Fossils discovered in recent years have added many physiological structural features, which can further study the brain structure and forelimb function of Spinosaurus. Spinosaurus is the largest theropod dinosaur in their ecosystem, and may be the top predator, feeding on large sauropods. Spinosaurus is smaller than its large relative, the southern monitor lizard, but it is still one of the very large theropod dinosaurs. At present, the largest known individual is 12.9 meters long and weighs an estimated 7 tons. The largest skull length is close to1.2m.. Like most other theropods, the head and skull of Spinosaurus were long, low and narrow. The preorbital foramen is quite large, accounting for about 1/4 of the head length and 2/3 of the head height, which can reduce the weight of the head. The surfaces on both sides of the maxilla and the upper side of the nasal bone are not as undulating as those of the southern behemoth and the shark tooth dragon. There is a long and low ridge on the nasal bone, starting from the nostril, along the sides of the nose and mouth, until the tear bone at the eye. [1] Allosauroidea has such ridges on its head. [2] Unlike Allosaurus, the lacrimal bone in front of the eyes of Spinosaurus had no horny crown. Their lacrimal bone and retroorbital bone healed, forming a thick eyebrow ridge above their eyes, which is the same as Abelilonidae, a unrelated family. There are 19 serrated and curved teeth on both sides of the upper jaw, but the number of teeth in the lower jaw is unknown. Spinosaurus' teeth were longer than Sharon's, and there was no tooth line like Kurt's. The front edge of the tooth bone of the mandible is square, like a southern beast; The upper and lower width of the tooth bone is narrow, while the upper and lower width of the posterior segment of the jaw bone is very wide. Spinosaurus and southern behemoths have broad and horizontal ridges on the upper corner of their jaws.
Spinosaurus is a large carnivorous dinosaur, which can grow to more than 4 meters high and weigh 5 tons, 1 1 meter long. The thorns on the back are 20 cm short and 50 cm long. Good at catching sauropods weighing 30~40 tons. If you compare the skull of dinosaur with that of Tyrannosaurus rex, you will find that the skull of Tyrannosaurus rex is wider than that of Tyrannosaurus rex, because Tyrannosaurus rex's teeth are used to crush bones, while Tyrannosaurus rex's teeth are used to shred meat; If you compare the forelimbs of Tyrannosaurus rex with those of Spinosaurus, you will think that the big one is Tyrannosaurus rex, then you are wrong. The forelimbs of Spinosaurus made up teeth, so they were sharper and longer than those of Tyrannosaurus Rex. The prey of Spinosaurus was Brachiosaurus and Liang Long. Brachiosaurus is 25 meters long, weighs 30 tons and is 16 meters high. The double-chambered dragon is 33 meters long, weighs 40 tons and is 16 meters high. However, the claws of Spinosaurus have one disadvantage: they can only stretch 25 degrees, and then they will dislocate. So Spinosaurus can only pounce on its prey with its teeth, attack it with its teeth, and the prey will feel tired, then bite its long neck and the prey will die. The most obvious feature of Spinosaurus is their tall neurites, which extend from the neck to the back, buttocks and the front of the tail, and the length can reach 2.5 times the length of the spine. [3] Other dinosaurs with high spines on their backs, some of which were bigger than Spinosaurus. For example, the spinosaurus living in Africa, its dorsal spine is about 1.8 meters high, which is about 1 1 times that of the connected vertebrae. [4] Different from the skin of spinosaurus spine support, spinosaurus spine is lower, which may be the attachment of strong muscles, similar to modern bison, with a high and thick ridge on its back. [3] The function of dorsal spine is unclear, which may be related to animal communication, fat storage or body temperature control. Both cervical vertebra and vertebra have obvious lateral cavities, and the lateral cavity of coccygeal vertebra is smaller. This feature is more similar to sauropodidae than heterosauridae. [5] In addition to the spine, Homosaurus also has a typical Allosauroidea skeleton. Spinosaurus is a bipedal dinosaur with a long and heavy tail, which can balance the weight of the head and body and keep the center of gravity at the hips. Compared with Allosaurus, the forelimbs of Allosaurus were shorter and thicker, but they were similar in other aspects. All hands have three fingers with claws. Different from small running dinosaurs, their femur was longer than tibia and metatarsal, [1][5] This shows that Spinosaurus was not good at running fast. [6] Compared with Allosaurus, Homosaurus had thicker hind limb bones. Like other theropods, Spinosaurus had four toes on the soles of its feet. The first toe was smaller than the other little toes, so it could not touch the ground.
Modern phylogenetic analysis classifies Spinosaurus into Allosauroidea, but its position in this superfamily is controversial. The Allosaurus superfamily is characterized by a pair of ridges above the nasal bone and lacrimal bone, a high protrusion on the cervical vertebra, and other features. [2] Homosaurus and Allosaurus were originally classified as Allosauridae, and some later studies also supported this statement. However, many other scientists classified it as a sauropod family with sauropods and southern behemoths. Like most other large theropod dinosaurs, Homosaurus was first discovered with only sporadic fossils, which made their classification change frequently. J. Willis Stovall and Wann Langston, Jr. originally classified Spinosaurus as Antrodemidae, which is synonymous with Allosauridae. 1956, Alfred Sherwood Romer reclassified Spinosaurus as a family of Bansauridae, which used to be considered as "the concentration of unclassified species". [12] In the 1960s, other scientists thought that the long axons on their spines represented the kinship with Spinosaurus. [13][ 14] The classification of Spinosaurus in the family Spinosauridae lasted until the 1980s, when [15] appeared in the semi-scientific literature. [ 16][ 17]
1884, a tall neurite was found in the early Cretaceous strata of England, which was once thought to be very similar to spinosaurus. [18] These bones were originally classified as Acrosaurus, an English theropod dinosaur with only teeth found. In 1988, Gregory S. Paul named these protrusions as the second species of spinosaurus, Acrocanthosaurus altispinax. [19] Paul's classification led at least one scientist to claim that Dinglong was synonymous with Dinglong. [18]1991year, Spinosaurus was rebuilt as an independent Beck Spinosaurus, not belonging to Spinosaurus and Spinosaurus.
If spinosaurus belongs to Allosaurinae, their close relatives should be Jurassic Allosaurus and sauropod Wang Long. [1] Those studies on the phylogenetic cladistic classification of the Tetraodontidae tend to place the Tetraodon in a more primitive position than the African Tetraodon and the South American Dragon. [2][5] A new dinosaur found in England is generally regarded as a more basic animal of the family Dinosauridae. [2] [5] [6] The new dragon hunting refers to the fangodonta that originated in Europe and then spread to Gondwana in the south. If Spinosaurus belongs to Sharidae, it means that Sharidae has also spread to North America. [5] All known sharks lived in the early to middle Cretaceous.
Spinosaurus got its name from its tall neurites. In ancient Greek, αξξα/akra means "high", αξανθα/akan tha means "thorn" or "thorn", and σ α υ υ υ? /sauros means "lizard". [2 1] Acrontosaurus ken dragon is the only species in Ato ken dragon, named after its discovery place, Atoka County, Oklahoma. The name of Spinosaurus was named by American paleontologists J. Willis Stovall and Wannangston, Jr. in 1950. [3]Langston mentioned the name Acracanthus atokaensis in his unpublished master's thesis in 1947, [22][23] but it was changed to Atoka spinosaurus when it was officially published. Like most other theropods, Spinosaurus' forelimbs couldn't touch the ground, so it didn't have the function of walking, but played the role of hunting. The complete forelimb of "Flange" is helpful to study the function and range of motion of the forelimb of Spinosaurus. [28] A study examined the surface of the bone connected to the bone to calculate the range of motion of the joint without dislocation. Like many existing dinosaurs, the bones of many hand joints are not exactly the same, indicating that these joints have certain cartilage. The study also pointed out that when Spinosaurus rested, its forelimbs would hang down from its shoulders, its humerus would swing back slightly, its elbows would bend, and its fingers and claws would move inward. [28]
Compared with humans, Spinosaurus' shoulder rotation was very small. Their arms can't rotate 360 degrees, but they can swing back about 109 degrees from the vertical plane, so the humerus can swing back above the oblique micro. The arm can rotate forward about 25 degrees beyond the vertical plane. The arm can't swing vertically downward, but it can extend to about 9 above the horizontal plane. Compared with humans, the elbow has a small range of motion, only about 57 degrees of rotation. The arm can't be completely straight, can't bend greatly, and the humerus can't bend 90 degrees. The radius and ulna are fixed to each other, so they cannot rotate inward or outward like a human forearm. [28]
There is no precise joint between the wrist bones, which means that there are a lot of cartilage in the wrist, which can make the wrist tough. Pull your fingers outward and you can almost touch your wrist. When fingers bend inward, the first finger can be parallel to the second finger, and the third finger can only bend inward. The first finger has the largest claw and always bends inward. The second finger is always bent, while the smallest third finger can swing inward and outward. [28]
In addition to calculating the range of motion of forelimb joints, this study also puts forward the hypothesis of hunting habits of Spinosaurus. Their forelimbs are not swinging enough to grasp the back of their prey. Because the forelimbs could not be used at the beginning of catching prey, Spinosaurus probably hunted with its mouth. In addition, the forelimbs can't keep the prey close. Only when the mouth bites the prey can the strong forelimbs draw the prey closer and hold it tightly to prevent the prey from escaping. When the prey tries to escape, Spinosaurus can pierce the prey's body with its bent first and second fingers. The rapid extension of fingers is an evolutionary adaptation, which enables Spinosaurus to catch struggling prey without the risk of joint loss. Once the prey is caught by the corpse, Spinosaurus can swallow them with its jaw. Another possible way of hunting is that Spinosaurus bites its prey with its jaws, pulls itself with its forelimbs and cuts a large wound with its claws. In 2005, scientists used X-ray tomography technology to analyze the internal space of the skull of the finished model of Spinosaurus, and made the skull cavity model of Spinosaurus. Before their death, these intracranial spaces should have meninges and cerebrospinal fluid besides the brain. This cranial cavity model can be used to judge the general characteristics of the brain and cranial nerves, and can also be compared with other cephalopods. The brain of Spinosaurus is similar to that of most theropods, and most similar to the Allosaurus superfamily. Their brains look more like sauropods and southern behemoths than Allosaurus or Tenontosaurus of China, which supports the claim that the Homosaurus belongs to sauropods. [ 1 1]
The brain shape of spinosaurus is slightly S-shaped, and the cerebral hemisphere is not very expanded, which is more similar to crocodiles than birds. Most non-osteoporotic theropods have this feature. The olfactory bulb of spinosaurus is very large and spherical, which shows that they have a good sense of smell. Reconstruction of the semicircular canal of the ear showed that the head kept an angle of 25 with the horizontal plane. This is by adjusting the model to make the lateral semicircular canal parallel to the ground, which shows that the gait of this animal is alert. In the Rose Valley stratum in central Texas, there are many dinosaur footprints, including the footprints of the large three-toed theropod dinosaur. One of the most famous footprint fossils was found near the ballas River in Dinosaur Valley State Park and is currently on display at the American Museum of Natural History in new york. [29] Several fossil footprints have been found nearby. [30][3 1] As no fossils have been found, it is impossible to define what animals these footprints belong to. But for a long time, scientists thought that these footprints might be related to Spinosaurus. [32] A study in 2001compared the footprints of Rose Valley strata with the soles of different large theropods, but they could not be clearly classified into any genus. However, the study found that the shape and size of footprints were similar to those of Spinosaurus. Because the geographical locations of Rose Valley Stratum, Lujiao Formation and Shuangzishan Formation are close to geological times, and the only large theropod dinosaur in these areas is Spinosaurus, this study thinks that these footprints are most likely left by Spinosaurus. [33]
The footprint of this famous theropod dinosaur belongs to several individuals, and it goes in the same direction as as many as 12 sauropods. Some theropods tracked on sauropods, indicating that they formed late, indicating that a small group of Spinosaurus was tracking a group of sauropods. [29] This interesting theory seems reasonable, but it is difficult to prove. There are other explanations. For example, after sauropods pass by, many individual theropods pass in the same direction at different times, as if they were tracking prey. Similarly, it can be said that the lizard's feet move alone, not as a whole. [34] When the footprints of a group of theropods crossed those of a group of sauropods, one footprint was missing, which was regarded as evidence of dinosaur attack. [35] However, other scientists questioned this explanation, because the footprints of these sauropods did not change their gait. If there were any large predators around sauropods, then dinosaurs should change their posture.
Fossils of Spinosaurus were found in the Shuangzishan Formation in northern Texas and the Antlers Formation in southern Oklahoma. These strata have not been dated by radioisotopes, but scientists use biostratigraphy to estimate their ages. According to the change of ammonite fossils, the stratum of Rose Formation in Dezhou is located at the junction of Apudian and Albian in the early Cretaceous, and the possible footprints of Spinosaurus are found in this stratum, which is located in the upper layer of Shuangzishan Formation. This shows that the Gemini group belongs to Apudia, and the Apudia era was from 65.438+0.25 billion years ago to 65.438+0./kloc-0.20 billion years ago. [36] The fossils of antlers also include Deinonychus and Tenontosaurus, which were also found in Clover Li Group in Montana. After measurement, the clover group from Apdia to Albuquerque was found, which indicates that the age of antlers should be the same. [37] Therefore, Spinosaurus probably lived between 654.38+0.25 billion years ago and 654.38+0 billion years ago.
During this period, Shuangzishan Formation and Lujiao Formation were large flood plains located near the continental margin sea. Millions of years later, this ocean expanded northward, forming an inland sea route in the west, which split North America in two and lasted almost the whole Late Cretaceous. The Rose Valley stratum is a coastal environment, and the possible footprints of Spinosaurus should be left on the muddy flat land near the ancient coast. Because Spinosaurus is a large carnivore, they should live in a large area and many different environments. [33] The prey of spinosaurus may be: Palaciosaurus of sauropods? (Paluxysaurus), [38] giant sauropods, [39] and large ornithopods such as Tenontosaurus. [40] Deinonychus also lived in the same area. They are small theropod dinosaurs, about 3 meters long, which may be a little competitive with Spinosaurus.