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.[2][3][4] 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).[5][6][7] The latest estimates suggest a weight of 6.4–7.5 tonnes (7.1–8.3 short tons).[6][7] 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.

Spinosaurus
Temporal range: EarlyLate Cretaceous, 112–93.5 Ma
Possible Campanian record[1]
Spinosaurus in Japan Expo
Reconstructed Spinosaurus skeleton in swimming posture
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Spinosauridae
Tribe: Spinosaurini
Genus: Spinosaurus
Stromer, 1915
Type species
Spinosaurus aegyptiacus
Stromer, 1915
Synonyms

Description

Longest theropods
Size comparison of selected giant theropod dinosaurs, S. aegyptiacus in red

Since its discovery, Spinosaurus has been a contender for the longest and largest theropod dinosaur.[8] Both Friedrich von Huene in 1926[9] 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 t (5.9 long tons; 6.6 short tons) in weight.[10] 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 (3.9 long tons; 4.4 short tons).[11]

Spinosaurus swimming size comparison
From left to right: size of the smallest, neotype, and largest known specimens of Spinosaurus compared to a human

Dal Sasso and colleagues (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 (6.9 to 8.9 long tons; 7.7 to 9.9 short tons) in weight.[4] The Dal Sasso and colleagues 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).[3]

Spinosaurus size comparison
The size range of Spinosaurus compared with a human

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.[3] 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 (11.8 to 20.6 long tons; 13.2 to 23.0 short tons).[3] The lower estimates for Spinosaurus would imply that the animal was shorter and lighter than Carcharodontosaurus and Giganotosaurus.[3] 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.[12][13] Improvement of the precision of size estimates for Spinosaurus requires the discovery of more complete remains as available for some other dinosaurs,[14] especially the limb bones of Spinosaurus which are "hitherto unknown".[4]

Skull

Spinosaurus skull en
Annotated skull diagram

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.[4] 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 and colleagues (2005) estimated that the skull of Spinosaurus was 1.75 meters (5.7 ft) long,[4] but more recent estimates suggest a length of 1.6–1.68 meters (5.2–5.5 ft).[15][16] The Dal Sasso and colleagues skull length estimate is questioned because skull shapes can vary across spinosaurid species and because MSNM V4047 may not belong to Spinosaurus itself.[3][17]

Neural spines

Reproduction of Stromer's Spinosaurus Display
Reconstruction of the holotype fossils

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.[18] The neural spines were slightly longer front to back at the base than higher up, and were unlike the thin rods seen in the pelycosaur finbacks Edaphosaurus and Dimetrodon, contrasting also with the thicker spines in the iguanodontian Ouranosaurus.[18]

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 may be an analog of the sail of the Permian synapsid Dimetrodon, which lived before the dinosaurs even appeared, produced by convergent evolution.[18]

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")[19] and by Jack Bowman Bailey in 1997.[18] 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.[18]

Discovery and naming

Naming of species

Spinosaurus aegyptiacus holotype skeletal
Skeletal restoration showing the holotype elements

Two species of Spinosaurus have been named: Spinosaurus aegyptiacus (meaning "Egyptian spine lizard") and the disputed Spinosaurus maroccanus (meaning "Moroccan spine lizard").[20][21]

The first described remains of Spinosaurus were found and described in the early 20th century. In 1912, Richard Markgraf discovered a partial skeleton of a dinosaur in the Bahariya Formation of western Egypt. In 1915, German paleontologist Ernst Stromer published an article assigning the specimen to a new genus and species Spinosaurus aegyptiacus.[19][20]

Fragmentary additional remains from Bahariya, including vertebrae and hindlimb bones, were designated by Stromer as "Spinosaurus B" in 1934.[22] Stromer considered them different enough to belong to another species, and this has been borne out. With the advantage of more expeditions and material, it appears that they pertain either to Carcharodontosaurus[23] or to Sigilmassasaurus.[21]

S. maroccanus was originally described by Dale Russell in 1996 as a new species based on the length of its neck vertebrae.[21] Specifically, Russell claimed that the ratio of the length of the centrum (body of vertebra) to the height of the posterior articular facet was 1.1 in S. aegyptiacus and 1.5 in S. maroccanus.[21] Later authors have been split on this topic. Some authors note that the length of the vertebrae can vary from individual to individual, that the holotype specimen was destroyed and thus cannot be compared directly with the S. maroccanus specimen, and that it is unknown which cervical vertebrae the S. maroccanus specimens represent. Therefore, though some have retained the species as valid without much comment,[24][25][26] most researchers regard S. maroccanus as a nomen dubium[4][27][28] or as a junior synonym of S. aegyptiacus.[23]

Specimens

Six main partial specimens of Spinosaurus have been described.

Spinosaurus holotype
Plate I in Stromer (1915) showing S. aegyptiacus holotype elements

BSP 1912 VIII 19, described by Stromer in 1915 from the Bahariya Formation, was the holotype.[19][20] The material consisted of the following items, most of which were incomplete: right and left dentaries and splenials from the lower jaw measuring 75 centimeters (30 in) long; a straight piece of the left maxilla that was described but not drawn; 20 teeth; 2 cervical vertebrae; 7 dorsal (trunk) vertebrae; 3 sacral vertebrae; 1 caudal vertebra; 4 thoracic ribs; and gastralia.[19] Of the nine neural spines whose heights are given, the longest ("i," associated with a dorsal vertebra) was 1.65 meters (5.4 ft) in length.[19] Stromer claimed that the specimen was from the early Cenomanian, about 97 million years ago.[19][20]

This specimen was destroyed in World War II, specifically "during the night of 24/25 April 1944 in a British bombing raid of Munich" that severely damaged the building housing the Paläontologisches Museum München (Bavarian State Collection of Paleontology).[20] However, detailed drawings and descriptions of the specimen remain. Stromer's son donated Stromer's archives to the Paläontologische Staatssammlung München in 1995, and Smith and colleagues analyzed two photographs of the Spinosaurus holotype specimen BSP 1912 VIII 19 discovered in the archives in 2000.[20] On the basis of a photograph of the lower jaw and a photograph of the entire specimen as mounted, Smith concluded that Stromer's original 1915 drawings were slightly inaccurate.[20] In 2003, Oliver Rauhut suggested that Stromer's Spinosaurus holotype was a chimera, composed of vertebrae and neural spines from a carcharodontosaurid similar to Acrocanthosaurus and a dentary from Baryonyx or Suchomimus.[28] This analysis was rejected in at least one subsequent paper.[4]

NMC 50791, held by the Canadian Museum of Nature, is a mid-cervical vertebra which is 19.5 centimeters (7.7 in) long from the Kem Kem Beds of Morocco.[21] It is the holotype of Spinosaurus maroccanus as described by Russell in 1996.[21] Other specimens referred to S. maroccanus in the same paper were two other mid-cervical vertebrae (NMC 41768 and NMC 50790), an anterior dentary fragment (NMC 50832), a mid-dentary fragment (NMC 50833), and an anterior dorsal neural arch (NMC 50813).[21] Russell stated that "only general locality information could be provided" for the specimen, and therefore it could be dated only "possibly" to the Albian.[21]

Spinosaurus marocannus
Specimen MNHN SAM 124 of S. maroccanus, Muséum National d'Histoire Naturelle, Paris

MNHN SAM 124, housed at the Muséum National d'Histoire Naturelle, is a snout (consisting of partial premaxillae, partial maxillae, vomers, and a dentary fragment).[29] Described by Taquet and Russell in 1998, the specimen is 13.4 to 13.6 centimeters (5.3–5.4 in) in width; no length was stated.[29] The specimen was located in Algeria, and "is of Albian age."[29] Taquet and Russell believed that this specimen along with a premaxilla fragment (SAM 125), two cervical vertebrae (SAM 126-127), and a dorsal neural arch (SAM 128), belonged to S. maroccanus.[29]

BM231 (in the collection of the Office National des Mines, Tunis) was described by Buffetaut and Ouaja in 2002.[27] It consists of a partial anterior dentary 11.5 centimetres (4.53 in) in length from an early Albian stratum of the Chenini Formation of Tunisia.[27] The dentary fragment, which included four alveoli and two partial teeth, was "extremely similar" to existing material of S. aegyptiacus.[27]

UCPC-2 in the University of Chicago Paleontological Collection consists mainly of two narrow connected nasals with a fluted (ridged) crest from the region between the eyes.[4] The specimen, which is 18.0 centimetres (7.09 in) long, was located in an early Cenomanian part of the Moroccan Kem Kem Beds in 1996 and described in the scientific literature in 2005 by Cristiano Dal Sasso of the Civic Natural History Museum in Milan and colleagues.[4]

Spinocombo
Specimen MSNM V4047 of S. aegyptiacus in the Civic Natural History Museum in Milan

MSNM V4047 (in the Museo di Storia Naturale di Milano), described by Dal Sasso and colleagues in 2005, consists of a snout (premaxillae, partial maxillae, and partial nasals) 98.8 centimetres (38.9 in) long from the Kem Kem Beds.[4] Like UCPC-2, it is thought to have come from the early Cenomanian. Arden and colleagues in 2018 tentatively assigned this specimen to Sigilmassasaurus brevicollis given its size. In the absence of associated material, however, it is difficult to be certain which material belongs to which taxon.[17]

FSAC-KK 11888 is a partial subadult skeleton recovered from the Kem Kem beds of North Africa. Described by Ibrahim and colleagues (2014) and designated as the neotype specimen (although Evers and colleagues 2015 reject the neotype designation for FSAC-KK-11888).[30] It includes cervical vertebrae, dorsal vertebrae, neural spines, a complete sacrum, femora, tibiae, pedal phalanges, caudal vertebra, several dorsal ribs, and fragments of the skull.[5] The body proportions of this specimen have been debated as the hind limbs are disproportionately shorter in the specimen than in previous reconstructions. However, it has been demonstrated by multiple paleontologists that the specimen is not a chimaera, and is indeed a specimen of Spinosaurus that suggests that the animal had much smaller hind limbs than previously thought.[31][32][33] Other known specimens consist mainly of very fragmentary remains and scattered teeth. These include:

  • A 1986 paper described prismatic structures in tooth enamel from two Spinosaurus teeth from Tunisia.[34]
  • Buffetaut (1989, 1992) referred three specimens from the Institut und Museum für Geologie und Paläontologie of the University of Göttingen in Germany to Spinosaurus: a right maxilla fragment IMGP 969-1, a jaw fragment IMGP 969-2, and a tooth IMGP 969-3.[35][36] These had been found in a Lower Cenomanian or Upper Albian deposit in southeastern Morocco in 1971.[35]
Spinoface
Reconstructed subadult skeleton from a private collection
  • Kellner and Mader (1997) described two unserrated spinosaurid teeth from Morocco (LINHM 001 and 002) that were "highly similar" to the teeth of the S. aegyptiacus holotype.[37]
  • Teeth from the Chenini Formation in Tunisia which are "narrow, somewhat rounded in cross-section, and lack the anterior and posterior serrated edges characteristic of theropods and basal archosaurs" were assigned to Spinosaurus in 2000.[38]
  • Teeth from the Echkar Formation of Niger were tentatively referred to Spinosaurus in 2007.[39]
  • A partial tooth 8 cm long purchased at a fossil trade show, reportedly from the Kem Kem Bed of Morocco and attributed to Spinosaurus maroccanus, showed 1–5 mm wide longitudinal striations and micro-structures (irregular ridges) among the striations in a 2010 paper.[26]

MHNM.KK374 to.KK378 are five isolated quadrates (skull bones) of different sizes which were collected by locals and acquired commercially in the Kem Kem region of southeastern Morocco, provided by François Escuillié and are deposited in the collections of the Muséum d’Histoire Naturelle of Marrakech. The quadrates show two different morphologies suggesting the existence of two spinosaurines in Morocco.[15]

Possible specimens

Material possibly belonging to Spinosaurus has been reported from the Turkana Grits of Kenya.[40]

Some scientists have considered the genus Sigilmassasaurus a junior synonym of Spinosaurus. In Ibrahim and colleagues (2014), the specimens of Sigilmassasaurus was referred to Spinosaurus aegyptiacus together with "Spinosaurus B" as the neotype and Spinosaurus maroccanus was considered as a nomen dubium following the conclusions of the other papers.[4][5][23] A 2015 re-description of Sigilmassasaurus disputed these conclusions, and considered the genus valid.[30] This conclusion was further supported in 2018 by Arden and colleagues, who consider Sigilmassasaurus to be a distinct genus, though a very close relative of Spinosaurus, the two unified in the tribe Spinosaurini, coined in the study.[17]

Classification

Спинозавр - новая реконструкция
Restoration based on the 2014 description
Spinosaurus sp Marocco Cenom
Tooth from Morocco
Spinosaurus skull steveoc
S. aegyptiacus head based on the 2005 Dal Sasso reconstruction

Spinosaurus gives its name to the dinosaur family Spinosauridae, 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, Sigilmassasaurus, Oxalaia, Siamosaurus, Ichthyovenator, Irritator from Brazil, and Angaturama (which maybe be synonymous with Irritator) from Brazil.[4][17] 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).[4][24]

An analysis of Spinosauridae by Arden and colleagues (2018) named the clade Spinosaurini and defined it as all spinosaurids closer to Spinosaurus aegyptiacus than to Irritator challengeri or Oxalaia quilombensis; it also found Siamosaurus suteethorni and Icthyovenator laosensis to be members of the Spinosaurinae.[17]

Phylogeny

The subfamily Spinosaurinae was named by Sereno in 1998, and defined by Holtz and colleagues (2004) as all taxa closer to Spinosaurus aegyptiacus than to Baryonyx walkeri. And the subfamily Baryonychinae was named by Charig & Milner in 1986. They erected both the subfamily and the family Baryonychinae for the newly discovered Baryonyx, before it was referred to the Spinosauridae. Their subfamily was defined by Holtz and colleagues in 2004, as the complementary clade of all taxa closer to Baryonyx walkeri than to Spinosaurus aegyptiacus. Examinations by Marcos Sales and Cesar Schultz and colleagues (2017) indicate that the South American spinosaurids Angaturama, Irritator, and Oxalaia were intermediate between Baronychinae and Spinosaurinae based on their craniodental features and cladistic analysis. This indicates that Baryonychinae may in fact be non-monophyletic. Their cladogram can be seen below.[41]

Spinosauridae

BaryonyxBaryonyx walkeri restoration

Cristatusaurus

SuchomimusSuchomimustenerensis (Flipped)

AngaturamaIrritator Life Reconstruction

Oxalaia

Spinosaurus Spinosaurus by Joschua Knüppe

The cladogram below depicts the findings of Arden and colleagues (2018):[17]

Spinosauridae

Praia das Aguncheiras taxon

Baryonychinae

Baryonyx walkeri Baryonyx walkeri restoration

Suchomimus tenerensis Suchomimustenerensis (Flipped)

Spinosaurinae

Siamosaurus suteethorni

Eumeralla taxon

Ichthyovenator laosensis Ichthyovenator laosensis by PaleoGeek (Flipped)

Irritator challengeri Irritator Life Reconstruction

Oxalaia quilombensis

Spinosaurini

Gara Samani taxon

Sigilmassasaurus brevicollis

Spinosaurus aegyptiacusSpinosaurus by Joschua Knüppe

Paleobiology

Function of neural spines

Spinosaurus vertebrae
1915 illustration of S. aegyptiacus dorsal vertebrae

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 make it appear even larger than it was, intimidating other animals.[18]

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 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.[42] However, Bailey (1997) was of the opinion that a sail could have absorbed more heat than it radiated.[18] 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.[18]

Many elaborate body structures of modern-day animals serve to attract members of the opposite sex during mating. It is possible that the sail of Spinosaurus was used for courtship, in a way similar to a peacock's tail. Stromer speculated that the size of the neural spines may have differed between males and females.[19]

Gimsa and colleagues (2015) suggest that the dorsal sail of Spinosaurus was analogous to the dorsal fins of sailfish and served a hydrodynamic purpose.[43] Gimsa and others point out that more basal, long-legged spinosaurids had otherwise round or crescent-shaped dorsal sails, whereas in Spinosaurus, the dorsal neural spines formed a shape that was roughly rectangular, similar in shape to the dorsal fins of sailfish. They therefore argue that Spinosaurus used its dorsal neural sail in the same manner as sailfish, and that it also employed its long narrow tail to stun prey like a modern thresher shark. Sailfish employ their dorsal fins for herding schools of fish into a "bait ball" where they cooperate to trap the fish into a certain area where the sailfish can snatch the fish with their bills. The sail could have possibly reduced yaw rotation by counteracting the lateral force in the direction opposite to the slash as suggested by Gimsa and colleagues (2015). Gimsa and colleagues specifically wrote :

Spinosaurus durbed
Restoration

Spinosaurus anatomy exhibits another feature that may have a modern analogy: its long tail resembled that of the thresher shark, employed to slap the water to herd and stun shoals of fish before devouring them (Oliver and colleagues, 2013). The strategies that sailfish and thresher sharks employ against shoaling fish are more effective when the shoal is first concentrated into a ‘bait ball’ (Helfman, Collette & Facey, 1997; Oliver and colleagues, 2013; Domenici and colleagues, 2014). Since this is difficult for individual predators to achieve, they cooperate in this effort. When herding a shoal of fish or squid, sailfish also raise their sails to make themselves appear larger. When they slash or wipe their bills through shoaling fish by turning their heads, their dorsal sail and fins are outstretched to stabilize their bodies hydrodynamically (Lauder & Drucker, 2004). Domenici and colleagues (2014) postulate that these fin extensions enhance the accuracy of tapping and slashing. The sail can reduce yaw rotation by counteracting the lateral force in the direction opposite to the slash. This means that prey is less likely to recognize the massive trunk as being part of an approaching predator (Marras and colleagues, 2015; Webb & Weihs 2015). Film footage available online impressively demonstrates the hunting strategies of sailfish and thresher sharks.

Spinosaurus exhibited the anatomical features required to combine all three hunting strategies: a sail for herding prey more efficiently, as well as flexible tail and neck to slap the water for stunning, injuring or killing prey. The submerged dorsal sail would have provided a strong centreboard-like counterforce for powerful sidewards movements of the strong neck and long tail, as performed by sailfish (Domenici and colleagues, 2014) or thresher sharks (Oliver and colleagues, 2013). While smaller dorsal sails or fins make the dorsal water volume better accessible for slashing, it can be speculated that their smaller stabilization effect makes lateral slashing less efficient (e.g. for thresher sharks). Forming a hydrodynamic fulcrum and hydrodynamically stabilizing the trunk along the dorsoventral axis, Spinosaurus’ sail would also have compensated for the inertia of the lateral neck by tail movements and vice versa not only for predation but also for accelerated swimming. This behaviour might also have been one reason for Spinosaurus’ muscular chest and neck reported by Ibrahim and colleagues (2014).

Diet

Spinosaurus new skull
Reconstructed skull and neck

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.[44] 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,[45] 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.[11] 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.[46] 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.[46]

CT scan of partial snout NHMUK 16665, used in a biomechanical study

In 2009, Dal Sasso and colleagues. reported the results of X-ray computed tomography of the MSNM V4047 snout.[47] 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.[47]

A 2010 isotope analysis by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid teeth, including teeth of Spinosaurus, indicate semiaquatic lifestyles.[48] 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.[48] 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.[48] The authors postulated that Spinosaurus switched between terrestrial and aquatic habitats to compete for food with large crocodilians and other large theropods respectively.[48] A 2013 study performed by scientists Andrew R. Cuff and Emily J. 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.[46]

A 2018 study by Donald Henderson, however, refutes the claim that Spinosaurus was semiaquatic. By studying the buoyancy in lungs of crocodilians and comparing it to the lung placement in Spinosaurus, it was discovered that Spinosaurus could not sink or dive below the water surface. It was also capable of keeping its entire head above the water surface while floating, much like other non-aquatic theropods. Furthermore, the study found that Spinosaurus had to continually paddle its hind legs to prevent itself from tipping over onto its side, something that extant semiaquatic animals do not need to perform. Henderson therefore theorized that Spinosaurus probably did not hunt completely submerged in water as previously hypothesized, but instead would have spent much of its time on land or in shallow water.[49][6]

Posture

Spinosaurus in Japan
Hip region of an older reconstruction
Spinosaurus hip
Hip region of the new reconstruction

Although traditionally depicted as a biped, it has been suggested since the mid-1970s that Spinosaurus was at least an occasional quadruped.[10][42] This was bolstered by the discovery of Baryonyx, a relative with robust arms.[50] Because of the mass of the hypothesized fatty dorsal humps of Spinosaurus, Bailey (1997) was open to the possibility of a quadrupedal posture,[18] leading to new restorations of it as such.[50] Theropods, including spinosaurids, could not pronate their hands (rotate the forearm so the palm faced the ground),[51] but a resting position on the side of the hand was possible, as shown by fossil prints from an Early Jurassic theropod.[52] The hypothesis that Spinosaurus had a typical quadrupedal gait since fell out of favor, however it was still believed that spinosaurids may have crouched in a quadrupedal posture, due to biological and physiological constraints.[44][51]

The possibility of a quadrupedal Spinosaurus was revived by a 2014 paper by Ibrahim and colleagues that described new material of the animal. The paper found that the hind limbs of Spinosaurus were much shorter than previously believed, and that its center of mass was located in the midpoint of the trunk region, as opposed to near the hip as in typical bipedal theropods. It was therefore proposed that Spinosaurus was poorly adapted for bipedal terrestrial locomotion, and must have been an obligate quadruped on land. The reconstruction used in the study was an extrapolation based on different sized individuals, scaled to what were assumed to be the correct proportions.[5] Palaeontologist John Hutchinson of the Royal Veterinary College of the University of London has expressed scepticism to the new reconstruction, and cautioned that using different specimens can result in inaccurate chimaeras.[53] Scott Hartman also expressed criticism because he believed the legs and the pelvis were inaccurately scaled (27% too short) and didn't match the published lengths.[54] However, Mark Witton expressed agreement with the proportions reported in the paper.[55] In their 2015 re-description of Sigilmassasaurus, Evers and colleagues argued that Sigilmassasaurus was in fact a distinct genus from Spinosaurus, and therefore doubted whether the material assigned to Spinosaurus by Ibrahim et. al. should be assigned to Spinosaurus or Sigilmassasaurus.[30] In 2018, an analysis by Henderson found that Spinosaurus probably was competent at bipedal terrestrial locomotion; the center of mass was instead found to be close to the hips, allowing Spinosaurus to stand upright like other bipedal theropods.[6]

Ontogeny

An ungual phalanx measuring 21 mm (0.83 in) belonging to a very young juvenile Spinosaurus indicates that the theropod developed its semiaquatic adaptations at a very young age or at birth and maintained them throughout its life. The specimen, found in 1999 and described by Simone Maganuco and Cristiano Dal Sasso and colleagues, is believed to have come from an animal measuring 1.78 m (5.8 ft) (assuming it resembled a smaller version of the adult), making it the smallest specimen of Spinosaurus currently known.[56]

Paleoecology

Spinosaurus with contemporaneous taxa
Spinosaurus with contemporaneous aquatic animals

The environment inhabited by Spinosaurus is only partially understood, and covers a great deal of what is now northern Africa. The region of Africa Spinosaurus is preserved in dates from 112 to 93.5 million years ago.[57][20][2] A 1996 study concluded from Moroccan fossils that Spinosaurus, Carcharodontosaurus, and Deltadromeus "ranged across north Africa during the late Cretaceous (Cenomanian)."[58] Those Spinosaurus that lived in the Bahariya Formation of what is now Egypt may have contended with shoreline conditions on tidal flats and channels, living in mangrove forests alongside similarly large dinosaurian predators Bahariasaurus and Carcharodontosaurus, the titanosaur sauropods Paralititan and Aegyptosaurus, crocodylomorphs, bony and cartilaginous fish, turtles, lizards, and plesiosaurs.[59] In the dry season it might have resorted to preying on pterosaurs.[60] This situation resembles that in the Late Jurassic Morrison Formation of North America, which boasts up to five theropod genera over 1 tonne (1.1 short tons) in weight, as well as several smaller genera (Henderson, 1998; Holtz and colleagues, 2004). Differences in head shape and body size among the large North African theropods may have been enough to allow niche partitioning as seen among the many different predator species found today in the African savanna (Farlow & Pianka, 2002).

In popular culture

Spinosaurus - Museu Blau - 2016 - 01
Sculpture based on the 2014 reconstruction, Museum of Natural Science, Barcelona

Spinosaurus appeared in the 2001 film Jurassic Park III, replacing Tyrannosaurus as the main antagonist.[61] The film's consulting paleontologist John R. Horner was quoted as saying: "If we base the ferocious factor on the length of the animal, there was nothing that ever lived on this planet that could match this creature [Spinosaurus]. Also my hypothesis is that T-rex was actually a scavenger rather than a killer. Spinosaurus was really the predatory animal."[62] He has since retracted the statement about T. rex being a scavenger. In the film, Spinosaurus was portrayed as larger and more powerful than Tyrannosaurus: in a scene depicting a battle between the two resurrected predators, Spinosaurus emerges victorious by snapping the Tyrannosaurus' neck.[63] In the fourth film Jurassic World, there is a nod to this fight where the T. rex smashes through the skeleton of a Spinosaurus in the climatic fight near the end of the film.[64]

Spinosaurus has long been depicted in popular books about dinosaurs, although only recently has there been enough information about spinosaurids for an accurate depiction. After an influential 1955 skeletal reconstruction by Lapparent and Lavocat[65] based on a 1936 diagram by Stromer,[66] it has been treated as a generalized upright theropod, with a skull similar to that of other large theropods and a sail on its back, even having four-fingered hands.[50]

In addition to films, action figures, video games, and books, Spinosaurus has been depicted on postage stamps from countries such as Angola, The Gambia, and Tanzania.[67][68]

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Further reading

  • Glut, D.F. "In search of Spinosaurus." In: Jurassic classics: a collection of saurian essays and Mesozoic musings, pp. 77–85. Jefferson, NC: McFarland, 2001. ISBN 0-7864-0961-4.
  • Nothdurft, W.; and Smith, J. The Lost Dinosaurs of Egypt. New York: Random House, 2002. ISBN 0-375-50795-7.
  • A Tribute to Ernst Stromer: Hundred Years of the Discovery of Spinosaurus aegyptiacus: Saubhik Ghosh

External links

Carcharodontosaurus

Carcharodontosaurus is a genus of carnivorous carcharodontosaurid dinosaurs that existed during the Cenomanian stage of the mid-Cretaceous Period. It is currently known to include two species: C. saharicus and C. iguidensis, which were among the larger theropods, nearly as large as or even larger than Tyrannosaurus, Giganotosaurus and Spinosaurus.

The genus Carcharodontosaurus is named after the shark genus Carcharodon, itself composed of the Greek karchar[os] (κάρχαρος, meaning "jagged" or "sharp") and odōn (ὀδών, "teeth"), and the suffix -saurus ("lizard").

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.

Cristatusaurus

Cristatusaurus is a genus of theropod dinosaur that lived during the Early Cretaceous Period of what is now Niger, 112 million years ago. It was a baryonychine member of the Spinosauridae, a group of large bipedal carnivores with well-built forelimbs and elongated, crocodile-like skulls. The type species Cristatusaurus lapparenti was named in 1998 by scientists Philippe Taquet and Dale Russell, on the basis of jaw bones and some vertebrae. Two claw fossils were also later assigned to Cristatusaurus. The animal's generic name, which means "crested reptile", alludes to a sagittal crest on top of its snout; while the specific name is in honor of the French paleontologist Albert-Félix de Lapparent. Cristatusaurus is known from the Albian to Aptian Erlhaz Formation, where it would have coexisted with sauropod and iguanodontian dinosaurs, other theropods, and various crocodylomorphs.

Originally proposed to be an indeterminate species of Baryonyx, the identity of Cristatusaurus has been subject to debate, in part due to the fragmentary nature of its fossils. Some argue that it is probably the same dinosaur as Suchomimus, which has also been found in Niger, in the same sediment layers. In that case the genus Cristatusaurus would have priority, since it was named two months earlier. Others have concluded, however, that Cristatusaurus is a nomen dubium, considering it indistinguishable from both Suchomimus and Baryonyx. Some distinctions between the fossils of Cristatusaurus and Suchomimus have been pointed out, but it is uncertain whether these differences separate the two genera or if they are due to ontogeny (changes in an organism during growth).

Cruxicheiros

Cruxicheiros (meaning "cross hand") is a genus of tetanuran theropod dinosaur which lived in the Middle Jurassic of England. The type species is C. newmanorum, described by Roger Benson and Jonathan Radley in 2010.

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.

Ernst Stromer

Ernst Freiherr Stromer von Reichenbach (12 June 1871 – in Nürnberg; 18 December 1952 in Erlangen) was a German paleontologist.

He described the following Cretaceous dinosaurs from Egypt: Aegyptosaurus, Bahariasaurus, Carcharodontosaurus, and the enigmatic theropod, Spinosaurus aegyptiacus. Stromer also described the giant crocodilian Stomatosuchus. The fossil bird genus Stromeria, named in his honor by Kálmán Lambrecht in 1929, is today synonymized with Eremopezus. The sauropod Paralititan stromeri is also named in his honor. The majority of his fossil discoveries were destroyed during World War Two and only photographs of some remain.

Irritator

Irritator is a genus of spinosaurid theropod dinosaur that lived in what is now Brazil during the Albian stage of the Early Cretaceous Period, about 110 million years ago. It is known from a nearly complete skull found in the Romualdo Formation of the Araripe Basin. Fossil dealers had acquired this skull and illegally sold it to the State Museum of Natural History Stuttgart. In 1996, the specimen became the holotype of the type species Irritator challengeri. The genus name comes from the word "irritation", reflecting the feelings of paleontologists who found the skull had been heavily damaged and altered by the collectors. The species name is an homage to the fictional character Professor Challenger from Arthur Conan Doyle's novels.

Many paleontologists regard Angaturama limai—known from a snout tip that was described later in 1996—as a potential junior synonym of Irritator. Both animals hail from the same stratigraphic units of the Araripe Basin. It was also previously proposed that Irritator and Angaturama's skull parts belonged to the same specimen. Although this has been cast into doubt, more overlapping fossil material is needed to confirm whether they are the same animal or not. Other spinosaurid skeletal material, some of which could belong to Irritator or Angaturama, was retrieved from the Romualdo Formation, allowing for a replica skeleton to be made and mounted for display at the National Museum of Rio de Janeiro in 2009.

Estimated at between 6 and 8 meters (20 and 26 ft) in length, Irritator weighed around 1 tonne (1.1 short tons), making it one of the smallest spinosaurids known. Its long, shallow and slender snout was lined with straight and unserrated conical teeth. Lengthwise atop the head ran a thin sagittal crest, to which powerful neck muscles were likely anchored. The nostrils were positioned far back from the tip of the snout, and a rigid secondary palate on the roof of the mouth would have strengthened the jaw when feeding. Belonging to a subadult, Irritator challengeri's holotype remains the most completely preserved spinosaurid skull yet found. The Angaturama snout tip expanded to the sides in a rosette-like shape, bearing long teeth and an unusually tall crest. One possible skeleton indicates it, like other spinosaurids, had enlarged first-finger claws and a sail running down its back.

Irritator had been mistaken initially for a pterosaur, and later a maniraptoran dinosaur. In 1996, the animal was identified as a spinosaurid theropod. The holotype skull was thoroughly prepared before being redescribed in 2002, confirming this classification. Both Irritator and Angaturama belong to the Spinosaurinae subfamily. A generalist diet—like that of today's crocodilians—has been suggested; Irritator might have preyed mainly on fish and any other small prey animals it could catch. Fossil evidence is known of an individual that ate a pterosaur, either from hunting or scavenging it. Irritator may have had semiaquatic habits, and inhabited the tropical environment of a coastal lagoon surrounded by dry regions. It coexisted with other carnivorous theropods as well as turtles, crocodyliforms, and a large number of pterosaur and fish species.

Jurassic Park III

Jurassic Park III is a 2001 American science fiction adventure film and the third installment in the Jurassic Park film series. The film stars Sam Neill, William H. Macy, Téa Leoni, Alessandro Nivola, Trevor Morgan, and Michael Jeter. It is the first film in the series Steven Spielberg did not direct; neither was it based on a book by Michael Crichton, although numerous scenes in the film were taken from Crichton's novels Jurassic Park and The Lost World. Events depicted in the film take place on Isla Sorna, an island off Central America's Pacific coast, where a divorced couple have tricked Dr. Alan Grant into helping them find their son.

After the success of Spielberg's film Jurassic Park, Joe Johnston expressed interest in directing a sequel. Spielberg gave Johnston permission to direct a third film in the series, if there was to be one. Production of Jurassic Park III began on August 30, 2000. Despite mixed reviews from critics, the film was successful at the box office, grossing $368 million worldwide. The next film in the series, Jurassic World, was released in June 2015.

Jurassic Park III (arcade game)

Jurassic Park III is a light gun arcade game based on the 2001 film of the same name. The game was developed by Konami and was first unveiled at the Japan Amusement Machinery Manufacturers Association in September 2001. The game had been released in Japan by November 2001, and was later released in the United States in March 2002. The game uses the same cabinet and motion sensor technology as Police 911, requiring players to dodge the oncoming dinosaur attacks. Alternatively, the standard cabinet provides a left and right button to perform evasive maneuvers. It was preceded by The Lost World: Jurassic Park in 1997, also a light gun game, but from Sega.

Libycosuchus

Libycosuchus is an extinct genus of North African crocodylomorph possibly related to Notosuchus. It was terrestrial, living approximately 95 million years ago in the Cenomanian stage of the Late Cretaceous. Fossil remains have been found in the Bahariya Formation in Egypt, making it contemporaneous with the crocodilian Stomatosuchus, and dinosaurs, including Spinosaurus. It was one of the few fossils discovered by Ernst Stromer that wasn't destroyed by the Royal Air Force during the bombing of Munich in 1944.

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.

List of cloned animals in the Jurassic Park series

Jurassic Park is an American science fiction adventure media franchise based on the 1990 best-selling novel of the same name by Michael Crichton, and its sequel, The Lost World (1995). Focused on the catastrophic events following the cloning of dinosaurs through the extraction of DNA from mosquitoes fossilized in amber, the film series also explores the ethics of cloning and genetic engineering, and the morals behind bringing back extinct animals. The first Jurassic Park film was directed by Steven Spielberg and released in 1993. It was followed by two films, The Lost World: Jurassic Park (1997) and Jurassic Park III (2001), completing the first trilogy. A fourth installment, Jurassic World, was released in 2015, marking the beginning of a new trilogy. The new trilogy starts 22 years after the events of the first, but still relies on the narrative of the original films and novels. Its sequel, Jurassic World: Fallen Kingdom, was released in 2018, and a sixth and final film of the second trilogy is scheduled for release in 2021. The film series has garnered critical acclaim for its innovations in CGI technology and animatronics.

47 species of cloned animals have been portrayed in the novels and films: 39 species of dinosaurs, three species of pterosaurs, three genetically-engineered animals, one species of prehistoric marine reptile, and at least one cloned Homo sapiens. Theropod dinosaurs like Tyrannosaurus rex and Velociraptor have had major roles throughout the series. Other species, including Triceratops, Brachiosaurus, and Spinosaurus have also played significant roles.

Megalosauroidea

Megalosauroidea (meaning 'great/big lizard forms') is a superfamily (or clade) of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period. The group is defined as Megalosaurus bucklandii and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus. Members of the group include Spinosaurus, Megalosaurus, and Torvosaurus.

Monsters Resurrected

Monsters Resurrected is an American documentary television series that premiered on September 13, 2009, on the Discovery Channel. The program reconstructs extinct animals of both Mesozoic and Cenozoic. It is also called Mega Beasts.

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.

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.

Sigilmassasaurus

Sigilmassasaurus ( see-jil-MAH-sə-SOR-əs; "Sijilmassa lizard") is a potentially dubious genus of tetanuran theropod dinosaur that lived approximately 100 to 94 million years ago during the middle of the Cretaceous Period in what is now northern Africa. Sigilmassasaurus was a moderately-built, ground-dwelling, bipedal carnivore, like most other theropods.

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.

Theropoda

Theropoda ( or , from Greek θηρίον "wild beast" and πούς, ποδός "foot") or theropods () are a dinosaur suborder that is characterized by hollow bones and three-toed limbs. They are generally classed as a group of saurischian dinosaurs, although a 2017 paper has instead placed them in the proposed clade Ornithoscelida as the closest relatives of the Ornithischia. Theropods were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.

Piatnitzkysauridae
Megalosauria

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