Siamosaurus

Siamosaurus (meaning "Siamese lizard") is a genus of theropod dinosaur from Barremian Sao Khua Formation in Thailand. The animal is a tooth taxon and therefore details on its size or classification are not certain. The type species, Siamosaurus suteethorni, was formally described by Buffetaut and Ingavat in 1986. It is known from teeth that closely resemble those of Spinosaurus; it may have eaten fish.[1]

Siamosaurus
Temporal range: Barremian, 130 Ma
Siamosaurus
Restoration
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Spinosauridae
Subfamily: Spinosaurinae
Genus: Siamosaurus
Buffetaut & Ingavat, 1986
Species
  • S. suteethorni Buffetaut & Ingavat, 1986 (type)

Palaeoecology

Sao Khua Formation V2
Phuwiangosaurus and Siamosaurus in their habitat

A 2010 publication by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid bones indicates semiaquatic lifestyles. Isotope ratios from teeth from the spinosaurids Baryonyx, Irritator, Siamosaurus, and Spinosaurus were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians. The study found that, among theropods, spinosaurid isotope ratios were closer to those of turtles and crocodilians. Siamosaurus specimens tended to have the largest difference from the ratios of other theropods, and Spinosaurus tended to have the least difference. The authors concluded that spinosaurids, like modern crocodilians and hippopotamuses, spent much of their daily lives in water. The authors also suggested that semi-aquatic habits and piscivory in spinosaurids might explain how spinosaurids coexisted with other large theropods: by feeding on different prey items and living in different habitats, the different types of theropods would have been out of direct competition. [2]

Phylogeny

The exact position of Siamosaurus within Spinosauridae is difficult to determine because it is only a tooth taxon. However a study by Arden et al. (2018) identified it as a member of the Spinosaurinae.[3]

References

  1. ^ Buffetaut, E.; and Ingevat, R. (1986). Unusual theropod dinosaur teeth from the Upper Jurassic of Phu Wiang, northeastern Thailand. Rev. Paleobiol. 5: 217-220.
  2. ^ Amiot, R.; Buffetaut, E.; Lécuyer, C.; Wang, X.; Boudad, L.; Ding, Z.; Fourel, F.; Hutt, S.; Martineau, F.; Medeiros, A.; Mo, J.; Simon, L.; Suteethorn, V.; Sweetman, S.; Tong, H.; Zhang, F.; Zhou, Z. (2010). "Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods". Geology. 38 (2): 139–142. doi:10.1130/G30402.1.
  3. ^ Arden, T.M.S.; Klein, C.G.; Zouhri, S.; Longrich, N.R. (2018). "Aquatic adaptation in the skull of carnivorous dinosaurs (Theropoda: Spinosauridae) and the evolution of aquatic habits in Spinosaurus". Cretaceous Research. In Press. doi:10.1016/j.cretres.2018.06.013.
"Sinopliosaurus" fusuiensis

"Sinopliosaurus" fusuiensis is a species of spinosaurid theropod dinosaur from the Early Cretaceous Xinlong Formation of Guangxi Province, southern China. It is known only from teeth that were initially identified as those of a pliosauroid, but are now known to have come from an animal similar to Siamosaurus.

1986 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1986.

Barremian

The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch (or Lower Cretaceous series). It is preceded by the Hauterivian and followed by the Aptian stage.

Cenomanian

The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding age. Both age and stage bear the same name.

As a unit of geologic time measure, the Cenomanian age spans the time between 100.5 ± 0.9 Ma and 93.9 ± 0.8 Ma (million years ago). In the geologic timescale it is preceded by the Albian and is followed by the Turonian. The Upper Cenomanian starts approximately at 95 M.a.

The Cenomanian is coeval with the Woodbinian of the regional timescale of the Gulf of Mexico and the early part of the Eaglefordian of the regional timescale of the East Coast of the United States.

At the end of the Cenomanian an anoxic event took place, called the Cenomanian-Turonian boundary event or the "Bonarelli Event", that is associated with a minor extinction event for marine species.

Ichthyovenator

Ichthyovenator (meaning "fish hunter") is a genus of spinosaurid theropod dinosaur that lived during the Early Cretaceous of what is now Laos, likely from the Aptian stage (113–125 million years ago). Ichthyovenator is known from fossils collected in the Grès supérieurs Formation. Like other members of its family, it had elongated neural spines forming a sail on its back, although Ichthyovenator's was unusual due to its particular wave-like curvature and being split in two over the hips. Ichthyovenator was initially thought to belong to the Baryonychinae subfamily, but more recent analyses place it in the Spinosaurinae.

Khok Kruat Formation

The Khok Kruat Formation is a rock formation found in northeastern Thailand. It is the uppermost formation of the Khorat Group. It is of Aptian stage (Early Cretaceous), and is notable for its fossils of dinosaurs. It is equivalent to the Gres superieurs Formation of Laos. The group is a fluvial formation consisting primarily of red siltstones and sandstones.

List of Asian dinosaurs

This is a list of dinosaurs whose remains have been recovered from Asia excluding the Indian Subcontinent, which was part of a separate landmass for much of the Mesozoic. This list does not include dinosaurs that live or lived after the Mesozoic era such as birds.

List of dinosaur genera

This list of dinosaurs is a comprehensive listing of all genera that have ever been included in the superorder Dinosauria, excluding class Aves (birds, both living and those known only from fossils) and purely vernacular terms.

The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered dinosaurs. Many listed names have been reclassified as everything from birds to crocodilians to petrified wood. The list contains 1559 names, of which approximately 1192 are considered either valid dinosaur genera or nomina dubia.

Oxalaia

Oxalaia (in reference to the African deity Oxalá) is a genus of spinosaurid theropod dinosaur that lived in what is now the Northeast Region of Brazil during the Cenomanian stage of the Late Cretaceous Period, sometime between 100.5 and 93.9 million years ago. Its only known fossils were found in 1999 on Cajual Island in the rocks of the Alcântara Formation, which is known for its abundance of fragmentary, isolated fossil specimens. The remains of Oxalaia were described in 2011 by Brazilian palaeontologist Alexander Kellner and colleagues, who assigned the specimens to a new genus containing one species, Oxalaia quilombensis. The species name refers to the Brazilian quilombo settlements. Oxalaia quilombensis is the eighth officially named theropod species from Brazil and the largest carnivorous dinosaur discovered there. It is closely related to the African genus Spinosaurus.

Although Oxalaia is known only from two partial skull bones, Kellner and colleagues found that its teeth and cranium had a few distinct features not seen in other spinosaurids or theropods, including two replacement teeth in each socket and a very sculptured secondary palate. Oxalaia's habitat was tropical, heavily forested, and surrounded by an arid landscape. This environment had a large variety of lifeforms also present in Middle-Cretaceous North Africa, due to the connection of South America and Africa as parts of the supercontinent Gondwana. As a spinosaurid, the traits of Oxalaia's skull and dentition indicate a partly piscivorous (fish-eating) lifestyle similar to that of modern crocodilians. Fossil evidence suggests spinosaurids also preyed on other animals such as small dinosaurs and pterosaurs.

Phu Wiang Dinosaur Museum

Phu Wiang Dinosaur Museum (Thai: พิพิธภัณฑ์ไดโนเสาร์ภูเวียง) is a geological museum mainly exhibiting fossils. It is under the administration of the Department of Mineral Resources, Ministry of Natural Resources and Environment, the Royal Thai Government, and situated in the Khok Sanambin public area in Tambon Nai Muang, Wiang Kao district, Khon Kaen province in the northeastern region of Thailand. The museum was constructed with a budget from the Tourism Authority of Thailand under supervision of the Department of Mineral Resources and comprises an area of 40 acres (160,000 m2). It has been open to the public since 2001.

Phuwiangosaurus

Phuwiangosaurus (meaning "Phu Wiang lizard") is a genus of titanosauriform dinosaur from the Early Cretaceous (Valanginian-Hauterivian) Sao Khua Formation of Thailand. The type species, P. sirindhornae, was described by Martin, Buffetaut, and Suteethorn in 1994; it was named to honour Princess Maha Chakri Sirindhorn of Thailand, who was interested in the geology and palaeontology of Thailand.

It was a mid-sized sauropod, measuring 15–20 m in length.

Phuwiangosaurus was originally assigned to Titanosauria, but more recent studies have placed it in a more basal position within the Titanosauriformes. Phylogenetic analyses presented by D'Emic (2012), Mannion et al. (2013), and Mocho et al. (2014) resolve Phuwiangosaurus within the Euhelopodidae, alongside genera such as Euhelopus and Tangvayosaurus. Other analyses have failed to find support for such a grouping, including some finding it to be paraphyletic at the base of Somphospondyli.

Planet Dinosaur

Planet Dinosaur, is a six-part documentary television series created by Nigel Paterson and Phil Dobree, produced by the BBC, and narrated by John Hurt. It first aired in the United Kingdom in 2011, with VFX studio Jellyfish Pictures as its producer. It is the first major dinosaur-related series for BBC One since Walking with Dinosaurs. There are more than 50 different prehistoric species featured, and they and their environments were created entirely as computer-generated images, for around a third of the production cost that was needed a decade earlier for Walking with Dinosaurs. Much of the series' plot is based on scientific discoveries made since Walking with Dinosaurs. The companion book to Planet Dinosaur was released on 8 September 2011, and the DVD and Blu-ray were released on 24 October 2011.

Sao Khua Formation

The Sao Khua Formation is a middle member of the Khorat Group. It consists of an alteration of pale red to yellowish-gray, fine to medium-grained sandstone and grayish-reddish brown siltstone and clay. Rare pale red to light gray conglomerates, containing carbonate pebbles, are also characteristic of this Formation. This geological formation in Thailand, dates to the Early Cretaceous age.

Dinosaur remains are among the fossils that have been recovered from the formation.

Spinosauridae

Spinosauridae (meaning "spined lizards") is a family of megalosauroidean theropod dinosaurs. The genus Spinosaurus, from which the family, subfamily, and tribe borrow their names, is the longest terrestrial predator known from the fossil record, and likely reached lengths of 15 m (49 ft). Most spinosaurids lived during the Cretaceous Period, with possible origins in the Late Jurassic, and fossils of them have been recovered worldwide, including in Africa, Europe, South America, Asia, and Australia, although none have been formally named from the latter continent. Spinosaur remains have generally been attributed to the Early to Mid Cretaceous, with the exception of the Ostafrikasaurus from the Late Jurassic.

Spinosaurids were large bipedal carnivores with elongated, crocodile-like skulls lined with conical teeth bearing little to no serrations, and small crests on top of their heads. The teeth in the front end of their lower jaws fanned out into a spoon-shaped structure similar to a rosette, which gave the animal a characteristic look. Their shoulders were robust, prominent and bore stocky forelimbs with giant "hooked" claws on the first finger of their hands. Many genera had unusually tall neural spines on their vertebrae, which supported sails or humps of skin or fat tissue.

Direct fossil evidence and anatomical adaptations indicate that spinosaurids were at least partly piscivorous, with additional fossil finds indicating they also hunted pterosaurs and small to medium-sized dinosaurs. Osteological analyses have suggested a semiaquatic lifestyle for some members of this clade.

Spinosaurus

Spinosaurus (meaning "spine lizard") is a genus of theropod dinosaur that lived in what now is North Africa, during the upper Albian to upper Turonian stages of the Cretaceous period, about 112 to 93.5 million years ago. This genus was known first from Egyptian remains discovered in 1912 and described by German paleontologist Ernst Stromer in 1915. The original remains were destroyed in World War II, but additional material has come to light in the early 21st century. It is unclear whether one or two species are represented in the fossils reported in the scientific literature. The best known species is S. aegyptiacus from Egypt, although a potential second species, S. maroccanus, has been recovered from Morocco.

Spinosaurus was among the largest of all known carnivorous dinosaurs, nearly as large as or even larger than Tyrannosaurus, Giganotosaurus and Carcharodontosaurus. Estimates published in 2005, 2007, and 2008 suggested that it was between 12.6–18 metres (41–59 ft) in length and 7 to 20.9 tonnes (7.7 to 23.0 short tons) in weight. New estimates published in 2014 and 2018 based on a more complete specimen, supported the earlier research, finding that Spinosaurus could reach lengths of 15–16 m (49–52 ft). The latest estimates suggest a weight of 6.4–7.5 tonnes (7.1–8.3 short tons). The skull of Spinosaurus was long and narrow, similar to that of a modern crocodilian. Spinosaurus is known to have eaten fish, and most scientists believe that it hunted both terrestrial and aquatic prey; evidence suggests that it lived both on land and in water as a modern crocodilian does. The distinctive spines of Spinosaurus, which were long extensions of the vertebrae, grew to at least 1.65 meters (5.4 ft) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that the spines were covered in fat and formed a hump. Multiple functions have been put forward for this structure, including thermoregulation and display.

Varavudh Suteethorn

Varavudh Suteethorn, or Warawut Suteethorn (Thai:วราวุธ สุธีธร; born October 10, 1948) is a Thai geologist and palaeontologist. He is the current director of the Palaeontological Research and Education Centre, Mahasarakham University. He is best known for his work on vertebrate palaeontology in northeastern Thailand, having contributed to the discovery of many fossil taxa and dig sites in the Khorat Plateau, as a part of a long-standing collaboration between Thai and French scientists.

Éric Buffetaut

Éric Buffetaut (born 19 November 1950) is a French paleontologist, author and researcher at the Centre national de la recherche scientifique since 1976 where he is a Doctor of Science and Director of Research. Buffetaut is a specialist of fossil archosaurs, mainly dinosaurs and pterosaurs, and has published a large number of books on paleontology. He is one of the major paleontologists to support the thesis of the fall of a meteorite as the main cause of the Cretaceous–Paleogene extinction event.

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