The Santana Group is a geologic group, formerly included as the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil . The group comprises the Crato , Ipubi and Romualdo Formations and is dated to the Aptian to Albian stages of the Early Cretaceous . The formations of the group were deposited in a lacustrine to subtidal shallow marine environment in the Araripe rift basin .
152-496: The Santana Group has provided a rich assemblage of fossils; flora, fish, arthropods insects, turtles, snakes, dinosaurs including Irritator , and pterosaurs such as Thalassodromeus . The stratigraphic units of the group contained several feathers of birds, among those the first record of Mesozoic birds in Brazil. The Romualdo and Crato Formations are renowned for their excellent conservation and designated Lagerstätten . In 2006,
304-540: A display function when the animal was alive. The preserved part of Irritator ' s crest is deepest above the antorbital fenestra and lacks the vertical ridges seen in the crest of Spinosaurus . Like others in its family , Irritator possessed a long and bony structure on the roof of its mouth called a secondary palate , separating the oral from the nasal cavity. This is a feature observed in extant crocodilians , but absent in most theropod dinosaurs. Also like its relatives, Irritator had two additional openings on
456-551: 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
608-557: A chalk concretion containing the rear of a large skull with lower jaws near the town of Santana do Cariri in northeastern Brazil . This fossil was acquired by dealers who sold it to Rupert Wild of the State Museum of Natural History Stuttgart , Germany. At the time it was assumed to be the skull of a giant basal pterosaur , or flying reptile, since the Chapada do Araripe region is famous for its copious pterosaur finds, and
760-627: A common dental trait among spinosaurids. Both sides of Irritator ' s teeth were fluted, as in Spinosaurus , whereas Baryonyx exhibited them only on the lingual (inward facing) side of its teeth. Irritator ' s teeth were circular in cross section, as opposed to the laterally flattened condition of most theropod teeth. The enamel (first layer of the teeth) was thin, with a finely wrinkled texture also observed in Baryonyx. Both of Irritator ' s maxillae preserve nine teeth, although
912-728: A consequence of the Atlantic Ocean , whose opening gradually separated the continents and contributed to differences between taxa. A similar scenario was suggested in 2014 by Brazilian paleontologist Manuel A. Medeiros and colleagues for the fauna of the Alcântara Formation, where Oxalaia has been found. But the paleobiogeography of spinosaurids remains highly theoretical and uncertain, with discoveries in Asia and Australia indicating that it may have been complex. The taphonomy (changes between death and fossilization) of
1064-994: A cranial capacity about 10 percent less than that of the male. However, later studies show that women's skulls are slightly thicker and thus men may be more susceptible to head injury than women. However, other studies shows that men's skulls are slightly thicker in certain areas. Some studies show that females are more susceptible to concussion than males. Men's skulls have also been shown to maintain density with age, which may aid in preventing head injury, while women's skull density slightly decreases with age. Male skulls can all have more prominent supraorbital ridges , glabella , and temporal lines . Female skulls generally have rounder orbits and narrower jaws. Male skulls on average have larger, broader palates , squarer orbits, larger mastoid processes , larger sinuses , and larger occipital condyles than those of females. Male mandibles typically have squarer chins and thicker, rougher muscle attachments than female mandibles. The cephalic index
1216-491: A distinct ecological niche , therefore avoiding competition with more terrestrial theropods. Spinosaurines appear to have been more adapted for such lifestyles than baryonychines. A 2018 study by British paleontologist Thomas M. S. Arden and colleagues examined the morphology of spinosaurine skull bones for possible aquatic traits. They found that the frontal bones of Irritator , Spinosaurus , and Sigilmassasaurus were similar in being arched, concave on top, and narrowed at
1368-576: A fire broke out at the palace housing the Museu Nacional, largely destroying the fossil collections and possibly the exhibited Angaturama skeleton and fossil elements. The holotype of Oxalaia quilombensis , which was stored in the same building, may also have been destroyed. Even by maximal size estimates, Irritator was smaller than other known spinosaurids. Gregory S. Paul calculated its length at 7.5 meters (25 ft) and weight at 1 tonne (1.1 short tons). Thomas R. Holtz Jr. published
1520-487: A higher estimate of 8 meters (26 ft), with a weight between 0.9 to 3.6 tonnes (0.99 to 3.97 short tons). Estimates by Dougal Dixon were lower at 6 meters (20 ft) long and 2 meters (6.6 ft) high. When scaled by Aureliano and colleagues, the reconstructions from the study by Sales and Schultz provided a length of 6.5 meters (21 ft) for the Irritator challengeri holotype, and 8.3 meters (27 ft) for
1672-509: A large amount of tension on the "obstetrical hinge", which is where the squamous and lateral parts of the occipital bone meet. A possible complication of this tension is rupture of the great cerebral vein . As growth and ossification progress, the connective tissue of the fontanelles is invaded and replaced by bone creating sutures . The five sutures are the two squamous sutures , one coronal , one lambdoid , and one sagittal suture . The posterior fontanelle usually closes by eight weeks, but
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#17327725974731824-543: A left tibia from a particularly large individual. As is common with fossils from the Araripe Basin , the majority of spinosaurid material from the Romualdo Formation was collected under uncontrolled circumstances for use in the illegal fossil trade. As such, many specimens are partly damaged and without precise geological field data. Some of the Romualdo Formation postcrania were used as the basis for
1976-602: A major sag phase, and is formed by two stratigraphic units: The upper and lower formations of the group are highly fossiliferous, with mainly insects, amphibians, fish, and flora dominating the lower Crato Formation, shrimps ( Araripenaeus timidus ), and various genera of dinosaurs and fish in the Romualdo Formation. A rich assemblage of pterosaur fossils are found in both formations, and the Ipubi Formation provided an indeterminate Pelomedusoides turtle. The Santana Group provided several feathers of birds, among those
2128-409: A member of the same genus, the latter would be the valid scientific name under rules of priority , since it was named almost a month earlier. The paleontologist Marco Schade and colleagues could not confirm the overlap in tooth positions in 2023 due to interpreting them differently, and could not provide information to resolve the issue. Besides the skull, the snout fragment, and some isolated teeth,
2280-477: A more developed obturator process , a blade-like structure on the bottom of the ischium. Martill and his team originally classified Irritator as a maniraptoran dinosaur in the clade Bullatosauria (a group no longer considered monophyletic ), as a close relative to the feathered ornithomimosaurs and troodontids . Given that its dental morphology , particularly long snout, and assumed fin-shaped crest were features unknown in "other" maniraptorans,
2432-450: A partial right tibia and fibula (shin and calf bones), most of the right femur (thigh bone), and part of an ulna (forearm bone). It also has the most complete hand known from a spinosaurid, including metacarpals , phalanges , one carpals , and one claw . Like in all spinosaurids, the claw of the first finger (the "thumb") was enlarged. The pelvic bones are well preserved, with
2584-726: A partly piscivorous (fish-eating) diet. Although much of the holotype's morphology turned out to be greatly different than they thought, later studies supported these observations. Spinosaurids had very narrow and elongated jaws with relatively homogeneous pointed teeth, an arrangement found particularly in animals like the Indian gharial —the most piscivorous extant crocodilian. The long conical teeth, which in spinosaurines did not possess serrated edges, were suitable for grabbing and holding prey. They differed from teeth of other theropods, which seemed geared towards tearing or cutting off seized body parts. Irritator shared with crocodilians
2736-478: A possible point of overlap, the third left maxillary tooth, and observed that the skull of Angaturama could have been larger than that of Irritator based on the proportions of the closely related genus Baryonyx . They therefore concluded that the two specimens do not belong to the same individual, Sales and Schultz noted that synonymy at the genus level would need to be verified by more extensively overlapping remains. If Angaturama and Irritator are regarded as
2888-482: A sagittal crest on Angaturama ' s premaxillae may correspond with that of Irritator ' s nasal bones. Some objection has been raised to these assertions. Kellner and Campos in 2000 and Brazilian paleontologist Elaine B. Machado and Kellner in 2005 expressed the opinion that the fossils come from two different genera, and that the holotype of Angaturama limai was clearly more laterally flattened than that of Irritator challengeri . A review of both fossils by
3040-436: A septarian concretion . The tip of the upper jaw was also missing. Since there were no signs of erosion, it had most probably broken off during or after the fossil's collection. Evident corrosion on certain bones indicates acid preparation had been attempted. A vertical fracture was present across the middle of the skull, which had apparently been sealed with car body filler. In hopes of making it look more complete and valuable,
3192-403: A series of only loosely connected bones. Lampreys and sharks only possess a cartilaginous endocranium, with both the upper jaw and the lower jaws being separate elements. Bony fishes have additional dermal bone , forming a more or less coherent skull roof in lungfish and holost fish. The lower jaw defines the chin. The simpler structure is found in jawless fish , in which the cranium
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#17327725974733344-552: A sideways-facing opening in the lower jaw, was oval and comparatively large. The dentary (tooth-bearing bone of the mandible) is unknown in Irritator , save for a possible remnant at the front of the surangular. Irritator challengeri ' s holotype is unique in that it is one of the few non-avian (or non-bird) dinosaur fossils found with a preserved stapes . Irritator had straight or only faintly recurved conical teeth, bearing sharply defined but unserrated edges. Flutes (lengthwise ridges) were present on its tooth crowns,
3496-477: A snout tip that was described a few weeks later also 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
3648-607: A spinosaurid and synonymized Irritatoridae with that family. Irritator was then assigned to the Baryonychidae along with Angaturama , Baryonyx , Suchomimus, and Spinosaurus by Oliver W.M. Rauhut in 2003. Thomas Holtz and colleagues in 2004 considered the Baryonychidae synonymous with Spinosauridae, and moved these genera to the latter family. Most later revisions have upheld these classifications. As spinosaurids, Irritator and Angaturama are placed within
3800-527: A stiff secondary palate and reduced antorbital fenestrae. In 2007, a finite-element analysis study by British paleontologist Emily J. Rayfield and colleagues found that these attributes, present in other spinosaurids as well, made the skull more resistant to torsion from prey item loads when feeding. The authors pointed out that in contrast, most theropods lacked secondary palates and had large antorbital fenestrae, exchanging strength for lighter skull builds. The nostrils of Irritator were shifted far back from
3952-418: 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
4104-453: A subadult, so the mature animal may have been larger. The holotype skull of Irritator challengeri , although heavily damaged in certain places, is largely complete; missing only the tip of the snout and the front of the mandible . The preserved skull is 16.5 cm (6.5 in) tall and 10 cm (3.9 in) wide, its full length has been estimated at 60 cm (24 in), based on comparisons with Baryonyx . Irritator ' s skull
4256-602: A system of grabens and half grabens. It is represented by the Abaiara Formation , that includes shales, siltstones , sandstones and conglomerates 4) Post-Rift I phase - Aptian to Albian - characterized by thermal subsidence. The lowermost unit Barbalha Formation , represents a fluviolacustrine phase and is composed of red and gray shales, siltstones and claystones. The Santana Group was formed during this stage and comprises three stratigraphic units: 5) Post-rift II phase - Albian to Cenomanian - characterized by
4408-449: A theropod's buoyancy to a significant extent. In 2020, German paleontologist Marco Schade and colleagues analyzed the anatomy of the holotype skull braincase through CT scans, revealing numerous details about behavioral capabilities of Irritator . With the scans, they created a 3D model of the skull and braincase, discovering that Irritator had elongated olfactory tracts and a relatively large floccular recesses (area that pierces through
4560-468: A total of 11 teeth each, similar to the number of 12 teeth in MSNM V4047, an upper jaw fossil referred to Spinosaurus . The hindmost tooth of the Irritator specimen's left maxilla was not yet fully erupted, and only the tip of it was visible. The holotype of Angaturama limai consists only of the front part of the upper jaw, comprising the tips of the paired premaxillae and the frontmost ends of
4712-444: Is a phenomenon wherein intense intracranial pressure disfigures the internal surface of the skull. The name comes from the fact that the inner skull has the appearance of having been beaten with a ball-peen hammer , such as is often used by coppersmiths . The condition is most common in children. Injuries to the brain can be life-threatening. Normally the skull protects the brain from damage through its high resistance to deformation;
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4864-555: Is a product of cephalization and vesicular enlargement of the brain, with several special senses structures such as the eyes , ears , nose , tongue and in fish specialized tactile organs such as barbels near the mouth. The skull is composed of three types of bone : cranial bones, facial bones and ossicles , which is made up of a number of fused flat and irregular bones . The cranial bones are joined at firm fibrous junctions called sutures and contains many foramina , fossae , processes , and sinuses . In zoology ,
5016-501: Is further distinguished from Baryonyx , Suchomimus , and Cristatusaurus by having slightly over half as many teeth in the maxilla, and from Spinosaurus due to its comparatively larger and more forwardly positioned nostril openings, which, unlike in Spinosaurus , are also formed by the premaxilla. The narrow sagittal crest, which ends in a knob-like process above the frontals, is another autapomorphy separating Irritator from other spinosaurids. Although Angaturama limai ' s snout
5168-785: Is generally narrower than in other spinosaurids, this might be due to damage sustained by the fossil; the holotype appears partly crushed and broken on its lower margin, with some of the preserved teeth having been sectioned off along their length. Therefore, Angaturama ' s only valid autapomorphy is its sagittal crest, which extends farther forwards on the rostrum and is more exaggerated than in other known spinosaurid skulls. Topology A: Benson and colleagues (2009) Baryonyx [REDACTED] Megalosauridae [REDACTED] Topology B: Sales and Schultz (2017) Baryonyx [REDACTED] In 1996, Martill and colleagues theorized that Irritator challengeri, with its elongated snout and unserrated conical teeth, likely had at least
5320-405: Is interpreted as a coastal lagoon with irregular freshwater influence that contended with cycles of transgressing and regressing sea levels . The climate of the formation was tropical and largely corresponded to today's Brazilian climate. The regions surrounding the formation were arid to semi-arid , with most of the local flora being xerophytic (adapted to dry environments). Cycadales and
5472-403: 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. The holotype of Irritator was excavated from
5624-405: Is no space for the brain to expand; this can result in significant brain damage or death unless an urgent operation is performed to relieve the pressure. This is why patients with concussion must be watched extremely carefully. Repeated concussions can activate the structure of skull bones as the brain's protective covering. Dating back to Neolithic times, a skull operation called trepanning
5776-414: Is normally represented by a trough-like basket of cartilaginous elements only partially enclosing the brain, and associated with the capsules for the inner ears and the single nostril. Distinctively, these fish have no jaws. Cartilaginous fish , such as sharks and rays, have also simple, and presumably primitive, skull structures. The cranium is a single structure forming a case around the brain, enclosing
5928-606: Is not known if it actively hunted these animals or simply scavenged the remains. In 2018, Aureliano and colleagues presented a possible scenario for the food web of the Romualdo Formation. The researchers proposed that spinosaurines from the formation may have also preyed on 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. Examinations and digital reconstructions of Irritator published in 2023 by Schade, Rauhut et al., suggests that
6080-423: Is one seventh of the size of the calvaria . (In the adult it is half the size). The base of the skull is short and narrow, though the inner ear is almost adult size. Craniosynostosis is a condition in which one or more of the fibrous sutures in an infant skull prematurely fuses, and changes the growth pattern of the skull. Because the skull cannot expand perpendicular to the fused suture, it grows more in
6232-452: Is the bone structure that forms the head in the human skeleton . It supports the structures of the face and forms a cavity for the brain . Like the skulls of other vertebrates, it protects the brain from injury. The skull consists of three parts, of different embryological origin—the neurocranium , the sutures , and the facial skeleton . The neurocranium (or braincase ) forms the protective cranial cavity that surrounds and houses
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6384-431: Is the ratio of the width of the head, multiplied by 100 and divided by its length (front to back). The index is also used to categorize animals, especially dogs and cats. The width is usually measured just below the parietal eminence , and the length from the glabella to the occipital point. Humans may be: The vertical cephalic index refers to the ratio between the height of the head multiplied by 100 and divided by
6536-406: Is typically a bony enclosure around the brain of a vertebrate . In some fish , and amphibians , the skull is of cartilage . The skull is at the head end of the vertebrate. In the human the skull comprises two prominent parts: the neurocranium , and the facial skeleton . which evolved from the first pharyngeal arch . The skull forms the frontmost portion of the axial skeleton and
6688-470: Is uncertain whether this specimen can be referred to Irritator or Angaturama , given that both are based only on skull material. In 2007, Machado and Kellner tentatively referred a rib fragment (MN 7021-V) to the Spinosauridae. However, the most complete spinosaur specimen retrieved from the Romualdo Formation is MN 4819-V, a partial skeleton lacking the skull. First reported in 1991, the specimen
6840-569: The external nares (bony nostrils). As in all spinosaurids, the maxillae (main upper jaw bones) extended below and past the nostrils in a long, low branch that formed the lower border of this opening, consequently separating the premaxillae and nasal bones in that location. Irritator ' s maxillary sinuses (located in the body of the maxillae) bore a large oval opening, as in Allosaurus . The nostril openings were oval and, as in all spinosaurids, positioned farther back on
6992-417: The postacetabular ala (rear expansion). The preacetabular ala were somewhat enlarged at the front, in contrast to the more slender condition of the postacetabular ala. The brevis fossa (groove at the bottom of the postacetabular ala) was concave, as was the rear margin of the ischium. The pubis bore a relatively large and almost closed obturator notch , an indentation in the lower margin of
7144-692: The Alcântara Formation of the Itapecuru Group, part of the São Luís Basin. This larger species, known only from an isolated snout tip and upper jaw fragment, lived during the Cenomanian stage, around six to nine million years after Irritator and Angaturama . Oxalaia quilombensis is differentiated from Angaturama limai by its broader, more rounded snout and lack of a sagittal crest on the premaxillae. In September 2018,
7296-467: The Angaturama limai holotype. Some of the skull bones of the former holotype had not yet fully co-ossified (fused), indicating that the specimen belonged to a subadult. The partial spinosaurine skeleton MN 4819-V represented a moderately sized individual, estimated by Machado at 5 to 6 meters (16 to 20 ft) in length. Many elements from this specimen were incorporated into the skeletal mount in
7448-414: The Irritator challengeri holotype specimen has been discussed by some researchers. The skull was found lying on its side. Preceding fossilization, several bones from the back of the braincase, as well as the dentary, splenial , coronoid, and right angular bones from the lower jaw, were lost. Other bones, mostly from the skull rear, had become disarticulated and displaced towards alternate regions of
7600-758: The Romualdo Formation , whose rocks are dated to the Albian stage of the Early Cretaceous Period , about 110 million years ago. During this time, the Southern Atlantic Ocean was opening, forming the series of circum-Atlantic basins of southern Brazil and southwestern Africa, but the northeastern part of Brazil and West Africa were still connected. The Romualdo Formation is part of the Santana Group and, at
7752-492: 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 a homage to the fictional character Professor Challenger from Arthur Conan Doyle 's novels. Some paleontologists regard Angaturama limai —known from
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#17327725974737904-403: The facial skeleton (14) are the vomer , two inferior nasal conchae , two nasal bones , two maxilla , the mandible, two palatine bones , two zygomatic bones , and two lacrimal bones . Some sources count a paired bone as one, or the maxilla as having two bones (as its parts); some sources include the hyoid bone or the three ossicles of the middle ear , the malleus, incus, and stapes, but
8056-738: The facial skeleton and splanchnocranium with the mandible being its largest bone. The mandible articulates with the temporal bones of the neurocranium at the paired temporomandibular joints . The skull itself articulates with the spinal column at the atlanto-occipital joint . Functions of the skull include physical protection for the brain, providing attachments for neck muscles , facial muscles and muscles of mastication , providing fixed eye sockets and outer ears ( ear canals and auricles ) to enable stereoscopic vision and sound localisation , forming nasal and oral cavities that allow better olfaction , taste and digestion , and contributing to phonation by acoustic resonance within
8208-405: The frontal bone ). The bones of the roof of the skull are initially separated by regions of dense connective tissue called fontanelles . There are six fontanelles: one anterior (or frontal), one posterior (or occipital), two sphenoid (or anterolateral), and two mastoid (or posterolateral). At birth, these regions are fibrous and moveable, necessary for birth and later growth. This growth can put
8360-448: The nasal cavity . Spinosaurus itself probably made heavier use of senses like vision or the mechanoreceptors on the tip of its snout, like those used by crocodilians to sense prey moving in the water. Another trait spinosaurs shared with gharials was an enlarged snout tip that wielded a rosette-shaped array of interlocking teeth, adept for impaling and catching fish. Although to a lesser degree than most known spinosaurs, this feature
8512-421: The skull base and its fossae , the anterior , middle and posterior cranial fossae changes rapidly. The anterior cranial fossa changes especially during the first trimester of pregnancy and skull defects can often develop during this time. At birth, the human skull is made up of 44 separate bony elements. During development, many of these bony elements gradually fuse together into solid bone (for example,
8664-609: The superfamily Megalosauroidea , with Spinosauridae being a possible sister taxon to the Megalosauridae . In 1998, Sereno and colleagues defined two subfamilies within the Spinosauridae based on craniodental (skull and tooth) characteristics. They were Spinosaurinae, where they placed Spinosaurus and Irritator ; and Baryonychinae, to which they assigned Baryonyx, Suchomimus, and Cristatusaurus . Spinosaurines were distinguished by their unserrated, straighter, and more widely spaced teeth, as well as smaller first teeth of
8816-404: The zygomatic processes . The fenestrae (from Latin, meaning windows ) are openings in the skull. The jugal is a skull bone that found in most of the reptiles, amphibians and birds. In mammals, the jugal is often called the zygomatic bone or malar bone. The prefrontal bone is a bone that separates the lacrimal and frontal bones in many tetrapod skulls. The skull of fish is formed from
8968-677: The Araripe Basin was designated a UNESCO Global Geopark . The Santana Group was formerly described as belonging to the Araripe Group. The fossiliferous Santana Formation was previously defined as containing the Crato and Romualdo Members, but redefinition of the stratigraphy led to the establishment of the Santana Group, replacing the middle part of the Araripe Group and the former Crato, Ipubi and Romualdo members were elevated to separate formations. The tectono-sedimentary evolution of
9120-701: The Araripe Basin, located in the Borborema Geologic Province, encompasses four stages, with five tectonostratigraphic phases: 1) Syneclise phase - Silurian to Devonian - characterized by tectonic quiescence in the Borborema Province. It is represented by the deposits of the Cariri Formation , that include medium to coarse-grained quartz sandstones , locally conglomeratic , deposited in large braided fluvial systems 2) Pre-rift phase - Tithonian - characterized by
9272-471: The Brazilian paleontologists Marcos A. F. Sales and Cesar L. Schultz in 2017 noted that the specimens also differ in other aspects of their preservation: the Irritator specimen is brighter in color and is affected by a vertical crack, while the Angaturama specimen bears many cavities; the damage to the teeth of the Irritator challengeri holotype is also much less severe. Sales and Schultz also identified
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#17327725974739424-482: The German museum often bought such pieces. As it promised to be a unique discovery of singular importance, German and British pterosaur experts were contacted to study the exemplar. A paper describing it as a pterosaur had already been submitted for publication when the authors, German paleontologist Eberhard Frey and British paleontologist David Martill, were disabused of this notion by the peer reviewers , who suggested
9576-467: The National Museum of Rio de Janeiro, which had a length of 6 meters (20 ft) and a height of 2 meters (6.6 ft). However, spinosaurids from the Romualdo Formation possibly attained greater sizes. Although LPP-PV-0042 is represented only by a tibia fragment, Aureliano and colleagues estimated its length at roughly 10 meters (33 ft). Bone histology indicates that this individual was
9728-408: The Romualdo Formation has also yielded postcrania l remains that may belong to spinosaurids, many of which are hitherto undescribed, and all of them pertaining to the Spinosaurinae subfamily . In 2004, parts of a spinal column (MN 4743-V) were unearthed at the formation. Brazilian paleontologist Jonathas Bittencourt and Kellner assigned these, due to their structure, to the Spinosauridae. It
9880-444: The Romualdo Formation is indeed exposed there, and the matrix encasing the holotype has the same color and texture as those rocks, this locality can be regarded as the probable site of the discovery of the fossil. Irritator challengeri was the first dinosaur described from the Romualdo Formation, and its holotype specimen represents the most completely preserved spinosaurid skull known. Angaturama limai , another spinosaurid from
10032-542: The Romualdo Formation tibia fragment. CT scanning of the specimen in the University of São Carlos revealed the presence of osteosclerosis (high bone density). This condition had previously only been observed in Spinosaurus aegyptiacus, as a possible way of facilitating submersion in water by making its bones heavier. The presence of this condition on the Brazilian leg fragment showed that compact bones had already evolved in spinosaurines at least 10 million years before
10184-569: The Romualdo Member of the then Santana Formation ). This assignment was confirmed by microfossils of the ostracod Pattersoncypris , and fish scales from the ichthyodectid Cladocyclus , both found in the Romualdo Formation. Questioning of local fossil dealers hinted at a locality near the village of Buxexé close to Santana Do Cariri at the flank of the Chapada do Araripe, at a height of approximately 650 meters (2,130 ft). Since
10336-630: The U.S., researchers replaced a large percentage of a patient's skull with a precision, 3D-printed polymer implant . About 9 months later, the first complete cranium replacement with a 3D-printed plastic insert was performed on a Dutch woman. She had been suffering from hyperostosis , which increased the thickness of her skull and compressed her brain. A study conducted in 2018 by the researchers of Harvard Medical School in Boston, funded by National Institutes of Health (NIH), suggested that instead of travelling via blood , there are "tiny channels" in
10488-514: The aboriginal Tupi Indian language of Brazil. The specific name honors the late Brazilian paleontologist Murilo R. de Lima, who informed Kellner of the specimen in 1991. In 1997, British paleontologists Alan J. Charig and Angela C. Milner considered Angaturama a likely junior synonym of Irritator , noting that both genera had retracted nostrils, long jaws, and characteristic spinosaurid dentition. Paul Sereno and colleagues in 1998 agreed with this possibility, and additionally observed that
10640-428: The anterior fontanel can remain open up to eighteen months. The anterior fontanelle is located at the junction of the frontal and parietal bones; it is a "soft spot" on a baby's forehead. Careful observation will show that you can count a baby's heart rate by observing the pulse pulsing softly through the anterior fontanelle. The skull in the neonate is large in proportion to other parts of the body. The facial skeleton
10792-536: The appearance of Spinosaurus in Morocco. According to phylogenetic bracketing —a method used to infer unknown traits in organisms by comparison with their relatives —osteosclerosis therefore might have been the norm in the Spinosaurinae. The significance of these traits was questioned in a later 2018 publication, where Canadian paleobiologist Donald Henderson argued that osteosclerosis would not have changed
10944-427: The authors to suggest a possible junior synonymy of Irritator with Spinosaurus . Sues and colleagues noted that more overlapping skull material was needed for further diagnosis. As more of Spinosaurus ' s skull became known, later research maintained separation of the two taxa. Although the site of discovery is uncertain, the specimen most probably stems from the Romualdo Formation (previously designated
11096-466: The bones either absent or wholly or partly replaced by cartilage. In mammals and birds, in particular, modifications of the skull occurred to allow for the expansion of the brain. The fusion between the various bones is especially notable in birds, in which the individual structures may be difficult to identify. The skull is a complex structure; its bones are formed both by intramembranous and endochondral ossification . The skull roof bones, comprising
11248-416: The bones of the facial skeleton and the sides and roof of the neurocranium, are dermal bones formed by intramembranous ossification, though the temporal bones are formed by endochondral ossification. The endocranium , the bones supporting the brain (the occipital, sphenoid , and ethmoid ) are largely formed by endochondral ossification. Thus frontal and parietal bones are purely membranous. The geometry of
11400-462: The brain and brainstem . The upper areas of the cranial bones form the calvaria (skullcap). The facial skeleton (membranous viscerocranium) is formed by the bones supporting the face, and includes the mandible . The bones of the skull are joined by fibrous joints known as sutures— synarthrodial (immovable) joints formed by bony ossification , with Sharpey's fibres permitting some flexibility. Sometimes there can be extra bone pieces within
11552-566: The cavities and sinuses. In some animals such as ungulates and elephants , the skull also has a function in anti-predator defense and sexual selection by providing the foundation for horns , antlers and tusks . The English word skull is probably derived from Old Norse skulle , while the Latin word cranium comes from the Greek root κρανίον ( kranion ). The human skull fully develops two years after birth. The human skull
11704-674: The creation of a replica Angaturama skeleton, later mounted at the Federal University-owned Museu Nacional do Rio de Janeiro ( National Museum of Rio de Janeiro ). The skeleton depicted the animal carrying an anhanguerid pterosaur in its jaws. It was the centerpiece of the Dinossauros no Sertão (Dinosaurs of Sertão) exhibit, which opened to the public in March 2009, becoming the first large carnivorous Brazilian dinosaur to be put on display. Some of
11856-438: The desired sex. These procedures can be an important part of the treatment of transgender people for gender dysphoria . Artificial cranial deformation is a largely historical practice of some cultures. Cords and wooden boards would be used to apply pressure to an infant's skull and alter its shape, sometimes quite significantly. This procedure would begin just after birth and would be carried on for several years. Like
12008-509: The examinations reaffirmed classification of spinosaurids as megalosauroids and that megalosauroids and allosauroidea were part of a monophyletic Carnosauria, with Monolophosaurus standing as a sister taxon to spinosauridae. Many spinosaurs likely had semiaquatic habits, as has been shown in studies using techniques like isotope analysis and bone histology . It has been found that they probably took advantage of aquatic prey and environments (usually marginal and coastal habitats ) to occupy
12160-439: The extinct conifer Brachyphyllum were the most widespread plants. This environment was dominated by pterosaurs, including: Anhanguera , Araripedactylus , Araripesaurus , Brasileodactylus , Cearadactylus , Coloborhynchus , Santanadactylus , Tapejara , Thalassodromeus , Tupuxuara , Barbosania , Maaradactylus , Tropeognathus , and Unwindia . The known dinosaur fauna besides Irritator
12312-531: The face, the skull and teeth can also indicate a person's life history and origin. Forensic scientists and archaeologists use quantitative and qualitative traits to estimate what the bearer of the skull looked like. When a significant amount of bones are found, such as at Spitalfields in the UK and Jōmon shell mounds in Japan, osteologists can use traits, such as the proportions of length, height and width, to know
12464-566: The feeling the authors felt (understated here) when discovering that the snout had been artificially elongated." The type species , Irritator challengeri, was named after Professor Challenger , a character in Arthur Conan Doyle 's novels, specifically The Lost World . Two years earlier, Frey and Martill had named a new pterosaur species from the Crato Formation Arthurdactylus conandoylei , after
12616-419: The first record of Mesozoic birds in Brazil. Irritator Irritator is a genus of spinosaurid dinosaur that lived in what is now Brazil during the Albian stage of the Early Cretaceous Period , about 113 to 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 sold it to
12768-418: The foramen magnum lies immediately above a single condyle , articulating with the first vertebra . There are, in addition, at various points throughout the cranium, smaller foramina for the cranial nerves. The jaws consist of separate hoops of cartilage, almost always distinct from the cranium proper. In ray-finned fish , there has also been considerable modification from the primitive pattern. The roof of
12920-436: The fossil belonged to a theropod dinosaur. The skull was flattened sideways somewhat and, as is common with fossils, was partly crushed. The right side was well preserved, while the left was extensively damaged during collection. Some of the skull's hindmost upper surface had eroded, and the lower jaw lacked its front end, both owing to breakage during fossilization. Parts of the specimen were also cracked due to being part of
13072-494: The fossil skeleton of one Baryonyx . Naish and colleagues in 2004 supported the theory that Irritator hunted both aquatic and terrestrial animals as a generalist within the coastal area and in addition probably searched for carrion . A tooth belonging to Irritator was discovered still inserted into the fossil neck vertebral column of an ornithocheirid pterosaur, likely with a wingspan of 3.3 m (11 ft). This indicates that Irritator ate pterosaurs as well, although it
13224-500: The fossil traders had severely obscured the skull beneath plaster; a widespread practice among local collectors in the Chapada do Araripe, especially on fish fossils. The buyers were unaware of the modifications to the specimen until it was sent to universities in the United Kingdom for CT scan imaging. This revealed the collectors had tried to reconstruct the skull by grafting parts of the maxilla (main upper jaw bone) onto
13376-491: The front of the rostrum (snout). The skull (designated SMNS 58022) became the holotype specimen of the new genus and species Irritator challengeri in February 1996 , when it was first scientifically described by paleontologists David M. Martill, Arthur R.I. Cruickshank, Eberhard Frey, Philip G. Small and Maria Clarke. In this paper, Martill and his team wrote that the generic name Irritator came "from irritation,
13528-478: The front; features that would have resulted in the eyes being positioned further up on the head than in other theropods. In particular, the broad lower jaw and narrowed frontals of Irritator resulted in the orbits facing at a steep incline towards the midline of the skull, whereas most theropods had laterally facing orbits. These traits would have permitted the animal to see above the waterline when submerged. In 2018, Aureliano and colleagues conducted an analysis on
13680-438: The frontal (top of head), parietal (back of head), premaxillary and nasal (top beak), and the mandible (bottom beak). The skull of a normal bird usually weighs about 1% of the bird's total bodyweight. The eye occupies a considerable amount of the skull and is surrounded by a sclerotic eye-ring, a ring of tiny bones. This characteristic is also seen in reptiles. Living amphibians typically have greatly reduced skulls, with many of
13832-418: The head before burial. Naish and colleagues in 2004 asserted that the Romualdo Formation dinosaur fauna is represented by animals that died near shorelines or rivers before being carried out to sea, where their floating remains were eventually fossilized. In 2018, Aureliano and colleagues argued against this scenario, stating that the Irritator challengeri holotype's mandible was preserved in articulation with
13984-457: The head body. In addition, the vestibular part of the endosseous labyrinth has a large anterior semicircular canal with a lateral oriented semicircular canal. Both floccular recesses and semicircular canal suggest that Irritator could coordinate fast head movements and had a downward inclined snout posture, enabling an unobstructed, stereoscopic forward vision, which is important for distance perception and therefore precise snatching movements of
14136-699: The head rapidly. In 2015, German paleontologist Serjoscha W. Evers and colleagues found evidence for similar adaptations in the African spinosaur Sigilmassasaurus . The neck vertebrae of this genus have a heavily furrowed undersurface. This is consistent with the attachment of powerful neck muscles for use in fishing or rapidly snatching small prey, a trait also observed in extant crocodilians and birds. Sales and Schultz in 2017 found that Irritator and baryonychines might have relied more on their sense of smell for hunting than Spinosaurus did, since they had larger, less retracted nostrils and more room in their skulls for
14288-558: The holotype of Angaturama seems to complete that of Irritator (meaning that they could belong to the same specimen). Authors including Éric Buffetaut and Mohamed Ouaja in 2002, Cristiano Dal Sasso and colleagues in 2005, Tor G. Bertin in 2010, Darren Naish in 2013, and Madani Benyoucef and colleagues in 2015 supported this conclusion. In their redescription of Irritator , Sues and colleagues pointed out that both holotypes are equally as narrow, and share transversely round teeth with defined yet unserrated edges. They also noted that
14440-648: The lagoon. Similarities between the fauna of the Romualdo and Crato Formations to that of Middle Cretaceous Africa suggest that the Araripe Basin was connected to the Tethys Sea , though this link was likely sporadic, because the lack of marine invertebrates indicates the basin had a non-marine depositional setting. Spinosaurids had already achieved a cosmopolitan distribution during the Early Cretaceous. Sereno and colleagues in 1998 suggested that with
14592-405: The left maxilla's tooth crowns are more intact, and there are traces of a tenth tooth in the rock matrix. The teeth were deeply inserted into the jaw and widely spaced towards the front of the maxilla. The first and second preserved maxillary teeth were the largest, at 32 mm (1.3 in) and 40 mm (1.6 in) in crown length. The seven remaining teeth became progressively smaller towards
14744-484: The length of the head. Humans may be: Trepanning , a practice in which a hole is created in the skull, has been described as the oldest surgical procedure for which there is archaeological evidence, found in the forms of cave paintings and human remains. At one burial site in France dated to 6500 BCE, 40 out of 120 prehistoric skulls found had trepanation holes. [REDACTED] This article incorporates text in
14896-418: The lessening of the weight of the skull, the aiding of resonance to the voice and the warming and moistening of the air drawn into the nasal cavity . The foramina are openings in the skull. The largest of these is the foramen magnum , of the occipital bone, that allows the passage of the spinal cord as well as nerves and blood vessels . The many processes of the skull include the mastoid process and
15048-453: The lower jaw is composed of multiple bones, only the most anterior of which (the dentary) is homologous with the mammalian mandible. In living tetrapods, a great many of the original bones have either disappeared or fused into one another in various arrangements. Birds have a diapsid skull, as in reptiles, with a prelacrimal fossa (present in some reptiles). The skull has a single occipital condyle. The skull consists of five major bones:
15200-422: The lower jaws of this spinosaurid could rotate and open laterally, with a gape similar to that of modern pelicans; this would have allowed the theropod to swallow very large prey items. It was also discovered to have a very weak but rapid bite as a result of this analysis. The study also reaffirms that Irritator likely possessed binocular vision and would have held its snout at an inclined orientation. Additionally,
15352-406: The lower surface and the sides, but always at least partially open at the top as a large fontanelle . The most anterior part of the cranium includes a forward plate of cartilage, the rostrum , and capsules to enclose the olfactory organs. Behind these are the orbits, and then an additional pair of capsules enclosing the structure of the inner ear . Finally, the skull tapers towards the rear, where
15504-510: The lush aquatic life as a primary food source. They also hypothesized that following storm events, pterosaur and fish carcasses might have washed up on the shoreline, providing theropods with plenty of carrion. Multiple piscivorous animals were present in the formation, which might in theory have led to high competition. Aureliano and colleagues stated there must have, therefore, been some degree of niche partitioning , where different animals would have fed on prey of varied sizes and locations within
15656-437: The maxillae. The specimen measures 19.2 cm (7.6 in) in height and 11 cm (4.3 in) in length, with the width of the palatal region being 4 to 5 mm (0.16 to 0.20 in). The suture between the maxilla and premaxilla was jagged at the front and straightened out towards the rear. The lower margin of the premaxillae was concave, with the concavity reaching its apex at the sixth premaxillary tooth. The front of
15808-655: The mechanical subsidence due to lithosphere thinning that preceded the rift. It is represented by the Brejo Santo Formation , that comprises red shales and claystones , and the Missão Velha Formation , constituted by medium to coarse-grained quartz-feldspathic sandstones, locally conglomeratic, that contains entire trunks and fragments of silicified wood ( Dadoxilon benderi ) conifer 3) Rift phase - Berriasian to Hauterivian - characterized by increasing mechanical subsidence that created
15960-441: The mid-nineteenth century, anthropologists found it crucial to distinguish between male and female skulls. An anthropologist of the time, James McGrigor Allan , argued that the female brain was similar to that of an animal. This allowed anthropologists to declare that women were in fact more emotional and less rational than men. McGrigor then concluded that women's brains were more analogous to infants, thus deeming them inferior at
16112-487: The novelist himself. When Martill and colleagues first described Irritator challengeri , the holotype was still extensively encased in calcareous rock matrix . Under the supervision of American paleontologist Hans-Dieter Sues, technician Diane M. Scott from the University of Toronto at Mississauga assumed the task of fully extracting the skull bones from the rock, allowing for a detailed redescription in 2002. Published by Sues, Frey, Martill, and Scott, this inspection of
16264-403: The now fully prepared specimen negated many of Martill and colleagues' original observations, which were based on misinterpretations of the damaged and largely concealed skull. The estimated length of the complete skull was 24 cm (9.4 in) shorter than previously proposed. What was originally thought to be a prominent head crest proved to be an unattached, indeterminate bone fragment. As in
16416-437: The old ones. Judging by the alveoli (tooth sockets), the premaxilla had seven teeth altogether, the third tooth being the largest. The frontmost three teeth of the maxilla were also preserved. The premaxillary teeth increased in size from the first to third, shrank from the third to the sixth, and enlarged again from the sixth premaxillary to third maxillary positions. A 16 cm (6.3 in) diastema (gap in tooth row)
16568-444: The one autapomorphy (distinguishing feature) diagnosed in maniraptorans at the time, which was having its jugal (cheek) bone forming part of the antorbital fenestra. He also pointed out that since Irritator challengeri ' s holotype lacked the tip of its snout, it would not be possible to know if Spinosaurus ' s dentary could complement it or not. Based on comparisons with Spinosaurus , Kellner resolved Irritator as
16720-645: The opening of the Tethys Sea, spinosaurines would have evolved in the south (Africa, in Gondwana ) and baryonychines in the north (Europe, in Laurasia ). In following, Machado and Kellner theorized in 2005 that spinosaurines would have then spread to South America from Africa. Sereno and colleagues postulated that divergent evolution between spinosaurines in South America and Africa likely occurred as
16872-401: The openings in the skull are called fenestrae , the most prominent of which is the foramen magnum , where the brainstem goes through to join the spinal cord . In human anatomy , the neurocranium (or braincase), is further divided into the calvarium and the endocranium , together forming a cranial cavity that houses the brain. The interior periosteum forms part of the dura mater ,
17024-402: The original postcranial elements (including the fossil pelvis and sacral vertebrae) were presented alongside the mount. In press releases of the exhibit's opening, Kellner informally implied MN 4819-V as belonging to Angaturama . This is also reflected in the specimen's inclusion in the skeletal mount. In 2011, a third Brazilian spinosaur, Oxalaia quilombensis , was named and described from
17176-442: The overall general consensus of the number of bones in the human skull is the stated twenty-two. Some of these bones—the occipital, parietal, frontal, in the neurocranium, and the nasal, lacrimal, and vomer, in the facial skeleton are flat bones . The skull also contains sinuses , air-filled cavities known as paranasal sinuses , and numerous foramina . The sinuses are lined with respiratory epithelium . Their known functions are
17328-493: The parallel direction. Sometimes the resulting growth pattern provides the necessary space for the growing brain, but results in an abnormal head shape and abnormal facial features. In cases in which the compensation does not effectively provide enough space for the growing brain, craniosynostosis results in increased intracranial pressure leading possibly to visual impairment, sleeping impairment, eating difficulties, or an impairment of mental development. A copper beaten skull
17480-420: The premaxilla. In 2005, Dal Sasso and colleagues assumed Irritator ' s nostrils as being located above the middle of the maxillary tooth row; more posteriorly than in baryonychines, but less so than in Spinosaurus . Sales and Schultz in 2017 found that Irritator ' s nostrils were in fact positioned closer to the front of the jaw, as in Baryonyx and Suchomimus ; this more forward nostril placement
17632-455: The presence of: hybodont sharks , guitarfish , gars , amiids , ophiopsids , oshuniids , pycnodontids , aspidorhynchids , cladocyclids , bonefishes , chanids , mawsoniids and some uncertain forms. According to Naish and colleagues, the lack of herbivorous dinosaurs could mean that the local vegetation was scant and thus incapable of sustaining a large population of them. The abundant carnivorous theropods would have then likely turned to
17784-436: The previous study, Sues and colleagues regarded the African and possibly South American genus Spinosaurus as the most similar taxon to Irritator , because they shared many dental features, including mostly straight conical tooth crowns , thin enamel , well-defined edges with no serrations , and lengthwise fluting. Since little was known of Spinosaurus ' s skull at the time, these similarities were enough for
17936-418: The rear part of the bone that allowed for the passage of the obturator nerve . The upwards projecting neural spines of the sacrum were elongated, as is typical in spinosaurs. In life, these would have been covered in skin, forming a " sail " down the animal's back. MN 4819-V is distinguished from Suchomimus due to its longer and shallower ilium with a less curved upper margin, and from Baryonyx by having
18088-400: The rear, one of the last ones measuring 6 mm (0.24 in) in estimated crown length. CT scans performed on the specimen revealed replacement teeth on both sides of the upper jaw. Their roots ran deep into the maxillae and converged close to the midline, nearly reaching the top of the skull. Based on comparisons with Irritator ' s relatives, the maxillae were probably lined with
18240-399: The relationships of the population of the study with other living or extinct populations. The German physician Franz Joseph Gall in around 1800 formulated the theory of phrenology , which attempted to show that specific features of the skull are associated with certain personality traits or intellectual capabilities of its owner. His theory is now considered to be pseudoscientific . In
18392-542: The researchers erected the new family Irritatoridae within the clade. They recognized Irritator ' s affinities with Spinosaurus , in that they both had similarly shaped and unserrated teeth, but noted that the latter's mandible would not conform with the front of Irritator ' s upper jaw, and that other non-avian dinosaurs like Compsognathus and Ornitholestes also bore no serrations on some or all of their teeth. Some of these claims were questioned in 1996 by Kellner who found that Irritator ' s skull lacked
18544-565: The rest of the skull, whereas it would have likely detached had the carcass been floating at sea. They also noted that the corpse would have quickly sunk due to the osteosclerosis of the skeleton. The researchers, therefore, concluded that fossils from the Santana Group represent organisms that were buried in their natural habitat, instead of having been deposited allochthonously (other than at their present position). [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Skull The skull , or cranium ,
18696-423: The right side better articulated than the left. The fused sacral vertebrae are still attached to the pelvis, which lacks the distal ends of both of its pubic bones and ischia (lower and rearmost hip bones). The ilium (main hip bone) is 55.3 cm (21.8 in) long. The preacetabular ala (front expansion) of the ilium was curved on the bottom and was somewhat shorter and deeper than
18848-484: 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
19000-488: The same time and place as Irritator challengeri , was described by the Brazilian paleontologists Alexander W. A. Kellner and Diogenes de Almeida Campos in February 1996. Kept today under specimen number USP GP/2T-5 at the University of São Paulo , the holotype specimen consists of an isolated snout tip from the Romualdo Formation. It was extracted from a calcareous nodule using a technique originally developed for pterosaur fossils. The generic name Angaturama means "noble" in
19152-428: The semicircular canals and connects the brain with the inner ear). The flocculus , itself, is an important element in the coordination and control of head and ocular movements during gaze stabilization (visual ability during head movement), by being involved in the coordination of the vestibulo-ocular (VOR) and vestibulo-collic (VCR) reflexes. The flocculus appears to be enlarged in taxa that rely on quick movements of
19304-474: The skull is formed from cartilage , and its overall structure is reduced. The skulls of the earliest tetrapods closely resembled those of their ancestors amongst the lobe-finned fishes . The skull roof is formed of a series of plate-like bones, including the maxilla, frontals , parietals , and lacrimals , among others. It is overlaying the endocranium , corresponding to the cartilaginous skull in sharks and rays . The various separate bones that compose
19456-455: The skull is generally well formed, and although the exact relationship of its bones to those of tetrapods is unclear, they are usually given similar names for convenience. Other elements of the skull, however, may be reduced; there is little cheek region behind the enlarged orbits, and little, if any bone in between them. The upper jaw is often formed largely from the premaxilla , with the maxilla itself located further back, and an additional bone,
19608-409: The skull is one of the least deformable structures found in nature, needing the force of about 1 ton to reduce its diameter by 1 cm. In some cases of head injury , however, there can be raised intracranial pressure through mechanisms such as a subdural haematoma . In these cases, the raised intracranial pressure can cause herniation of the brain out of the foramen magnum ("coning") because there
19760-410: The skull roof (called the postnasal fenestrae) as well as long and only partially diverging basipterygoid processes (bony extensions connecting the braincase with the palate ). The back of the lower jaw was deep, its rear upper surface consisting mainly of the large surangular bone, which articulated with the shallower angular bone below it. The mandibular fenestra ,
19912-465: The skull than in typical theropods. Irritator ' s nostrils were both proportionately and absolutely smaller than in Suchomimus and Baryonyx , but larger than those of Spinosaurus . The opening behind the orbit (eye socket), the lateral temporal fenestra , was very large, while the antorbital fenestra , in front of the eyes, was long and elliptical. The orbit itself was deep and wider at
20064-459: The skull through which the immune cells combined with the bone marrow reach the areas of inflammation after an injury to the brain tissues. Surgical alteration of sexually dimorphic skull features may be carried out as a part of facial feminization surgery or facial masculinization surgery , these reconstructive surgical procedures that can alter sexually dimorphic facial features to bring them closer in shape and size to facial features of
20216-409: 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
20368-401: The snout tip; this, along with the secondary palate, which separated the animal's nasal passages from the inside of its mouth, made respiration possible even if most of the jaw was underwater or held prey. In particular, the sagittal crest of Irritator is an indication for pronounced neck musculature, which would have been necessary to close the jaws quickly against water resistance and withdraw
20520-402: The snout was expanded, forming the spoon-shaped terminal rosette characteristic of spinosaurids. This concave underside of the premaxillae would have complemented a convex and enlarged mandible tip. The premaxillae connected with each other on the bottom to form Angaturama ' s secondary palate, which was also partially contributed to by two processes extending from the maxillae. The snout
20672-497: The snout. These inferences seem to be an agreement with a piscivore life-style. They also noted that the relatively well-developed cochlear duct may have enable an average hearing frequency of 1,950 Hz with a frequency band width of 3,196 Hz. However, they considered these ranges as rough estimates and established an overall frequency range of 350–3,550 Hz, making Irritator to be placed under bird hearing but above crocodiles. Irritator and Angaturama are known from
20824-404: The suture known as Wormian bones or sutural bones . Most commonly these are found in the course of the lambdoid suture . The human skull is generally considered to consist of 22 bones—eight cranial bones and fourteen facial skeleton bones. In the neurocranium these are the occipital bone , two temporal bones , two parietal bones , the sphenoid , ethmoid and frontal bones . The bones of
20976-457: The symplectic, linking the jaw to the rest of the cranium. Although the skulls of fossil lobe-finned fish resemble those of the early tetrapods, the same cannot be said of those of the living lungfishes . The skull roof is not fully formed, and consists of multiple, somewhat irregularly shaped bones with no direct relationship to those of tetrapods. The upper jaw is formed from the pterygoids and vomers alone, all of which bear teeth. Much of
21128-413: The temporal bone of humans are also part of the skull roof series. A further plate composed of four pairs of bones forms the roof of the mouth; these include the vomer and palatine bones . The base of the cranium is formed from a ring of bones surrounding the foramen magnum and a median bone lying further forward; these are homologous with the occipital bone and parts of the sphenoid in mammals. Finally,
21280-473: The thinner frontal bones, situated behind them, were smooth and concave on top; both of these bones formed the upper rim of the orbit. A thin sagittal crest , constructed from the elongate nasal bones, extended along the skull midline before stopping just above the eye in a slightly flattened bulge. Although the complete shape and height of this structure is unknown in Irritator , these head crests were commonplace in spinosaurids, having possibly served
21432-725: The time Irritator was described, was thought to be a member of what was then considered the Santana Formation. The Romualdo Formation is a Lagerstätte (a sedimentary deposit that preserves fossils in excellent condition) consisting of limestone concretions embedded in shales , and overlies the Crato Formation. It is well known for preserving fossils three-dimensionally in limestone concretions, including many pterosaur fossils. In addition to muscle fibres of pterosaurs and dinosaurs, fish, preserving gills, digestive tracts, and hearts, have been found there. The formation
21584-554: The time. To further these claims of female inferiority and silence the feminists of the time, other anthropologists joined in on the studies of the female skull. These cranial measurements are the basis of what is known as craniology . These cranial measurements were also used to draw a connection between women and black people. Research has shown that while in early life there is little difference between male and female skulls, in adulthood male skulls tend to be larger and more robust than female skulls, which are lighter and smaller, with
21736-427: The top (where the eyeball was placed) than the bottom. The lacrimal bone separated the orbit from the antorbital fenestra, forming the upper and lower rear margins of the latter with two processes that enclosed a 40-degree angle; similar to Baryonyx , where it enclosed 35 degrees. Unlike in Baryonyx , Irritator ' s lacrimal did not form a bony horn core. The prefrontal bones were large and sturdy, while
21888-570: The top of the crest may have extended even farther over and forwards from that point. The front of Angaturama ' s snout hence had a vertically straight or concave margin, atypical from the more smoothly sloping snouts of other spinosaurs. In the premaxilla, a broken-off tooth with partial tooth crown was recovered. The strongly extended and straight teeth with unserrated conical crowns, which measured 6 to 40 mm (0.24 to 1.57 in) in length, were singly embedded. This indicates continuous tooth replacement where new teeth were pushed up between
22040-408: Was also present in the Angaturama limai holotype. In 2002, Sues and colleagues pointed out, however, that there would be no reason to assume that the Spinosauridae specialized completely in fishing. They stressed rather that this head morphology indicates a generalistic feeding , particularly on small prey animals. In fact, portions of a young Iguanodon , a terrestrial herbivore, were found inside
22192-400: Was long, narrow, and somewhat triangular in cross section. The braincase was inclined backwards, and deeper than it was long. Extending from it was an elongate and low snout, with both sides relatively flat and slightly angled towards the skull midline. Only the rear ends of the paired premaxillae (frontmost snout bones) remain intact, forming the front upper and lower borders of
22344-492: Was present between the last premaxillary and first maxillary tooth. Though no skeletal remains were discovered with the original Angaturama snout tip, one partial skeleton (MN 4819-V) from a different location may belong to the genus. But since there is no overlapping material between the two specimens, direct comparisons cannot be made. MN 4819-V comprises a largely intact pelvis , some dorsal (back) and caudal (tail) vertebrae , five sacral (hip) vertebrae,
22496-415: Was referred by Kellner to the Spinosauridae in 2001 because of its tall sacral neural spines and the enlarged condition of the hand claw . The skeleton was fully described in 2010 in an as-of-yet unpublished master's thesis by Machado. An incomplete hind limb (MPSC R-2089) mentioned in 2013 might also pertain to the Spinosauridae. In 2018 , Tito Aureliano and his team described LPP-PV-0042, part of
22648-508: Was represented by other theropods like the tyrannosauroid Santanaraptor , the compsognathid Mirischia , an indeterminate unenlagiine dromaeosaurid , and a megaraptoran . The crocodyliforms Araripesuchus and Caririsuchus , as well as the turtles Brasilemys , Cearachelys , Araripemys , Euraxemys , and Santanachelys , are known from the deposits. There were also clam shrimps , sea urchins , ostracods, and molluscs . Various well-preserved fish fossils record
22800-400: Was sometimes performed. This involved drilling a burr hole in the cranium. Examination of skulls from this period reveals that the patients sometimes survived for many years afterward. It seems likely that trepanning was also performed purely for ritualistic or religious reasons. Nowadays this procedure is still used but is normally called a craniectomy . In March 2013, for the first time in
22952-440: Was strongly compressed laterally, and the premaxillae gently tapered towards the top to form a tall sagittal crest 1 to 2 mm (0.039 to 0.079 in) in thickness. This crest was larger and extended farther forwards on the snout than in other known spinosaurids. The frontmost upper border of the premaxilla had a small bulge that overhung the base of the crest. This bulge was apparently damaged on its upper surface, indicating that
23104-447: Was typically considered characteristic of baryonychines. Nevertheless, Irritator also bore unserrated teeth, a trait associated with spinosaurines. Sales and Schultz thus noted that the Araripe Basin spinosaurids Irritator and Angaturama might represent intermediate forms between the earlier baryonychines and later spinosaurines, and that further research may eventually render the former a paraphyletic (unnatural) group. Irritator
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