DEINONYCHUS

Deinonychus was far from being one of the largest carnivorous dinosaurs, but what it lacked in size it made up for in intelligence, terrifying looks, and hunting skills. This scary looking dinosaur was what the director of Jurassic Park films based the terrifying Velociraptor on in the films.

Deinonychus which is pronounced die-non-ih-kuss and in Greek translates into ‘Terrible Claw’ as like other raptors it had a huge sickle like claw on each of its feet. More on this later.

Deinonychus is a close relative of the much smaller but still vicious Velociraptor, they both had many similar features and characteristics with the most noticeable difference being the size of the animal.

Fred Wierum, CC BY-SA 4.0, via Wikimedia Commons

HOW FAST WAS Deinonychus?

With Deinonychus being described as being a fleet-footed dinosaur it is often assumed that Deinonychus could run incredibly fast, as was dramatized in the Jurassic Park films running at Olympic pace chasing down its prey. This unfortunately isn’t true.

It is hypothesised that Deinonychus could ‘trot’ at a leisurely 6mph. The average walking pace of a human is around 3-4mph so certainly not that quick at all. When it ran, it rotated its huge foot-claw upwards and ran on the other toes.

Quick Deinonychus Facts

Name	Deinonychus (die-non-ih-kuss)
First Found:	1931, Barnum Brown
When it lived:	Cretaceous, 115 – 108 million years ago
Weight:	8 tonnes
Length	3.4 meters (11 ft)
Diet:	Carnivore, meat

when did Deinonychus live?

Deinonychus walked the earth 108-115 million years ago in the Cretaceous Period.

The type of environment Deinonychus would have lived in would have been a floodplain or swamp like habitat.

It lived alongside dinosaurs such as the ferocious Spinosaurus, Archaeornithomimus (another swift, bird-like theropod), Probactrosaurus (an iguanodontid) and giant sauropods such as Titanosaurs and Tenontosaurus.

feathers and flight

Palaeontologists believe that Deinonychus would have had feathers along its tail which was flexible and could bend to the sides with a high degree of flexibility. It would also have feathers around its head and on its arms. Deinonychus arms were more than likely covered in feathers and many have hypothesised could have aided in some form of flight.

When we say flight, we don’t mean like a bird can fly but more or a ‘jump and glide’. It is also believed to be able to climb using its large claws, which is believed to allow it to jump and glide from trees. Deinonychus’s arms are to be believed to have acted as stabilisers whilst in flight or gliding towards its prey. These wing-like arms would have also acted as stability whilst wrestling with its prey, pinned down by large claws on both feet.

Deinonychus Head

The head of Deinonychus would have also displayed feathers and the skull of Deinonychus had one noticeable feature in that the opening between the eye and its nostrils (also known as the ‘antorbital fenestra’) was pretty large in comparison to other theropods.

This large opening would have reduced the weight of the head of Deinonychus head, making it more agile.

There are a lot of comparisons between Deinonychus jaws and other theropods in terms of ‘bite pressure / force’. However, given the size of the dinosaur its bite still would have packed a punch, around the same as a modern-day crocodile.

Rob Hurson, CC BY-SA 2.0, via Wikimedia Commons

Its jaw was also packed full of super sharp, seventy curved teeth built for gripping a ripping flesh away from its prey.

Studies of the skull have progressed a great deal over the decades. Ostrom reconstructed the partial, imperfectly preserved skulls that he had as triangular, broad and quite similar to the Allosaurus. The skull of Deinonychus was different from that of the Velociraptor in that it had a more robust skull roof like that of Dromaeosaurus and did not have the depressed nasals of Velociraptor. Both the skull and the lower jaw had fenestrae (skull openings) which reduced the weight of the skull.

Deinonychus ‘Terrible claw’

Finally let’s discuss Deinonychus’ large and rather scary claws or as we’ve mentioned earlier the ‘terrible claws’. On each foot Deinonychus had one sickle-shaped claw on the second toe of each foot. Fossil discoveries and reconstructions of this claw estimate it to be roughly 12cm long or 4.7inches.

Much like Velociraptor, Deinonychus would have used this giant claw as its primary killing and pinning down its prey.

Didier Descouens, CC BY-SA 4.0, via Wikimedia Commons

As found on other raptor dinosaurs this large claw was thin and curved almost like sickle and would have been covered by a bony sheath like a nail. Deinonychus would have kept this claw in an upright position when not in use. Keeping its large second toes off the ground in an upright position kept its primary weapon, poised ready for action and sharp.

For a dinosaur of its size Deinonychus had large hands with three claws on each finger, these large hands would have helped Deinonychus hold on its prey and as we discussed earlier climb. Deinonychus fingers consisted of one short first digit and was shortest with the second finger being the longest.

WHAT DID DeinonychuS EAT?

Deinonychus was a predator or carnivorous. It is widely accepted that Deinonychus would have exhibited feeding behaviour like that of modern day Komodo dragons or crocodiles.

The most dominant Deinonychus would have eaten first and would have been territorial around its prey.

Deinonychus may have hunted in packs, attacking even very large dinosaurs, perhaps even large sauropods and ankylosaurids. Deinonychus, along with the other dromaeosaurids, were among the smartest of the dinosaurs, as calculated from their brain:body weight ratio. This made them very deadly predators. Deinonychus remains have been found closely associated with those of the ornithopod Tenotosaurus. Teeth discovered associated with Tenotosaurus specimens imply it was hunted or at least scavenged upon by Deinonychus. Deinonychus must have been one of the most terrifying animals to live in the Cretaceous period.

HOW BIG WAS Deinonychus?

It is estimated that Deinonychus could reach 3.4 meters (11 ft) in length, and a weigh between 73kg (161lb) and up to 100kg (220lb).

Deinonychus was a lightly built, fast-moving, agile, bipedal (walked on two legs), bird-like dinosaur. It was built to kill. This meat-eater had a curved, flexible neck and a large head with sharp, serrated teeth in very powerful jaws. Each of its 3 fingers on each hand had large, sharp, curved claws. It had 4 toes on each foot, the second toe had a 5 inch (13 centimetre) sickle-like claw, and the other toes had smaller claws. Its long tail had bony rods running along the spine, giving it rigidity. Its tail was used for balance and fast turning ability. Deinonychus had a relatively large brain and large, keen eyesight.

No machine-readable author provided. Dinoguy2 assumed (based on copyright claims)., CC BY-SA 2.5, via Wikimedia Commons

WHO DISCOVERED Deinonychus?

Barnum Brown who was a famous American palaeontologist who discovered the very first Deinonychus in 1931. Unfortunately, Barnum Brown was so fixated on finding a more “Headline Grabbing” dinosaurs such as Tenontosaurus that when he discovered a specimen of Deinonychus, he named it Daptosaurus, dug it up, boxed it up and then forgot about it…

Up until 1964 experts thought there were only two separate types of theropod. The first being big and heavy such as the Tyrannosaurus Rex and the second type were much smaller such as Velociraptor. That was until a discovery in Montana, USA unearthed a theropod that displayed features of both types of theropods, that was Deinonychus.

From the fossil palaeontologist were able to clearly see that this Dinosaur would have walked on its back legs, was fleet footed and had one terrifying claw on each foot like that found on Velociraptor specimens. This wickedly sickle like claw was even bigger than that found on Velociraptor.

Ironically, if Barnum Brown hadn’t been so blind sighted, he may have recognised one of the most exciting dinosaur discoveries, as Deinonychus allowed palaeontologist to discover some of the most exciting facts about dinosaurs previously unknown to science.

Deinonychus eggs

It wasn’t until the year 2000 that Deinonychus eggs were discovered for the first time. Furthermore, a study that was published in 2018 proposed that Deinonychus eggs were blue in colour, likely to camouflage them in open top nests.

When you first read that the thought of blue eggs does sound rather strange however, many modern birds such as the Blackbird, Song Thrush and Starlings lay blue eggs which shows evidence of dinosaurs evolving into birds.

A forward-thinking palaeontologist called John H. Ostrom noticed how similar Deinonychus was to modern day birds. This was quite a theory, and as you can imagine it caused a lot of discussion around 1970 in America.

Mike R, CC BY-SA 3.0, via Wikimedia Commons

The thought that dinosaurs never really died out, they just evolved became more and more plausible the more science evolved. In the end what may have come across as a wild theory some 40 years ago is now accepted by some scientists.

Similar dinosaurs to Deinonychus

Velociraptor

Velociraptor was a very strange looking Dinosaur. Almost like a large ‘bird of prey’ but completely flightless. It had plenty of feathers, (more on this later) which ran all the way down its tail. Velociraptor did not have a beak however, just a short and powerful jaw packed full of razor-sharp teeth.

Velociraptor was grouped with several other dinosaurs who had a similar foot structure. They were given the nickname ‘terrible claw’. The reason Velociraptor and others’ close relations were given this nickname was due to the size of its second toe on both feet.

On each foot Velociraptor had one large, razor sharp claw roughly 8cm or 3 inches long. It is believed that Velociraptor would have used this giant claw as its primary way of hunting, using it to great effect, using it to stab at its prey.