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).[1] 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,[2] 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.

Spinosauridae
Temporal range: Late JurassicLate Cretaceous, 152–85 Ma
Spinosaurus swimming black background
Skeletal reconstruction of Spinosaurus aegyptiacus, National Geographic Museum, Washington, D.C.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Superfamily: Megalosauroidea
Clade: Megalosauria
Family: Spinosauridae
Stromer, 1915
Type species
Spinosaurus aegyptiacus
Stromer, 1915
Subgroups
Synonyms
  • Baryonychidae Charig & Milner, 1986
  • Irritatoridae Martill et al., 1996
  • Sigilmassasauridae Russel, 1996

Description

Body size

Spinosauridae Size Diagram by PaleoGeek - Version 2
Size comparison of various spinosaurids with a human

Although reliable size and weight estimates for most taxa are hindered by the lack of good material, all known spinosaurids were large animals.[3] The smallest, Irritator, was between 6 and 8 meters in length and 1 tonne (1.1 short tons) in weight.[4][5] While Ichthyovenator, Baryonyx, and Suchomimus ranged from 7.5 to 11 meters long, and weighing between 1 and 5.2 tonnes (1.2 and 5.7 short tons).[6][5][7] Spinosaurus was the largest, capable of reaching lengths of around 15 meters (49 ft)[1] and weighing around 6.4–7.2 tonnes (7.1–7.9 short tons).[8] This consistency in large body size among spinosaurids could have evolved as a byproduct of their preference for semiaquatic lifestyles, as without the need to compete with other large theropods for food, they would have been able to grow to tremendous lengths.[9]

Skull

Spinosaurid skull anatomy is similar in many respects to that of crocodilians. Spinosaurid skulls were long, low and narrow.[3] As in other theropods, various fenestrae (openings) in the skull aided in reducing its weight. In spinosaurs however, the antorbital fenestrae were greatly reduced, akin to those of crocodilians.[10] The tips of the premaxillae (frontmost snout bones) and dentaries (tooth bearing bones of the mandible) were expanded, forming what has been called a "terminal rosette" of enlarged teeth. Behind this expansion, the upper and lower jaws were notched.[3] The maxillae (main upper jaw bones) were long and formed a low branch under the nostrils that connected to the rear of the premaxillae.[11] Spinosaurid teeth were subconical, with an oval to circular cross section and either absent or very fine serrations. Typically, their teeth were either straight or only slightly recurved front to back, and bore a varying number of flutes (ridges) running lengthwise across their tooth crowns.[12][13]

Spinosaurus skull en
Annotated skull diagram of Spinosaurus

Lengthwise atop the skull ran a thin and shallow sagittal crest that was usually tallest near or above the eyes, either becoming shorter or disappearing entirely towards the front of the head.[3][8][12] Spinosaurus's head crest was comb shaped and bore distinct vertical ridges,[8] while those of Baryonyx and Suchomimus looked like small triangular bumps.[14][2] Irritator's median crest stopped above the eyes in a bulbous, flattened shape. However, given that the upper surface of its holotype skull was damaged and the tip of its snout was missing, the complete shape of Irritator's crest is unknown.[11] Angaturama (a possible synonym of Irritator) had an unusually tall crest on its premaxillae that nearly overhung the tip of the snout with a small protrusion.[12]

The nostrils were set far back on the skull, at least behind the teeth of the premaxillae, instead of at the front of the snout as in most theropods.[3] Those of Baryonyx and Suchomimus were large and started between the first and fourth maxillary teeth, while Spinosaurus's nostrils were far smaller and more retracted. Irritator's nostrils were positioned similarly to those of Baryonyx and Suchomimus, and were between those of Spinosaurus and Suchomimus in size.[12] Spinosaurids had long secondary palates, bony and rugose structures on the roof of their mouths that are also found in extant crocodilians, but not in most theropod dinosaurs.[10] Oxalaia had a particularly wrinkled and elaborate secondary palate, while most spinosaurs had smoother ones.[15]

Postcranial skeleton

Spinosauridae "Sails" Comparison by PaleoGeek
Neural spine sail variation in three spinosaurid species

Spinosaurids had relatively large and well-built forelimbs, the radius (forearm bone) was stout and usually only half as long as the humerus (upper arm bone). Each manus (hand) wielded an enlarged, strongly recurved claw on the first digit (or "thumb"), and were otherwise typical of tetanurans, bearing three digits.[3][6] The coracoids were hook shaped.[2] The hindlimbs were somewhat short and mostly conventional of other megalosauroid theropods.[3][6] Spinosaurus however, had a particularly small pelvic (hip) region and hindlimbs proportional to body size.[16]

The upwards projecting neural spines of spinosaurid vertebrae were very tall, more so than in most theropods. When alive, these spines would have been covered in skin or fat tissue and formed a dorsal sail down the animal's back, a condition that has also been observed in some carcharodontosaurid and ornithopod dinosaurs.[3][17] The eponymous neural spines of Spinosaurus were extremely long, some of the dorsal (back) vertebrae being over 1-metre (3 ft 3 in) tall.[18] Suchomimus had a lower, ridge-like sail across the majority of its back, hip, and tail region.[2] Baryonyx showed a reduced sail, with only few of the rearmost vertebrae being elongated.[14] Ichthyovenator had a sinusoidal (wave-like) sail that split in two over the pelvic region, with the ends of some neural spines fanning out and bearing elongate, finger-like processes on their rear upper margins.[19] One partial skeleton possibly refferable to Angaturama also had elongated neural spines on its hip region.[20][21] The presence of a sail in fragmentary genera like Sigilmassasaurus is unknown.[22]

History of discovery

The holotype specimen of Spinosaurus aegyptiacus as illustrated by Ernst Stromer in 1915

The first spinosaurid fossil, a single conical tooth, was discovered circa 1820 by British paleontologist Gideon Mantell in the Wadhurst Clay Formation.[23] In 1841 Sir Richard Owen mistakenly assigned it to a crocodilian he named Suchosaurus ("crocodile lizard"),[24][25] a second species, S. girardi, was later named in 1897.[26] However, the spinosaurid nature of Suchosaurus was not recognized until a 1998 redescription of Baryonyx.[27]

The first fossils referred to a spinosaurid were discovered in 1912 at the Bahariya Formation in Egypt. Consisting of dorsal vertebrae, skull fragments, and teeth, these remains became the holotype specimen of the new genus and species Spinosaurus aegyptiacus in 1915, when they were described by German paleontologist Ernst Stromer. The dinosaur's name meant "egyptian spine lizard", in reference to the unusually long neural spines not seen previously in any other theropod. In April 1944, the holotype of S. aegyptiacus was destroyed during an allied bombing raid in World War II.[28][29] In 1934, Stromer referred a partial skeleton also from the Bahariya Formation to a new species of Spinosaurus,[30] this specimen has since been alternatively assigned to another African spinosaurid, Sigilmassasaurus.[22]

In 1983, a relatively complete skeleton was excavated from the Smokejacks pit in Surrey, Engand. These remains were described by British paleontologists Alan J. Charig and Angela C. Milner in 1986 as the holotype of a new species, Baryonyx walkeri. After the discovery of Baryonyx, many new genera have since been described, the majority on very incomplete remains. However, other finds bear enough fossil material and distinct anatomical features to be assigned with confidence. Paul Sereno and colleagues described Suchomimus in 1998, a baryonychine from Niger on the basis of a partial skeleton found in 1997. Later in 2004, partial jaw bones were recovered from the Alcântara Formation, these were referred to a new genus of spinosaurine named Oxalaia in 2011 by Alexander Kellner.[29]

Classification

Four spinosaurids by Abelov2014
Anachronistic restoration of four spinosaurids, clockwise from the left: Suchomimus, Spinosaurus, Irritator, and Baryonyx

The family Spinosauridae was named by Stromer in 1915 to include the single genus Spinosaurus. The clade was expanded as more close relatives of Spinosaurus were uncovered. The first cladistic definition of Spinosauridae was provided by Paul Sereno in 1998 (as "All spinosauroids closer to Spinosaurus than to Torvosaurus").[31]

Taxonomy

Traditionally, Spinosauridae is divided into two subfamilies: Spinosaurinae, which contains the genera Icthyovenator, Irritator, Oxalaia, Sigilmassasaurus and Spinosaurus, is marked by unserrated, straight teeth, and external nares which are further back on the skull than in Baryonychinae.[31][32] And Baryonychinae, which contains the genera Baryonyx and Suchomimus,[33] is marked by serrated, slightly curved teeth, smaller size, and more teeth in the lower jaw behind the terminal rosette than in spinosaurines.[31][32] Others, such as Siamosaurus, may belong to either Baryonychinae or Spinosaurinae, but are too incompletely known to be assigned with confidence.[33] Siamosaurus was classified as a spinosaurine in 2018, but the results are provisional and not entirely conclusive.[34]

Phylogeny

The subfamily Spinosaurinae was named by Sereno in 1998, and defined by Holtz and colleagues in 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 in 2017 by Marcos Sales and Cesar Schultz indicate that the South American spinosaurids Angaturama and Irritator 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.[12]

Suchomimus and Baryonyx
Skeletons of Suchomimus (above) and Baryonyx (below) to scale
Spinosauridae

BaryonyxBaryonyx walkeri restoration

Cristatusaurus

SuchomimusSuchomimustenerensis (Flipped)

AngaturamaIrritator Life Reconstruction

Oxalaia

Spinosaurus Spinosaurus by Joschua Knüppe

The next cladogram displays an analysis of Tetanurae simplified to show only Spinosauridae from Allain colleagues in 2012:[19]

Spinosauridae
Spinosaurinae

Irritator Irritator Life Reconstruction

Spinosaurus Spinosaurus by Joschua Knüppe

Baryonychinae

Ichthyovenator Ichthyovenator laosensis by PaleoGeek (Flipped)

Suchomimus Suchomimustenerensis (Flipped)

Baryonyx Baryonyx walkeri restoration

The 2018 phylogenetic analysis by Arden and colleagues, which included many unnamed taxa, resolved Baryonychinae as monophyletic, and also coined the new term Spinosaurini for the clade of Sigilmassasaurus and Spinosaurus.[34]

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 aegyptiacus Spinosaurus by Joschua Knüppe

Paleobiology

Diet and feeding

Comparative evolution of jaws between Muraenesocidae (A) and Spinosauridae (B)
Comparison of a spinosaurid skull with that of Dubreuillosaurus and two extant pike conger eels

Spinosaurid teeth resemble those of crocodiles, which are used for piercing and holding prey. Therefore, teeth with small or no serrations, such as in spinosaurids, were not good for cutting or ripping into flesh but instead helped to ensure a strong grip on a struggling prey animal.[35] Spinosaur jaws were likened by Vullo and colleagues to those of the pike conger eel, in what they hypothesized was convergent evolution for aquatic feeding.[36] Both kinds of animals have some teeth in the end of the upper and lower jaws that are larger than the others and an area of the upper jaw with smaller teeth, creating a gap into which the enlarged teeth of the lower jaw fit, with the full structure called a terminal rosette.[36]

Baryonyx BW
Life restoration of Baryonyx with a fish in its jaws

In the past, spinosaurids have often been considered piscivores (fish-eaters) in the main, based on comparisons of their jaws with those of modern crocodilians.[32] British paleontologist Emily J. Rayfield and colleagues, in 2007, conducted biomechanical studies on the skull of Baryonyx, which had a long, laterally compressed skull, comparing it to gharial (long, narrow, tubular) and alligator (flat and wide) skulls. They found that the structure of baryonychine jaws converged on that of gharials, in that the two taxa showed similar response patterns to stress from simulated feeding loads, and did so with and without the presence of a (simulated) secondary palate. The gharial, exemplar of a long, narrow, and tubular snout, is a fish specialist. However, this snout anatomy does not preclude other options for the spinosaurids. The gharial is the most extreme example and a fish specialist; Australian freshwater crocodiles (Crocodylus johnstoni), which have similarly shaped skulls to gharials, also specialize more on fish than sympatric, broad snouted crocodiles and are opportunistic feeders which eat all manner of small aquatic prey, including insects and crustaceans. Thus, spinosaurids' snouts correlate with piscivory; this is consistent with hypotheses of this diet for spinosaurids, in particular baryonychines, but it does not indicate that they were solely piscivorous.[37]

Spinosaurus skull steveoc
Life restoration of the head of Spinosaurus

Further study by Andrew R. Cuff and Rayfield in 2013 on the skulls of Spinosaurus and Baryonyx did not recover similarities in the skulls of Baryonyx and the gharial that the previous study did. Baryonyx had, in models where the size difference of the skulls was corrected for, greater resistance to torsion and dorsoventral bending than both Spinosaurus and the gharial, while both spinosaurids were inferior to the gharial, alligator, and slender-snouted crocodile in resisting torsion and medio-lateral bending. When the results from the modeling were not scaled according to size, then both spinosaurids performed better than all the crocodilians in resistance to bending and torsion, due to their larger size. Thus, Cuff and Rayfield suggest that the skulls are not efficiently built to deal well with relatively large, struggling prey, but that spinosaurids may overcome prey simply by their size advantage, and not skull build.[38] Sues and colleagues studied the construction of the spinosaurid skull, and concluded that their mode of feeding was to use extremely quick, powerful strikes to seize small prey items using their jaws, whilst employing the powerful neck muscles in rapid up-and-down motion. Due to the narrow snout, vigorous side-to-side motion of the skull during prey capture is unlikely.[35] Based the size and positions of their nostrils, Sales & Schultz in 2017 suggested that Spinosaurus possessed a greater reliance on its sense of smell and had a more piscivorous lifestyle than Irritator and baryonychines.[12]

2013-03 Naturkundemuseum Berlin Dickschupperfisch Lepidotes maximus anagoria
A fossil of the fish Scheenstia, prey of Baryonyx

Direct fossil evidence shows that spinosaurids fed on fish as well as a variety of other small to medium-sized animals, including dinosaurs. Baryonyx was found with scales of the prehistoric fish Scheenstia in its body cavity, and these were abraded, hypothetically by gastric juices. Bones of a young Iguanodon, also abraded, were found alongside this specimen. If these represent Baryonyx’s meal, the animal was, whether in this case a hunter, or a scavenger, an eater of more diverse fare than fish.[32][35][14] Moreover, there is a documented example of a spinosaurid having eaten a pterosaur, as one Irritator tooth was found embedded within the fossil vertebrae of an ornithocheirid pterosaur found in the Romualdo Formation of Brazil. This may represent a predation or a scavenging event.[39][40] In the Sao Khua Formation of Thailand, isolated tooth crowns from Siamosaurus have been found in association with sauropod remains, indicating possible predation or scavenging.[41]

A 2018 study by Hassler and colleagues of calcium isotopes in the teeth of North African theropods found that spinosaurids had a mixed diet of fish and herbivorous dinosaurs, whereas the other theropods examined (abelisaurids and carcharodontosaurids) mainly fed on herbivorous dinosaurs. This might indicate ecological partitioning between these theropods.[42]

Forelimb function

Suchomimus arm Museum of Anchient Life
Reconstructed arm of Suchomimus, Museum of Ancient Life, Utah

The use of the robust forelimbs and giant recurved claws of spinosaurs remains a debated topic. Charig and Milner speculated in 1986 that Baryonyx may have crouched by the riverbank and used its claws to gaff fish out of the water, similarly to grizzly bears.[43] In 1987, British biologist Andrew Kitchener argued that with both its crocodile-like snout and enlarged claws, Baryonyx seemed to have too many adaptations for piscivory when one would have been enough. Kitchener instead postulated that Baryonyx more likely used its arms to scavenge the corpses of large dinosaurs, such as Iguanodon, by breaking into the carcass with the large claws, and subsequently probing for viscera with its long snout.[44] In their 1997 article, Charig and Milner rejected this hypothesis, pointing out that in most cases, a carcass would have already been largely emptied out by its initial predators.[14] Later research has also ruled out this sort of specialized scavenging.[3] Charig and Milner further suggested that the robust forelimbs and giant thumb claws would have been Baryonyx's primary method of capturing, killing, and tearing apart large prey; whereas its long snout would have been used mostly for fishing.[14] A 2005 study by Canadian paleontologist the François Therrien and colleagues agreed that spinosaur forelimbs were probably used for hunting larger prey items, given that their snouts could not resist the bending stress.[45] In a 2017 review of the family, David Hone and Holtz considered a possible function in digging for water sources or hard to reach prey, as well as burrowing into soil to construct nests.[3]

Cranial crests and neural spines

Theropod heads were often decorated with some form of crest, horn, or rugose structure.[46] Although there has been little discussion on the head crests of spinosaurs, Hone and Holtz in 2017 considered that their most likely use was for displaying to potential mates or as a means of threatening rivals and predators.[3] Such has been suggested for theropod cranial structures before, which may have been aided by unusual or bright coloration to provide further visual cues.[46] Many theories have been proposed over the years for the use of spinosaurid dorsal sails, such as thermoregulation;[47] to aid in swimming;[48] to store energy or insulate the animal; or for display purposes, such as intimidating rivals and predators, or attracting mates.[49][50]

Ontogeny

Juvenile spinosaurid fossils are exceedingly rare and almost unknown. However, an ungual phalanx measuring 21 mm (0.83 in) belonging to a very young Spinosaurus indicates that Spinosaurus and probably by extent other spinosaurids, may have developed their semiaquatic adaptations at birth or while at a very young age and maintained these adaptations throughout their lives. The specimen, found in 1999 and described by Simone Maganuco and Cristiano Dal Sasso and colleagues in 2018, is believed to have come from a very small juvenile measuring 1.78 m (5.8 ft), making said specimen the smallest known example of a spinosaurid currently described.[51][52]

Paleoecology

Habitat preference

Spinosaurus durbed
Restoration of Spinosaurus wading in a floodplain

A 2010 publication by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid bones indicates semiaquatic lifestyles. Isotope ratios from teeth from Baryonyx, Irritator, Siamosaurus, and Spinosaurus were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians. The study found that, among theropods, spinosaurid isotope ratios were closer to those of turtles and crocodilians. Siamosaurus specimens tended to have the largest difference from the ratios of other theropods, and Spinosaurus tended to have the least difference. The authors concluded that spinosaurids, like modern crocodilians and hippopotamuses, spent much of their daily lives in water. The authors also suggested that semiaquatic habits and piscivory in spinosaurids can explain how spinosaurids coexisted with other large theropods: by feeding on different prey items and living in different habitats, the different types of theropods would have been out of direct competition.[53]

In 2018, an analysis was conducted on the partial tibia of an indeterminate spinosaurine from the early Albian, the bone was from a sub-adult between 7–13 m (22–42 ft) in length still growing moderately fast before its death. This specimen (LPP-PV-0042) was found in the Araripe Basin of Brazil and taken to the University of San Carlos for a CT Scan, where it revealed osteosclerosis (high bone density).[9] This condition had previously only been observed in Spinosaurus, as a possible way of controlling its buoyancy.[16] The presence of this condition on the leg fragment showed that semi-aquatic adaptations in spinosaurids were already present at least 10 million years before Spinosaurus aegyptiacus appeared. According to the Phylogenetic bracketing method, this high bone density might have been present in all spinosaurines.[9]

Distribution

Spinosauridae Fossil Map by PaleoGeek
Map illustrating spinosaurid fossil discoveries

Spinosaurids are known to exist from as early as the Late Jurassic, through characteristic teeth which were found in Tendaguru, Tanzania, and attributed to Ostafrikasaurus.[54] Baryonychines were common, as represented by Baryonyx, which lived during the Barremian of England and Spain. Baryonyx-like teeth are found from the earlier Hauterivian and later Aptian sediments of Spain, as well as the Hauterivian of England, and the Aptian of Niger. The earliest record of spinosaurines is from Africa; they are present in Albian sediments of Tunisia and Algeria, and in Cenomanian sediments of Egypt and Morocco. Spinosaurines are also found in Hauterivian and Aptian-Albian sediments of Thailand, and Southern China. In Africa, baronychines were common in the Aptian, and then replaced by spinosaurines in the Albian and Cenomanian.[33]

Some intermediate specimens extend the known range of spinosaurids past the youngest dates of named taxa. A single baryonychine tooth was found from the mid-Santonian, in the Majiacun Formation of Henan, China.[55]

Australian Spinosaurid
NMV P221081, cervical vertebra of an Australian spinosaurid from various angles, compared with that of Baryonyx (bottom right)

Confirmed spinosaurids have been found on every continent except for North America and Antarctica, the first of which was discovered in 1912 at the Bahariya Formation in Egypt and described in 1915 as Spinosaurus aegyptiacus.[50] Africa has shown a great abundance in spinosaurid discoveries,[56] such as in the Kem Kem beds of Morocco, which housed an ecosystem containing many large coexisting predators.[57][53] A fragment of a spinosaurine lower jaw from the Early Cretaceous was also reported from Tunisia, and referred to Spinosaurus.[33] Spinosaurinae's range has also extended to South America, particularly Brazil, with the discoveries of Irritator, Angaturama, and Oxalaia.[40][15] There was also a fossil tooth in Argentina which has been referred to spinosauridae by Leonardo Salgado and colleagues.[58] This referral is doubted by Gengo Tanaka, who offers Hamadasuchus, a crocodilian, as the most likely animal of origin for these teeth.[59]

Baryonychines have been found in Africa, with Suchomimus and Cristatusaurus,[33][60][61] as well as in Europe, with Baryonyx and Suchosaurus.[62] Baryonyx-like teeth are also reported from the Ashdown Sands of Sussex, in England, and the Burgos Province, in Spain. A partial skeleton and many fossil teeth indicate spinosaurids were widespread in Asia. As of 2012, three have been named: Ichthyovenator, Siamosaurus and "Sinopliosaurus" fusuiensis.[19][33][55] In 2014, a spinosaurid tooth was discovered in Malaysia; the first dinosaur remains discovered in the country.[63] At la Cantalera-1, a site in the Early Barremanian Blesa Formation in Treul, Spain, two types of spinosaurid teeth were found, and they were assigned, tentatively, as indeterminate spinosaurine and baryonychine taxa.[64] An intermediate spinosaurid was discovered in the Early Cretaceous Eumeralla Formation, Australia.[65] It is known from a single 4 cm long partial cervical vertebra, designated NMV P221081. It is missing most of the neural arch. The specimen is from a juvenile estimated to be about 2 to 3 meters long (6–9 ft). Out of all spinosaurs it most closely resembles Baryonyx.[66]

References

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External links

"Sinopliosaurus" fusuiensis

"Sinopliosaurus" fusuiensis is a species of spinosaurid theropod dinosaur from the Early Cretaceous Xinlong Formation of Guangxi Province, southern China. It is known only from teeth that were initially identified as those of a pliosauroid, but are now known to have come from an animal similar to Siamosaurus.

Afrovenator

Afrovenator (; "African hunter") is a genus of megalosaurid theropod dinosaur from the middle Jurassic Period of northern Africa.

Baryonyx

Baryonyx () is a genus of theropod dinosaur which lived in the Barremian stage of the Early Cretaceous Period, about 130–125 million years ago. The first skeleton was discovered in 1983 in the Weald Clay Formation of Surrey, England, and became the holotype specimen of B. walkeri, named by palaeontologists Alan J. Charig and Angela C. Milner in 1986. The generic name, Baryonyx, means "heavy claw" and alludes to the animal's very large claw on the first finger; the specific name, walkeri, refers to its discoverer, amateur fossil collector William J. Walker. The holotype specimen is one of the most complete theropod skeletons from the UK (and remains the most complete spinosaurid), and its discovery attracted media attention. Specimens later discovered in other parts of the United Kingdom and Iberia have also been assigned to the genus.

The holotype specimen, which may not have been fully grown, was estimated to have been between 7.5 and 10 m (25 and 33 ft) long and to have weighed between 1.2 and 1.7 t (1.3 and 1.9 short tons). Baryonyx had a long, low, and narrow snout, which has been compared to that of a gharial. The tip of the snout expanded to the sides in the shape of a rosette. Behind this, the upper jaw had a notch which fitted into the lower jaw (which curved upwards in the same area). It had a triangular crest on the top of its nasal bones. Baryonyx had a large number of finely serrated, conical teeth, with the largest teeth in front. The neck formed an S-shape, and the neural spines of its dorsal vertebrae increased in height from front to back. One elongated neural spine indicates it may have had a hump or ridge along the centre of its back. It had robust forelimbs, with the eponymous first-finger claw measuring about 31 cm (12 in) long.

Now recognised as a member of the family Spinosauridae, Baryonyx's affinities were obscure when it was discovered. Some researchers have suggested that Suchosaurus cultridens is a senior synonym (being an older name), and that Suchomimus tenerensis belongs in the same genus; subsequent authors have kept them separate. Baryonyx was the first theropod dinosaur demonstrated to have been piscivorous (fish-eating), as evidenced by fish scales in the stomach region of the holotype specimen. It may also have been an active predator of larger prey and a scavenger, since it also contained bones of a juvenile Iguanodon. The creature would have caught and processed its prey primarily with its forelimbs and large claws. Baryonyx may have had semiaquatic habits, and coexisted with other theropod, ornithopod, and sauropod dinosaurs, as well as pterosaurs, crocodiles, turtles and fishes, in a fluvial environment.

Cajual Island

The island of Cajual is located in the Baía de São Marcos near to Alcântara, Maranhão, Brazil.The island is an important Brazilian paleontological site, where fossils of animals such as Spinosaurus and Sigilmassasaurus were found, and also such plants as conifers and ferns. The finds include the remains of the largest carnivorous dinosaur in Brazil. Traces of the maxillary and nostril of the specimen were found. Known as Oxalaia quilombensis, the species is part of the family of dinosaurs known as Spinosauridae, with elongated skulls and spines along the back.

The presence of fossils also present in Africa proves that the continents were once united, forming Gondwana. The "Lage of the Joker", where the fossils are found, is up to 2 meters below the water at high tide, so it can only be visited for only a few hours a day.

Currently, the island of Cajual is home to a small community of quilombolas.

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).

Ichthyovenator

Ichthyovenator (meaning "fish hunter") is a genus of spinosaurid theropod dinosaur that lived during the Early Cretaceous of what is now Laos, likely from the Aptian stage (113–125 million years ago). Ichthyovenator is known from fossils collected in the Grès supérieurs Formation. Like other members of its family, it had elongated neural spines forming a sail on its back, although Ichthyovenator's was unusual due to its particular wave-like curvature and being split in two over the hips. Ichthyovenator was initially thought to belong to the Baryonychinae subfamily, but more recent analyses place it in the Spinosaurinae.

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.

Megalosauridae

Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the order Megalosauroidea, closely related to the family Spinosauridae. Some members of this family include Megalosaurus, Torvosaurus, Eustreptospondylus, and Afrovenator. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dinosaurs, although they became extinct by the end of the Jurassic period. They were a relatively primitive group of basal tetanurans containing two main subfamilies, Megalosaurinae and Afrovenatorinae, along with the basal genus Eustreptospondylus, an unresolved taxon which differs from both subfamilies.The defining megalosaurid is Megalosaurus bucklandii, first named and described in 1824 by William Buckland after multiple finds in Stonesfield, Oxfordshire, UK. Megalosaurus was the first formally described dinosaur and was the basis for the establishment of the clade Dinosauria. It is also one of the largest known Middle Jurassic carnivorous dinosaurs, with the best-preserved femur at 805 mm and a proposed body mass of around 943 kg. Megalosauridae is recognized as a mainly European group of dinosaurs, based on fossils found in France and the UK. However, recent discoveries in Niger have led some to consider the range of the family. Megalosaurids appeared right before the split of the supercontinent Pangaea into Gondwana and Laurasia. These large theropods therefore may have dominated both halves of the world during the Jurassic.The family Megalosauridae was first defined by Thomas Huxley in 1869, yet it has been contested throughout history due to its role as a ‘waste-basket’ for many partially described dinosaurs or unidentified remains. In the early years of paleontology, most large theropods were grouped together and up to 48 species were included in the clade Megalosauria, the basal clade of Megalosauridae. Over time, most of these taxa were placed in other clades and the parameters of Megalosauridae were narrowed significantly. However, some controversy remains over whether Megalosauridae should be considered its own distinct group, and dinosaurs in this family remain some of the most problematic taxa in all Dinosauria. Some paleontologists, such as Paul Sereno in 2005, have disregarded the group due to its shaky foundation and lack of clarified phylogeny. However, recent research by Carrano, Benson, and Sampson has systematically analyzed all basal tetanurans and determined that Megalosauridae should exist as its own family.

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.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Ostafrikasaurus

Ostafrikasaurus is a genus of spinosaurid theropod dinosaur known from the Jurassic of Tendaguru, southeastern Tanzania. It contains a single species, Ostafrikasaurus crassiserratus.

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 to 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.

Quadrate bone

The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint (the other part is the articular bone at the rear end of the lower jaw).

It is formed by endochondral ossification and is formed from the hindmost part of the primitive cartilaginous upper jaw.

Romualdo Formation

The Romualdo Formation is a geologic Konservat-Lagerstätte in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together. The geological formation, previously designated as the Romualdo Member of the Santana Formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau. It was discovered by Johann Baptist von Spix in 1819. The strata were deposited during the Albian stage of the Early Cretaceous in a lacustrine rift basin with shallow marine incursions of the proto-Atlantic. At that time, the South Atlantic was opening up in a long narrow shallow sea.

The Romualdo Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse fossil faunal assemblage. Some 25 species of fossil fishes are often found with stomach contents preserved, enabling paleontologists to study predator–prey relationships in this ecosystem. There are also fine examples of pterosaurs, reptiles and amphibians, invertebrates (particularly insects), crocodylomorphs, and plants. Even dinosaurs are represented (Spinosauridae, Tyrannosauroidea, Compsognathidae). The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy. In preservation, the nodules are etched away with acid, and the fossils often prepared by the transfer technique.Local mining activities for cement and construction damage the sites. Trade in illegally collected fossils has sprung up in the last decade, driven by the remarkable state of preservation and beauty of these fossils and amounting to a considerable local industry. An urgent preservation program is being called for by paleontologists.

In addition, the weathering of Romualdo Formation rocks has contributed soil conditions unlike elsewhere in the region. The Araripe manakin (Antilophia bokermanni) is a very rare bird that was discovered only in the late 20th century; it is not known from anywhere outside the characteristic forest that grows on the Chapada do Araripe soils formed ultimately from Romualdo Formation rocks.

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 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.

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. 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). The latest estimates suggest a weight of 6.4–7.5 tonnes (7.1–8.3 short tons). 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.

Suchomimus

Suchomimus (meaning "crocodile mimic") is a genus of spinosaurid theropod dinosaur that lived between 125 to 112 million years ago in what is now Niger, during the Aptian to early Albian stages of the Early Cretaceous Period. The animal was named and described by Paul Sereno and colleagues, based on a partial skeleton from the Erlhaz Formation. Its long and shallow skull, similar to that of a crocodile, earns it its genus name, while the species Suchomimus tenerensis alludes to the locality of its first remains, the Ténéré Desert. Some palaeontologists consider the animal to be an African species of the European spinosaurid Baryonyx, B. tenerensis. Suchomimus might also be a junior synonym of the contemporaneous spinosaurid Cristatusaurus lapparenti, although the latter taxon is based on much more fragmentary remains.

Suchomimus was 9.5 to 11 metres (31 to 36 ft) long and weighed between 2.5 to 5.2 tonnes (2.8 to 5.7 short tons), although the holotype specimen may not have been fully grown. Suchomimus's narrow skull was perched on a short neck, and its forelimbs were powerfully built, bearing a giant claw on each thumb. Along the midline of the animal's back ran a low dorsal sail, built from the long neural spines of its vertebrae. Like other spinosaurids, it likely had a diet of fish and small prey animals.

Tetanurae

Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, maniraptorans, and birds. Tetanurans are defined as all theropods more closely related to modern birds than to Ceratosaurus and contain the majority of predatory dinosaur diversity. Tetanurae likely diverged from its sister group, Ceratosauria, during the late Triassic. Tetanurae first appeared in the fossil record by the Early Jurassic about 190 mya and by the Middle Jurassic had become globally distributed.The group was named by Jacques Gauthier in 1986 and originally had two main subgroups: Carnosauria and Coelurosauria, the clade containing birds and related dinosaurs such as compsognathids, tyrannosaurids, ornithomimosaurs, and maniraptorans. The original Carnosauria was a polyphyletic group including any large carnivorous theropod. Many of Gauthier’s carnosaurs, such as tyrannosaurids, have since been re-classified as coelurosaurs or primitive tetanurans. Carnosauria has been reclassified as a group containing allosaurids that split from the Coelurosauria at the Neotetanurae/Avetheropoda node. Members of Spinosauroidea are believed to represent basal tetanurans.Tetanuran evolution was characterized by parallel diversification of multiple lineages, repeatedly attaining large body size and similar locomotor morphology. Cryolophosaurus has been claimed as the first true member of the group, but subsequent studies have disagreed on whether it is a dilophosaurid or tetanuran. Arcucci and Coria (2003) classified Zupaysaurus as an early tetanuran, but it was later placed as a sister taxon to the clade containing dilophosaurids, ceratosaurs, and tetanurans.Shared tetanuran features include a ribcage indicating a sophisticated air-sac-ventilated lung system similar to that in modern birds. This character would have been accompanied by an advanced circulatory system. Other tetanuran characterizing features include the absence of the fourth digit of the hand, placement of the maxillary teeth anterior to the orbit, a strap-like scapula, maxillary fenestrae, and stiffened tails. During the Late Jurassic and Early Cretaceous, large spinosaurids and allosaurs flourished but possibly died out in the northern hemisphere before the end of the Cretaceous, and were replaced as apex predators by tyrannosauroid coelurosaurs. At least in South America, carcharodontosaurid allosaurs persisted until the end of the Mesozoic Era, and died out at the same time the non-avian coelurosaurs.

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