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85-669: The divergence rate between the two plates along the ridge is believed to vary from about 5.4 centimetres per year (2.1 in/year) near 65°S to 7.4 centimetres per year (2.9 in/year) near the Udintsev Fracture Zone at 55°S. The ridge is related to the Late Cretaceous breakup of Gondwana . To the southeast the historic Bellingshausen Plate separated the Pacific and Antarctic plates between about 84 to 61 million years ago. Until about 33 million years ago,

170-530: A baryonychine from Niger , on the basis of a partial skeleton found in 1997. 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 . On 2021 a recent discovery in Isle of Wight an island off the south coast of England, remains of a spinosaurid which is said to be of a new species

255-460: A semiaquatic lifestyle for some members of this clade . This is further indicated by various anatomical adaptations, such as retracted eyes and nostrils; and the deepening of the tail in some taxa, which has been suggested to have aided in underwater propulsion akin to that of modern crocodilians . Spinosaurs are proposed to be closely related to the megalosaurid theropods of the Jurassic. This

340-674: A European origin for spinosaurids in 2021, with an expansion to Asia and Gondwana during the first half of the Early Cretaceous. In contrast to Sereno, these authors suggested there had been at least two dispersal events from Europe to Africa, leading to Suchomimus and the African part of Spinosaurinae. 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

425-416: A greater reliance on its sense of smell and had a more piscivorous lifestyle than Irritator and baryonychines. 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

510-501: A high degree of similarity with those of other non-maniraptoriform theropods. Lengthwise atop their skulls 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. Spinosaurus 's head crest was comb-shaped and bore distinct vertical grooves, while those of Baryonyx and Suchomimus looked like small triangular bumps. Irritator ' s median crest stopped above and behind

595-535: A monophyletic Megalosauroidea inside a more inclusive Carnosauria that is made up of both allosauroids and megalosauroids. The first spinosaurid fossil , a single conical tooth, was discovered circa 1820 by British paleontologist Gideon Mantell in the Wadhurst Clay Formation . In 1841 , naturalist Sir Richard Owen mistakenly assigned it to a crocodilian he named Suchosaurus (meaning "crocodile lizard"). A second species, S. girardi ,

680-637: A new spinosaur was announced with the name of Riojavenatrix lacustris . Originally discovered in La Rioja in 2005, it is the 5th spinosaur species to be discovered in the Iberian Peninsula. It was found to have lived 120 million years ago and was around 7-8 metres long with a 1.5 metric ton body mass. Although reliable size and weight estimates for most known spinosaurids are hindered by the lack of good material, all known spinosaurids were large animals. The smallest genus known from good material

765-653: A northward course towards Asia. In the Southern Hemisphere, Australia and Antarctica seem to have remained connected and began to drift away from Africa and South America. Europe was an island chain. Populating some of these islands were endemic dwarf dinosaur species. In the Late Cretaceous, the hadrosaurs , ankylosaurs , and ceratopsians experienced success in Asiamerica (Western North America and eastern Asia). Tyrannosaurs dominated

850-399: A phylogenetic analysis incorporating a general range of theropods, but mostly focusing on Spinosauridae. The results of the analysis appear below: Megalosauridae [REDACTED] Baryonyx [REDACTED] "Spinosaurus B" MSNM V4047 FSAC-KK 11888 See also the phylogenetic results in the 2022 article describing Iberospinus . Spinosaurids appear to have been widespread from

935-667: A relatively complete skeleton was excavated from the Smokejacks pit in Surrey , England . 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, with the majority from 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 ,

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1020-444: A spoon-shaped structure similar to a rosette , behind which there was a notch in the upper jaw that the expanded tip of the lower jaw fit into. The nostrils of spinosaurids were retracted to a position further back on the head than in most other theropods, and they had bony crests on their heads along the midline of their skulls. Their robust shoulders wielded stocky forelimbs, with three-fingered hands that bore an enlarged claw on

1105-471: A strong grip on a struggling prey animal. Spinosaurid jaws were likened by Romain Vullo and colleagues to those of the pike conger eel , in what they hypothesized was convergent evolution for aquatic feeding. 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

1190-536: A very different dinosaurian fauna, with most predators being abelisaurids and carcharodontosaurids ; and titanosaurs being among the dominant herbivores. Spinosaurids were also present during this time. Birds became increasingly common, diversifying in a variety of enantiornithe and ornithurine forms. Early Neornithes such as Vegavis co-existed with forms as bizarre as Yungavolucris and Avisaurus . Though mostly small, marine Hesperornithes became relatively large and flightless, adapted to life in

1275-458: A weight of 5 to 7 t (5.5 to 7.7 short tons; 4.9 to 6.9 long tons). The largest known genus is Spinosaurus , which was capable of reaching lengths of 14 m (46 ft) and weighed around 7.4 t (8.2 short tons; 7.3 long tons), making it the longest known theropod dinosaur and terrestrial predator . The closely allied Sigilmassasaurus may have grown to a similar or greater length, though its taxonomic relationship with Spinosaurus

1360-414: 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. Moreover, there is a documented example of a spinosaurid having eaten a pterosaur , as one Irritator tooth was found lodged within the fossil vertebrae of an ornithocheirid pterosaur found in

1445-430: Is Irritator , which was between 6 and 8 meters (20 and 26 feet) long and around 1 metric ton (1.1 short tons ; 0.98 long tons ) in weight. Ichthyovenator , Baryonyx , and Suchomimus ranged from 7.5 to 11 m (25 to 36 ft) long, and weighed between 1 and 5.2 t (1.1 and 5.7 short tons; 0.98 and 5.12 long tons). Oxalaia may have reached a length of between 12 and 14 m (39 and 46 ft) and

1530-572: Is a clade or family of tetanuran theropod dinosaurs comprising ten to seventeen known genera . Spinosaurid fossils have been recovered worldwide, including Africa , Europe , South America and Asia . Their remains have generally been attributed to the Early to Mid Cretaceous . Spinosaurids were large bipedal carnivores . Their crocodilian -like skulls were long, low and narrow, bearing conical teeth with reduced or absent serrations . The tips of their upper and lower jaws fanned out into

1615-492: Is due to both groups sharing many features such an enlarged claw on their first manual ungual and an elongated skull. However, some propose that this group (which is known as the Megalosauroidea) is paraphyletic and that spinosaurs represent either the most basal tetanurans or as basal carnosaurs which are less derived than the megalosaurids. Some have proposed a combination of the two ideas with spinosaurs being in

1700-687: Is found. As per the findings, it is about 10 meters in length and weighed several tons. The prehistoric bones of the spinosaurid were found in a geological layer of rock known as the Vectis Formation in Compton Chine, it is the first identifiable theropod from the Vectis Formation. The study was led by Christopher Barker, a PhD doctoral student in vertebrate paleontology at the University of Southampton . In February 2024,

1785-479: Is it particularly evident that a true systematic decline was ever in place, especially with the discovery of smaller pterosaur species. Several old mammal groups began to disappear, with the last eutriconodonts occurring in the Campanian of North America . In the northern hemisphere, cimolodont , multituberculates , metatherians and eutherians were the dominant mammals, with the former two groups being

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1870-575: Is marked by unserrated, straight teeth, and external nares which are further back on the skull than in baryonychines, and Baryonychinae, which contains the genera Baryonyx , Cristatusaurus , Suchosaurus , Suchomimus , Ceratosuchops , and Riparovenator, which is marked by serrated, slightly curved teeth, smaller size, and more teeth in the lower jaw behind the terminal rosette than in spinosaurines. Others, such as Siamosaurus , may belong to either Baryonychinae or Spinosaurinae, but are too incompletely known to be assigned with confidence. Siamosaurus

1955-640: Is the longest known terrestrial predator from the fossil record, with an estimated length of up to 14 meters (46 ft) and body mass of up to 7.4 metric tons (8.2 short tons) (similar to the weight of an African elephant ). The closely related genus Sigilmassasaurus may have reached a similar or greater size, though its taxonomy is disputed. Direct fossil evidence and anatomical adaptations indicate that spinosaurids were at least partially piscivorous (fish-eating), with additional fossil finds indicating they also fed on other dinosaurs and pterosaurs . The osteology of spinosaurid teeth and bones has suggested

2040-582: Is the most extreme example and a fish specialist; Australian freshwater crocodiles , 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. Further study by Andrew R. Cuff and Rayfield in 2013 on

2125-606: Is theorized to be probable that the Spinosaurus 's feet were webbed . The upward-projecting neural spines of spinosaurid vertebrae (backbones) were very tall, more so than in most theropods. In life, these spines would have been covered in skin or fat tissue and formed a sail down the animal's back, a condition that has also been observed in some carcharodontosaurid and ornithopod dinosaurs. The eponymous neural spines of Spinosaurus were extremely tall, measuring over 1 m (3 ft 3 in) in height on some of

2210-443: Is uncertain. 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 theropod dinosaurs for food, they would have been able to grow to massive lengths. Spinosaurid skulls —similar in many respects to those of crocodilians—were long, low and narrow. As in other theropods, various fenestrae (openings) in

2295-652: The Barremian to the Cenomanian stages of the Cretaceous period , about 130 to 95 million years ago. Possibly the earliest remains of spinosaurids are known from the Middle Jurassic of Niger and India, the latter of which otherwise has no remains of spinosaurids. They shared features such as long, narrow, crocodile-like skulls; sub-circular teeth, with fine to no serrations; the terminal rosette of

2380-694: The Cretaceous Period is divided in the geologic time scale . Rock strata from this epoch form the Upper Cretaceous Series . The Cretaceous is named after creta , the Latin word for the white limestone known as chalk . The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period. During the Late Cretaceous, the climate was warmer than present, although throughout

2465-583: The Deccan Traps , both of which have been firmly dated to the time of the extinction event. In theory, these events reduced sunlight and hindered photosynthesis , leading to a massive disruption in Earth's ecology . A much smaller number of researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate . Spinosauridae *disputed validity; = Spinosaurus ? Spinosauridae (or spinosaurids )

2550-921: The Proto-Antipodes Fracture Zone well to the south separated two independent spreading centers, now merged, being the Antarctic–Pacific Ridge and that of the Antarctic–Campbell Plateau. Stretching for 4,300 km north-west from the Eltanin Fault System which intersects the Pacific-Antarctic Ridge to the Osbourn Seamount at Tonga and Kermadec Junction is a long line of seamounts called the Louisville Ridge –

2635-838: The Romualdo Formation of Brazil. This may represent a predation or a scavenging event. A fossil snout referred to Spinosaurus was discovered with a vertebra from the sclerorhynchid Onchopristis embedded in it. 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. The Portuguese Iberospinus fossils were also found associated with isolated Iguanodon teeth, and those cases are listed; along with other such associations as support for opportunistic feeding behaviour in spinosaurids. A 2018 study by Auguste Hassler and colleagues of calcium isotopes in

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2720-417: The crown was often ornamented with longitudinal grooves or ridges. The coracoid bones of the shoulders in spinosaurids were robust and hook shaped. The arms were relatively large and well-built; the radius (long bone of the forearm) was stout and usually only half as long as the humerus (upper arm bone). Spinosaurid hands had three fingers, typical of tetanurans , and wielded an enlarged ungual on

2805-419: The dorsal (back) vertebrae. Suchomimus had a lower, ridge-like sail across the majority of its back, hip, and tail region. Baryonyx showed a reduced sail, with a few of the rearmost vertebral spines being somewhat elongated. Ichthyovenator had a sinusoidal (wave-like) sail that was separated in two over the hips, with the upper ends of some neural spines being broad and fan-shaped. A neural spine from

2890-409: The hallux (first toe) being reduced and elevated off the ground— Spinosaurus walked on four functional toes, with an enlarged hallux that came in contact with the ground. The unguals of its feet, in contrast with the deeper, smaller and recurved unguals of other theropods, were shallow, long, large in relation to the foot, and had flat bottoms. Based on comparisons with those of modern shorebirds , it

2975-635: The supercontinent Pangea , but split with the opening of the Tethys Sea . Spinosaurines would then have evolved in the south (Africa and South America: in Gondwana ) and baryonychines in the north (Europe: in Laurasia ), with Suchomimus the result of a single north-to-south dispersal event . Buffetaut and the Tunisian palaeontologist Mohamed Ouaja also suggested in 2002 that baryonychines could be

3060-500: The Cenomanian anywhere in the world. They attributed the disappearance of spinosaurids and other shifts in the fauna of Gondwana to changes in the environment, perhaps caused by transgressions in sea level . Malafaia and colleagues stated in 2020 that Baryonyx remains the oldest unquestionable spinosaurid, while acknowledging that older remains had also been tentatively assigned to the group. Barker and colleagues found support for

3145-859: The Cretaceous Period derived from the German name Kreidezeit , and T is the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). The event marks the end of the Mesozoic Era and the beginning of the Cenozoic Era. "Tertiary" being no longer recognized as a formal time or rock unit by the International Commission on Stratigraphy ,

3230-620: 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. In a 2017 review of the family, David Hone and Holtz considered possible functions in digging for water sources or hard to reach prey, as well as burrowing into soil to construct nests. Theropod heads are often decorated with some form of crest, horn, or rugose structure, which in life, would have been extended by keratin. Though there has been little discussion on

3315-633: The Iberian region was a stepping stone between Europe and Africa, which is supported by the presence of baryonychines in Iberia. The direction of the dispersal between Europe and Africa is still unknown, and subsequent discoveries of spinosaurid remains in Asia and possibly Australia indicate that it may have been complex. In 2016, the Spanish palaeontologist Alejandro Serrano-Martínez and colleagues reported

3400-850: The K-T event is now called the Cretaceous—Paleogene (or K-Pg) extinction event by many researchers. Non- avian dinosaur fossils are found only below the Cretaceous–Paleogene boundary and became extinct immediately before or during the event. A very small number of dinosaur fossils have been found above the Cretaceous–Paleogene boundary, but they have been explained as reworked fossils , that is, fossils that have been eroded from their original locations then preserved in later sedimentary layers. Mosasaurs , plesiosaurs , pterosaurs and many species of plants and invertebrates also became extinct. Mammalian and bird clades passed through

3485-425: The also expanded tips of the dentaries (tooth bearing bones of the mandible) fit into, with a notch behind the expansion of the dentary. The maxillae (main upper jaw bones) were long and formed a low branch under the nostrils that connected to the rear of the premaxillae. The teeth at the frontmost part of the maxillae were small, becoming significantly larger soon after and then gradually decreasing in size towards

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3570-556: The ancestors of spinosaurines, which appear to have replaced the former in Africa. Milner suggested in 2003 that spinosaurids originated in Laurasia during the Jurassic, and dispersed via the Iberian land bridge into Gondwana, where they radiated . In 2007, Buffetaut pointed out that palaeogeographical studies had demonstrated that Iberia was near northern Africa during the Early Cretaceous, which he found to confirm Milner's idea that

3655-515: The animal; or for display purposes, such as intimidating rivals and predators, or attracting mates. 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. In 1915, Stromer speculated that the size of the neural spines may have differed between males and females. In 2012, French paleontologist Ronan Allain and colleagues suggested considering

3740-468: The back of the jaw. Analysis of the teeth of spinosaurids and their comparison to the teeth of tyrannosaurids suggest that the deep roots of spinosaurids helped to better anchor the teeth of these animals and distribute the stress against lateral forces generated during bites in predation and feeding scenarios. Despite their highly modified skulls, analysis of the endocasts of Baryonyx walkeri and Ceratosuchops inferodios reveals spinosaurid brains shared

3825-524: The boundary with few extinctions, and evolutionary radiation from those Maastrichtian clades occurred well past the boundary. Rates of extinction and radiation varied across different clades of organisms. Many scientists hypothesize that the Cretaceous–Paleogene extinctions were caused by catastrophic events such as the massive asteroid impact that caused the Chicxulub crater , in combination with increased volcanic activity , such as that recorded in

3910-638: The carcass with the large claws, and subsequently probing for viscera with its long snout. 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. Later research has also ruled out this sort of specialized scavenging. In 1986, Charig and Milner 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. A 2005 study by Canadian paleontologist

3995-474: 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. Based on the size and positions of their nostrils, Marcos Sales and Cesar Schultz in 2017 suggested that Spinosaurus possessed

4080-791: The diet of spinosaurines from this environment may have included—in addition to pterosaurs—terrestrial and aquatic crocodyliforms , juveniles of their own species, turtles, and small to medium-sized dinosaurs. This would have made spinosaurines apex predators within this particular ecosystem. A 2024 study by D'Amore et al., further vindicates the theory that spinosaurids were similar in niche to generalist or macro-generalist crocodilians. This study likewise suggests their jaws and teeth were well-suited to quick strikes and deep, puncturing bites, but not for slicing flesh or crushing bones. In particular, baryonychine spinosaurids probably did little oral processing of their prey when feeding, but by comparison, spinosaurines were found to be quite capable of processing

4165-404: The eyes in a bulbous, flattened shape. However, given that no fully preserved skulls are known for the genus, the complete shape of Irritator 's crest is unknown. Cristatusaurus and Suchomimus (a possible synonym of the former) both had narrow premaxillary crests. Angaturama (a possible synonym of Irritator ) had an unusually tall crest on its premaxillae that nearly overhung the tip of

4250-615: The family Baryonychidae for the newly discovered Baryonyx , before it was referred to 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. A study by Arden et al. 2018 named

4335-406: The first digit . In many species , the upwards-projecting neural spines of the vertebrae (backbones) were significantly elongated and formed a sail on the animal's back (hence the family's etymology), which supported either a layer of skin or a fatty hump. The genus Spinosaurus , from which the family, one of its subfamilies (Spinosaurinae) and tribes (Spinosaurini) borrow their names,

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4420-577: The first finger (or "thumb"), which formed the bony core of a keratin claw. In genera like Baryonyx and Suchomimus , the phalanges (finger bones) were of conventional length for large theropods, and bore hook-shaped, strongly curved hand claws. Based on fragmentary material from the forelimbs of Spinosaurus , it appears to have had longer, more gracile hands and straighter claws than other spinosaurids. The hindlimbs of Suchomimus and Baryonyx were somewhat short and mostly conventional of other megalosauroid theropods. Ichthyovenator 's hip region

4505-709: The former features are shared with their megalosaurid relatives. They also suggested that the spinosaurines and baryonychines diverged before the Barremian age of the Early Cretaceous. Several theories have been proposed about the biogeography of the spinosaurids. Since Suchomimus was more closely related to Baryonyx (from Europe) than to Spinosaurus —although that genus also lived in Africa—the distribution of spinosaurids cannot be explained as vicariance resulting from continental rifting . Sereno and colleagues proposed that spinosaurids were initially distributed across

4590-513: 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 other predators. Such has been suggested for theropod cranial structures before, which may have been aided by unusual or bright coloration to provide further visual cues. Many theories have been proposed over the years for the use of spinosaurid dorsal sails, such as thermoregulation ; to aid in swimming; to store energy or insulate

4675-540: The high diversity in neural spine elongation observed in theropod dinosaurs, as well as histological research done on the sails of synapsids (stem mammals), the sinusoidal sail of Ichthyovenator was likely used for courtship display or recognising members of its own species . In a 2013 blog post, Darren Naish considered the latter function unlikely, favouring the hypothesis of sexual selection for Ichthyovenator ' s sail because it appears to have evolved on its own, without very close relatives. Naish also notes it

4760-430: The holotype of Vallibonavenatrix shows a similar morphology to those of Ichthyovenator , indicating the presence of a sail in this genus as well. One partial skeleton possibly referable to Angaturama also had elongated neural spines on its hip region. The presence of a sail in fragmentary taxa like Sigilmassasaurus is unknown. In members of the subfamily Spinosaurinae, like Ichthyovenator and Spinosaurus ,

4845-613: The large predator niche in North America. They were also present in Asia, although were usually smaller and more primitive than the North American varieties. Pachycephalosaurs were also present in both North America and Asia. Dromaeosaurids shared the same geographical distribution, and are well documented in both Mongolia and Western North America. Additionally therizinosaurs (known previously as segnosaurs) appear to have been in North America and Asia. Gondwana held

4930-524: The longest such chain in the Pacific – thought to have formed from the Pacific Plate sliding over a long-lived center of upwelling magma called the Louisville hotspot . 61°59′58″S 157°00′01″W  /  61.999555°S 157.000165°W  / -61.999555; -157.000165 Late Cretaceous The Late Cretaceous (100.5–66 Ma ) is the younger of two epochs into which

5015-515: The lower jaw fit, with the full structure called a terminal rosette. 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. In 2007, British paleontologist Emily J. Rayfield and colleagues 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

5100-404: The meat of relatively large vertebrate prey. None of these findings suggest any spinosaurids from either subfamily were restricted only to fish and small aquatic vertebrates. 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

5185-636: The most common mammals in North America. In the southern hemisphere there was instead a more complex fauna of dryolestoids , gondwanatheres and other multituberculates and basal eutherians ; monotremes were presumably present, as was the last of the haramiyidans , Avashishta . Mammals, though generally small, ranged into a variety of ecological niches, from carnivores ( Deltatheroida ), to mollusc-eater ( Stagodontidae ), to herbivores (multituberculates, Schowalteria , Zhelestidae and Mesungulatidae ) to highly atypical cursorial forms ( Zalambdalestidae , Brandoniidae ). True placentals evolved only at

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5270-411: The neural spines of the caudal (tail) vertebrae were tall and reclined, accompanied by also elongated chevrons —long, thin bones that form the underside of the tail. This was most pronounced in Spinosaurus , in which the spines and chevrons formed a large paddle-like structure, deepening the tail significantly along most of its length. The family Spinosauridae was named by Stromer in 1915 to include

5355-401: The new term Spinosaurini for the clade of Sigilmassasaurus and Spinosaurus . Baryonyx walkeri [REDACTED] Eumeralla taxon Gara Samani taxon In 2021, Chris Barker, Hone, Darren Naish , Andrea Cau , Lockwood, Foster, Clarkin, Schneider, and Gostling described two new spinosaurid species, Ceratosuchops inferodios and Riparovenator milnerae . In the paper, they performed

5440-540: The numerous teleost fishes, which in turn evolved into new advanced and modern forms ( Neoteleostei ). Ichthyosaurs and pliosaurs , on the other hand, became extinct during the Cenomanian-Turonian anoxic event . Near the end of the Cretaceous Period, flowering plants diversified. In temperate regions, familiar plants like magnolias , sassafras , roses , redwoods , and willows could be found in abundance. The Cretaceous–Paleogene extinction event

5525-673: The oldest known spinosaurid fossil, a tooth from the Middle Jurassic of Niger, which they found to suggest that spinosaurids originated in Gondwana, since other known Jurassic spinosaurid teeth are also from Africa, but they found the subsequent dispersal routes unclear. Some later studies instead suggested this tooth belonged to a megalosaurid . Candeiro and colleagues suggested in 2017 that spinosaurids of northern Gondwana were replaced by other predators, such as abelisauroids , since no definite spinosaurid fossils are known from after

5610-407: The open sea. Though primarily represented by azhdarchids , other forms like pteranodontids , tapejarids ( Caiuajara and Bakonydraco ), nyctosaurids and uncertain forms ( Piksi , Navajodactylus ) are also present. Historically, it has been assumed that pterosaurs were in decline due to competition with birds, but it appears that neither group overlapped significantly ecologically, nor

5695-539: The period a cooling trend is evident. The tropics became restricted to equatorial regions and northern latitudes experienced markedly more seasonal climatic conditions. Due to plate tectonics , the Americas were gradually moving westward, causing the Atlantic Ocean to expand. The Western Interior Seaway divided North America into eastern and western halves; Appalachia and Laramidia . India maintained

5780-402: The result of a dietary change from terrestrial prey to fish. Unlike crocodiles, the post-cranial skeletons of baryonychine spinosaurids do not appear to have aquatic adaptations. Sereno and colleagues proposed in 1998 that the large thumb-claw and robust forelimbs of spinosaurids evolved in the Middle Jurassic, before the elongation of the skull and other adaptations related to fish-eating, since

5865-469: 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 suggested that the skulls were 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. In 2002, Hans-Dieter Sues and colleagues studied

5950-487: The roof of their mouths that are also found in extant crocodilians, but not in most theropod dinosaurs. Oxalaia had a particularly elaborate secondary palate, while most spinosaurs had smoother ones. The teeth of spinosaurids were conical, with an oval to circular cross section and either absent or very fine serrations . Their teeth ranged from slightly recurved, such as those of Baryonyx and Suchomimus , to straight, such as those of Spinosaurus and Siamosaurus , and

6035-460: 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 "). Traditionally, Spinosauridae is divided into two subfamilies: Spinosaurinae, which contains the genera Icthyovenator , Irritator , Oxalaia , Sigilmassasaurus and Spinosaurus ,

6120-399: The skull aided in reducing its weight. In spinosaurs however, the antorbital fenestrae were greatly reduced, akin to those of crocodilians. The tips of the premaxillae (frontmost snout bones) were expanded in a spoon shape, forming what has been called a "terminal rosette " of enlarged teeth. Behind this expansion, the upper jaw had a notch bearing significantly smaller teeth, into which

6205-475: 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

6290-610: The snout with a small forward protrusion. Spinosaurid 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. 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. Spinosaurids had long secondary palates , bony and rugose structures on

6375-481: The snout; and a secondary palate that made them more resistant to torsion. In contrast, the primitive and typical condition for theropods was a tall, narrow snout with blade-like (ziphodont) teeth with serrated carinae. The skull adaptations of spinosaurids converged with those of crocodilians ; early members of the latter group had skulls similar to typical theropods, later developing elongated snouts, conical teeth, and secondary palates. These adaptations may have been

6460-411: 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

6545-461: 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. Later in 2018, Tito Aureliano and colleagues presented a possible scenario for the food web of Brazilian Romualdo Formation. The researchers proposed that

6630-830: The tribe Spinosaurini to include Spinosaurus and Sigilmassasaurus , the latter of which's validity as a spinosaurid is debated. In 2021 Barker et al. named the new tribe Ceratosuchopsini within the Baryonychinae to encompass Suchomimus , Riparovenator , and Ceratosuchops . The 2017 study mentioned above indicates that Baryonychinae may in fact be non-monophyletic. Their cladogram can be seen below. Baryonyx [REDACTED] The next cladogram displays an analysis of Tetanurae simplified to show only Spinosauridae from Allain colleagues in 2012: Baryonyx [REDACTED] The 2018 phylogenetic analysis by Arden and colleagues, which included many unnamed taxa, resolved Baryonychinae as monophyletic, and also coined

6715-548: 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 . In 1934, Stromer referred a partial skeleton also from the Bahariya Formation to a new species of Spinosaurus; the specimen has since been alternatively assigned to another African spinosaurid, Sigilmassasaurus . In 1983,

6800-433: The very end of the epoch; the same can be said for true marsupials . Instead, nearly all known eutherian and metatherian fossils belong to other groups. In the seas, mosasaurs suddenly appeared and underwent a spectacular evolutionary radiation. Modern sharks also appeared and penguin-like polycotylid plesiosaurs (3 meters long) and huge long-necked elasmosaurs (13 meters long) also diversified. These predators fed on

6885-399: The water, similarly to grizzly bears . 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

6970-537: Was a large-scale mass extinction of animal and plant species in a geologically short period of time, approximately 66  million years ago (Ma). It is widely known as the K–T extinction event and is associated with a geological signature, usually a thin band dated to that time and found in various parts of the world, known as the Cretaceous–Paleogene boundary (K–T boundary). K is the traditional abbreviation for

7055-399: Was classified as a spinosaurine in 2018, but the results are provisional and not entirely conclusive. The subfamily Spinosaurinae was named by Sereno in 1998, and defined by Thomas Holtz and colleagues in 2004 as all taxa closer to Spinosaurus aegyptiacus than to Baryonyx walkeri . The subfamily Baryonychinae was named by Charig & Milner in 1986. They erected both the subfamily and

7140-668: Was later named in 1897 . However, the spinosaurid nature of Suchosaurus was not recognized until a 1998 redescription of Baryonyx . The first fossils referred to a spinosaurid were discovered in 1912 at the Bahariya Formation in Egypt. Consisting of 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

7225-462: Was reduced, having the shortest pubis (pubic bone) and ischium (lower and rearmost hip bone) in proportion to the ilium (main hip bone) of any other known theropod. Spinosaurus had an even smaller pelvis and hindlimbs in proportion to its body size; its legs composed just over 25 percent of the total body length. Substantially complete spinosaurid foot remains are only known from Spinosaurus . Unlike most theropods—which walk on three toes, with

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