Deinonychus

The deinonychus is a carnivorous dinosaur, they are flourished in western North America during the Early Cretaceous Period. The early cretaceous period was about 145.5 million to 99.6 million years ago. Deinonychus were a member of the dromaeosaur group that are bipedal species, which means they are walking with two legs and like all other theropod dinosaurs. Usually, the deinonychus claw is long, which facilitate them to catch their prey. The large sickle-like talons of about 13 cm long and were found in the second toe of each foot of Deinonychus was their principal killing devices. Deinonychus’s slender, outstretched tail was enclosed by the bundles of bony rods. The main function of these extensions of tail vertebrae was ideal and provide balance for the animals while running and attacking their prey. 

Important deinonychus facts that the Deinonychus was the model for the “raptor” dinosaurs shown in the motion picture Jurassic Park. The dromaeosaurs were named after ‘raptor’ in general as a contraction for Velociraptor, a genus of dromaeosaur that was considerably smaller than Deinonychus. The term raptor is derived from the Greek word, which means ‘seize’ or ‘grab’. The term is also correctly applied for the birds such as hawks and eagles, which grasp prey with their talons. The average deinonychus size is about 50 to 75 kg and they can reach a maximum height of about 2.5 to 3 metres. The Deinonychus was the evidently fast agile predator and their large intelligent brain enabled them to perform relatively complex movements during the chase and kill.

Both the Dromaeosaurs and troodontids are the closest known relative species of Archaeopteryx and other existing birds. These dinosaurs have many resemblances to bird features. They have unusually long arms and hands with the wrist which help them to flex sideways. Such adaptations apparently helped the species of Dromaeosaurs and troodontids to hunt their prey and enabled birds to generate an effective flight stroke.

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The above image shows the Deinonychus. Deinonychus meaning carnivorous species that belong to the dinosaur family. 

Characteristics of Deinonychus

Study Based on Behaviour of Deinonychus

The first study on Deinonychus was done by the Yale Quarry in the Cloverly of Montana with numerous teeth, four adult Deinonychus and one juvenile Deinonychus. After the clear study of deinonychus skeletons in a single quarry suggests that the Deinonychus must be the carnivorous animal and perhaps hunting other species for food. Later, Ostrom and Maxwell have used the information of Yale Quarry and speculate that Deinonychus might have lived and hunted in packs. The second quarry was from the Antlers Formation of Oklahoma. Researchers compared the site to six partial skeletons of Tenontosaurus of various sizes, with one partial skeleton and many teeth of Deinonychus. The humerus of the tenontosaur also bears the tooth mark of Deinonychus. In 1998, Brinkman et al found that the adult deinonychus mass was about 70 - 100 kg. But the average mass of adult tenontosaurs was about 1 to 4 metric tons. The Deinonychus were a solitary species, So that could not kill an adult tenontosaur. Later, he also suggested that pack hunting is possible in Deinonychus  to attack tenontosaurs .

According to the study of Roach and Brinkman in 2007, they questioned the cooperative pack hunting behaviour of Deinonychus. Based on the same method, modern carnivores are hunting and the taphonomy of tenontosaur sites. Even the modern crocodiles, Komodo dragons and birds are also showing cooperative hunting, sometimes these species are also solitary hunters. So, Deinonychus must previously kill carcasses, where various conflicts must occur between Deinonychus of the same species.  The best example from the modern species is Komodo dragons. They usually eat together. The largest individual in their group eats first and also tries to attack smaller Komodos, which are an attempt to feed. If the smaller animals of the species are killed, then they are cannibalized. This same situation was applied for the tenontosaur sites and was consistent with Deinonychus having a Komodo or crocodile-like feeding strategy. 

Most of the skeletons of Deinonychus remains found at sites are from subadults with missing parts. So, researchers found that they are consistent with having been eaten by other Deinonychus. And many other research papers found that they have similar foot spacing and parallel trackways with uncoordinated feeding behaviour. The species of deinonychus may be drained out due to competitive fighting for food. According to the study of Manning and colleagues in 2009, the dromaeosaur claw tips of Deinonychus are functioning as a puncture and gripping element. Further, the expansion of a rear portion of the claw transferred load stress through the structure. The hand claws of Deinonychus support a pre-capture/grappling/climbing function. To shift their entire body weight, they get locked in the claws passively, allowing their jaws to dispatch prey. 

As per Denver Fowler and colleague’s suggestion in 2011, Deinonychus and other dromaeosaurs may have captured and restrained prey. Like, birds pinning their prey under their body weight and clutching it tightly with the large, sickle-shaped claws. This method of capturing prey is known as the "raptor prey restraint" (RPR) model of predation. By the RPR process, Using deinonychus claw, they must attach their prey. Generally, Deinonychus anatomy shows that their characteristics must be similar to the modern bird hunting characteristics. Further, the RPR method of predation was proved after analysing the Deinonychus's anatomy, which has unusual jaw and arm morphology. The Deinonychus arms were covered by the long feathers, the Deinonychus may have been used as flapping stabilizers for balance while adapting struggling prey, along with the stiff counterbalancing tail. As per the research on deinonychus jaws, they may have a weak bite force, So deinonychus may use their jaws for saw motion bites, like the modern Komodo dragon which also has a weak bite force that does not have enough power to finish off its prey. 

In 2005, the first study was conducted to estimate the bite force of Deinonychus, which was based on reconstructed jaw musculature. As per the study, the maximum bite force of the Deinonychus was only about 15% of the modern American alligator. In 2010, Paul Gignac and colleagues attempted to estimate the exact bite force of Deinonychus directly based on newly discovered Deinonychus tooth puncture marks in the bones of a Tenontosaurus. According to that, the puncture marks came from a large individual and provided the first evidence that large Deinonychus could bite through bone. 

Gignac's team also attempted to find the bite force of Deinonychus using the tooth marks and estimated by biomechanical studies. They found that the bite force of Deinonychus to be between 4,100 and 8,200 newtons, which is greater than living carnivorous mammals including the hyena, and equivalent to another similar-sized alligator.

Study Based on Limb function

The shape and curvature of the sickle claw of the Deinonychus are showing distinct features for deinonychus from other species in dinosaurs, In 1969, Ostrom described the specimens with strongly curved sickle claws. In 1976, new specimens, which had claws that had a weaker curvature, which was similar to the 'normal' claws on the remaining toes. Based on that, Ostrom found that the deinonychus size and shape of the sickle claws may vary depending on the deinonychus sexual, or age but he could not prove his study. Later, the nails of deinonychus were found to describe their anatomical features. 

According to Ostrom’s study, the  Deinonychus must kick their prey using a sickle claw to cut and slash them. Later found that the Deinonychus used their sickle claws to deliver small stabs to the victim. As per the test run by Manning and colleagues in 2005, the robotic replica was perfectly matched between the anatomy of Deinonychus and Velociraptor. Further analysed that, they should use their hydraulic rams to make the robot strike a pig carcass. Also found that the talons of deinonychus effectively helped them for climbing the trees or mountains rather than killing blows. Deinonychus claws were resistant to forces acting in a single plane due to gravity and supported them for climbing.

Later Ostrom compared Deinonychus with the modern ostrich and cassowary birds and noted that even these birds can cause serious injury using their large claws on the second toe. But the claws of the cassowary were only about 125 millimetres. Usually, Cassowaries use their claws to defend themselves, to attack threatening animals and they are providing agonistic displays to threaten other species. The deinonychus claws must have the same role. 

In 2002, Biomechanical studies by Ken Carpenter found the function of Deinonychus forelimbs, which was grasping the prey, as the lengths of forelimbs are high and it would have permitted them to reach longer distances than other theropods. The large elongated coracoid present in the Deinonychus showed that they have powerful muscles in the forelimbs, which are strengthened for interpretation. But the bone cast in Deinonychus showed that they cannot fold their arms like modern birds. Even the feathered fingers and wings have limited the motion range of Deinonychus’s forelimbs. Likewise, the functions of Deinonychus’s fingers must be limited by their feathers. The study of Parsons and Parsons showed differences in morphological characteristics among juvenile and subadult specimens of Deinonychus adults. Like, the arm of young deinonychus was longer than the adults. Also, the deinonychus claw curvature becomes straight while they are getting old.

Speed of Deinonychus 

Deinonychus meaning carnivorous species that belong to the dinosaur family. But they are not a fast-running species and Deinonychus had fleet-footed. Later, Ostrom found the length of the femur. And he noted the ratio of the femur to the tibia, Which may have any relation between the speed of deinonychus. The foot-tibia ratio of modern fleet-footed birds like an ostrich is about 95. But the femur to the tibia of the deinonychus is 48. Finally concluded that the Deinonychus were slow-moving species while comparing to other species of dinosaurs

The low foot to lower leg ratio in Deinonychus is mainly due to unusually short upper foot bones. The ratio of the low foot to the lower leg is large in smaller individuals and smaller in the larger ones. Also, he found that the short metatarsus of large creatures reduced overall stress on the leg bones during an attack, and interpreted the unusual arrangement of muscle attachments in the Deinonychus leg also supported his idea that a different set of muscles was used in the predatory stroke during walking or running. In 1981, Richard Kool studied the Canadian dinosaur footprints and produced the rough walking speed of different species. Likewise, he estimated the trackway and running speed of Deinonychus, which is about 10.1 kilometres per hour. 

Deinonychus Eggs

In 2000, the Deinonychus eggs were identified, which was one of the original specimens that allowed comparison with other theropod dinosaurs in terms of egg structure, nesting, and reproduction. Later,  Makovicky and Grellet-Tinner examined the specimens in 2006 and proposed the possibility that the dromaeosaurid had been feeding on the egg, or the egg fragments had been associated with the Deinonychus skeleton. Further, this idea dismissed the concept that the eggs may be the meal for a theropod. The Deinonychus laid blue coloured eggs, which were covered by their open nest. According to the study, modern birds may have a habit of creating open nests and laying eggs must have been adapted from  Deinonychus and other dinosaurs, through this they protected their eggs from predators. 

After examining the microstructure of Deinonychus eggs confirmed that they belong to a theropod. Also, the Deinonychus eggs had similar characteristics to theropod eggs. But they are different from ornithischian and sauropod eggs. Grellet-Tinner and Makovicky found the diameter of Deinonychus eggs based on the width of the deinonychus pelvic canal, which is about 7 centimetres. The size of deinonychus eggs is similar to the Citipati eggs. Important deinonychus facts are that the thicknesses of Citipati and Deinonychus eggshells are almost identical.