Spinosaurus (meaning "spine lizard") is a genus of theropod dinosaur which lived in what is now North Africa, from the lower Albian to lower Cenomanian stages of the Cretaceous period, about 112 to 97 million years ago. This genus was first known 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 recent years. 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 may be the largest of all known carnivorous dinosaurs, even larger than Tyrannosaurus and Giganotosaurus. Estimates published in 2005 and 2007 suggest that it was 12.6 to 18 metres (41 to 59 ft) in length and 7 to 20.9 tonnes (7.7 to 23.0 short tons) in weight. The skull of Spinosaurus was long and narrow like that of a modern crocodilian. Spinosaurus is known to have eaten fish; evidence suggests that it lived both on land and in water like a modern crocodilian. 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.

Size

Since its discovery, Spinosaurus has been a contender for the longest and largest theropod dinosaur. Both Friedrich von Huene in 1926 and Donald F. Glut in 1982 listed it as among the most massive theropods in their surveys, at 15 meters (49 ft) in length and upwards of 6 tons in weight. In 1988, Gregory Paul also listed it as the longest theropod at 15 meters (49 ft), but gave a lower mass estimate of 4 tonnes (4.4 short tons).

Dal Sasso et al. (2005) assumed that Spinosaurus and Suchomimus had the same body proportions in relation to their skull lengths, and thereby calculated that Spinosaurus was 16 to 18 meters (52 to 59 ft) in length and 7 to 9 tonnes (7.7 to 9.9 short tons) in weight.[5] The Dal Sasso et al. estimates were criticized because the skull length estimate was uncertain, and (assuming that body mass increases as the cube of body length) scaling Suchomimus which was 11 meters (36 ft) long and 3.8 tonnes (4.2 short tons) in mass to the range of estimated lengths of Spinosaurus would produce an estimated body mass of 11.7 to 16.7 tonnes (12.9 to 18.4 short tons).

François Therrien and Donald Henderson, in a 2007 paper using scaling based on skull length, challenged previous estimates of the size of Spinosaurus, finding the length too great and the weight too small. Based on estimated skull lengths of 1.5 to 1.75 meters (4.9 to 5.7 ft), their estimates include a body length of 12.6 to 14.3 meters (41 to 47 ft) and a body mass of 12 to 20.9 tonnes (13 to 23.0 short tons). The lower estimates for Spinosaurus would imply that the animal was shorter and lighter than Carcharodontosaurus and Giganotosaurus. The Therrien and Henderson study has been criticized for the choice of theropods used for comparison (e.g., most of the theropods used to set the initial equations were tyrannosaurids and carnosaurs, which have a different build than spinosaurids), and for the assumption that the Spinosaurus skull could be as little as 1.5 meters (4.9 ft) in length. Improvement of the precision of size estimates for Spinosaurus requires the discovery of more complete remains as available for some other dinosaurs, especially the limb bones of Spinosaurus which are "hitherto unknown.

Neural spines

Very tall neural spines growing on the back vertebrae of Spinosaurus formed the basis of what is usually called the animal's "sail." The lengths of the neural spines reached over 10 times the diameters of the vertebral bodies from which they extended. The neural spines were slightly longer front to back at the base than higher up, and were unlike the thin rods seen in the pelycosaurfinbacks Edaphosaurus and Dimetrodon, contrasting also with the thicker spines in the contemporary iguanodont Ouranosaurus.

Spinosaurus sails were unusual, although other dinosaurs, namely the ornithopod Ouranosaurus, which lived a few million years earlier in the same general region as Spinosaurus, and the South American sauropod Amargasaurus, might have developed similar structural adaptations of their vertebrae. The sail is possibly analogous that is, evolved independently of but due to parallel evolutionsimilar to the sails of the Permian synapsid Dimetrodon, which lived before the dinosaurs even appeared.

The structure may also have been more hump-like than sail-like, as noted by Stromer in 1915 ("one might rather think of the existence of a large hump of fat [German: Fettbuckel], to which the [neural spines] gave internal support") and by Jack Bowman Bailey in 1997. In support of his "buffalo-back" hypothesis, Bailey argued that in Spinosaurus, Ouranosaurus, and other dinosaurs with long neural spines, the spines were relatively shorter and thicker than the spines of pelycosaurs (which were known to have sails); instead, the dinosaurs' neural spines were similar to the neural spines of extinct hump-backed mammals such as Megacerops and Bison latifrons.

Skull

The skull had a narrow snout filled with straight conical teeth that lacked serrations. There were six or seven teeth on each side of the very front of the upper jaw, in the premaxillae, and another twelve in both maxillae behind them. The second and third teeth on each side were noticeably larger than the rest of the teeth in the premaxilla, creating a space between them and the large teeth in the anterior maxilla; large teeth in the lower jaw faced this space. The very tip of the snout holding those few large anterior teeth was expanded, and a small crest was present in front of the eyes. Using the dimensions of three specimens known as MSNM V4047, UCPC-2, and BSP 1912 VIII 19, and assuming that the postorbital part of the skull of MSNM V4047 had a shape similar to the postorbital part of the skull of Irritator, Dal Sasso et al. (2005) estimated that the skull of Spinosaurus was 1.75 meters (5.7 ft) long. The Dal Sasso et al. skull length estimate was questioned because skull shapes can vary across spinosaurid species.

A newly made study performed by scientists Andrew R. Cuff and Emily Rayfield showed that Spinosaurids like Spinosaurus had relatively poor resistance in their skulls for torsion compared to other members of this group (Baryonyx) and modern alligators, thus showing Spinosaurus preyed more regularly on fish than it did on land animals, although considered predators of the former too.

Classification

Spinosaurus gives its name to the Spinosauridae family of dinosaurs, which includes two subfamilies: Baryonychinae and Spinosaurinae. The Baryonychinae include Baryonyx from southern England and Suchomimus from Niger in central Africa. The Spinosaurinae include Spinosaurus, Irritator from Brazil, and Angaturama (which is probably synonymous with Irritator) from Brazil. The Spinosaurinae share unserrated straight teeth that are widely spaced (e.g., 12 on one side of the maxilla), as opposed to the Baryonychinae which have serrated curved teeth that are numerous (e.g., 30 on one side of the maxilla).

Function of neural spines

The function of the dinosaur's sail or hump 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 even larger than it was, intimidating other animals.

The structure may have been used for thermoregulation. If the structure 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 structure 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 large dinosaurs added considerably to the skin area of their bodies, 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. However, Bailey (1997) was of the opinion that a sail could have absorbed more heat than it radiated. Bailey proposed instead that Spinosaurus and other dinosaurs with long neural spines had fatty humps on their backs for energy storage, insulation, and shielding from heat.

Elaborate body structures of many modern-day animals usually serve to attract members of the opposite sex during mating. It is quite possible that the sails or humps 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.

Finally, it is quite possible that the sail or hump 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, it has been suggested since the mid-1970s that Spinosaurus was at least an occasional quadruped. This has been bolstered by the discovery of Baryonyx, a relative with robust arms. Because of the mass of the hypothesized fatty dorsal humps of Spinosaurus, Bailey (1997) was open to the possibility of a quadrupedal posture, leading to new restorations of it as such. The hypothesis that Spinosaurus had a typical quadrupedal gait has fallen out of favor, though spinosaurids may have crouched in a quadrupedal posture.Theropods, including spinosaurids, could not pronate their hands (rotate the forearm so the palm faced the ground),but a resting position on the side of the hand was possible, as shown by fossil prints from an Early Jurassic theropod.

Feeding

It is unclear whether Spinosaurus was primarily a terrestrial predator or a piscivore, as indicated by its elongated jaws, conical teeth and raised nostrils. The hypothesis of spinosaurs as specialized fish eaters has been suggested before by A. J. Charig and A. C. Milner for Baryonyx. They base this on the anatomical similarity with crocodilians and the presence of digestive acid-etched fish scales in the rib cage of the type specimen. Large fish are known from the faunas containing other spinosaurids, including the Mawsonia, in the mid-Cretaceous of northern Africa and Brazil. Direct evidence for spinosaur diet comes from related European and South American taxa. Baryonyx was found with 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 pterosaurs, but 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 or medium-sized prey. A study by Cuff and Rayfield (2013) concluded that bio-mechanical data suggests that Spinosaurus was not an obligate piscivore and that its diet was more closely associated with each individual's size. The characteristic rostral morphology of Spinosaurus allowed its jaws to resist bending in the vertical direction, however its jaws were poorly adapted with respect to resisting lateral bending.

In 2009, Dal Sasso et al. reported the results of X-ray computed tomography of the MSNM V4047 snout. As the foramina on the outside all communicated with a space on the inside of the snout, the authors speculated that Spinosaurus had pressure receptors inside the space that allowed it to hold its snout at the surface of the water to detect swimming prey species without seeing them.

A 2010 isotope analysis by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid teeth, including teeth of Spinosaurus, indicate semiaquatic lifestyles. Isotope ratios from tooth enamel and from other parts of Spinosaurus (found in Morocco and Tunisia) and of other predators from the same area such as Carcharodontosaurus were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians. The study found that Spinosaurus teeth from five of six sampled localities had oxygen isotope ratios closer to those of turtles and crocodilians when compared with other theropod teeth from the same localities. The authors postulated that Spinosaurus switched between terrestrial and aquatic habitats to compete for food with large crocodilians and other large theropods respectively.

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Spinosaurus

Spinosaurus (Dari Bahasa Yunani, Spino= Tulang belakang atau duri, dan Sauros= kadal[1])merupakan dinosaurus terbesar dari anggota Spinosaurida. Spinosaurus juga merupakan satu dari tiga Theropoda terbesar sepanjang masa, yang hidup di daerah yang kini bisa dikenali sebagai Afrika bagian Utara. Spinosaurus cukup terkenal saat ini, karena ukurannya mengalahkan Tyrannosaurus dan Mapusaurus.

Deskripsi

Spinosaurus merupakan Theropoda raksasa yang dapat tumbuh hingga 13, 8 m dengan tinggi lebih dari 6 m (sampai layarnya)dan berat mencapai 7, 6 ton. Panjang tengkorak Spinosaurus 1, 75 m dengan seratus gigi-gigi runcing yang lurus sepanjang kira-kira 17 cm. Ciri khas Spinosaurus adalah tulang belakangnya yang meninggi hingga 1, 8 atau 2 m dan merupakan layar yang dilapisi kulit. Di bawah lapisan kulit keras yang liat tersebut terdapat pembuluh darah yang berguna untuk mengatur suhu tubuh Spinosaurus atau untuk menarik perhatian betina saat musim kawin, karena diperkirakan layar Spinosaurus dapat berubah warna seperti kulit bunglon. Spinosaurus juga mempunyai lubang hidung yang tidak terletak di ujung moncong seperti kebanyakan Theropoda, melainkan di dekat matanya.

Perilaku

Spinosaurus hidup di Afrika Utara, terutama di Mesir dan Maroko. Sejauh ini terdapat dua spesies Spinosaurus, yaitu Spinosaurus aegyptiacus dari Mesir dan Spinosaurus marocconus dari Maroko. Spinosaurus Mesir berukuran lebih besar daripada Spinosaurus Maroko. Spinosaurus hidup di daerah dataran banjir dekat sungai. Para ilmuwan yakin bahwa dinosaurus ini adalah semacam dinosaurus akuatik. Itu berarti kemungkinan besar Spinosaurus bisa berenang dengan baik. Spinosaurus hidup tidak sepenuhnya dari dinosaurus lain, karena mereka sama seperti Spinosaurida lain, adalah pemakan ikan juga. Spinosaurus bisa berburu ikan sungai seperti Onchopristis dan Mawsonia, yang merupakan sumber protein yang bagus untuk dinosaurus sebesar ini. Tidak menutup kemungkinan Spinosaurus juga memburu dinosaurus herbivora seperti Ouranosaurus, Lurdusaurus, atau Sauropoda seperti Aegyptosaurus. Rahang Spinosaurus yang terhitung lemah dan gigi-gigi yang tidak cocok untuk mencabik daging padat membuat para Paleontolog berpikir bahwa Spinosaurus tidak memangsa dinosaurus berukuran besar atau mungkin hanya bangkainya saja. Spinosaurus juga diketahui dengan senang hati menelan Pterosaurida seperti Azhdarchid.

Dalam Kebudayaan Populer

Spinosaurus terkenal terutama karena ukurannya melebihi Tyrannosaurus rex. Spinosaurus dimunculkan dalam film fiksi ilmiah Jurassic Park 3 yang datang saat pesawat yang ditumpangi rombongan Dr. Alan Grant hendak meninggalkan Isla Sorna (Lokasi B) tepat di depan pesawat, yang membuat mereka terlempar jauh ke hutan. Disana, Spinosaurus tampak menghancurkan pesawat dan menewaskan beberapa orang. Spinosaurus ditampilkan dapat membunuh T. rex dengan mudah dengan memelintir lehernya, walau tindakan seperti itu belum bisa dipastikan kebenarannya. Spinosaurus juga dapat menjebol pagar listrik non-aktif dengan mudah, namun berhasil diusir oleh Grant dengan membakar air sekitarnya. Spinosaurus juga ditampilkan dalam film terbaru BBC One yang berjudul 'Planet Dinosaur' dalam episode 1:Lost World.

Source : http://id.wikipedia.org