Sarmientosaurus Temporal range: | |
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Skull in side views | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | † Sauropodomorpha |
Clade: | † Sauropoda |
Clade: | † Macronaria |
Clade: | † Titanosauriformes |
Clade: | † Somphospondyli |
Clade: | † Diamantinasauria |
Genus: | † Sarmientosaurus Martínez et al., 2016 |
Type species | |
Sarmientosaurus musacchioi Martínez et al., 2016 |
Sarmientosaurus is a genus of titanosaurian sauropod dinosaur belonging to the Titanosauria. [1] It lived in what is now South America, specifically Argentina, during the Upper Cretaceous Period about 95 million years ago. [2] The type species is Sarmientosaurus musacchioi.
In 1997, paleontologist Rubén D.F. Martínez, at the Estancia Laguna Palacios of the Goicoechea family in Chubut province, discovered a sauropod skull. This proved to be connected to the first few cervical vertebrae. [3]
In 2016, the type species Sarmientosaurus musacchioi was named and described by Rubén Darío Francisco Martínez, Matthew Carl Lamanna, Fernando Emilio Novas, Ryan C. Ridgely, Gabriel Andrés Casal, Javier E. Martínez, Javier R. Vita and Lawrence M. Witmer. The generic name refers to the town of Sarmiento. The specific name honours the late Eduardo Musacchio, an educator at the Universidad Nacional de la Patagonia San Juan Bosco . The Life Science Identifiers are 537DFE26-54EC-4978-AC86-E83A04FA74DE for the genus and C1090B8D-D051-44F3-B869-8B4A0C802176 for the species. [3]
The holotype, MDT-PV 2, was found in the upper Lower Member of the Bajo Barreal Formation, dating from the Cenomanian to Turonian ages. It consists of an almost complete skull with lower jaws, articulated with the first seven vertebrae of the front neck. Several neck parts, among them the entire atlas and fourth neck vertebra, were too eroded to be salvaged. The specimen represents an elderly individual. It is one of the few titanosaurs for which skull material has been found. [3] Uniquely, at the side of the neck an elongated structure was discovered that was identified as an ossified tendon. [3]
From the Bajo Barreal Formation another titanosaur sauropod is known, Epachthosaurus . It cannot be determined whether both taxa are identical because the material of their holotypes is not overlapping. However, the authors considered an identity as improbable because in their cladistic analysis both genera occupied different positions in the evolutionary tree. Also, fragmentary fossils, of postcranial bones that differ from those of Epachthosaurus and skull bones that are dissimilar to the Sarmientosaurus cranium, show that in any case several titanosaur species were present in the habitat. [3]
Sarmientosaurus has an estimated length of twelve metres and a weight of ten tonnes.
The describing authors indicated nine unique distinguishing traits, autapomorphies. The eye socket is large, equalling 40% of the length of the skull. The ascending branch of the maxilla has a complex connection with a top process of the lacrimal bone, being wedged between its outer side and inner side. The inner edge of the rear part of the ascending branch of the maxilla touches the rim of the bony nostril with a low but distinct ridge. The ascending branch of the quadratojugal has at its lower rear a tongue-shaped process overlapping the rear of the quadrate. In the braincase there are three separate exits for the nervus trigeminus . An inner vein channel connecting the infundibulum with the brains stem, is lacking. The premaxillary teeth are positioned vertically, the maxillary teeth are inclining to the front and the dentary teeth are inclining to the rear. The middle neck vertebrae have strut-like, instead of plate-shaped, ridges between the front joint processes and the vertebral centrum. A long and thin ossified tendon is running along the low side of the series of neck vertebrae and neck ribs. [3]
The skull has a length of forty-three centimetres. In top view the skull is more or less tongue-shaped. The antorbital fenestra is small but the eye socket is exceptionally large. In side view the snout is flat with a concave upper profile and surface. The maxilla touches the prefrontal. The jugal bone has an unusual L-shape with a very long front branch and an almost absent rear branch. The fifth cranial nerve, the nervus trigeminus, has extra exits for the branches towards the maxilla and the lower jaw, whereas other sauropods possess but single exit. The front of the lower jaw has an almost constant height. [3]
The praemaxilla bears four teeth, the maxilla eleven (right side) or twelve (left), and the dentary thirteen. The premaxillary teeth are positioned vertically, the maxillary teeth incline to the front while the teeth of the lower jaw incline to behind, a unique configuration. The build of the teeth is in-between the more spatulate form of basal sauropods and the pencil shape of derived species. The teeth are moderately elongated. They each have sharply-angled wear facets in a high and a low position which, together with their strange orientation, indicates some special, as yet not fully understood, way of cropping vegetation. [3]
The neck vertebrae are long and elongated. Their internal structure is camellated, i.e. with many small air spaces inside. The middle neck vertebrae have oval, narrow and deep pleurocoels in their sides, pneumatic excavations that nearly touch each other on the midline, separated by a narrow bone plate. The rear joint processes are uncommonly long, reaching beyond the edge of the vertebral body. The front joint processes are supported from below by struts with an oval cross-section, apparently formed by a perforation of the normally plate-shaped ridges in this position. The neck ribs are delicate, thin and rod-shaped. [3]
Parallel to the ribs, on the outer side of the neck a cable-shaped structure was discovered with a constant diameter of three millimetres. It had an oval cross-section and a rough and striated surface. The structure originated directly behind the skull and continued over a length of several vertebrae, thus of some metres. It was interpreted by the describing authors as an ossified tendon. The alternative hypothesis that it might be a neck rib was rejected because the ribs are thicker and should have a different position. Such tendons might have been a continuation of the neck ribs, but again, its position did not confirm this. Instead, it was assumed to have been internal to some neck muscle. Such ossified tendons have never before been found in any fossil dinosaur but some extant bird groups such as the cranes show them, though they are relatively shorter, at most two vertebrae long. Possible muscles, where it could have been located, are the Musculus rectus capitis anterior ventralis, the Musculus longus colli ventralis or the Musculi intertransversarii. The internal structure of the tendon, with much reworked bone tissue, indicated a swift ossification at a young age. [3]
Martínez and colleagues placed Sarmientosaurus in a basal position within the clade Lithostrotia, above Malawisaurus in the evolutionary tree. [3] However, in 2021, Stephen Poropat and colleagues instead identified it as part of the new clade Diamantinasauria, along with Savannasaurus and Diamantinasaurus . [4]
It had very large eye sockets, meaning that it may have had better vision than other titanosaurs. Based on the ear and neck tendon, Sarmientosaurus most likely hung its head and neck down "like an enormous Eeyore". This posture implies that Sarmientosaurus may have eaten much lower-lying plants than other sauropods. [5] The correlation between inner ear structure and head posture has been questioned in previous studies. [6] [7]
Bonitasaura is a genus of titanosaurian dinosaur hailing from uppermost layers of the Late Cretaceous (Santonian) Bajo de la Carpa Formation, Neuquén Group of the eastern Neuquén Basin, located in Río Negro Province, Northwestern Patagonia, Argentina. The remains, consisting of a partial sub-adult skeleton jumbled in a small area of fluvial sandstone, including a lower jaw with teeth, a partial vertebrae series, and limb bones, were described by Sebastian Apesteguía in 2004.
Saichania is a genus of herbivorous ankylosaurid dinosaur from the Late Cretaceous period of Mongolia and China.
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Epachthosaurus was a genus of titanosaurian sauropod dinosaur from the Late Cretaceous. It was a basal lithostrotian titanosaur. Its fossils have been found in Central and Northern Patagonia in South America.
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Miragaia is a long-necked stegosaurid dinosaur. Its fossils have been found in Upper Jurassic rocks in Portugal and possibly also Wyoming, United States. Miragaia has the longest neck known for any stegosaurian, which included at least seventeen vertebrae. Some researchers consider this taxon to be a junior synonym of Dacentrurus.
Vancleavea is a genus of extinct, armoured, non-archosaurian archosauriforms from the Late Triassic of western North America. The type and only known species is V. campi, named by Robert Long & Phillip A Murry in 1995. At that time, the genus was only known from fragmentary bones including osteoderms and vertebrae. However, since then many more fossils have been found, including a pair of nearly complete skeletons discovered in 2002. These finds have shown that members of the genus were bizarre semiaquatic reptiles. Vancleavea individuals had short snouts with large, fang-like teeth, and long bodies with small limbs. They were completely covered with bony plates known as osteoderms, which came in several different varieties distributed around the body. Phylogenetic analyses by professional paleontologists have shown that Vancleavea was an archosauriform, part of the lineage of reptiles that would lead to archosaurs such as dinosaurs and crocodilians. Vancleavea lacks certain traits which are present in most other archosauriforms, most notably the antorbital, mandibular and supratemporal fenestrae, which are weight-saving holes in the skulls of other taxa. However, other features clearly support its archosauriform identity, including a lack of intercentra, the presence of osteoderms, an ossified laterosphenoid, and several adaptations of the femur and ankle bones. In 2016, a new genus of archosauriform, Litorosuchus, was described. This genus resembled both Vancleavea and more typical archosauriforms in different respects, allowing Litorosuchus to act as a transitional fossil linking Vancleavea to less aberrant archosauriforms.
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This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.
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Lohuecotitan is an extinct genus of titanosaurian sauropod dinosaur which lived during the Late Cretaceous in Spain. The only species known in the genus is Lohuecotitan pandafilandi, described and named in 2016.
Savannasaurus is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Winton Formation of Queensland, Australia. It contains one species, Savannasaurus elliottorum, named in 2016 by Stephen Poropat and colleagues. The holotype and only known specimen, originally nicknamed "Wade", is the most complete specimen of an Australian sauropod, and is held at the Australian Age of Dinosaurs museum. Dinosaurs known from contemporary rocks include its close relative Diamantinasaurus and the theropod Australovenator; associated teeth suggest that Australovenator may have fed on the holotype specimen.
Magnamanus is an extinct genus of herbivorous iguanodontian dinosaur that lived during the Early Cretaceous in what is now Spain in the Golmayo Formation. It contains a single species, Magnamanus soriaensis.
Mansourasaurus is a genus of herbivorous lithostrotian sauropod dinosaur from the Quseir Formation of Egypt. The type and only species is Mansourasaurus shahinae.
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Mnyamawamtuka is a genus of lithostrotian titanosaur sauropod dinosaur from the Cretaceous Galula Formation in Tanzania. The type and only species is M. moyowamkia.
Nullotitan is a genus of lithostrotian titanosaur from the Chorrillo Formation from Santa Cruz Province in Argentina. The type and only species is Nullotitan glaciaris. It was a contemporary of the ornithopod Isasicursor which was described in the same paper.
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The team called this new species sarmientosaurus, a member of a subgroup of sauropods called titanosaurs.
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