Ouranosaurus

Ouranosaurus (meaning "brave (monitor) lizard", alternatively "sky lizard" after the primordial Greek god Ouranos) is a genus of herbivorous iguanodont dinosaur that lived during the early Cretaceous (Aptian to early Albian age) at some point between 125 and 112 million years ago, in what is now Africa. Ouranosaurus measured about 7 to 8.3 metres (23 to 27 ft) long. Two rather complete fossils were found in the Elrhaz Formation, Gadoufaoua deposits, Agadez, Niger, in 1965 and 1972.[1] The animal was named in 1976 by French paleontologist Philippe Taquet; the type species being Ouranosaurus nigeriensis.

Ouranosaurus
Temporal range: Early Cretaceous, 125–112 Ma
Ouranosaurus nigeriensis, ROM
Mounted skeleton cast, ROM
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Clade: Styracosterna
Clade: Hadrosauriformes
Genus: Ouranosaurus
Taquet, 1976
Species:
O. nigeriensis
Binomial name
Ouranosaurus nigeriensis
Taquet, 1976

Description

Ouranosaurus was a relatively large euornithopod. Taquet in 1976 estimated the body length at 7 metres (23 feet), the weight at 4 tonnes (4.4 short tons). Gregory S. Paul in 2010 gave a higher length estimate of 8.3 metres (27 feet) but a lower weight of 2.2 t (2.4 short tons), emphasizing that the animal was relatively light-built.[2] The femur is 811 millimetres (2.661 ft) long.

Postcranial skeleton

Ouranosaurus MSNVE 3714
Mounted skeleton, Museo di Storia Naturale of Venice.

The most conspicuous feature of Ouranosaurus is a large "sail" on its back, supported by long, wide, neural spines, that spanned its entire rump and tail, resembling that of Spinosaurus, a well-known meat-eating dinosaur also known from northern Africa.[1][3] These tall neural spines did not closely resemble those of sail-backs such as Dimetrodon of the Permian Period. The supporting spines in a sailback become thinner distally, whereas in Ouranosaurus the spines actually become thicker distally and flatten. The posterior spines were also bound together by ossified tendons, which stiffened the back. Finally, the spine length peaks over the forelimbs.

The first four dorsal vertebrae are unknown; the fifth already bears a 32-centimetre-long spine (1.05 ft) that is pointed and slightly hooked; Taquet presumed it might have anchored a tendon to support the neck or skull. The tenth, eleventh and twelfth spines are the longest, at about 63 cm (25 in). The last dorsal spine, the seventeenth, has a grooved posterior edge, in which the anterior corner of the lower spine of the first sacral vertebra is locked. The spines over the six sacral vertebrae are markedly lower, but those of the tail base again longer; towards the end of the tail the spines gradually shorten.

The dorsal "sail" is usually explained as either functioning as a system for thermoregulation or a display structure. An alternative hypothesis is that the back might have carried a hump consisting of muscle tissue or fat, resembling that of a bison or camel, rather than a sail. It could have been used for energy storage to survive a lean season.[4]

Ouranosaurus - dorsal vertebrae
Dorsal vertebrae

The axial column consisted of eleven neck vertebrae, seventeen dorsal vertebrae, six sacral vertebrae and forty tail vertebrae. The tail was relatively short.

The front limbs were rather long with 55% of the length of the hind limbs. A quadrupedal stance would have been possible. The humerus was very straight. The hand was lightly built, short and broad. On each hand Ouranosaurus bore a thumb claw or spike that was much smaller than that of the earlier Iguanodon. The second and third digits were broad and hoof-like, and anatomically were good for walking. To support the walking hypothesis, the wrist was large and its component bones fused together to prevent its dislocation. The last digit (number 5) was long. In related species the fifth finger is presumed to have been prehensile: used for picking food like leaves and twigs or to help lower the food by lowering branch to a manageable height. Taquet assumed that with Ouranosaurus this function had been lost because the fifth metacarpal, reduced to a spur, could no longer be directed sideways.

The hindlimbs were large and robust to accommodate the weight of the body and strong enough to allow a bipedal walk. The femur was slightly longer than the tibia. This may indicate that the legs were used as pillars, and not for sprinting. Taquet concluded that Ouranosaurus was not a good runner because the fourth trochanter, the attachment point for the large retractor muscles connected to the tail base, was weakly developed. The foot was narrow with only three toes and relatively long.

Ouranosaurus nigeriensis restoration
Restoration of Ouranosaurus nigeriensis based on skeletal diagrams and casts, fossils, and related species

In the pelvis, the prepubis was very large, rounded and directed obliquely upwards.

Skull

Ouranosaurus - skull
Skull.

Ouranosaurus had a skull 67 centimetres (26 in) long. The head was very elongated and flat, and carried a much longer snout than its relative Iguanodon: this rostrum was not curved but straight, off-set from the back of the skull in an oblique line. The snout was toothless and covered in a horny sheath during life, forming a very wide beak together with a comparable sheath on the short predentary bone at the extreme front of the lower jaws. However, after a rather large diastema with the beak, there were large batteries of cheek teeth on the sides of the jaws: the gaps between the teeth crowns were filled by the points of a second generation of replacement teeth, the whole forming a continuous surface. Contrary to the situation with some related species, a third generation of erupted teeth was lacking. There were twenty-two tooth positions in both lower and upper jaw, for a total of eighty-eight.

Ouranosaurus head
Restoration of the head.

The jaws were apparently operated by relatively weak muscles. Ouranosaurus had only small temporal openings behind the eyes, from which the larger capiti-mandibularis muscle was attached to the coronoid process on the lower jaw bone. Small rounded horns in front of its eyes made Ouranosaurus the only known horned ornithopod.[1] The back of the skull was rather narrow and could not compensate for the lack of a greater area of attachment for the jaw muscle, that the openings normally would provide, allowing for more power and a stronger bite. A lesser muscle, the musculus depressor mandibulae, used to open the lower jaws, was located at the back of the skull and was connected to a strongly projecting, broad and anteriorly oblique processus paroccipitalis. Ouranosaurus probably used its teeth to chew up tough plant food. A diet has been suggested of leaves, fruit, and seeds as the chewing would allow to free more energy from high quality food;[3] the wide beak on the other hand indicates a specialisation in eating large amounts of low quality fodder. Ouranosaurus lived in a river delta.

The nasal passage was large and placed close to the beak. The nostrils were in a high position. On each side of the top of the skull there was a low bump between the nasal opening and the eye socket; the significance of both protuberances is unknown, but they may have been used for socialisation or mating displays. A secondary palpebral bone was lacking.

Discovery and naming

Ouranosaurus Scale
Size of Ouranosaurus compared to a human

In January 1965 Philippe Taquet discovered dinosaurian fossils at the Camp des deux Arbres site near Gadoufaoua. The material was recovered in 1966. Taquet described the type species Ouranosaurus nigeriensis from the fossils in 1976. The generic name is derived from Tuareg ourane meaning "monitor lizard" — a totem animal to the Tuareg who consider it their ancestral maternal uncle — but itself related to Arab waran, "brave". The specific name refers to Niger.[5]

The holotype specimen MNHN GDF 300, was found in the Upper Elrhaz Formation dating to the Aptian, between 125 and 112 million years old.[6][7] It consists of an almost complete skeleton with skull, that is today mounted in the Nigerien capital Niamey; the Museum national d'histoire naturelle displays a cast. Other finds include the paratype specimen GDF 381, a second skeleton found in 1972, and the referred specimens GDF 301, a large coracoid, and GDF 302, a femur.

Classification

Ouranosaurus teeth 3
Teeth.

Taquet originally assigned Ouranosaurus to the Iguanodontidae, within the larger Iguanodontia. However, although it shares some similarities with Iguanodon (such as a thumb spike), Ouranosaurus is no longer usually placed in the iguanodontid family, a grouping that is now generally considered paraphyletic, a series of subsequent offshoots from the main stem-line of iguandontian evolution. It is instead placed in the clade Hadrosauriformes, closely related to the Hadrosauroidea, which contains the Hadrosauridae (also known as "duck-billed dinosaurs") and their closest relatives. Ouranosaurus appears to represent an early specialized branch in this group, showing in some traits independent convergence with the hadrosaurids. It is thus a basal hadrosauriform.

The simplified cladogram below follows an analysis by Andrew McDonald and colleagues, published in November 2010 with information from McDonald, 2011.[8][9]

Iguanodontia

Rhabdodontidae

Tenontosaurus

Dryomorpha

Dryosauridae

Ankylopollexia

Camptosaurus

Styracosterna

Cumnoria

Uteodon

Hippodraco

Theiophytalia

Cedrorestes

Dakotadon

Iguanacolossus

Lanzhousaurus

Hadrosauriformes

Iguanodon

Mantellisaurus

Ouranosaurus

Hadrosauroidea

Paleoecology

The Elrhaz Formation consists mainly of fluvial sandstones with low relief, much of which is obscured by sand dunes.[10] The sediments are coarse- to medium-grained, with almost no fine-grained horizons.[11]

Other herbivores from the same formation include Nigersaurus, Lurdusaurus, Elrhazosaurus, and an unnamed titanosaur. It also lived alongside the theropods Kryptops, Suchomimus, and Eocarcharia, and a yet-unnamed noasaurid. Crocodylomorphs like Sarcosuchus, Anatosuchus, Araripesuchus, and Stolokrosuchus also lived there. In addition, remains of a pterosaur, chelonians, fish, a hybodont shark, and freshwater bivalves have been found.[10]

References

  1. ^ a b c Benton, Michael J. (2012). Prehistoric Life. Edinburgh, Scotland: Dorling Kindersley. p. 338. ISBN 978-0-7566-9910-9.
  2. ^ Paul, G.S. (2010). The Princeton Field Guide to Dinosaurs, Princeton University Press. p. 292
  3. ^ a b Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 144. ISBN 1-84028-152-9.
  4. ^ Bailey, J.B. (1997). "Neural spine elongation in dinosaurs: sailbacks or buffalo-backs?". Journal of Paleontology. 71 (6): 1124–1146. doi:10.1017/S0022336000036076.
  5. ^ Taquet, P. 1976. Geologie et paleontologie du gisement de Gadoufaoua (Aptien du Niger), Cahier Paleont., C.N.R.S. Paris, 1-191
  6. ^ P. Taquet, 1970, "Sur le gisement de Dinosauriens et de Crocodiliens de Gadoufaoua (République du Niger)", Comptes Rendus de l'Académie des Sciences à Paris, Série D 271: 38-40
  7. ^ Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
  8. ^ McDonald, A.T.; Kirkland, J.I.; DeBlieux, D.D.; Madsen, S.K.; Cavin, J.; Milner, A.R.C.; Panzarin, L. (2010). Farke, Andrew Allen (ed.). "New Basal Iguanodontians from the Cedar Mountain Formation of Utah and the Evolution of Thumb-Spiked Dinosaurs". PLoS ONE. 5 (11): e14075. doi:10.1371/journal.pone.0014075. PMC 2989904. PMID 21124919.
  9. ^ Andrew T. McDonald (2011). "The taxonomy of species assigned to Camptosaurus (Dinosauria: Ornithopoda)" (PDF). Zootaxa. 2783: 52–68. doi:10.11646/zootaxa.2783.1.4.
  10. ^ a b Sereno, P. C.; Brusatte, S. L. (2008). "Basal abelisaurid and carcharodontosaurid theropods from the Lower Cretaceous Elrhaz Formation of Niger". Acta Palaeontologica Polonica. 53 (1): 15–46. doi:10.4202/app.2008.0102.
  11. ^ Sereno, P. C.; Wilson, J. A.; Witmer, L. M.; Whitlock, J. A.; Maga, A.; Ide, O.; Rowe, T. A. (2007). "Structural extremes in a Cretaceous dinosaur". PLoS ONE. 2 (11): e1230. doi:10.1371/journal.pone.0001230. PMC 2077925. PMID 18030355..

Bibliography

  • Ingrid Cranfield, ed. (2000). Dinosaurs and other Prehistoric Creatures. Salamander Books. pp. 152–154.
  • Richardson, Hazel (2003). Dinosaurs and Other Prehistoric Animals. Smithsonian Handbooks. p. 108.
  • Dixon, Dougal (2006). The Complete Book of Dinosaurs. Hermes House.
  • Cox, Barry; Colin Harrison; R.J.G. Savage; Brian Gardiner (1999). The Simon & Schuster Encyclopedia of Dinosaurs and Prehistoric Creatures: A Visual Who's Who of Prehistoric Life. Simon & Schuster.

External links

Ankylopollexia

Ankylopollexia is an extinct clade of ornithischian dinosaurs that lived from the Late Jurassic to the Late Cretaceous. It is a derived clade of iguanodontian ornithopods and contains the subgroup Styracosterna.

The name stems from the Greek word, “ankylos”, mistakenly taken to mean stiff, fused (in fact the adjective means bent or curved; used of fingers, it can mean hooked), and the Latin word, “pollex”, meaning thumb. Originally described in 1986 by Sereno, this most likely synapomorphic feature of a conical thumb spine defines the clade.First appearing around 156 million years ago, in the Jurassic, Ankylopollexia became an extremely successful and widespread clade during the Cretaceous, and were found around the world. The group died out at the end of the Maastrichtian. Even though they grew to be quite large, comparable to some carnivorous dinosaurs, they were universally herbivorous. Most ankylopollexians were bipedal.

Aptian

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.

Aralosaurini

Aralosaurini is a tribe of basal lambeosaurine hadrosaurs endemic to Eurasia. It currently contains Aralosaurus (from the Aral sea of Kazakhstan) and Canardia (from Toulouse, Southern France).

Bayannurosaurus

Bayannurosaurus is a non-hadrosauriform ankylopollexian ornithopod described in 2018 by Xu et al from the Barremian (Early Cretaceous) found in the Bayin-Gobi Formation of China. The genus includes a new species Bayannurosaurus perfectus. A phylogenetic analysis of Bayannurosaurus indicates that it is more derived than Hypselospinus but less derived than Ouranosaurus just outside of Hadrosauriformes. It had a skull length of 80 cm, making it a mid-sized iguanodont. By comparison Ouranosaurus had a 67 cm skull, and a length of 7 to 8.3 meters (23 to 27 feet). Though inexact, if this is used as a comparison to scale to, Bayannurosaurus would be 8.3 to 10 meters (27 to 33 feet) long.

Burianosaurus

Burianosaurus is a genus of ornithopod dinosaur that lived in what is now the Czech Republic (it was found in 2003 near the city of Kutná Hora), being the first validly named dinosaur from that country. It was named B. augustai in 2017; the genus name honours the Czech palaeoartist Zdeněk Burian, and the species name honours the Czech palaeontologist Josef Augusta. The holotype specimen is a femur discovered in 2003, which was described as possibly belonging to an iguanodont in 2005.

Cumnoria

Cumnoria is a genus of herbivorous iguanodontian dinosaur. It was a basal iguanodontian that lived during the Late Jurassic period (Kimmeridgian age) in what is now Oxfordshire, United Kingdom.

Dinosaurs Alive! (attraction)

Dinosaurs Alive! is an animatronic dinosaur themed area located at several Cedar Fair parks. Kings Island was the first park to open the attraction in 2011, while the other parks opened their attraction in 2012 or 2013. The version of this attraction at Kings Island was the world's largest animatronic dinosaur park. A $5–6.00 fee is charged to enter the attraction. At Carowinds, admission is free with a Gold or Platinum Pass. Each park also features Dinostore, a gift shop filled with dinosaur toys and souvenirs. After October 27, 2019, all of the remaining Dinosaurs Alive! exhibits will be closed.The exhibits are created by Dinosaurs Unearthed. Some markets, like Toronto, have previously staged their touring exhibit at other venues. Some reviewers have noted that seeing a roller coaster in the background was an "incongruity". A sand pit allows children to "dig" for dinosaurs at an area near the end of the attraction.

Elrhazosaurus

Elrhazosaurus is a genus of basal iguanodontian dinosaur, known from isolated bones found in Lower Cretaceous rocks of Niger. These bones were initially thought to belong to a species of the related dryosaurid Valdosaurus, but have since been reclassified.

Fukuisaurus

Fukuisaurus (meaning "Fukui lizard") is a genus of herbivorous dinosaur from the Early Cretaceous. It was an ornithopod which lived in what is now Japan.

Remains of Fukuisaurus were discovered in 1989, in the Kitadani formation in Katsuyama, Fukui Prefecture, in rocks from the Kitadani Formation, dating to the Barremian. The type species, Fukuisaurus tetoriensis, was described in 2003 by Yoshitsugu Kobayashi and Yoichi Azuma. The genus name refers to Fukui; the specific name to the geological Tetori Group. The type specimens or cotypes are FPDM-V-40-1, a right maxilla, and FPDM-V-40-2, a right jugal. Further elements of a skull and a right sternal plate had been recovered. Since 2003 much more extensive finds have been made and much of the skeleton is now known.

Fukuisaurus is a relatively small species. In 2010 Gregory S. Paul estimated the length at 4.5 meters, the weight at four hundred kilograms. Being a bipedal, optionally quadrupedal, animal, it was similar in general build to Iguanodon, Ouranosaurus and Altirhinus. According to the describers Fukuisaurus was exceptional in that its skull was not kinetic: the tooth-bearing maxilla would be so strongly fused to the vomer that a sideways chewing motion would have been impossible.

A cladistic analysis showed that Fukuisaurus was a basal member of the Hadrosauroidea, less derived than Altirhinus.

Gideonmantellia

Gideonmantellia is an extinct genus of basal ornithopod dinosaur known from the Early Cretaceous (Barremian stage) of Galve, Province of Teruel, Spain. It contains a single species, Gideonmantellia amosanjuanae.

Hadrosauroidea

Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and all dinosaurs more closely related to them than to Iguanodon.They are from Asia, Europe and Africa. Many primitive hadrosauroids, such as the Asian Probactrosaurus and Altirhinus, have traditionally been included in a paraphyletic (unnatural grouping) "Iguanodontidae". With cladistic analysis, the traditional Iguanodontidae has been largely disbanded, and probably includes only Iguanodon and perhaps its closest relatives.

Iguanodontia

Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include Camptosaurus, Dryosaurus, Iguanodon, Tenontosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodontians were one of the first groups of dinosaurs to be found. They are among the best known of the dinosaurs, and were among the most diverse and widespread herbivorous dinosaur groups of the Cretaceous period.

List of African dinosaurs

This is a list of dinosaurs whose remains have been recovered from Africa. Africa has a rich fossil record, but it is patchy and incomplete. It is rich in Triassic and Early Jurassic dinosaurs. African dinosaurs from these time periods include Coelophysis, Dracovenator, Melanorosaurus, Massospondylus, Euskelosaurus, Heterodontosaurus, Abrictosaurus, and Lesothosaurus. In the Middle Jurassic, the sauropods Atlasaurus, Chebsaurus, Jobaria, and Spinophorosaurus, flourished, as well as the theropod Afrovenator. The Late Jurassic is well represented in Africa, mainly thanks to the spectacular Tendaguru Formation. Veterupristisaurus, Ostafrikasaurus, Elaphrosaurus, Giraffatitan, Dicraeosaurus, Janenschia, Tornieria, Tendaguria, Kentrosaurus, and Dysalotosaurus are among the dinosaurs whose remains have been recovered from Tendaguru. This fauna seems to show strong similarities to that of the Morrison Formation in the United States and the Lourinha Formation in Portugal. For example, similar theropods, ornithopods and sauropods have been found in both the Tendaguru and the Morrison. This has important biogeographical implications.

The Early Cretaceous in Africa is known primarily from the northern part of the continent, particularly Niger. Suchomimus, Elrhazosaurus, Rebbachisaurus, Nigersaurus, Kryptops, Nqwebasaurus, and Paranthodon are some of the Early Cretaceous dinosaurs known from Africa. The Early Cretaceous was an important time for the dinosaurs of Africa because it was when Africa finally separated from South America, forming the South Atlantic Ocean. This was an important event because now the dinosaurs of Africa started developing endemism because of isolation.

The Late Cretaceous of Africa is known mainly from North Africa. During the early part of the Late Cretaceous, North Africa was home to a rich dinosaur fauna. It includes Spinosaurus, Carcharodontosaurus, Rugops, Bahariasaurus, Deltadromeus, Paralititan, Aegyptosaurus, and Ouranosaurus.

Lurdusaurus

Lurdusaurus ('heavy lizard') is a genus of large ornithopod dinosaur that lived in the Aptian stage of the Early Cretaceous, sometime between 121 and 112 million years ago.

Mantellisaurus

Mantellisaurus is a genus of iguanodontian dinosaur that lived in the Barremian and early Aptian ages of the Early Cretaceous Period of Europe. Its remains are known from Belgium (Bernissart), England and Germany. The type and only species is M. atherfieldensis. Formerly known as Iguanodon atherfieldensis, the new genus Mantellisaurus was erected for the species by Gregory Paul in 2007. According to Paul, Mantellisaurus was more lightly built than Iguanodon and more closely related to Ouranosaurus, making Iguanodon in its traditional sense paraphyletic. It is known from many complete and almost complete skeletons. The genus name honours Gideon Mantell, the discoverer of Iguanodon.

Philippe Taquet

Philippe Taquet (b. April 25, 1940 Saint-Quentin, Aisne) is a French paleontologist who specializes in dinosaur systematics of finds primarily in northern Africa.He is a member of the French Academy of Sciences since November 30, 2004, president since 2012. He has studied and described a number of new dinosaur species from Africa, especially from the Aptian site of Gadoufaoua in Niger (such as Ouranosaurus). He also researches the Lower Cretaceous stratigraphic relationship between western Africa and Brazil by reconstructing the paleobiology from fossil floras and faunas. He was president of the French National Museum of Natural History from 1985 to 1990.He received the Sue Tyler Friedman Medal in 2009 for work in the history of geology.

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.

Wadi Milk Formation

The Wadi Milk Formation is a geological formation in Sudan whose strata date back to the Late Cretaceous. Originally, the formation was thought to be Albian to Cenomanian, later research has provided dating to the Campanian to Maastrichtian. Dinosaur remains are among the fossils that have been recovered from the formation. It stretches from the lower Wadi Al-Malik across the Wadi Muqaddam into the Bayuda Desert.

Yunganglong

Yunganglong is an extinct genus of basal hadrosauroid dinosaur known from the early Late Cretaceous lower Zhumapu Formation of Zuoyun County, Shanxi Province of northeastern China. It contains a single species, Yunganglong datongensis.

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