Deinonychus‭ (‬Terrible claw‭)

Short Info

Deinonychus‭ (‬Terrible claw‭)

Phonetic : Die-non-e-cus.

Named By : Ostrom‭ ‬-‭ ‬1969

Diet : Carnivore

Size : Estimated 63-3.5 meters long

Type of Dinosaur : Small Theropod

Type Species : D.‭ ‬antirrhopus (type)

Found in : USA

When it Lived : Early Cretaceous, 120-110 million years ago

Deinonychus (/daI’nanIk@sor dy-NON-i’-k@s from Greek deinos deinos “terrible” and “onux Onux, also known as genitive onukhos, onuchos “claw”) is one of the geniuses that belongs to dromaeosaurid theropod dinosaurs that has one known species, Deinonychus antirrhopus. This species, which is believed to be 3.4 meters (11 feet) in length, was a resident of the first part of the Cretaceous Period, about 115-108 million years ago (from the mid-Aptian period to the early Albian stage). Fossils have been found in The U.S. states of Montana, Utah, Wyoming, and Oklahoma in the sedimentary rocks from the Cloverly Formation, Cedar Mountain Formation and Antlers Formation However, teeth thought to be belonging to Deinonychus have been discovered further than the eastern part of Maryland.

Deinonychus FMNHJonathan Chen, CC BY-SA 4.0, via Wikimedia Commons

John Ostrom’s research into the paleontologist’s Deinonychus in the late 1960s changed the ways scientists thought about dinosaurs, which led to an “dinosaur renaissance” and igniting the debate about what kind of dinosaurs existed, whether warm blooded, or cold-blooded. Prior to this, the common concept of dinosaurs was one of slow, reptilian giants. Ostrom observed the diminutive body, the sleek horizontal posture, spine that resembled a ratite, and the large raptorial claws on the feet that suggest the presence of a fast, agile predator.

Deinonychus patte arrière gaucheDidier Descouens, CC BY-SA 4.0, via Wikimedia Commons

“Terrible claw” refers to the large, sickle-shaped talon that is located on the 2nd toe on the hind foot. This fossil has the largest, most strongly curving unnatural. Archosaurs live in a horny sheath around this bone, and it prolongs its length. Ostrom studied claws from crocodiles as well as birds, and recreated the claw for YPM 5205, which is more than 120 millimetres (4.7 in) long. Antirrhopus, the name given to the species, refers to “counter balance”, which is a reference to the idea of Ostrom about the purpose for the tail. Similar to other dromaeosaurids that have tail vertebrae, they are super-elongated tendons, ossified tendons, and super- processes. These characteristics could have turned the tail a rigid counterbalance, however fossils of the similar Velociraptor mongoliensis (IGM 100/986) is equipped with an articulated tail bone, which is bent laterally into a long, S-shape. This suggests that in its natural state the tail can extend to the sides, with an impressive degree of flexibility. In both Cloverly or Antlers formations, the remains of Deinonychus were found to be closely related to ones of ornithopod Tenontosaurus. Teeth found in Tenontosaurus samples suggest they were hunted or at least scavenged by Deinonychus.

Harvard DeinonychusJeremy Thompson, CC BY 2.0, via Wikimedia Commons

The fossilized remains of Deinonychus have been discovered in the Cloverly Formation of Montana and Wyoming and also in the contemporaneous Antlers Formation of Oklahoma, in North America. The Cloverly formation is dated from the mid-late Aptian through the early Albian stage of the Cretaceous approximately 120 to 108 Ma. Furthermore, teeth from the Arundel Clay Facies (mid-Aptian) from the Potomac Formation on the Atlantic Coastal Plain of Maryland could be placed in the Genus.

Deinonychus antirrhopus - AMNH - DSC06297Daderot, CC0, via Wikimedia Commons

First remains of the dinosaur were discovered in 1931 in the southern part of Montana close to the city of Billings. The paleontologist who led the team, Barnum Brown was mostly focused on preparing and excavating for the remains of ornithopod dinosaur Tenontosaurus However, when he submitted his report of the site of excavation for the American Museum of Natural History in 1931, he described that he had discovered a tiny carnivore close to the Tenontosaurus Skeleton “but encased in lime difficult to prepare.” The animal was informally named “Daptosaurus agilis” and made arrangements for describing it as well as having the bones, the specimen AMNH 3015, placed in a display, but never completed his work. Brown returned from the Cloverly Formation the small theropod’s skeleton with teeth that seemed to be larger than the rest, which was named informally “Megadontosaurus”. John Ostrom, reviewing this document a decade later, discovered that the teeth belonged to Deinonychus. However, the skeleton belonged to an entirely different animal. The skeleton was named Microvenator by John Ostrom.

About three decades later in the month of August 1964 the paleontologist John Ostrom led an expedition from Yale’s Peabody Museum of Natural History that found more skeletal remains close to Bridger. In the next two summers found over 1,000 bone fragments including at least three people. Because the connection between the bones found in the various excavations was weak and the precise amount of animals that were depicted impossible to identify accurately The type specimen (YPM 5205) of Deinonychus was confined to the entire left foot and a part of the right foot that certainly belonged to the same person. The other specimens were cataloged in 50 separate entries in the Yale Peabody Museum although they could be from as little as three people.

The subsequent research conducted of Ostrom as well as Grant E. Meyer analyzed their own materials along with Brown’s “Daptosaurus” in detail and concluded that they were the identical species. Ostrom initially published the findings of his study in January 1969. naming all the material referred to as the name Deinonychus antirrhopus. The precise designation “antirrhopus”, from Greek antirropos, translates to “counterbalancing” and refers to the probable reason for stiffened tails. On July 29, 1969, Ostrom released an comprehensive monograph on Deinonychus.

While a vast array of bones were available in 1969, some of the most important ones were missing or difficult to understand. There were only a few postorbital skull parts, no femurs no sacrum, and no furcula or the sternum, no vertebrae and (Ostrom believed) just a tiny piece of the coracoid. Ostrom’s reconstruction of the skeleton of Deinonychus included a unique pelvic bone, a pubis that was flat and trapezoidal unlike the other theropods. It was about the same length as the ischium and was located in front of it.

Based on the few maturing specimens of Deinonychus, it may attain 3.4 meters (11 feet) in length. It had skull lengths of 400 millimeters (16 in) as well as the high hip of 0.87 meters (2.9 feet) and the weight of 73kg (161 lbs) although there is a greater estimation of 100 kilograms (220 pounds). The skull was fitted with strong jaws that were lined with approximately seventy curving, blade-like teeth. The skull’s studies have advanced significantly throughout the years. Ostrom rebuilt the incomplete imperfectly preserved skulls were triangular, wide, and remarkably like Allosaurus. The skull of Deinonychus and closely related species that have excellent three-dimensional preservation prove that the palate is more elevated than Ostrom believed, making the snout much narrower and the jugals were flared wide which allowed for better stereovision. Deinonychus’ skull Deinonychus was distinct from that of Velociraptor however, by having a much stronger skull roof, similar to the skull of Dromaeosaurus but was not equipped with nasal ridges that were depressed like those of Velociraptor. The skull and lower jaws had Fenestrae (skull openings) which helped reduce their weight. In Deinonychus, the anterior the fenestra, an opening in the skull between the nostril and eye was especially large.

Deinonychus was a massive “hands” (manus) with three claws on each forelimb. First digits were shorter and the other was the longest. Each hind foot had a claw-like shape at the end of the second number that was likely to be used in predation.

Skin impressions have never been discovered in connection the fossils belonging to Deinonychus. The evidence indicates that Dromaeosauridae which includes Deinonychus was a feathered species. The Microraptor genus is older geologically, and more primitive in phylogenetically than Deinonychus and is part of that same family. Numerous fossils from Microraptor contain feathers that are vaned, pennaceous like the modern bird feathers on the legs, arms and tails, along with feathers that covert and contour. Velociraptor is geologically more ancient than Deinonychus however, it is more closely related to Deinonychus. The fossil of Velociraptor was discovered with quill knobs on its ulna. Quill knobs indicate where ligaments of the follicular follicular connect, and can be a clear indicator of feathers in modern-day form.

Source: Wikipedia