SPINOSAURUS

'''Spinosaurus''' (meaning "spine lizard") was a genus of theropod dinosaur that lived in what is now North Africa, from the Albian to early Cenomanian stages of the Cretaceous Period, about 95 to 93 million years ago. It is unclear whether there are one or two species. The best known is ''S. aegyptiacus'' from Egypt, though a second species (''S. marocannus'') has been recovered from Morocco. It was first known from Egyptian remains discovered in the 1910s and described by German paleontologist Ernst Stromer. The original remains were destroyed in World War II, but additional skull material has come to light in recent years.
The distinctive "spines" of ''Spinosaurus'', which were long extensions of the vertebrae, grew up to 2 metres (6.6 ft) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that they were covered in muscle and formed a hump or ridge. Multiple functions have been put forward for this structure, including thermoregulation and display. According to recent estimates, it is the largest of all known carnivorous dinosaurs, even larger than ''Tyrannosaurus rex'' and ''Giganotosaurus''; these estimates suggest that it was 16 - 18 meters in length (52.5 - 59.1 ft), around 6 meters tall (20 ft), and 9 tonnes (9.9 tons) in weight,^[1] although these figures have not been universally accepted.

Contents

Description

Classification

Discovery and species

Paleoecology

Feeding ecology

Paleobiology

Size

Sail

Posture

In popular culture

References

External links

Description

Although ''Spinosaurus'' is well-known to dinosaur enthusiasts due to its size, sail, and elongated skull, it is mostly known from remains that have been destroyed, aside from a few more recently discovered teeth and skull elements. Additionally, so far only the skull and backbone have been described in detail, and limb bones have not been found. Jaw and skull material published in 2005 show that it had one of the longest skulls of any carnivorous dinosaur, estimated at about 1.75 meters long (5.75 ft). The skull had a narrow snout filled with conical teeth that lacked serrations, not unlike what is seen in other spinosaurids. A small crest was present in front of the eyes.
The sail of ''Spinosaurus'' is formed of very tall neural spines growing on the back vertebrae. These spines are seven to eleven times the height of the vertebrae from which they grow. The Dinosauria, , Ralph E., Molnar, University of California Press, 1990, The spines are slightly longer front to back at the base than higher up, and are unlike the thin rods seen in the pelycosaur finbacks ''Edaphosaurus'' and ''Dimetrodon''.

Classification

''Spinosaurus'' gives its name to a family of dinosaurs, the Spinosauridae, of which other members include ''Baryonyx'' from southern England, ''Irritator'' and ''Angaturama'' (probably synonymous with ''Irritator'') from Brazil, ''Suchomimus'' from Niger in central Africa, and possibly ''Siamosaurus'', which is known from fragmentary remains in Thailand. It is closest to ''Irritator'', which shares its unserrated straight teeth, and the two are included in the subfamily Spinosaurinae. The Dinosauria (second edition), Holtz, Jr., T.R., Molnar, R.E, and Currie, P.J., , , University of California Press, 2004, ISBN 0-520-24209-2 In 2003, Rauhut suggested that Stromer's ''Spinosaurus'' holotype was a chimera, consisting of dorsal vertebrae from a carcharodontosaurid similar to ''Acrocanthosaurus'' and a dentary from a large theropod similar to ''Baryonyx''. The interrelationships and evolution of basal theropod dinosaurs, Rauhut, O.W.M., , , Special Papers in Palaeontology, 2003 This analysis, however, has been rejected in recent papers.

Discovery and species

The first described remains of ''Spinosaurus'' were found in the Bahariya Valley of Egypt in 1912, and were named by German paleontologist Ernst Stromer in 1915.^[2] Fragmentary additional remains from Bahariya, including vertebrae and hindlimb bones, were designated by Stromer as "''Spinosaurus'' B" in 1934. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharîje-Stufe (unterstes Cenoman). 13. Dinosauria, , E., Stromer, Abhandlungen der Bayerischen Akademie der Wissenschaften Mathematisch-naturwissenschaftliche Abteilung, Neue Folge, 1934 Stromer considered them different enough to belong to another species, and this has been borne out; they either pertain to ''Carcharodontosaurus'' A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids, , P.C., Sereno, Science, 1998 or to ''Sigilmassasaurus''. Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco, , D.A., Russell, , 1996 Some of the ''Spinosaurus'' fossils were damaged during transport back to the Deutsches Museum, Munich, Germany, and the remaining bones were completely lost due to Allied bombing in 1944.
Two species of ''Spinosaurus'' have been named: ''Spinosaurus aegyptiacus'' (meaning "Egyptian spine lizard") and ''Spinosaurus marocannus'' (meaning "Moroccan spine lizard"). ''S. marocannus'' was originally described by Russell as a new species based on the length of its neck vertebrae. However, several later authors considered the length of the neck vertebrae to be variable from individual to individual and therefore consider ''S. marocannus'' to be a synonym of ''S. aegyptiacus''.^[3]
Six partial specimens of ''Spinosaurus'' have been described, the first having been destroyed during World War II. However, detailed drawings and descriptions of the specimen remain. The probable size of these individual spinosaurs can be estimated using comparison to known material from other spinosaurid dinosaurs. The estimates below are based on the Theropod Database and Dal Sasso ''et al'', 2005.

Illustration of the original ''Spinosaurus'' material by Ernst Stromer.

'IPHG 1912 VIII 19', described by Stromer in 1915, and based on a subadult specimen, was destroyed during Allied bombing in WWII. It is estimated to be around 14 meters in length and to have weighed about 6.7 tons. The material consists of a maxillary fragment (750 mm), an incomplete dentary (the skull is estimated to be 1.45 meters long with a mandible approximately 1.34 meters long), nineteen teeth (62, 126 mm), two incomplete cervical vertebrae, seven dorsal vertebrae (190-210 mm), dorsal ribs, gastralia, and eight caudal centra. This is the specimen that Rauhut thought was chimeric.
'CMN 50791', described by Russell in 1996, is the holotype of ''Spinosaurus marocannus''. The material it is based on includes a mid cervical vertebra which is 195 millimeters long, an anterior dorsal neural arch, an anterior dentary, and a mid dentary.
'MNHN SAM 124', described by Taquet and Russell in 1998, is estimated to be about 14 meters long and to have weighed about 6.7 tons. The material consists of partial premaxillae, partial maxillae, vomers, and a dentary fragment. (The skull is estimated at approximately 1.42 meters long)
'Office National des Mines nBM231', described by Buffetaut and Ouaja in 2002, consists of an anterior dentary from Tunisia which is very similar to existing material of ''S. aegyptiacus''.Buffetaut, E & Ouaja, M (2002) A new specimen of ''Spinosaurus'' (Dinosauria, Theropoda) from the Lower Cretaceous of Tunisia, with remarks on the evolutionary history of the Spinosauridae. ''Bulletin de la Société Géologique de France'' '173': 415–421.
'MSNM V4047', described by Cristiano Dal Sasso of the Civic Natural History Museum in Milan and his colleagues in 2005, is estimated to have been around 16-18 meters in length and weighed around 7 to 9 tonnes (7.7 to 9.9 tons). The massive skull is estimated at 1.75 meters long (5.74 ft). The fossils consist of premaxillae, partial maxillae, and partial nasals, which together measure 988 millimeters long (3.24 ft).
'UCPC-2', also described by Dal Sasso ''et al.'' in 2005, which consists of a 'fluted crest'.

Paleoecology

The environment inhabited by ''Spinosaurus'' is only partially understood, and covers a great deal of northern Africa. Those that lived in what is now Egypt, for example, may have contended with shoreline conditions on tidal flats and channels, living in mangrove forests alongside similarly large dinosaurian predators ''Bahariasaurus'' and ''Carcharodontosaurus'', giant titanosaur sauropod ''Paralititan'', smaller titanosaur ''Aegyptosaurus'', 10 meter long (33 ft) crocodilian ''Stomatosuchus'', and the coelacanth ''Mawsonia''. A Giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt, , J.B., Smith, Science, 2001

Feeding ecology

It is unclear whether ''Spinosaurus'' was primarily a terrestrial predator or a fisher, as indicated by its elongated jaws, conical teeth and raised nostrils. The only direct evidence for spinosaur diet comes from related European and South American species. ''Baryonyx'' was found with both fish scales and bones from juvenile ''Iguanodon'' in its stomach, while a tooth embedded in a South American pterosaur bone suggests that spinosaurs occasionally preyed on these flying archosaurs.^[4] ''Spinosaurus'' was likely to have been a generalized and opportunistic predator, possibly a Cretaceous equivalent of large grizzly bears, being biased toward fishing, though it undoubtedly scavenged and took many kinds of small-to medium-sized prey.

Paleobiology

''Spinosaurus'' has some unusual features which have been the subject of debate thus far:

Size

Size comparison of selected giant theropod dinosaurs

Since its discovery, ''Spinosaurus'' has been a top contender for longest and largest theropod dinosaur, though this fact did not reach the public consciousness until its depiction in the film ''Jurassic Park III'' and the description of a new specimen in 2005. Both Friedrich von Huenevon Huene, F. R. (1926). "The carnivorous saurischia in the Jura and Cretaceous formations principally in Europe." ''Rev. Mus. La Plata'', '29', 35-167 and Donald F. Glut,Glut, D.F. (1982). ''The New Dinosaur Dictionary''. Citadel Press, Secaucus, New Jersey, 226-228. ISBN 0-8065-0782-9 decades apart, listed it as among the most massive theropods or the most massive in their surveys, at upwards of 6 tons in weight and 15 meters (50 feet) in length. In 1988, Gregory S. Paul also listed it as the longest theropod at 15 meters (50 feet), but gave a lower mass estimate.Paul, G.S. (1988). ''Predatory Dinosaurs of the World.'' New York: Simon and Schuster. 464 pp. Recent estimates, based on new specimens, list ''Spinosaurus'' at 16 - 18 metres (53.3 to 60 feet) long and 7 - 9 tonnes in weight (7.7 to 9.9 tons). At least one unpublished survey suggested that ''Spinosaurus'' reached sizes of 12 - 19 tonnes in weight. These high-end weight estimates were based on the author's estimated 17.4 meter length which was based on comparing the holotype's largest known vertebra (210 mm) with the largest known ''Baryonyx'' vertebra. This implied an extremely large overall mass, with an unknown upper bound as apparently the holotype specimens are from animals that weren't fully grown. Re: Spinosaurus weight And the Largest Theropod Is... However, the author of these estimates has recently reduced them to similar sizes suggested by dal Sasso ''et al.'' Theropod Database Christmas update
François Therrien and Donald Henderson, in a recent paper using scaling based on skull length, have challenged previous estimates, finding the length too great and the weight too small. Their estimates include a length of 12.6 to 14.3 meters (41.3 to 47.0 ft) and a mass of 12.0 to 20.9 tonnes (13.2 to 23.0 tons). My theropod is bigger than yours...or not: estimating body size from skull length in theropods, , F., Therrien, Journal of Vertebrate Paleontology, 2007 Their study has been criticized for the choice of large theropods used for comparison (most of the skeletons of large theropods used to set the initial equations are of tyrannosaurids and carnosaurs, which have a different build than spinosaurids) and for issues relating to their spinosaurid skull reconstructions. Comments on Therrien and Henderson's new paper Resolution awaits more complete remains.

Sail

Illustration of ''Spinosaurus'' dorsal vertebrae by Ernst Stromer.

''Spinosaurus'' sails were unusual, although other dinosaurs of the same time and area, namely the ornithopod ''Ouranosaurus'' and the sauropod ''Rebbachisaurus,'' might have developed a similar structural adaptation of their dorsal vertebrae (however, this is not uncontroversial; see the articles about these animals for more information). The sail is possibly analogous (not homologous) to that of the Permian mammal-like reptile, ''Dimetrodon'', which lived before the dinosaurs even appeared (these similarities are presumably due to parallel evolution). The sail may also have been more hump-like than sail-like; as noted by Jack Bowman Bailey most recently, spinosaur spines are not thin rods but broad front to back, rather like those of some types of buffalo, and so may have supported a thicker, fatty structure as opposed to a skin sail. Neural spine elongation in dinosaurs: sailbacks or buffalo-backs?, , Jack Bowman, Bailey, Journal of Paleontology, 1997
The function of these sails is uncertain; scientists have proposed several hypotheses including heat regulation and display. In addition, such a prominent feature on its back could also make it appear larger than it was, intimidating other animals.
If the sail contained abundant blood vessels, the animal could have used the sail's large surface area to absorb heat. This would imply that the animal was only partly warm-blooded at best and lived in climates where nighttime temperatures were cool or low and the sky usually not cloudy. It is thought that ''Spinosaurus'' and ''Ouranosaurus'' both lived in or at the margins of an earlier version of the Sahara Desert, which could explain this. It is also possible that the sail was used to radiate excess heat from the body, rather than to collect it. Large animals, due to the relatively small ratio of surface area of their body compared to the overall volume (Haldane's principle), face far greater problems of dissipating excess heat at higher temperatures than gaining it at lower. Sails of these dinosaurs added considerably to the skin area of the body, with minimum increase of volume. Furthermore, if the sail was turned away from the sun, or positioned at a 90 degree angle towards a cooling wind, the animal would quite effectively cool itself in the warm climate of Cretaceous Africa. The Evolution and Ecology of the Dinosaurs, , L.B., Halstead, Peter Lowe, 1975,
Elaborate body structures of many modern-day animals usually serve to attract members of opposite sex during mating. It is quite possible that the sails of these dinosaurs were used for courtship, in a way similar to a peacock's tail. Stromer speculated that males and females may have differed in the size of the neural spine. Stromer E (1915) Wirbeltier-Reste der baharije-Stufe (unterstes Cenoman).3. Das Origianl des Theropoden ''Spinosaurus aegyptiacus'' nov. gen. et nov. spec. ''Abhandl. K. Bayer. Akad. Wiss. Math.-phys. Kl.'' '28': 1-32 If this was the case, the sails may have been brightly colored, but this is purely speculative.
Finally, it is quite possible that the sail combined these functions, acting normally as a heat regulator, becoming a courting aid during the mating season, being used to cool itself and, on occasions, turning into an intimidating device when an animal was feeling threatened.

Posture

Although traditionally depicted as a biped, ''Spinosaurus'' has been suggested as at least an occasional quadruped since the early 1980s. The New Dinosaur Dictionary, , Donald F., Glut, Citadel Press, 1982, This has been bolstered by the discovery of ''Baryonyx'', a relative with robust arms. Dinosaurs: The Encyclopedia. 1st Supplement, , Donald F., Glut, McFarland & Company, Inc., 2000, Bailey (1997) was sympathetic to a possible quadrupedal posture, leading to new restorations of it as such. This hypothesis has fallen out of favor, at least as a typical gait. Spinosaurids may have crouched in a quadrupedal posture, though. ''Baryonyx walkeri'', a fish-eating dinosaur from the Wealden of Surrey, , Alan J., Charig, Bulletin of the Natural History Museum, Geology Series, 1997

In popular culture

The animatronic ''Spinosaurus'' from ''Jurassic Park III''.

''Spinosaurus'' has long been depicted in popular books about dinosaurs, although only recently has there been enough information about spinosaurids for an accurate depiction to be made. Traditionally, it has been restored as a generalized upright theropod with a sail on its back, after an influential 1955 skeletal reconstruction by Lapparent and Lavocat.
''Spinosaurus'' was featured as the main antagonist in the 2001 film ''Jurassic Park III''. It was portrayed as larger and more powerful than ''Tyrannosaurus'', in a scene depicting a battle between the two resurrected predators where ''Spinosaurus'' emerges victorious by snapping the tyrannosaur's neck. In reality, such a battle could never have taken place while the species were still extant, since ''Spinosaurus'' and ''Tyrannosaurus'' lived thousands of miles and millions of years apart.
After appearing in ''Jurassic Park III'', ''Spinosaurus'' was featured in a wide variety of merchandise related to the ''Jurassic Park'' films, including a number of video games such as '' from Vivendi Universal. ''Spinosaurus'' was also featured in the television documentary ''The Lost Dinosaurs of Egypt'', in which it was seen wading through the marshlands of Cretaceous Egypt.

References

1. New information on the skull of the enigmatic theropod ''Spinosaurus'', with remarks on its sizes and affinities, , C., dal Sasso, Journal of Vertebrate Paleontology, 2005
2. Wirbeltier-Reste der baharije-Stufe (unterstes Cenoman).3. Das Origianl des Theropoden ''Spinosaurus aegyptiacus'' nov. gen. et nov. spec., , E., Stromer, Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften Mathematisch-physikalische Klasse Abhandlung, 1915
3. Megalosauroidea
4. Buffetaut, E., D. Martill & F. Escuillié (2004). "Pterosaurs as part of a spinosaur diet." ''Nature'', '430': 33.

External links

★ ''Spinosaurus'' in the Dino Directory

★ ''Spinosaurus'' at DinoData

★ The Biggest Carnivore: Dinosaur History Rewritten

★ ''Spinosaurus'' Jaws

★ Discover Magazine