers to the members of the Sino-Japan Silk Road Dinosaur Expedition but can also be read as "central part" in Chinese, a pun on the Japanese Chunichi Shimbun press group, which financed the research.

<i>Patagosaurus</i> Extinct genus of dinosaurs

Patagosaurus is an extinct genus of eusauropod dinosaur from the Middle-Late Toarcian of Patagonia, Argentina. It was first found in deposits of the Cañadón Asfalto Formation, which date to around 179 to 177 million years ago. Although originally twelve specimens were assigned to the taxon, at least one of them may belong to a different genus. Patagosaurus probably lived alongside genera as Piatnitzkysaurus, Condorraptor and Volkheimeria.

<i>Ohmdenosaurus</i> Extinct species of reptile

Ohmdenosaurus is a genus of sauropod dinosaur that lived during the Early Jurassic epoch in what is now Germany. The only specimen – a tibia (shinbone) and ankle – was discovered in rocks of the Posidonia Shale near the village of Ohmden. The specimen, which was originally identified as a plesiosaur, is exhibited in a local museum, the Urweltmuseum Hauff. In the 1970s, it caught the attention of German palaeontologist Rupert Wild, who recognised it as the remains of a sauropod. Wild named Ohmdenosaurus in a 1978 publication; the only known species is Ohmdenosaurus liasicus.

<i>Yuanmousaurus</i> Extinct genus of dinosaurs

Yuanmousaurus 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. It may be a dubious genus. The only and type species was Yuanmousaurus jiangyiensis.

<i>Turiasaurus</i> Extinct genus of dinosaurs

Turiasaurus 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.

<span class="mw-page-title-main">Camarasauridae</span> Extinct family of dinosaurs

Camarasauridae is a family of sauropod dinosaurs. 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.

<span class="mw-page-title-main">Neosauropoda</span> Extinct clade of dinosaurs

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.

<i>Daxiatitan</i> Extinct genus of dinosaurs

Daxiatitan is a genus of sauropod dinosaur known from the Lower Cretaceous of Gansu, China. Its type and only species is Daxiatitan binglingi. It is known from a single partial skeleton consisting of most of the neck and back vertebrae, two tail vertebrae, a shoulder blade, and a thigh bone. At the time of its discovery in 2008, Daxiatitan was regarded as potentially the largest known dinosaur from China.

<span class="mw-page-title-main">Mamenchisauridae</span> Extinct family of dinosaurs

Mamenchisauridae is a family of sauropod dinosaurs belonging to Eusauropoda known from the Jurassic and Early Cretaceous of Asia and Africa. Some members of the group reached gigantic sizes, amongst the largest of all sauropods.

<i>Spinophorosaurus</i> Middle Jurassic genus of sauropod dinosaur

Spinophorosaurus is a genus of sauropod dinosaur that lived in what is now Niger during the Middle Jurassic period. The first two specimens were excavated in the 2000s by German and Spanish teams under difficult conditions. The skeletons were brought to Europe and digitally replicated, making Spinophorosaurus the first sauropod to have its skeleton 3D printed, and were to be returned to Niger in the future. Together, the two specimens represented most of the skeleton of the genus, and one of the most completely known basal sauropods of its time and place. The first skeleton was made the holotype specimen of the new genus and species Spinophorosaurus nigerensis in 2009; the generic name refers to what was initially thought to be spiked osteoderms, and the specific name refers to where it was found. A juvenile sauropod from the same area was later assigned to the genus.

<i>Zby</i> Genus of sauropod dinosaur

Zby is an extinct genus of turiasaurian sauropod dinosaur known from the Late Jurassic of the Lourinhã Formation, central west Portugal. It contains a single species, Zby atlanticus. It is named after Georges Zbyszewski, who studied the geology and paleontology of Portugal.

<i>Xingxiulong</i> Extinct genus of reptiles

Xingxiulong is a genus of bipedal sauropodiform from the Early Jurassic of China. It contains a single species, X. chengi, described by Wang et al. in 2017 from three specimens, two adults and an immature individual, that collectively constitute a mostly complete skeleton. Adults of the genus measured 4–5 metres (13–16 ft) long and 1–1.5 metres tall. Phylogenetic analysis suggests that Xingxiulong is most closely related to its contemporary Jingshanosaurus, although an alternative position outside of both the Sauropodiformes and Massospondylidae is also plausible.

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