Sauroposeidon (/ˌsɔːroʊpoʊˈsaɪdən/ SOR-o-po-SY-dən; meaning "lizard earthquake god", after the Greek god Poseidon[1][2]) is a genus of sauropod dinosaur known from several incomplete specimens including a bone bed and fossilized trackways that have been found in the American states of Oklahoma, Wyoming, and Texas. The fossils were found in rocks dating from near the end of the Early Cretaceous (Aptian–early Albian), a time when sauropod diversity in North America had greatly diminished. It was the last known North American sauropod prior to an absence of the group on the continent of roughly 40 million years that ended with the appearance of Alamosaurus during the Maastrichtian.

While the holotype remains were initially discovered in 1994, due to their unexpected age and unusual size they were initially misclassified as pieces of petrified wood. A more detailed analysis in 1999 revealed their true nature which resulted in a minor media frenzy, and formal publication of the find the following year.[3]

Paleoecological analysis indicates that Sauroposeidon lived on the shores of the Gulf of Mexico, in a river delta. Extrapolations based on the more completely known Brachiosaurus indicate that the head of Sauroposeidon could reach 17–18 m (56–59 ft) in height with its neck extended, which would make it the tallest known dinosaur. With an estimated length of 27–34 m (89–112 ft) and a mass of 40–60 t (44–66 short tons), it also ranks among the longest and heaviest. However, this animal may not be as closely related to Brachiosaurus as previously thought, so these estimates may be inaccurate.

While initially described as a brachiosaurid closely related to Brachiosaurus and Giraffatitan, the discovery of additional remains in the Cloverly Formation of Wyoming suggested that it was in fact more closely related to the titanosaurs, in the group Somphospondyli. Analysis of these remains and comparison with others from Texas supported this conclusion, and demonstrated that the more completely known sauropods from the Twin Mountains Formation (including a partial skull and fossil trackways) previously named Paluxysaurus jonesi also belonged to Sauroposeidon.[4] It is the state dinosaur of Texas.[5]

Temporal range: Early Cretaceous, 112 Ma
Sauroposeidon Scale Diagram Steveoc86
Size comparison, showing the isolated vertebrae of the holotype specimen.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Clade: Somphospondyli
Genus: Sauroposeidon
Wedel, Cifelli & Sanders, 2000
S. proteles
Binomial name
Sauroposeidon proteles
Wedel, Cifelli & Sanders, 2000

Paluxysaurus jonesi Rose, 2007


Sauroposeidon quarry
Sauroposeidon was discovered in the southeast portion of Atoka County, Oklahoma

The first fossils classified as Sauroposeidon were four neck vertebrae discovered in rural Oklahoma, not far from the Texas border, in a claystone outcrop that dates the fossils to about 110 million years ago (mya). This falls within the Early Cretaceous Period, specifically between the Aptian and Albian epochs. These vertebrae were discovered in May 1994 at the Antlers Formation in Atoka County, Oklahoma by dog trainer Bobby Cross and secured by Dr. Richard Cifelli and a team from the Oklahoma Museum of Natural History in May 1994 and August 1994. Initially the fossils were believed to be simply too large to be the remains of an animal, and due to the state of preservation, believed to be tree trunks. In fact, they are the longest such bones known in dinosaurs. Thus, the vertebrae were stored until 1999, when Dr. Cifelli gave them to a graduate student, Matt Wedel, to analyze as part of a project. Upon their realization of the find's significance, they issued a press release in October 1999, followed by official publication of their findings in the Journal of Vertebrate Paleontology in March 2000. The new species was named S. proteles, and the holotype is OMNH 53062.

The generic name comes from sauros (Greek σαύρος for "lizard"), and Poseidon (Ποσειδών), the sea god in Greek mythology, who is also associated with earthquakes, that facet styled as Ennosigaios or Enosikhthōn, "Earthshaker". This is a reference to the notion that a sauropod's weight was so great that the ground shook as it walked.

The specific descriptor proteles also comes from the Ancient Greek πρωτέλης and means "perfect before the end", which refers to Sauroposeidon's status as the last and most specialized giant sauropod known in North America, during the Early Cretaceous. In 2012, numerous other sauropod remains that had been known for decades under various different names were also classified in the genus Sauroposeidon.[4] Sauropod bones and trackways had long been known from the Paluxy River area of Texas, usually referred to the genus Pleurocoelus, including partial skeletons (particularly from the Glen Rose Formation, above the Twin Mountains Formation). In the mid 1980s, students from the University of Texas at Austin discovered a bonebed on a ranch in Hood County, but early work stopped in 1987. The quarry was reopened in 1993 and was subsequently worked by parties from Southern Methodist University, the Fort Worth Museum of Science and History, and Tarleton State University. All sauropod remains from this bonebed appear to come from the same genus of sauropod. Petrified logs are also known from the site. The site was fluvial when its rocks were being deposited, with channel sands and muds, and concretions of calcite-cemented sandstone containing fossils. Following excavation and preparation of the majority of the fossils from the site, its sauropod species was given the name Paluxysaurus jonesi.[6]

Neck vertebrae

The name Paluxysaurus was based on the specimen FWMSH 93B-10-18, a partial skull including an associated left maxilla, nasal, and teeth. Other bones from the quarry included a partial neck of seven vertebrae, thirteen vertebrae from the back and 30 from the tail, and examples of all limb and girdle bones except some hand and foot bones. It was distinguished from all other sauropods by vertebral details, and has various morphological differences in other bones compared to other sauropods of the Early Cretaceous of North America. The genus was limited to the bonebed remains; for example, the partial skeleton from Wise County known as Pleurocoelus sp. (SMU 61732) is not referred to Paluxysaurus; instead that specimen is the holotype of Astrophocaudia slaughteri D'Emic 2012, another somphospondylan sauropod. There are differences in the remains of P. sp. and Paluxysaurus, but they cannot be distinguished with confidence.[6] In 2012, re-analysis of these specimens in light of additional Sauroposeidon remains led paleontologists D'Emic and Foreman to conclude that Paluxysaurus was the same animal as Sauroposeidon, and thus a junior synonym of S. proteles.[4]


Sauroposeidon dinosaur
Size comparison

It's truly astonishing. It's arguably the largest creature ever to walk the earth.

— Richard Cifelli, discoverer of Sauroposeidon[7]

The press release in 1999 immediately garnered international media attention, which led to many (inaccurate) news reports of "the largest dinosaur ever!". While Sauroposeidon likely represents the tallest known dinosaur taxon, it does not hold records for either the longest or most massive. Patagotitan or Argentinosaurus make better candidates for the title "World's Largest Dinosaur" (presuming to ignore, as is conventional, Amphicoelias), though incomplete fossil evidence makes exact rankings impossible.

The original Sauroposeidon find was composed of four articulated, mid-cervical vertebrae (numbers 5 to 8), with the cervical ribs in place. The vertebrae are extremely elongated, with the largest one having an overall length of 1.4 m (4.6 ft), making it the longest sauropod neck vertebra on record.[8] Examination of the bones revealed that they are honeycombed with tiny air cells, and are very thin, like the bones of a chicken or an ostrich, making the neck lighter and easier to lift.[8] The cervical ribs were remarkably long as well, with the longest measurable rib (on vertebra 6) measuring 3.42 m (11.2 ft) – about 18% longer than the longest rib reported for Giraffatitan, but exceeded in length by the cervical ribs of Mamenchisaurus.[3]

Sauroposeidon proteles
Hypothetical restoration

Estimates of Sauroposeidon's size are based on a comparison between the four Sauroposeidon vertebrae and the vertebrae of the HM SII specimen of Giraffatitan brancai, located in the Berlin's Natural History Museum. The HM SII is the most complete brachiosaur known, though since it is composed of pieces from different individuals its proportions may not be totally accurate. Comparisons to the other relatives of Sauroposeidon are difficult due to limited remains.[3] The neck length of Sauroposeidon is estimated at 11.25–12 m (37–39 ft), compared to a neck length of 9 m (30 ft) for the HM SII Giraffatitan. This is based on the assumption that the rest of the neck has the same proportions as Giraffatitan, which is a reasonably good conjecture.[3]

Sauroposeidon was probably able to raise its head 17–18 m (56–59 ft) above the ground, which is as high as a six-story building. In comparison, Giraffatitan could probably raise its head 13.5 m (44 ft) into the air.[3]

Sauroposeidon's shoulder height has been estimated at 6–7 m (20–23 ft) based on an interpretation of the animal as a brachiosaurid. Estimates of its total possible length have ranged from 27 m (89 ft) to 34 m (112 ft).[1][3][9][10]

The mass of Sauroposeidon is estimated at 40–60 t (44–66 short tons). While the vertebrae of Sauroposeidon are 25–33% longer than Giraffatitan', they are only 10–15% larger in diameter. This means that while Sauroposeidon probably has a larger body than Giraffatitan its body is smaller in comparison to the size of its neck, so it did not weigh as much as a scaled-up Giraffatitan. By comparison, Giraffatitan might have weighed 36–40 t (40–44 short tons). This estimate of the Giraffatitan is an average of several different methodologies.[3][10]

However, Sauroposeidon has a gracile neck compared to Giraffatitan. If the rest of the body turns out to be similarly slender, the mass estimate may be too high. This could be similar to the way the relatively robust Apatosaurus weighs far more than the longer but much slimmer Diplodocus. In addition, it is possible that sauropods may have had an air sac system, like those in birds, which could reduce all sauropod mass estimates by 20% or more.


Sauroposeidon feeding
The feeding range of Brachiosaurus and Sauroposeidon

Sauroposeidon was an unexpected discovery, because it was a huge, gas-guzzling barge of an animal in an age of subcompact sauropods.

— Matt Wedel, Sauroposeidon team leader[11]

Sauropods, which include the largest terrestrial animals of all time, were a very wide-ranging and successful group. They first appeared in the Early Jurassic and soon spread across the world. By the time of the late Jurassic, North America and Africa were dominated by the diplodocids and brachiosaurids and, by the end of the Late Cretaceous, titanosaurids were widespread (though only in the southern hemisphere). Between these periods, in the Early Cretaceous, the fossil record is sparse. Few specimens have been found in North America from that time and those specimens that do exist are often fragmentary or represent juvenile members of their species. Most of the surviving sauropods at the time were also shrinking in size to a mere 15 m (49 ft) in length, and maybe 10–15 t (11–17 short tons), which makes the discovery of an extremely specialized super-giant like Sauroposeidon very unusual.

Sauroposeidon lived on the shores of the Gulf of Mexico, which ran through Oklahoma at that time, in a vast river delta similar to the Mississippi delta today. This paleoenvironment, which has been preserved in the Antlers Formation, also stretches from southwest Arkansas through southeastern Oklahoma and into northeastern Texas. This geological formation has not been dated radiometrically. Scientists have used biostratigraphic data and the fact that it shares several of the same genera as the Trinity Group of Texas, to surmise that this formation was laid down during the Albian stage of the Early Cretaceous Period, approximately 110 mya.[12] The area preserved in this formation was a large floodplain that drained into a shallow inland sea. Several million years later, this sea would expand to the north, becoming the Western Interior Seaway and dividing North America in two for nearly the entire Late Cretaceous period. The paleoenvironment of Sauroposeidon consisted of tropical or sub-tropical forests, river deltas, coastal swamps, bayous and lagoons, probably similar to that of modern-day Louisiana.[13] There were few predators which could attempt to attack a full-grown Sauroposeidon, but juveniles were likely to be preyed on by the contemporary Acrocanthosaurus atokensis [14] (a carnosaur slightly smaller than a Tyrannosaurus), which likely were the apex predators in this region,[15] and the small coelurosaur Deinonychus antirrhopus. Sauroposeidon also shared its paleoenvironment with other dinosaurs, such as the sauropod Astrodon (Pleurocoelus)[16] and the most common dinosaur in this region, the ornithopod Tenontosaurus. Other vertebrates present during this time included the amphibian Albanerpeton arthridion, the reptiles Atokasaurus metarsiodon and Ptilotodon wilsoni, the cartilaginous fish Hybodus buderi and Lissodus anitae, the ray-finned fish Gyronchus dumblei, the crocodilians Goniopholis, Bernissartia, and Paluxysuchus, and the turtles Glyptops and Naomichelys.[17][18] Possible indeterminate bird remains are also known from the Antlers Formation. The fossil evidence suggests that the gar Lepisosteus was the most common vertebrate in this region. The early mammals known from this region included Atokatherium boreni and Paracimexomys crossi.[19]


  1. ^ a b Wedel, Mathew J.; Cifelli, Richard L. (Summer 2005). "Sauroposeidon: Oklahoma's Native Giant" (PDF). Oklahoma Geology Notes. 65 (2): 40–57. Archived from the original (PDF) on 2007-06-21.
  2. ^ According to Wedel et al. (2005), the etymology of the name is based on Poseidon's association with earthquakes, not the sea.
  3. ^ a b c d e f g Wedel, Mathew J.; Cifelli, R. L.; Sanders, R.. K. (2000). "Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon" (PDF). Acta Palaeontologica Polonica. 45: 343–3888.
  4. ^ a b c D'Emic, M.D.; Foreman, B.Z. (2012). "The beginning of the sauropod dinosaur hiatus in North America: insights from the Lower Cretaceous Cloverly Formation of Wyoming". Journal of Vertebrate Paleontology. 32 (4): 883–902. doi:10.1080/02724634.2012.671204.
  5. ^ "Texas State Symbols". Texas State Legislature. Retrieved 13 December 2017.
  6. ^ a b Rose, Peter J. (2007). "A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships" (web pages). Palaeontologia Electronica. 10 (2). Archived (PDF) from the original on 3 November 2013.
  7. ^ "Biggest dinosaur identified". Sci/Tech. BBC News. 1999-11-03. Retrieved 2008-08-14.
  8. ^ a b Wedel, Mathew J.; Cifelli, R.L.; Sanders, R.K. (March 2000). "Sauroposeidon proteles, a new sauropod from the Early Cretaceous of Oklahoma" (PDF). Journal of Vertebrate Paleontology. 20 (1): 109–114. doi:10.1671/0272-4634(2000)020[0109:SPANSF]2.0.CO;2.
  9. ^ Carpenter, Kenneth (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36. Albuquerque: New Mexico Museum of Natural History and Science. pp. 131–138.
  10. ^ a b Paul, G.S., 2016, The Princeton Field Guide to Dinosaurs 2nd edition, Princeton University Press p. 230
  11. ^ Brusatte, Steve (2000). "Matt Wedel". Paleontology Interviews. Dino Land. Archived from the original on 2009-10-26. Retrieved 2008-08-14.
  12. ^ Wedel, M.J.; Cifelli, R.L. (2005). "Sauroposeidon: Oklahoma's native giant". Oklahoma Geology Notes. 65 (2): 40–57.
  13. ^ Forster, C. A. (1984). "The paleoecology of the ornithopod dinosaur Tenontosaurus tilletti from the Cloverly Formation, Big Horn Basin of Wyoming and Montana". The Mosasaur. 2: 151–163.
  14. ^ d'Emic, Michael D.; Melstrom, Keegan M.; Eddy, Drew R. (2012). "Paleobiology and geographic range of the large-bodied Cretaceous theropod dinosaur Acrocanthosaurus atokensis". Palaeogeography, Palaeoclimatology, Palaeoecology. 333–334: 13–23. doi:10.1016/j.palaeo.2012.03.003.
  15. ^ Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Le Loeuff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth, M.P.; and Noto, Christopher R. (2004). ""Dinosaur Distribution"", in The Dinosauria (2nd), p. 264.
  16. ^ Brinkman, Daniel L.; Cifelli, Richard L.; Czaplewski, Nicholas J. (1998). "First occurrence of Deinonychus antirrhopus (Dinosauria: Theropoda) from the Antlers Formation (Lower Cretaceous: Aptian – Albian) of Oklahoma". Oklahoma Geological Survey Bulletin. 146: 1–27.
  17. ^ Nydam, R.L.; Cifelli, R. L. (2002a). "Lizards from the Lower Cretaceous (Aptian-Albian) Antlers and Cloverly formations". Journal of Vertebrate Paleontology. 22 (2): 286–298. doi:10.1671/0272-4634(2002)022[0286:lftlca];2.
  18. ^ Cifelli, R. Gardner; Nydam, R.L.; Brinkman, D.L. (1999). "Additions to the vertebrate fauna of the Antlers Formation (Lower Cretaceous), southeastern Oklahoma". Oklahoma Geology Notes. 57: 124–131.
  19. ^ Kielan-Jarorowska, Z.; Cifelli, R.L. (2001). "Primitive boreosphenidan mammal (?Deltatheroida) from the Early Cretaceous of Oklahoma". Acta Palaeontologica Polonica. 46: 377–391.

External links

  • A non-technical article on Dino Land, with links to various news reports.

The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma (million years ago). The Albian is preceded by the Aptian and followed by the Cenomanian.

Antlers Formation

The Antlers Formation is a stratum which ranges from Arkansas through southern Oklahoma into northeastern Texas. The stratum is 150 m (490 ft) thick consisting of silty to sandy mudstone and fine to coarse grained sandstone that is poorly to moderately sorted. The stratum is cemented with clay and calcium carbonate. In places the sandstone may be conglomeratic or ferruginous (rich in iron oxides).

Based on correlation with the Trinity Group of Texas, the Antlers Formation is estimated to be late Aptian-early Albian. This age range is supported by the presence of two dinosaurs that are also known from the Cloverly Formation, Deinonychus and Tenontosaurus.


The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.The Aptian partly overlaps the upper part of the regionally used (in Western Europe) stage Urgonian.

The Selli Event, also known as OAE1a, was one of two oceanic Anoxic events in the Cretaceous period, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years. The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma.


Bruhathkayosaurus (; meaning "huge-bodied lizard") is a genus of dinosaur found in India. The fragmentary remains were originally described as a theropod but later publications listed it as a sauropod. Estimates by researchers exceed those of the titanosaur Argentinosaurus, as longer than 35 metres (115 ft) and weighing over 80-200 tons. All the estimates are based on the dimensions of the fossils described in Yadagiri and Ayyasami's 1987 paper, which announced the find. In 2017 it was reported that the original fossils had disintegrated and no longer exist.

Clash of the Dinosaurs

Clash of the Dinosaurs is a four-part television mini-series produced by Dangerous LTD for Discovery Channel. The show premiered on December 6, 2009 with the first two episodes scheduled back-to-back.

Clash of the Dinosaurs was poorly received, with critics citing leaps of logic and repetitive reenactments. The series also became the target of controversy when it emerged that a paleontologist interviewed onscreen had been quote-mined; the dispute was resolved by reediting the offending scene.


Ferganasaurus was a genus of dinosaur first formally described in 2003 by Alifanov and Averianov. The type species is Ferganasaurus verzilini. It was a sauropod similar to Rhoetosaurus. The fossils were discovered in 1966 in Kyrgyzstan from the Balabansai Formation and date to the Callovian stage of the Middle Jurassic.


Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.


Giraffatitan (name meaning "titanic giraffe") is a genus of sauropod dinosaur that lived during the late Jurassic Period (Kimmeridgian–Tithonian stages). It was originally named as an African species of Brachiosaurus (B. brancai), but this has since been changed. Giraffatitan was for many decades known as the largest dinosaur but recent discoveries of several larger dinosaurs prove otherwise; giant titanosaurians appear to have surpassed Giraffatitan in terms of sheer mass. Also, the sauropod dinosaur Sauroposeidon is estimated to be taller and possibly heavier than Giraffatitan.

All size estimates for Giraffatitan are based on the specimen HMN SII, a subadult individual between 21.8–22.5 metres (72–74 ft) in length and about 12 meters (39 ft) tall. Mass estimates are varied and range from as little as 15 tonnes (17 short tons) to as much as 78.3 tonnes (86.3 short tons) but there is evidence supporting that these animals could grow larger; specimen HMN XV2, represented by a fibula 13% larger than the corresponding material on HMN SII, might have attained 26 metres (85 ft) in length or longer.


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.


Mamenchisaurus ( mah-MUN-chi-SAWR-əs,[1] or spelling pronunciation ) is a sauropod dinosaur genus including several species, known for their remarkably long necks which made up half the total body length. It is known from numerous species which ranged in time from 160 to 114 million years ago, from the Oxfordian age of the late Jurassic Period to possibly the Aptian age of early Cretaceous Period in China. The largest species may have reached 35 m (115 ft) in length and possibly weighed 50 to 75 tons.

Matt Wedel

Mathew John Wedel is an American paleontologist. He is associate professor at the Western University of Health Sciences Department of Anatomy in California. Mathew studies sauropods and the evolution of pneumatic bones in dinosaurs. At Western University, Mathew teaches gross anatomy. He has authored papers naming Aquilops (2014), Brontomerus (2011), and Sauroposeidon (2000).Along with paleontologists Darren Naish and Mike P. Taylor, he founded the paleontology blog Sauropod Vertebrae Picture of the Week.


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.


Paluxysuchus is an extinct genus of neosuchian crocodyliform known from the Early Cretaceous Twin Mountains Formation (late Aptian stage) of north-central Texas. It contains a single species, Paluxysuchus newmani. Paluxysuchus is one of three crocodyliforms known from the Early Cretaceous of Texas, the others being Pachycheilosuchus and an unnamed species referred to as the "Glen Rose Form". Paluxysuchus has a long, flat skull that is probably transitional between the long and narrow skulls of many early neosuchians and the short and flat skulls of later neosuchians.


Ruyangosaurus (Ruyang County lizard) is a genus of titanosauriform sauropod dinosaur recovered from the Early Cretaceous Haoling Formation of China. The type species is R. giganteus, described in 2009 by Lü Junchang et al. Along with Huanghetitan and Daxiatitan, Ruyangosaurus is among the largest dinosaurs discovered in Cretaceous Asia.


Sibirotitan ("Siberian titan") is a genus of somphospondyl sauropod from the Ilek Formation of Russia. The type and only species is S. astrosacralis.


Somphospondylans are an extinct clade of titanosauriform sauropods that lived throughout the world from the Late Jurassic through the Cretaceous in North America, South America, Europe, Asia, Africa and Australia. The group can be defined as "the most inclusive clade that includes Saltasaurus loricatus but excludes Brachiosaurus altithorax". Features found as diagnostic of this clade by Mannion et al. (2013) include the possession of at least 15 cervical vertebrae; a bevelled radius bone end; sacral vertebrae with camellate internal texture; convex posterior articular surfaces of middle to posterior caudal vertebrae; biconvex distal caudal vertebrae; humerus anterolateral corner "squared"; among multiple others.


Tenontosaurus ( ti-NON-toh-SOR-əs; meaning "sinew lizard") is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 and 108 million years ago.

The genus contains two species, Tenontosaurus tilletti (described by John Ostrom in 1970) and Tenontosaurus dossi (described by Winkler, Murray, and Jacobs in 1997). Many specimens of T. tilletti have been collected from several geological formations throughout western North America. T. dossi is known from only a handful of specimens collected from the Twin Mountains Formation of Parker County, Texas.

Twin Mountains Formation

The Twin Mountains Formation, also known as the Twin Mountain Formation, is a sedimentary rock formation, within the Trinity Group, found in Texas of the United States of America. It is a terrestrial formation of Aptian age (Lower Cretaceous), and is notable for its dinosaur fossils. Dinosaurs from this formation include the large theropod Acrocanthosaurus, the sauropod Sauroposeidon, as well as the ornithopods Tenontosaurus and Convolosaurus. It is the lowermost unit of the lower Cretaceous, lying unconformably on Carboniferous strata. It is overlain by the Glen Rose Formation. It is the lateral equivalent of the lower part of the Antlers Formation.


Xenoposeidon (meaning "strange or alien Poseidon", in allusion to Sauroposeidon) is a genus of rebbachisaurid sauropod dinosaur from the Early Cretaceous of England, living about 140 million years ago. It is known from a single partial vertebra with unusual features, unlike those of other sauropods. This bone was first discovered in the early 1890s but received little attention until it was found by University of Portsmouth student Mike Taylor, who formally described and named it in 2007 with Darren Naish.


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