Hi world how are you???? Good i hope. So lets get to it December is almost over and we all know what happens when that last day comes. We have to say goodbye to 2015 and hello to 2016!!! So in the spirit of Christmas Dino-Claws is gonna give the world non stop tales,stores and other surprises in these next few blogs. So let's get started with the naughty of the Dromaeosaurs.
At the time of writing Acheroraptor is only known from a maxilla and dentary with additional referred teeth. These however have been enough to at least confirm that Acheroraptor was actually a North American cousin of the famous Velociraptor that lived in Asia. Comparison of the known Acheroraptor fossils at least suggest that the total length of the holotype individual of Acheroraptor would have been somewhere in the region of about two meters in length.
Acheroraptor was the only dromaeosaurid dinosaur known from the Hell Creek Formation until 2015 when the genus Dakotaraptor was named. At least five and half meters in length however, Dakotaraptor would have been significantly larger than Acheroraptor.
Care should be taken not to confuse Acheroraptor with Archaeoraptor.
Achillobator
Although discovered in a joint Mongolian and Russian dig in 1989, Achillobator did not get named until 1999. These remains are very fragmentary but do suggest that Achillobator was a particularly large dromaeosaurid dinosaur. The achilles tendons seem to have been particularly well developed, probably to account for the extra size and weight of the body, and were referenced in the naming of the genus.
Achillobator has in the past been accused of being a fossil chimera, which in the simplest terms means that the fossil material attributed to the genus actually represents more than one kind of dinosaur. The main support for this theory is that the pubis (most forward bone of the hips) points vertically down. In all other known dromaeosaurids the pubis points backwards similar to birds, something that often leads to the pubis pointing in the same direction as the ischium (the bone at the rear of the hips). Despite this claim however some of the skeletal remains of Achillobator were found partially articulated, and the other bones all show dromaeosaurid characteristics. General opinion today points to Achillobator being a dromaeosaurid, but one with a unique hip structure.
Additional study of Achillobator has yielded the conclusion that it was most closely related to the dromaeosaurids Dromaeosaurus and Utahraptor, the latter being a particularly large dromaeosaurid.
Acheroraptor
Acheroraptor was the first confirmed genus of dromaeosaurid dinosaur to be known as coming from the world famous Hell Creek Formation of North America. Dromaeosaurid teeth had been known before this time, but they had often been presumed to have come from either Dromaeosaurus or Saurornitholestes, though these teeth are now more commonly referred to Acheroraptor.At the time of writing Acheroraptor is only known from a maxilla and dentary with additional referred teeth. These however have been enough to at least confirm that Acheroraptor was actually a North American cousin of the famous Velociraptor that lived in Asia. Comparison of the known Acheroraptor fossils at least suggest that the total length of the holotype individual of Acheroraptor would have been somewhere in the region of about two meters in length.
Acheroraptor was the only dromaeosaurid dinosaur known from the Hell Creek Formation until 2015 when the genus Dakotaraptor was named. At least five and half meters in length however, Dakotaraptor would have been significantly larger than Acheroraptor.
Care should be taken not to confuse Acheroraptor with Archaeoraptor.
Although discovered in a joint Mongolian and Russian dig in 1989, Achillobator did not get named until 1999. These remains are very fragmentary but do suggest that Achillobator was a particularly large dromaeosaurid dinosaur. The achilles tendons seem to have been particularly well developed, probably to account for the extra size and weight of the body, and were referenced in the naming of the genus.
Achillobator has in the past been accused of being a fossil chimera, which in the simplest terms means that the fossil material attributed to the genus actually represents more than one kind of dinosaur. The main support for this theory is that the pubis (most forward bone of the hips) points vertically down. In all other known dromaeosaurids the pubis points backwards similar to birds, something that often leads to the pubis pointing in the same direction as the ischium (the bone at the rear of the hips). Despite this claim however some of the skeletal remains of Achillobator were found partially articulated, and the other bones all show dromaeosaurid characteristics. General opinion today points to Achillobator being a dromaeosaurid, but one with a unique hip structure.
Additional study of Achillobator has yielded the conclusion that it was most closely related to the dromaeosaurids Dromaeosaurus and Utahraptor, the latter being a particularly large dromaeosaurid.
Adasaurus
At just under two meters long, Adasaurus is roughly on the smaller average end of the size range for dromaeosaurs. Close study of Adasaurus remains have identified it as a dromaeosaurine dromaeosaurid, meaning that it is more closely related to dromaeosaurs such as Yurgovuchia, Dromaeosaurus, Achillobator and Utahraptor. Like with its relatives, Adasaurus was a hunter of other animals, quite probably other dinosaurs. The primary killing weapons for Adasaurus would have been the two enlarged sickle claws on its feet, which may have been used to jab at prey. Although not confirmed, because Adasaurus is a dromaeosaurid dinosaur, it is expected to have had at least some feathers present on the body in life.
Adasaurus was named after an evil spirit called Ada which appears in Mongolian mythology. The species name mongoliensis simply means ‘From Mongolia’. Adasaurus is one of many dinosaurs recovered from the world famous Nemegt Formation, which also holds other notable dinosaur genera such as Alioramus, Gallimimus, Avimimus, Therizinosaurus and Tarbosaurus amongst an ever increasing number of discovered dinosaurs.
Atrociraptor
Atrociraptor has been described from very incomplete remains, but two clear observations can be made about this dinosaur. One is that the snout appears to be both deeper and shorter than most other dromaeosaurs, something that could indicate a strong bite due to larger muscles and the outer teeth being placed closer to the fulcrum of the jaw articulation. Second is that the teeth have very large serrations, something that would greatly improve the slicing ability. Additionally the teeth in the mouth are of different sizes but otherwise have an identical form to one another. These two things together might indicate a prey specialisation in animals with tougher hides that would require a stronger bite force, as well as larger serrations for more efficient cutting.
Because the teeth are so distinctive, further isolated teeth that were previously assigned to Saurornitholestes have now been included with Atrociraptor. The type species of Atrociraptor, A. marshalli, is in honour of Wayne Marshall who discovered the first remains back in 1995.
Austroraptor
Although not as large as the North American Utahraptor, Austroraptor is still the largest dromaeosaurid currently known from South America. However to mark Austroraptor down for just this reason would be doing the genus a grave injustice as Austroraptor displays many features that make it unique among the other members of its group. First are the proportionately small forearms, limbs that are usually well developed in other dromaeosaurids so that they can get a better hold on prey as they use their sickle claws to make a kill. The skull of Austroraptor is also quite narrow and elongated which indicates a lack of developed biting muscles that in turn means a proportionately weaker bite force. Finally the teeth are not laterally compressed or serrated like other dromaeosaurids but conical and suited more for holding prey.
It’s plausible that Austroraptor may have been a niche predator that focused upon just one type of prey. The underdeveloped arms meant that Austroraptor probably did not leap onto the sides of large prey, and as such it possibly hunted smaller animals. The describers of the genus also compared the conical teeth as being similar to those of spinosaurids, a group of specialised theropods widely thought to be fish eaters. Include the weaker bite force into this mix and you have a predator that is better adapted to small prey despite its larger size.
It’s also possible that Austroraptor may have been more of a scavenger, using its size to drive off smaller predators from their kills while using its speed to avoid larger ones, but this does not support the presence of specialised teeth. Conical teeth like these are suited for holding small and possibly slippery prey like fish, not tearing flesh from a carcass. Also just as spinosaurids used the large claws on their hands to tear apart fish, Austroraptor may have used its sickle claws in a similar fashion. Although the sickle claws are more associated with stabbing rather than slashing, they may well have still been able to pull apart smaller animals so that the conical teeth and weaker jaw muscles were not a hindrance.
If the above is correct then hunting behaviour for Austroraptor may involve it using its speed to chase down small animals and using its claws to stab into their backs. Austroraptor may have also used its claws to strike out at fish in shallow water where it could then pick them out with its specialised teeth holding them firm in its mouth. On shore it could then use its claws to pull the fish into bite sized chunks for easier eating.
Balaur
The dromaeosaurids are a very popular group of dinosaurs that all share a few common features. These include reasonably lightweight build, long stiff tails for balance, legs and pelvis adapted for very fast running and a large sickle shaped claw on the second toe of each foot. Balaur however is a dromaeosaur with a difference; instead of having one sickle shaped claw on each foot it had two. These claws were on the second and first toes, and seem to be the principal killing weapons since the hands are known to have one digit less than most other known dromaeosaurids.
In popular fiction the large sickle claws are usually interpreted as slashing weapons that could open up the side of an animal in a single stroke, an idea based upon very early ideas about dinosaurs like Balaur. However more modern analysis has produced scenarios where the sickle claws are more suited to stabbing rather than slashing. Additionally they may have also been used for getting a grip onto similarly sized or larger prey, and in the case of Balaur, the two sickle claws may have been to compensate for a lack of one of the hand digits.
Balaur has a number of other distinctive features that distinguish it from other dromaeosaurids, but overall it seems to have been more heavily built than its relatives. Palaeontologists are able to tell this because the bones, particularly those of the limbs, are shorter and more robust than in the closest relatives. This suggests that Balaur was built for power rather than high speed. It is curious that a dinosaur from a typically fast and lightweight family line would deviate so much from the others, but the reasons for why may be down to environmental factors from where it lived.
So far Balaur remains have only been found in Romania from a part that back in the late Cretaceous period was actually separated from the mainland. Today we now call this landmass Hateg Island (after the Hateg Basin, which it would form after its collision with mainland Europe), and this island is particularly noted for the large variety of dinosaurs that have been recovered from there. The most interesting fact about this dinosaur is that they included varieties such as sauropods and ornithopod hadrosauroids. On the mainland these varieties could comfortably grow up to ten meters long and probably more for certain genera, but on Hateg Island the typically large dinosaurs like sauropods grew much smaller than their mainland relatives.
The reason for this is a process called insular dwarfism. Island ecosystems are fragile because there is a reduced land mass for plants to grow upon. This means that herbivorous animals that feed upon plants have less food, and no option to search elsewhere because they are surrounded by so many miles of sea, they cannot reach other areas upon the mainland. Another factor to consider is that for a species of herbivores to survive, you need many individuals, perhaps as many as a few hundred to avoid any negative effects on inbreeding. The one logical result for large animals that find themselves living in such restricted ecosystems is that they grow smaller, something that means they do not need to eat so much food, so they don’t exhaust the available supply.
With an estimated size around the two meter mark, Balaur does not seem to have grown small by insular dwarfism, many mainland varieties of dromaeosaur also grew to this size with some being larger, and some even being smaller. But on Hateg Island Balaur would have had access to dwarf sauropods like Magyarosaurus and hadrosaurids like Telmatosaurus. Although much smaller than their mainland counterparts, these types of herbivorous dinosaurs would have still been quite powerfully built, and arguably not that fast, at least when compared to a dromaeosaurid like Balaur. This could be where the more muscular legs and double sickle claws on each foot could have come in; they would have given dinosaurs like Balaur a significant edge when attacking them. Additionally in the absence of large theropods like those known in larger continental landmasses, dromaeosaurids like Balaur would have found itself elevated to the status of apex predator for the ecosystems.
The name Balaur is a reference to a dragon in Romanian folklore. Although many prehistoric animals have been after dragons (for example the archosaur Smok was named after a dragon in Polish folkore) the name has a double meaning since dragons are seen as winged flying creatures, and dromaeosaurid dinosaurs are treated as being very close to the ancestors of birds. The type species name B. bondoc means ‘boned oak’ and is based upon the squat appearance of the holotype remains. Out of all the other dromaeosaurids, Balaur is considered to be most closely related to those like Velociraptor from Asia.
*Special note - While Hateg Island is especially well noted for its dwarf dinosaurs, at least one giant has been found there. This refers to the pterosaur Hatzegopteryx, and although known from only partial remains, these indicate that it was one of the largest pterosaurs of all time.
Bambiraptor
Named after the title character in the 1942 film Bambi, Bambiraptor was a small dromaeosaur dinosaur that has caused a lot of excitement in the science of palaeontology. Discovered by a fourteen year-old Wes Linster in 1993, the Bambiraptor holotype is of an exceptionally well preserved individual that is estimated to be around a ninety-five per cent complete dinosaur. In addition to this the bones display very little distortion (fossils often become distorted due to the immense pressures of layers of rock lying on top of them, especially in lightly built animals) so it has been relatively easy for palaeontologists to reconstruct this dinosaur when compared to what they usually have to work with. This has led to Bambiraptor being popularly dubbed a ‘Rosetta stone’ after the discovery of the stone that allowed for the decryption of Ancient Egyptian hieroglyphs, but in Bambiraptor the reference is more to it revealing answers about the dromaeosaur dinosaurs.
The holotype fossil for which Bambiraptor is named is of a juvenile dinosaur, something that has led to some controversy over the facts and actual validity of this genus. Firstly is that Bambiraptor is often credited at being ninety centimetres long, but because the most complete specimen is only that of a juvenile, it is a certainty that adult Bambiraptor would have been bigger than this. In 2010 Gregory S. Paul estimated the length of an adult Bambiraptor at a larger one hundred and thirty centimetres long, which if accurate would still make Bambiraptor small, but nearer the size of other small dromaeosaurs.
Another misconception is that of intelligence, since Bambiraptor is thought to have had a large brain in relation to the size of its body. The size of the brain in proportion to the size of the body is termed Encephalization quotient, or EQ for short and basically works upon the principal that the larger the brain is in relation to the body the more intelligent the animal. This is why dinosaurs with a high EQ level like Troodon are often credited as being the most intelligent dinosaurs, but the theory is a controversial one. The main problem here is that the method for determining EQ does not fully take into account the kind of brain tissues involved, which is why an animal with a brain double the size of another animal with a same sized body can be seen on paper to have double the intelligence, even if the extra size was only attributed to something like extra brain cells for a greater sense of smell. The animal with a smaller brain however might have a larger cognitive centre (memory, problem solving, etc.) and actually be more intelligent than the larger brained animal but with less capable senses (smell, vision, etc.). Additionally you have to remember that the Bambiraptor holotype is of a juvenile, and juvenile creatures usually do have proportionately larger brains than adults because even though their bodies are still growing, they still need to be smart enough to process their surroundings. As such determining EQ especially from a juvenile can give a skewed interpretation of an animal’s actual intelligence.
Another thing that needs to be considered is that animals, and particularly some dinosaurs have been seen to make marked morphological changes as they reach different ages (a good example being the leg proportions between juvenile and adult tyrannosaurs), and being described from a juvenile specimen, some palaeontologists have considered the possibility of Bambiraptor actually being a juvenile of a previously described genus. Here some have pointed to the similar Saurornitholestes as the possible adult form of Bambiraptor, however most other palaeontologists continue to support the idea that Bambiraptor should be treated as a distinct genus.
One thing that is likely for Bambiraptor whether it was a juvenile or adult is the presence of feathers. Although not confirmed to be present in the holotype or any other remains so far attributed to the genus, many of the other dinosaurs that Bambiraptor is related to be known to have had them. Additionally some that have not had feathers preserved do also sometimes have the attachments for even better developed feathers. If indeed present upon the body, then Bambiraptor probably would have had a covering of primitive downy feathers that served as insulation.
Because of its small size, Bambiraptor is thought to have been a hunter of small mammals and reptiles like lizards which would have been very common small prey during the Late Cretaceous. The arms of Bambiraptor are thought to have been very dexterous as well as fingers that were semi opposable. What this means is that Bambiraptor could have possibly held small prey in its arms and actually lift them up to its mouth for easier feeding. It’s also possible that this greater dexterity may have also been for climbing. Bambiraptor however would have faced competition from slightly larger related dinosaurs such as the aforementioned Troodon and Saurornitholestes as well as Dromaeosaurus. Other threats could have also been the tyrannosaurs Daspletosaurus and Gorgosaurus, particularly juveniles of these two genera which would have been a lot faster and more agile than adults.
Bambiraptor has sometimes been credited with two species names when in fact it currently only has one. The species name B. feinbergi is in honour of both Michael and Ann Feinberg who bought the holotype from a fossil dealer and then donated it to science. However because feinbergi is in the singular vernacular, a pluralised version of feinbergorum was later proposed. This was used by a few people at first, but under naming guidelines set out by the ICZN (the body that governs the naming of animals) the first species name is not only valid but still has priority over the new version. For this reason Bambiraptor feinbergorum is now treated as a synonym to Bambiraptor feinbergi.
Buitreraptor
Buitreraptor was small, even for a dromaeosaurid dinosaur. Buitreraptor however is markedly different to most other currently known dromaeosaurid genera, especially by its skull. The jaws of Buitreraptor are long and slender, both advantages that could theoretically help in seizing prey like small lizards and mammals that might be hiding amongst rocks. The teeth, while small, recurve around so that the tips angle towards the back of the mouth, meaning that they would act like hooks to prevent prey wriggling off and moving forward out of the jaws. The serrations of the teeth also would have allowed for easy cutting into the flesh of soft bodied prey like the aforementioned lizards and mammals. Interestingly the sickle claw, usually so well developed in dromaeosaurids, is actually quite short and thick. It may be that while the sickle claw was likely a killing weapon in other genera, Buitreraptor simply used it to pin the bodies of small prey to the ground while it pulled off pieces with its mouth.
Like with its relatives, Buitreraptor is expected to have had a covering of feathers over its body, either completely or in certain parts like the arms and tail. Although no feathers have been found to conclusively prove that Buitreraptor had them, this lack of evidence has been factored down to lack of preservation, especially as remains have so far never been found to be one hundred percent complete anyway. The expectation for feathers in Buitreraptor arises from the observation from the discoveries of very well preserved dromaeosaurid individuals which have either been preserved with the feathers or the attachment points for them.
Although a predator itself, the small size of Buitreraptor meant that individuals of the genus were themselves likely prey for larger and more powerful predators. Two possible examples of these predators include Mapusaurus and Giganotosaurus, large carcharodontosaurids that were roaming around South America at roughly the same time as Buitreraptor.
Dakotaraptor
The one thing that immediately stands out about Dakotaraptor at first glance is simply the large size of this dromaeosaurid dinosaur. Most dromaeosaurid dinosaurs measure in at under two meters in length, with a few genera ranging between two and three meters long. The Holotype individual of Dakotaraptor however has a reconstructed length of five and a half meters. At the time of the 2015 description, this makes Dakotaraptor the second largest dromaeosaurid dinosaur known, with the largest being Utahraptor.
As far as comparison between Dakotaraptor and Utahraptor goes, Utahraptor lived in North America around Utah (clue is in the name) during the Early Cretaceous roughly one hundred and twenty-six million years ago. Dakotaraptor also lived in North America but around South Dakota towards the end of the Late Cretaceous some sixty-six million years ago. Not only are Dakotaraptor and Utahraptor separated by a wide temporal gulf, study of the known fossils of Dakotaraptor show that in body proportions this genus was actually more like genera such as Deinonychus and Dromaeosaurus than it was Utahraptor, making a direct link between Dakotaraptor and Utahraptor unlikely.
Studies of dromaeosaurid dinosaurs going back to the late twentieth century indicate that dromaeosaurid dinosaurs almost certainly had feathers. These feathers were not necessarily all over the body, but were likely on the thorax and abdomen and almost certain on the arms. Dakotaraptor supports this theory in that fossils of the ulna (one of the forearm bones) show attachment points for large pennaceous feathers. It is unknown to what extent feathers would have covered Dakotaraptor, but smaller insulating feathers are known to have covered the body in even larger theropod dinosaurs such as the tyrannosaur Yutyrannus. However other dinosaurs living in North America during the late Cretaceous such as the ornithomimosaur Ornithomimus are known to have had small feathers on the back and sides of the body, but have legs that were devoid of feathers. The coverage of feathers on Dakotaraptor were likely a reflection of environmental factors first, and additional functions such as display and egg insulation second.
In the early twenty-first century there has been a lot of debate concerning the relationship between dromaeosaurid dinosaurs and the evolution of birds, with the classic idea being that birds evolved from maniraptoran dinosaurs. There are now alternate theories that maniraptoran dinosaurs may have evolved from birds, or perhaps even to birds and back again, but the ideas are simply too long to explain and off topic for this article. The key point is that some dromaeosaurs may have had a limited flight ability even if only gliding as has been speculated for genera such as Microraptor. As far as Dakotaraptor is concerned, flight was almost certainly an impossibility, mainly for the simple fact that at about five and a half meters long Dakotaraptor would have simply been too big. There was also no way for Dakotaraptor to use its arms to generate anywhere near enough lift. The original study of the forearms of Dakotaraptor into wings, indicated the total ‘wingspan’ of Dakotaraptor would have been about one hundred and twenty centimetres, which is even less than what an average human adult could achieve if they held their arms out to the side.
Although certainly too big to fly, Dakotaraptor was still no slouch on the ground. Proportions of the leg show that the lower leg bones of the tibia and fibula were longer than the femur which makes up the upper leg. This allows for a significantly longer stride of the leg which directly translates to an increase in speed and ability to run fast. The vertebrae of Dakotaraptor were also pneumatised, meaning that they had air spaces within them. This dramatically reduces the weight of the bone, and with this factor in mind, Dakotaraptor would have actually been quite lightweight for its size. Not only would this allow for larger size growth, but it would also allow Dakotaraptor to retain some of the speed and agility that dromaeosaurid dinosaurs are known for.
At the original fossil site of Dakotaraptor, remains of more than one individual were found. The Holotype individual is the most complete of these, however there also seems to have been a notable difference in build between the holotype which is by far the most robust (heavily built), and the others which are more gracile (lightly built). All individuals seem to have been fully grown adults, so one train of thought is that these may represent a collection of male and female individuals. However that still does not make it certain which is which, as while in the animal kingdom males are usually the more robustly built, it is not unknown for females to have been the larger (the moa bird Dinornis is a good example). Only further study and fossil remains can tell us for sure.
Dakotaraptor is the second dromaeosaurid dinosaur known from the Hell Creek Formation, with the first being the much smaller Acheroraptor. The only predator known to have been around at the same time and location and also be bigger than Dakotaraptor is the mighty Tyrannosaurus. Possible prey dinosaurs for Dakotaraptor could include anything from ceratopsian dinosaurs such as Triceratops and Leptoceratops, ankylosaurs and nodosaurs such as Ankylosaurus and Edmontonia, pachycephalosaurs such as Pachycephalosaurus, and hadrosaurs and ornithopods such as Edmontosaurus and Thescelosaurus.
Deinonychus
Although Deinonychus was first discovered in 1931, it would not be until the 1960s with the advent of more discoveries that it would get named and studied in detail. These studies helped lead to one of the most radical ideas put forward in the field of palaeontology; at least some of the dinosaurs were warm blooded.
Dinosaurs had always been compared to the reptiles of today which are always slow and sluggish until they can warm themselves up by exposing themselves to heat sources such as basking in strong sunlight. Dinosaurs as a whole had always been considered to be ‘just big lizards’ but smaller Dinosaurs such as Deinonychus were built to be very small and very fast. Such a lifestyle necessitates the need for a faster metabolism. This in turn is better provided for by being warm blooded, which in turn again requires adaptations for conserving body heat. While there is no direct evidence to support the placement of feathers on Deinonychus, it is a member of the dromaeosaur family, whose members through other fossil evidence are accepted to have had feathers. It would actually be very surprising if Deinonychus did not have feathers.
When first discovered the skulls of Deinonychus were fragmented and in a state of poor preservation, giving rise to an appearance not unlike Allosaurus. Later, more and better preserved skull material brought in a re-construction that had the skull being similar to that of Dromaeosaurus, yet still not as robust. The palate was strongly vaulted allowing for a narrowing of the snout, which in turn allowed for improved stereoscopic version. This means that Deinonychus had very good depth perception allowing it to gauge distances of prey items with greater accuracy. The jugals on the skull were wide to accommodate the strong biting muscles and it is generally accepted that larger individuals could easily bite through bone. The skull has very large fenestrae, including two in the lower jaw that would line up beneath the orbital fenestra when the mouth was closed.
The tail is constructed in a similar way to other members of its group with each tendon overlapping several vertebrae, making the tail a rigid ‘pole’ that could only move at the base. This could be used as a counterbalance when running and turning at speed helping to close the gap on prey items before they could run away.
Many palaeontologists (although not all) consider Deinonychus to have hunted in packs. Evidence for this comes from the frequent remains of Deinonychus found around Tenontosaurus fossils. Tenontosaurus is much larger than Deinonychus, and a single animal would have had great difficulty in taking down an adult Tenontosaurus. This has led to the pack hunter theory, although doubters of the theory have claimed it could just be an example of mobbing behaviour, or many Deinonychus scavenging the kill of a larger carnivore.
Deinonychus was well suited for using its forelimbs to grasp onto its prey, but like with Velociraptor, the ‘killing claw’ on the second toe of each foot seems to be better suited for stabbing than slashing. It could be that the claw was used to stab at a critical spot such as the neck. It may even have been used as a defence against others of its species for territorial defence or in pack domination fights. The only thing that we can be relatively sure of is that the old idea of a Deinonychus slashing open a dinosaurs belly in a single stroke is not very likely. One little thing of note about the claw is that it seems to have been held back so that it did not hit the ground while it was walking. This does prove that Deinonychus did at least have a special purpose for the claw.
Dromaeosauroides
Dromaeosauroides is what is called a ‘tooth taxon’ as so far this dinosaur only has fossil teeth attributed to it. These teeth seem to come from a dromaeosaurid theropod dinosaur, and this is reason why for the name which means Dromaeosaurus-like. Comparison of these teeth to those of other dromaeosaurids suggests that Dromaeosauroides attained lengths of about three to four meters. Large fossil teeth attributed to the genus Nuthetes may actually represent further fossils of Dromaeosauroides.
Because Dromaeosauroides is only known from teeth, many consider the genus to be dubious given that it would be very difficult to attribute bones to the genus without a direct asssociation to the teeth. That said, Dromaeosauroides remains one of the so far few dinosaur genera to come from Scandinavia.
Dromaeosaurus
Although as the name suggests this was the first dromaeosaurid to be discovered, it was not well understood until some of the other dromaeosaurids were discovered and studied. This has allowed for the gaps to be filled in, giving a much more accurate representation of what Dromaeosaurus was like.
While Dromaeosaurus still had the sickle shaped claws on its feet, its skull was larger and much more powerful than most of the other dromaeosaurids, suggesting that it had a greater reliance on its jaws as a weapon. How the jaws were used is still incertain as they could have been for holding onto prey, crunching more heavily armoured prey, or simply have been a primitive trait from earlier forms. The larger skull also had an enlarged nasal cavity suggesting an enhanced sense of smell.
Graciliraptor
Though only known from fragmentary remains, Graciliraptor has been a key find for our understanding of dromaeosaurid dinosaurs as it represents one of the earliest known appearances of such a creature. At the time of its description in 2004, Graciliraptor was considered to be a close relative of the famous Microraptor, and like Microraptor, Graciliraptor was of a small size and probably had an extensive covering of feathers in life.
Itemirus
Itemirus is a genus of dromaeosaurid dinosaur that so far is only known from very incomplete fossil remains.
Hesperonychus
As so often happens in the dinosaur world, the incomplete fossil of Hesperonychus was unearthed (in Canada's Dinosaur Provincial Park) a full two decades before paleontologists got around to examining it.
It turns out that this tiny, feathered theropod was one of the smallest dinosaurs ever to live in North America, with a weight of about five pounds, dripping wet. Like its close relative, the Asian Microraptor, Hesperonychus probably lived high up in trees, and glided from branch to branch on its feathered wings to avoid larger, ground-dwelling predators.
Linheraptor
Smaller velociraptorine dromaeosaurs seem to have been one of the most important types of dinosaur in Asia during the Late Cretaceous as evidenced by the ever growing number of remains and genera. Linheraptor was similar in form to most others such as Velociraptor and it may have lived and hunted in pretty much the same way as them, principally using the enlarged sickle-shaped claws on their second toes as their main killing weapons. In depth analysis of these dinosaurs has revealed that Linheraptor is probably most closely related to the dinosaur Tsaagan.
Linheraptor is a reference to the Linhe district of Mongolia where the holotype remains were found (another dinosaur named after this district is Linhenykus). The species name L. exquisitus is in recognition of the exceptionally well preserved remains of the holotype.
Luanchuanraptor
Luanchuanraptor can go down in palaeontological history as the first Asian dromaeosaurid found outside of the Gobi Desert. Beyond this however the partial remains of the holotype make it hard to establish details about this genus. Luanchuanraptor was a dromaeosaurid meaning that it was a relatively small theropod dinosaur similar to others such as Dromaeosaurus and Velociraptor, though how close is currently hard to say. Luanchuanraptor has been described as being a ‘moderately sized' theropod. yet size estimates can vary greatly upon source from as little as one meter long, a more common one and a half meters all the up to three to even four meters long.
As a dromaeosaurid, Luanchuanraptor is expected to have had enlarged sickle shaped claws on its feet which may have served as killing weapons against prey. Also although not preserved with the holotype, Luanchuanraptor likely had feathers in life since this seems to have been the norm for the dromaeosaurids, though how much and in what places is completely unknown for Luanchuanraptor.
Mahakala
Named in 2007, Mahakala has been widely accepted as one of the most primitive formed dromaeosaurids so far discovered. Key to this idea is the observation that the third metatarsal is not compressed, whereas in more advanced dromaeosaurids and troodonts it is. However another fact to consider is that Mahakala lived during the Campanian of the Cretaceous, a time when dromaeosaurids had long been established. This means that Mahakala was a late surviving form that co-existed with the development of more advanced forms, perhaps specialising as a niche predator. This also does not disprove evolutionary theory, as it should be remembered that evolutionary processes only drive animals to change when there is a need too. When there is no need, an animal’s evolution can slow down and even stop.
Currently Mahakala is best known from the hind limbs and anterior half of the tail, but forelimb remains are also known and these are interesting as they are proportionally much shorter than the arms of other dromaeosaurids. These shorter limbs may or may not be another primitive feature, they may have been an adaptation unique to the genus. As mentioned above the small size of Mahakala probably meant that it was a specialised hunter of small animals such as lizards and primitive mammals like Zalambdalestes, perhaps even larger insects. This meant that Mahakala did not directly compete with its larger relatives such as the dromaeosaurs Tsaagan and the famous Velociraptor.
Microraptor
Microraptor was first presented to the world as part of the composite fossil called Archaeoraptor, where the tail of a Microraptor was added to the upper body of a Yanornis. Archaeoraptor was a scandalous fake that made headlines around the world, but in the aftermath of this, Microraptor would become known to science.
Because Arcaheoraptor was found to be a fake before it was ever officially named it was never an officially recognised genus. In fact its full name, Archaeoraptor liaoningensis, was printed before it was officially granted as a recognised specimen. In the wake of the discovery of Archaeoraptor being a fake, the avian paleontologists Storrs L. Olson tried to get the name Archaeoraptor assigned to the part that was from Microraptor to remove the Archaeoraptor taint from the palaeornithological record.
However Xu Xing, one of the palaeontologists who was part of the Arhcaeoraptor study team, had already found the counter slab and further remains, naming them Microraptor zhaoianus. Although Olson was first, he named the Microraptor part as a lectotype, a name that is taken from a group of specimens of the same name. But remember, the name Archaeoraptor was never officially recognised, and the specimen was only named as such in the media which does not count. As such no part of Archaeoraptor could be assigned the name as a lectotype, and it is for this reason Xu's name and description has gained wider acceptance and is now used the world over.
Microraptor is very special and is often called a 'four-winged' dromaeosaur. This is because not only did Microraptor have extensive feather coverage over its arms, it also has a similar extent of feather growth on its legs too. Although not a flyer like a true bird would be, Microraptor may have been able to use these feathered areas along with its small size and light build to glide across the tree canopies of the forests of Cretaceous China. As an arboreal dinosaur, Microraptor may well have lived like a bird. As a living animal, Microraptor is thought to have been most active at night as evidenced by the scleral rings. Stomach contents have also been preserved, revealing that smaller mammals formed at least a part of Microraptor's diet.
How Microraptor moved through the air is quite interesting. Initially it was thought that the arms and legs would have been held at the same level, and perhaps overlaid one another. However in 2005 the palaeontologist Sankar Chattrerjee said that an overlaid posture was not anatomically possible and instead proposed what has been termed the 'biplane method'. The biplane method is where the hind legs are held at a different height to the arms so that when viewed from the front, Microraptor would look like it had two pairs of wings. Chatterjee also constructed computer model that demonstrated Microraptor actually being capable of powered level flight, and if the living creature did indeed do this, Microraptor would have had quite a considerable range when airborne.
Other researchers have done their own studies on the flight ability of Microraptor, and while some of these recognise the 'biplane' method as possible, some consider it to have been inefficient and suggested that Microraptor had a different orientation when flying. What can also be considered is that Microraptor may not have had just one method of gliding and may have adapted different configurations to changing needs.
Neuquenraptor
Neuquenraptor was very nearly the first dromaeosaurid dinosaur to be discovered on the South American continent. First discovered in 1996, the holotype specimen was unofficially named Araucanoraptor argentinus in 1997. Also in 1997 another dromaeosaurid genus named Unenlagia was named from the same formation, and because this genus had a proper description, Unenlagia became the first ‘official’ dromaeosaurid dinosaur to be named in South America.
The remains known as Araucanoraptor were finally officially named in 2005, but this time as Neuquenraptor. The future for Neuquenraptor however is now uncertain because now there is speculation that the fossils of Neuquenraptor are actually further remains of Unenlagia, and since Unenlagia was officially named eight years before, Neuquenraptor may become a junior synonym to it Unenlagia.
The presence of dromaeosaurs in South America is yet further proof that South America was not the isolated continent that it was long presumed to be, or at least temporally but periodically connected to other continents. The presence of spinosaurid and carcharodontosaurid theropod dinosaurs in both South America and Africa during the later stages of the Early Cretaceous and beginning of the Late Cretaceous is proof that a faunal exchange was happening between these continents. The presence of hadrosaurs such as Secernosaurus and Willinakaqe is also possible proof that some dinosaurs managed to travel from North America into South America. The question remains, which route did the dromaeosaurs take?
Nuthetes
Originally thought to be a juvenile of a species of Megalosaurus, Nuthetes was later established as a distinct genus. Today Nuthetes is thought to represent a possible dromaeosaurid dinosaur, but the key word here is ‘possible’. So far Nuthetes is only known from teeth and a fragment of jawbone, making such things as an exact indification very difficult. It is also hard to estbalish any further details and the only lead that paleontoligsts have is that the Nuthetes material represents a possible dromaeosaur. If true than comparisons to other dromaeosaurs indicate that Nuthetes, if a dromaeosaur, would have been about two meters long.
There is also some confusion with the genus Dromaeosauroides from Denmark, as some larger fossil teeth that have been referred to Nuthetes may actually belong to Dromaeosauroides. Likewise, other teeth from Jurassic aged rocks may actually come from proceratosaurid dinosaurs (those related to Proceratosaurus). Overall, Nuthetes is considered to be a dubious dinosaur genus as it will be very difficult to infer further fossil remains based only upon the teeth.
Ornithodesmus
The story of Ornithodesmus can be a confusing one as for a long time the genus was credited with being a pterosaur, whereas we now know this was a mistake. It all began in 1887 when Harry Govier Seeley described a set of six sacral vertebrae that he thought belonged to a bird. Seeley came up with the name Ornithodesmus which means (bird link). Then later in 1887 John Hulke (in a paper without his name on it) made the suggestion that Ornithodesmus was not a bird but actually a pterosaur. Seeley later conceded this and he too began to classify Ornithodesmus as a pterosaur, even creating a second species O. latidens in 1901. Seeley however still thought the original holotype specimen of Ornithodesmus was very bird like, and so began to propose the notion that birds and pterosaurs shared a common ancestry (something we now consider to simply not be true).
The second species of Ornithodesmus was based upon far more complete pterosaur remains, and for this reason O. latidens was the public face presented to the wider public. Then in 1993 a startling discovery was made concerning the holotype specimen. In a 1993 study concerning the original sacral vertebrae that had been used to establish the type species in 1887, Stafford C. Howse and Andrew Milner concluded that the holotype was not a bird nor even a pterosaur, but actually a theropod dinosaur. Howse and Milner considered the holotype to have come from a small troodontid, but later research by Peter Makovicky and Mark Norell showed that it was actually a dromaeosaurid, and while others have speculated that this specimen may have actually been a ceratosaur or coelophysid, most palaeontologists now agree that the holotype specimen of Ornithodesmus was a dromaeosaur.
Because the holotype specimen of Ornithodesmus is now confirmed as a dromaeosaurid dinosaur, all of the pterosaur fossils once attributed to the genus, including the second species have now been had a new genus created for them called Istiodactylus. Details about the lifestyle of Ornithodesmus are uncertain due to the lack of fossil remains for the genus, but we do know that as a dromaeosaurid dinosaur Ornithodesmus would have been a lightly built predator of small animals, featuring a sickle shaped killing claw on the second toe of each foot. Comparison to the body proportions of other dromaeosaurid dinosaurs indicates that Ornithodesmus would have grown to just under two meters in length.
Pamparaptor
Argentina's Neuquen province, in Patagonia, has proven to be a rich source of dinosaur fossils dating to the late Cretaceous period.
Originally diagnosed as a juvenile of another South American raptor, Neuquenraptor, Pamparaptor was elevated to genus status on the basis of a well-preserved hind foot (sporting the single, curved, elevated claw characteristic of all raptors). As dromaeosaurs go, the feathered Pamparaptor was on the tiny end of the scale, only measuring about two feet from head to tail and weighing a few pounds soaking wet.
Pyroraptor
Pyroraptor acquired its name from the circumstances of its discovery. In 1992 the partially preserved remains of this dinosaur where discovered after a forest fire had swept through the area. Despite the very incomplete remains it has been possible to identify Pyroraptor as a distinct genus from the unique form of the sickle-shaped claws, features that are common to dromaeosaurid dinosaurs. Another common feature of the dromaeosaurid dinosaurs is the presence of primitive feathers on the body, something that Pyroraptor is also thought to have had despite the current lack of evidence proving it did.
From the same of region of France that Pyroraptor hails from, another dromaeosaurid named Variraptor has also been named. In the past there has been speculation that Pyroraptor may actually just be further remains of Variraptor which is also known from very incomplete remains. A 2009 study by Phomphen Chanthasit however pointed out differences in the shape of the ulnas (lower arm bones) that seems to support keeping Pyroraptor and Variraptor as separate genera.
Pyroraptor was one of the main dinosaurs featured in the 2003 Discovery Channel TV series Dinosaur Planet (not to be confused with 2011 BBC series Planet Dinosaur). The episode titled Pod’s Travels shows a speculative reconstruction where a lone Pyroraptor named Pod gets stranded upon a small island after a Tsunami, where he comes into contact with much smaller dwarf forms of the dinosaurs that he knew from the mainland including Magyarosaurus and Tarascosaurus.
Rahonavis
As a creature that displays both dinosaurian and avian features, it is not known for certain how Rahonavis fits in with the evolution of birds from dinosaurs. This is problem shared with other discoveries such as Xiaotingia and even Archaeopteryx as the difining line of when a bird becomes a bird and not a dinosaur is very hard to establish. One theory which is quite plausible is that flight evolved several times to be lost again in later descendents, whose descendents in turn would regain the ability, the pattern continuing until the establishment of the line towards Modern birds.
Although sometimes conceived as a bird, it’s possible that Rahonavis was more like a dromaeosaurid dinosaur. Again the possibility of Rahonavis evolving from flying ancestors is quite possible and the term secondarily flightless is often applied. Still some consider Rahonavis as being capable of flight as evidenced by the long fore limbs and attachments for ligaments to the shoulder that prove Rahonavis had the necessary degrees of wing motion for flight. Considering that the holotype specimen was found within the remains of a titanosaurid dinosaur, Rahonavis may have flown around Mesozoic Madagascar looking for carrion.
Rahonavis has been accused of being a fossil chimera, the remains of more than one animal being constructed into a single incorrect representation. However this claim has been strongly refuted on the grounds that the main skeleton was found articulated with parts of the wing and shoulder bones all found within the same small area to one another, indicating they all belonging to one animal.
Saurornitholestes
First discovered in the Canadian Province of Alberta by Irene Vanderloh in 1974 and named by Hans-Dieter Sues in 1978, Saurornitholestes was a small dromaeosaur that is thought to have been similar to the Asian Velociraptor in form. In 2006 a second species called Saurornitholestes robustus was named by Robert Sullivan. The ‘robustus’ part is in reference to the more robust build of the thicker bones of this specimen which indicates that this species was more heavily and powerfully built than the more northern types species S. langstoni.
Like with many other members of the Dromaeosauridae, Saurornitholestes would have had a small skull and jaws, but did possess the large sickle shaped claws that are a signature feature of this group that were probably the primary killing weapons. Saurornitholestes is usually depicted as a low level predator that would have focused upon hunting similarly sized dinosaurs and other small vertebrates like mammals and lizards. There is fossil evidence however that upon at least one occasion a Saurornitholestes fed upon the giant pterosaur Quetzalcoatlus, although the specimen of this pterosaur is thought to have come from a juvenile and hence smaller individual. It’s also possible that the Quetzalcoatlus in question may have already been dead and that the Saurornitholestes had scavenged the body, commonplace behaviour for predatory animals today that rarely pass up the chance for a free meal.
Saurornitholestes would have faced predatory competition from other small theropods like Dromaeosaurus and Troodon that were actually distantly related to Saurornitholestes. However none of these dinosaurs were the apex predators of Late Cretaceous North America, that title belongs to the tyrannosaurs and there is fossil evidence to lend some support to this. A dentary (lower jaw bone) from the Dinosaur Park Formation was described in 2001 by Aase Roland Jacobsen as having tooth marks in the form of grooves across the bone. Although the size and spacing of the marks is similar to that of another dromaeosaur, the shape is closer to that of tyrannosaur teeth. Together this leads to the conclusion that Saurornitholestes was eaten by a juvenile tyrannosaur, something which is actually quite likely when you consider that juvenile tyrannosaurs had proportionately longer legs than adults which means that they could have run faster by comparison and with some juvenile tyrannosaurs showing similar leg proportions to ornithomimid dinosaurs (thought to possibly be the fastest dinosaurs), a dromaeosaur like Saurornitholestes would have had no chance of escape by running away.
The exact culprit of this kill is still unknown, but two tyrannosaur genera that are from the Dinosaur Park Formation at the same time as Saurornitholestes are Daspletosaurus and Gorgosaurus (a third tyrannosaur called Albertosaurus is also known from this formation but from a later period in the Cretaceous). Gorgosaurus is of particular interest since this had a more gracile build than Daspletosaurus meaning it would likely have been the faster of the two. Southern populations of Saurornitholestes would have also had to live in the shadow of a different kind of tyrannosaur, the slightly shorter snouted Bistahieversor.
Shanag
During the early Cretaceous period, 130 million years ago, it was difficult to distinguish one small, feathered dinosaur from the next--the boundaries separating raptors from "troodontids" from plain-vanilla, bird-like theropods were still in flux.
As far as paleontologists can tell, Shanag was an early raptor closely related to the contemporary, four-winged Microraptor, but also shared some characteristics with the line of feathered dinosaurs that went on to spawn the late Cretaceous Troodon. Since all we know of Shanag consists of a partial jaw, further fossil discoveries should help determine its exact place on the dinosaur evolutionary tree.
Sinornithosaurus
Sinornithosaurus was especially well preserved, and not only were the presence of feathers clearly revealed; they showed indications of having differing colours for different body areas. The feathers, while not exactly like those of modern birds, are still more advanced than in other species, including some of the later dromaeosaurids. This is significant as it helps cement the argument that birds evolved from dinosaurs, but not from the later and larger dromaesarids, which detractors to the theory say is impossible. Instead it proves that the transition happened earlier with smaller dinosaurs that possibly also led arboreal lifestyles.
As a living creature, Sinornithosaurus probably hunted around the forest floor looking for things like small mammals. Very interestingly the scleral rings indicate a cathermal lifestyle, meaning that Sinornithosaurus would have been active for small periods throughout the day or night. Aside from the usual night or day scenario, this would be good advantage for a forest hunter as light levels would be constantly changing as it moved through varying vegetation densities in the forest.
Sinornithosaurus once had the suggestion put forward that it had a venomous bite. This was based on an interpretation of the front teeth being elongated and grooved to allow poison to run through, with space for poison glands in the skull. However a subsequent study has cast significant doubts against this theory on the basis that grooved teeth are known throughout all theropods, and are not indicative of poison delivery. The study also explained the elongated teeth simply as regular sized teeth that had partially fallen out as a result of the skull being crushed during the preservation process. No evidence was found to support the presence of poison glands on the basis that all the internal skull areas were as expected to be, with no special area for glands.
Tianyuraptor
Although not very well known, Tianyuraptor is important to many palaeontologists because it is often regarded as a transitional form that links northern and southern genera of dromaeosaurids. Tianyuraptor is noted for having a smaller than usual furcula and arms that are proportionately much smaller than those of other dromaeosaurid genera. Overall, Tianyuraptor is actually quite a bit larger than most other known microraptorian dromaeosaurs, though it still has the long hind leg proportions, meaning that it was likely a very fast runner for its size. The proportionately much smaller arms however mean that there was practically no chance that it could glide for short distances, as has been proposed for some other smaller microraptorian genera like Microraptor.
Tsaagan
Originally thought to be another specimen of Velociraptor, a CAT scan in 1998 revealed that the fossil was of a new though closely related genus. Additional study of Tsaagan has indicated that it is most closely related to Linheraptor. Tsaagan probably lived and hunted like most other small Asian dromaeosaurids, hunting either other small dinosaurs as well as possibly smaller vertebrates such as lizards or even small mammals like Zalambdalestes.
Unenlagia
Initially thought to be a juvenile Megaraptor, Unenlagia was found to not only be a separate species but one that would challenge the notions for the origins of flight. Unenlagia fits into the Unenlagiinae group, which is also considered by some to be the rightful home of the dromaeosaur Rahonavis. If correct, that would mean that Unenlagia either lost the ability of flight after evolving from flying ancestors, or that Rahonavis had evolved flight from others independent from the accepted Archaeopteryx lineage.
Unenlagia is considered to be too large for flight itself, and the wings while having a high degree of motion, are thought to not being able to being raised above the spine. One consideration is that the wings were held out and used as stabilisers while chasing prey.
Utahraptor
Superficially, Utahraptor appears to be an earlier, scaled up version of Deinonychus. Specimens of Utahraptor are fragmentary but suggest a potential size of up to seven meters long, with some more conservative estimates falling nearer six meters long. These estimates make Utahraptor a contender for one of the largest known dromaeosaurids, but if that were not enough there are some specimens that hint to Utahraptor possibly being even larger.
Being a larger animal, Utahraptor also had a larger claw estimated to potentially be twenty-four centimetres long. Utahraptor had thick leg bones and are not what you would expect from a fast hunter. They may have instead had extra powerful muscles for driving the killing claw forwards into its prey. Bringing all of the above together, Utahraptor probably focused upon its attentions to larger prey items such as hadrosaurs or smaller sauropods.
As a dromaeosaurid, Utahraptor probably shared the same phylogenetic features of the group, including having feathers. While no feathers have been found with Utahraptor remains, it would be an exception to the 'group rule' if it did not have them. One thing to consider however is that the large size of Utahraptor may have meant it had a degree of gigantothermy that would not have been present in its smaller group relatives. If so then it may have had a reduced or altered arrangement of feathers instead.
Variraptor
Reconstruction of Variriaptor from available fossils is difficult as only partial remains exist. Discovered fossils do appear to be superficially similar to Deinonychus, although Variraptor appears to be of an overall smaller build. Some size estimates do have Variraptor reaching up to three meters in length, although the smaller estimate of two meters is more common.
Variraptor has been considered by some to be a Nomen dubium due to lack of identifying features from existing remains. Additionally Variraptor is has been considered by some to have a potential synonymy with Pyroraptor.
Velociraptor
The overall appearance of Velociraptor was that of a lightweight bipedal hunter built for speed, unlike other known Dromaeosaurids by having an upturned snout at the front of a long, low skull. The skull was filled with small teeth, suitable for taking meat off a carcass, but not for killing. Instead of a ‘killing bite’, Velociraptor would instead utilise the enlarged sickle shaped claws that it had on the second toe of each foot. Its hands were large and suitable for grabbing onto prey. The tail had a special series of tendons that kept it stiffened and erect, providing a crucial form of balance when running and manoeuvring at speed. Examination of the scleral rings has drawn comparison with modern birds that are nocturnal, also hinting at a nocturnal lifestyle for Velociraptor.
Velociraptor is one of the dinosaurs that without question had feathers. Evidence for this comes from the quill knobs on the fossil material, particularly the forearms. These are where feathers were anchored in place, and without feathers there would be no quill knobs (although on the other hand, lack of quill knobs does not mean lack of feathers). The feathers on Velociraptor would have provided insulation allowing it to maintain a high metabolism, a vital requirement for a very agile and active hunter. Also Velociraptor lived in a fairly arid landscape and the feathers would have provided extra protection against the cold nights that are often associated with arid environments. A further idea is that the feathers may have also served a display purpose.
The claw seems to have been used in a stabbing motion as opposed to the much popularised slashing motion. While sharp at the point, it is not particularly sharp along the inner curve as you might expect for a ‘slashing’ weapon. Further, analysis of a fossil discovered in 1971 that shows a Velociraptor locked in combat with a Protoceratops, suggests that the claw was being used to stab at the neck. This is a very intelligent place to strike with a small weapon as you would have both the carotid artery and Jugular veins transporting a key blood supply between the heart and brain. All Velociraptor would have to do is stab any one, and the Protoceratops would have been dead within minutes.
Velociraptor is the best known of the dromaeosaurids with the largest number of complete skeletons recovered. Velociraptor entered popular culture in a big way in the 1993 blockbuster movie Jurassic park, as well as subsequent sequels. The Velociraptor dinosaurs in these films are actually not accurate to the fossils and are instead more closely modelled on related dinosaurs such as Deinonychus.
Xiaotingia
The discovery of Xiaotingia caused some upset in the paleontological community because of its similarities to the world famous Archaeopteryx which has been hailed as the first bird since its discovery in 1861. This is because Xiaotingia is thought to be a dinosaur that is similar to a bird rather than a bird that is similar to a dinosaur. If those definitions seem blurry then that’s because they are and therein lays the problem of establishing the first 'true' bird.
Palaeontologists are split on whether or not Archaeopteryx was the first bird or the dinosaur that that preceded it, and were so for a long time before the discovery of Xiaotingia, although Xiaotingia does seem to point towards Archaeopteryx being closer to dinosaurs. Although there are many points of Xiaotingia that point to it being closer to dinosaurs, one bit of evidence that was mentioned by Xu Xing when talking about the discovery was the presence of an extensible second pedo-digit; The part that would become the trademark characteristic of the deinonychosaurs like Deinonychus and Velociraptor.
Ultimately the understanding of birds and their exact origin in dinosaurs will only be settled with further fossil material and study. While the discovery of Xiaotingia has cast doubt upon Archaeopteryx being the first bird, new discoveries may yet cast doubt on Xiaotingia being a dinosaur.
Yurgovuchia
Yurgovuchia was a small dromaeosaurine theropod that is often described as being ‘coyote sized’. Although Yurgovuchia is only known from very incomplete remains, mapping the known bones to the proportions of related but better preserved dromaeosaurs has yielded a rough estimate of around two and a half meters, though much of this figure would have been tail. As a member of the Dromaeosaurinae sub group of the Dromaeosauridae, Yurgovuchia is thought to be related to other members of this group such as Dromaeosaurus, Achillobator and Utahraptor. Utahraptor in particular seems to have had a close association with Yurgovuchia given that, fossils of both of these genera are known from the same geological area, though Utahraptor was considerably larger than Yurgovuchia.
The type species name is in honour of the geologist Helmut Doelling who is well known for his extensive work mapping Utah as well as discovering the Doelling’s Bowl fossil sites where the Yurgovuchia holotype remains were later discovered by Donald D. DeBlieux in 2005.
Zapsalis
Named in 1876 upon the description of some teeth, we know that Zapsalis was a dromaeosaurid dinosaur, but that’s about it. For this reason the genus is often listed as dubious, as like with most tooth taxons it would be very difficult to attribute actual fossils of bones. Zapsalis was initially described from teeth found in the Dinosaur park Formation of Canada, with further teeth from the Judith River Formation of Montana, USA also been credited to belonging from the genus. Teeth attributed to the genus from other fossil bearing Formations have now been questioned as many of them are superficially dromaeosaurid without any truly unique features. The Hell Creek Formation in particular is one example of this, as since the naming of the first confirmed dromaeosaurid genus from this Formation, Acheroraptor in 2013, many dromaeosaurid teeth from here are now attributed to this genus, though the 2015 naming of Dakotaraptor indicates that more genera may yet be found.
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