Dromaeosauridae

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Dromaeosauridae
Utahraptor ostrommaysorum, a dromaeosaur from the Lower Cretaceous North America

Utahraptor ostrommaysorum , a dromaeosaur from the Lower Cretaceous North America

Temporal occurrence
Middle Jurassic to Upper Cretaceous ( Bathonian to Maastrichtian )
168.3 to 66 million years
Locations
Systematics
Dinosaur (dinosauria)
Lizard dinosaur (Saurischia)
Theropoda
Coelurosauria
Deinonychosauria
Dromaeosauridae
Scientific name
Dromaeosauridae
Matthews & Brown , 1922

The Dromaeosauridae are a group of theropod dinosaurs within the Deinonychosauria . They were small to medium-sized, two-legged carnivores that were probably closely related to the birds (Aves). Characteristic of these feathered dinosaurs were a narrow snout, long arms reinforced with curved claws, a stiffened tail and an enlarged sickle-shaped claw on the foot. Dromaeosaurids were discovered in Asia , Europe , North America , South America , Africa and Antarctica and existed for about 100 million years, from the Central Jurassic to the Upper Cretaceous . In popular culture , dromaeosaurids are also known as raptors.

features

Size and fossil record

Size comparison of some dromaeosaurs
Skeleton of Bambiraptor in the Oxford University Museum of Natural History

Dromaeosaurids were small to medium-sized animals. The size ranged from 47 to 63 centimeters in length and 200 to 600 grams in weight for Microraptor zhaoianus to over six meters in length for Achillobator and Utahraptor . According to studies by paleontologists around Alan H. Turner (2007), the generally small body dimensions of the basal species, i.e. those at the beginning of the evolutionary line, suggest that the common ancestor of all dromaeosaurids was only about 65 centimeters long and 700 grams in weight. An analogy can also be found in the related group Troodontidae . The researchers therefore suspect that a small body size was not first developed by the birds, but already existed in the common ancestors of the birds, the dromaeosaurids and the troodontids - a group that is also summarized as paraves . In the course of the evolution of the dromaeosaurids, the size increased drastically at least three times independently of one another: In Deinonychus and Unenlagia it was more than two orders of magnitude each , while the size of the grouping Achillobator + Utahraptor increased by three orders of magnitude.

With more than a dozen skeleton finds, Velociraptor is the best known member of the Dromaeosauridae. Quite complete skeletal material is also known from Deinonychus , Microraptor and Sinornithosaurus . Different genera such as Bambiraptor , Buitreraptor and Tianyuraptor are each known by a single almost complete skeleton. All other genera are only passed down through very incomplete remains.

skull

Skull of Dromaeosaurus in the Muséum national d'histoire naturelle in Paris
Skull scheme of a dromaeosaurid

The skull was relatively large and had a very narrow and elongated snout. The approximately triangular shape of the skull when viewed from above enabled eyes to be directed forward, which indicates spatial vision . The skull was short and deep. As with all theropods, the skull had several cranial windows : the eye socket was large and rounded, which indicates large eyes. The nostrils were large and shaped like a lying oval. The intermaxillary bone, a bone at the front end of the upper jaw , formed a long, rearwardly directed extension that separated the upper jaw from the nasal opening - thus the nasal opening was only limited by the intermaxillary bone and the nasal bone . The cranial fossa (fossa antorbitalis) in front of the eyes was long and interspersed with three further cranial windows - the fenestra antorbitalis , the fenestra maxillary and the fenestra promaxillaris. The lower jaw showed a thin and elongated mandibular fenestra. At the rear end of the top of the skull, the pair of parietal bones and the scaled bones formed a sharp, upwardly directed skull crest .

The skull shows various unique features that distinguish the group from other groups ( autapomorphies ). The paired frontal bone was T-shaped and showed a sinusoidal border of the fenestra supratemporalis , a skull window behind the eyes. Other unique features of the skull are an overhanging process of the scaly bone that extended above the head of the square leg , as well as a wing-like process of the os quadratum , which touched the os quadratojugale on the upper side ( dorsal ).

A complete palate has not yet been found in any specimen, although most of the bones of the palate are known. Only recent studies have shown that dromaeosaurids have a secondary palate (a bony partition between the mouth and nose). The intermaxillary bone had an almost square main body and four slightly curved teeth, while the upper jaw had 9 to 15 teeth. The row of teeth in the upper jaw ended before the beginning of the eye socket. The lower jaw was long and thin in Velociraptor , but deeper and more robust in Deinonychus and Dromaeosaurus . In the dentary , the tooth-bearing part of the lower jaw, there were 11 to 16 teeth. The surangular , a jawbone behind the dental, showed a prominent hole (foramen). The teeth were large, slightly curved back and, except for Buitreraptor, serrated on the back. It was characteristic of dromaeosaurids that the sawing became larger towards the tip of the tooth.

Trunk skeleton and limbs

Skeleton of Deinonychus
Foot skeleton of Dromaeosaurus

Almost completely preserved spinal columns are only known from Velociraptor , which had 9 cervical, 12 back, 5 to 6 fused sacrum, and at least 43 tail vertebrae. The neck of the living animal was clearly S-shaped. The vertebral centers of most of the cervical and dorsal vertebrae were shorter and wider than that of other coelurosaurs. A unique feature of the dromaeosaurids was the enlarged parapophyses of the vertebrae, extensions on the underside of vertebrae. The tail was long and reinforced by very elongated, rod-like prezygapophyses (mechanical connecting elements of the vertebrae). Elongated prezygapophyses were formed from the eleventh caudal vertebra and ran forward in interwoven bundles along the vertebral arches . A single one of these vertebral outgrowths could connect up to ten other vertebrae. Analogous to the prezygapophyses, the chevron bones on the underside of the caudal vertebrae also formed long, forward-facing processes that each surmounted several vertebrae and were arranged in interwoven bundles. In his description of the Deinonychus , John Ostrom (1969) suspects that these connecting elements stiffened the tail so that it was only movable at the base of the tail. A more recent find of a velociraptor shows a tail in the anatomical compound, which was horizontally bent in an S-shape without affecting the arrangement of the prezygapophyses. This indicates considerable lateral mobility of the tail.

The arms were among the relatively longest of all theropods and made up 65 percent of the length of the hind legs in Velociraptor and 80 percent in Sinornithosaurus . The forearm is 75 percent of the length of the upper arm in Deinonychus and 70 percent in Velociraptor . The hand was long and made up 40 percent of the arm length of Deinonychus . Each of the three rays of the hand ended in large, curved claws. The first ray was the shortest while the second ray was the longest. The third beam was a little shorter but significantly thinner than the second beam. The second and third phalanges of the third ray were extremely shortened - similar to Archeopteryx , but different from other coelurosaurs. Biomechanical studies have shown that dromaeosaurids could grab objects with the help of both hands. Bambiraptor was able to place the first and third fingers opposite each other and thus grasp objects with only one hand - such opposable fingers are not known from any other theropod.

The pubic bone was long and sloping backwards, but the basal ulcers were vertical. The thigh was 10 to 20 percent shorter than the lower leg, except for Achillobator , which showed a longer thigh than the lower leg. The metatarsus was short. The metatarsal II, III and IV were well developed and about the same size as the first and fifth metatarsal bones were reduced. The second toe showed an enlarged, sickle-like curved claw. The size of this "sickle claw" varied greatly in different genera - while it was extremely enlarged in Deinonychus and Velociraptor, for example , it was rather small in Adasaurus . At least some dromaeosaurids wore the second toe with the enlarged claw while moving above the ground, so they were functionally two-toed. This is indicated by two-toed footprints and many well-preserved skeletons in which the sickle claw has been preserved in an upright position. Fossil footprints also indicate that the base of the foot was supported by a fleshy pad, unlike other theropods.

Paleobiology

Function of the sickle claw

The famous "fighting dinosaurs"

Already Ostrom (1969) speculated in his description of Deinonychus ("terrible claw") that the enlarged "sickle claw" on the second toe could have served to kill prey. According to Ostrom's imagination, Deinonychus could hold large ornithopod dinosaurs with his long arms and slit open their bellies with his claws. To support this hypothesis, Ostrom points to reports of today's ratites such as cassowaries or ostriches , which have slashed people with their elongated claws on the second (inner) toe.

The spectacular find of the "fighting dinosaurs" made in Mongolia in 1971 supports the idea that the "sickle claw" could have been used to kill. This famous find shows the skeletons of Velociraptor and the Ceratopsia Protoceratops , which were apparently in the middle of a fight when they died: While the Velociraptor specimen - lying on the right side - placed the left foot with the sickle claw pointing downwards into the neck region of the Protoceratops stretches out, the right foot seems to be enclosed under the lying body of the Protoceratops specimen. Velociraptor's left hand rests directly behind Protoceratops ' cheek horn , while the latter holds Velociraptor's right forearm with its beak. In this position the fighting animals could have been surprised by a sandstorm and buried - it is also possible that the dead animals were covered by drifting sand . Since the sickle claw was stretched towards the neck, Kenneth Carpenter (1998) suspects that it was not used for slitting, but for piercing the neck veins or the trachea. So the claw could not have sliced ​​open the particularly thick skin of the abdomen and its muscles; the presumed cutting edge of the claw was also rounded, and the keratin coating in the living animal would probably have been less sharp than a blunt knife. In response to the reports given by Ostrom about ratites that can slash animals and people with their extended claws, Carpenter writes that these are very rare occurrences and that the slashing is due to the great weight of the ratites, not the cutting action of the ratites Claw itself - this makes it seem unlikely that the lightweight dromaeosaurids could perform a cutting effect with their sickle claw.

Researchers working with Phillip Manning (2005) suspect that the claw acted like a crampon with which the animals could hold on to large prey. Experiments with a hydraulic robot model of Deinonychus' foot have shown that the claw produced small and rounded puncture holes and that the tissue below the puncture holes was pushed together strongly, which gave the claw additional support. According to the imagination of these researchers, dromaeosaurids jumped on large prey and could cause many injuries with their sawed teeth, while they were firmly anchored to the prey with their foot and arm claws.

A more recent study led by Manning (2009) comes to the conclusion that the sickle claw and the other strongly curved claws of the hands and feet were not only suitable for catching prey, but also ideal for climbing. To do this , the researchers x-rayed a Velociraptor's claw , created a three-dimensional contour diagram from it and compared it with the claws of today's eagle owl in order to investigate the distribution of stress on the claw. As earlier studies on modern mammals and birds have shown, tree-dwelling animals can be distinguished from ground-dwelling animals by the curvature of their claws. The strong curvature of the claws of dromaeosaurids resembles those of today's tree-dwelling animals, which, according to the researchers, indicates a tree-dwelling way of life. The researchers also suspect that the second toe, which had the sickle claw, locked mechanically when gripping, thanks to modified tendons, and could only be released again when the foot was lifted. This adaptation is found in today's tree-dwelling birds and enables, for example, sleeping on branches without falling off. In dromaeosaurids, such an adaptation could have been helpful in climbing and clinging to large prey.

Pack life and footprints

Velociraptor leaves footprints in the sand

In Montana , bones of at least three Deinonychus individuals were discovered along with the remains of the herbivorous Tenontosaurus . Ostrom and Maxwell (1995) suspect that a group of Deinonychus attacked the much larger herbivore and that the Deinonychus bones found came from animals that perished in the ensuing fight. Deinonychus teeth are occasionally found along with the remains of Tenontosaurus , from which these researchers conclude that Tenontosaurus was Deinonychus' main prey . Carpenter (1998) notes, however, that it is just as likely that Deinonychus only ate the Tenontosaurus carcasses as a scavenger . Brinkman and Roach (2007) suspect that Deinonychus and other theropods were not pack animals, but, like today's crocodiles, gathered as competing solitary animals on carcasses. The researchers found evidence of cannibalism in Deinonychus .

Two-toed footprints from Shandong (China), probably from dromaeosaurids, indicate that these animals have at least occasionally formed groups. The site shows six tracks that run parallel to each other in the same direction, closely spaced. The distance between the individual step seals is roughly the same for all tracking sequences, which indicates that all individuals walked at the same speed. The absence of dry cracks on the tracks indicates that the tracks were covered by sediments soon after they formed. Li and colleagues (2008) therefore note that it is very unlikely that the traces were not generated by a group, but successively by independent individuals.

The traces presumably come from a large dromaeosaurid , over five meters long and comparable to Achillobator , as indicated by the 26 to 28 centimeter long treads. They were described as a new type of trace (so-called Ichnospecies ) and called Dromaeopodus . Such Ichnospecies are not part of the classical biological system, but belong to a classification system especially for fossil footprints, which is completely decoupled from the classical system. Another Ichnospecies, probably attributable to the dromaeosaurids, is Velociraptorichnus , which shows smaller, about ten centimeters long prints. Two-toed footprints that could belong to dromaeosaurids are very rare and only known from China ( Gansu , Sichuan and Shandong ), South Korea and the United States ( Utah ).

Additional advice on diet and toxicity

Although it is often suggested that dromaeosaurids could hunt large prey such as ornithopods, they likely fed on both small and large prey, like today's predators . The skeleton of a azhdarchiden pterosaur (Pterosauria) from the Dinosaur Provincial Park of Alberta (Canada) has bite marks and a broken tooth of Dromaeosauriden saurornitholestes langstoni on which the Shin puts the find. Whether the Dromaeosauridae hunted the pterosaur is questionable, as the pterosaur with an estimated wingspan of six meters was many times larger than the less than two meter large Dromaeosauridae. In this case, the Dromaeosauridae was probably a scavenger .

A more recent study from 2009 found evidence of a poisonous bite in Sinornithosaurus , a small feathered dromaeosaurid belonging to the Jehol group . In addition to unusual dentition, this genus shows notched teeth, a cavity, which presumably represented a poison gland, and a canal that led from this poison gland to the tooth base. These characteristics are analogous to today's poisonous lizards. The researchers suspect that Sinornithosaurus and related dromaeosaurids may have hunted birds.

feathers

Sinornithosaurus fossil , the first evidence of feathers in dromaeosaurids

The first direct evidence of feathers in dromaeosaurids came in 1999 with the description of Sinornithosaurus . This skeleton shows areas with structures approximately four centimeters long on different parts of the body, but the anatomy of which is not recognizable. Various other feathered dromaeosaurids have been discovered since this discovery. The type specimen of Microraptor zahoianus described in 2000 shows imprints, which presumably come from feather shafts (rachis), which suggests real contour feathers. Another fossil described in 2001, possibly belonging to Sinornithosaurus , shows feathers on all parts of the body except the lower portion of the legs. Other Microraptor fossils , in particular the Microraptor gui finds , suggest arm and leg wings that were constructed similar to the wings of today's birds. Some of these flight feathers have asymmetrical spring flags, which suggests an aerodynamic function. Some wing feathers could be more than twice as long as the femur.

All feathered dromaeosaurids come from the Jehol group in Liaoning ( China ), an important fossil deposit. At the time of these deposits, volcanic ashes made a decisive contribution to the formation of exceptionally complete fossils, so that feathers were also preserved that are rarely found in fossils elsewhere. Direct references to feathers outside the Jehol fauna can be found in Velociraptor and Rahonavis : In these genera, attachment points for feathers (English quill knobs ) were found on the ulna of the forearm, which suggests long arm feathers . Feathers may originally have served as body insulation. Special head springs on Microraptor could have been used for display. Long arm feathers, as suspected in Velociraptors , could also have had an isolating function during the incubation of the eggs, which is indicated by findings of the Oviraptorosaur Citipati , which show this animal in a bird-like breeding position above a nest.

flight

Microraptor gui fossil with imprints of feathery wings

Basal dromaeosaurids show very similar adaptations to flight as the primordial bird Archeopteryx . Differences in the flight apparatus can only be found in the proportions of the arms, which, for example, were longer in Archeopteryx than in Dromaeosaurids. Active flight or gliding ability has been suggested for at least two species. Microraptor gui showed wings with asymmetrical flight feathers on arms and legs, which he could probably use for gliding from tree to tree. In their description of this animal, Xu and co-workers assume that the long leg feathers would have made it impossible to move quickly on the ground and that basal dromaeosaurids would have been arboreal. According to these researchers, Microraptor gui was able to extend its leg wings laterally analogous to the arm wings, in order to glide with a front and a rear pair of wings. In a more recent study, however, Chatterjee and Templin suspect a stepped biplane-like arrangement of the wings: According to these researchers, the legs were not horizontally, but vertically aligned along the sagittal plane and drawn in in a Z-shape, while the flight feathers were laterally aligned. The leg wings were probably held lower than the arm wings and could thus be stretched out under the arm wings. Presumably, Microraptor was able to cover distances of over 40 meters with a wave-like gliding flight at a speed of 9 to 15 m / s. The researchers believe that limited active flight in Microraptor is theoretically possible. Microraptor gui is interpreted as a possible indication that there was an intermediate stage with four wings in the development of bird flight, until the configuration with two wings prevailed, as it was already shown by Archeopteryx . Alternatively, the four-winged configuration of Microraptor could have been an evolutionary dead end.

For another basal dromaeosaurid of the Jehol group, Cryptovolans pauli , the ability to active flight was suggested, whereby Cryptovolans is probably identical with Microraptor . Rahonavis from the Upper Cretaceous Madagascar could also have been capable of active flight, which is indicated by clear adaptations - in particular, the structure of the shoulder girdle of this species is more similar to that of today's birds than that of Archeopteryx . Chiappe and Dyke (2006) suggest that Rahonavis , like Archeopteryx, was a weaker and less agile flier than most of the birds living today. Rahonavis is traditionally considered a real bird and has only been classified within the Dromaeosauridae in more recent studies.

Paleoecology, Origin and Paleobiogeography

Dromaeosaurids are known from a wide range of different habitats. While the remains of Deinonychus , Dromaeosaurus and Saurornitholestes come from fluvial sediments deposited in rivers, Velociraptor was discovered in sandy sediments, suggesting a dry, desert-like habitat. Although they are traditionally portrayed as nimble, terrestrial predators, Chatterjee (1997) suspected that some dromaeosaurids were tree-dwelling because of the rearward-pointing pubic bone and features on the hand. Recently, with the description of the microraptorin Hesperonychus from the Dinosaur Park Formation of Alberta (Canada), it became known that microraptorins could have occupied the niche of small predators not only in the Chalk of Asia, but also in the Chalk of North America. Tooth finds from Germany's Upper Jurassic ( Oker , Lower Saxony) and Portugal indicate that dromaeosaurids were widespread in the European archipelago at this time.

Ostrom (1990) suspects that the Dromaeosauridae originated during the Lower Cretaceous (Barremium) in North America and then spread over Asia and Europe. In any case, the Dromaeosauridae were identified as early as 1992 from the middle Jurassic ( Bathonium ) - a tooth find from the English county of Gloucestershire is the oldest evidence of this group that has been discovered to date. Meanwhile, Norell and Makovicky (2004) consider an origin of the group in Asia to be likely, since most and especially the most basal genera come from this continent. However, some recent studies assume that the Dromaeosauridae originated at a time when all land masses were still united to form the supercontinent Pangea . The dromaeosaurids, like other dinosaur groups, could have been cosmopolitan over Pangea before it broke up in the middle or upper Jurassic into the northern continent Laurasia and the southern continent Gondwana . These studies see indications in a few dromaeosaurids from Gondwana, all of which can be combined into an independent, basal group, the Unenlagiinen. Makovicky and colleagues (2005) suspect that the Unenlagiinen have developed independently of the other dromaeosaurids of the northern continents since Gondwana separated from Laurasia. Turner and colleagues (2007) contradict this hypothesis of a monophyletic group restricted to the southern hemisphere, and refer to Shanag , whom they see as a Unenlagiinen from the northern hemisphere. However, Longrich and Currie (2009) list Shanag as microraptorins.

Systematics

External systematics and relationship with birds

According to popular belief, the troodontids were the closest relatives of the dromaeosaurids. Together these two groups form the Deinonychosauria, a group within the maniraptor theropods . Ostrom (1973) was the first to recognize clear similarities between dromaeosaurids and birds and concluded in later work that these two groups are closely related - a presumption that has since been confirmed by many studies. However, the exact relationships between dromaeosaurids and birds are still the subject of much debate. Most researchers assume that the birds form the sister group of the Deinonychosauria - these two groups are also summarized as Paraves .

Mark Norell and colleagues (2001) see the dromaeosaurids as more closely related to the birds than to the troodontids - they even suspect that the dromaeosauridae include the birds as a paraphyletic group, i.e. that all birds are descended from dromaeosaurids. Larry Martin (2004) suspects that the entire group of Maniraptora, including the dromaeosaurids, were not dinosaurs but were secondary flightless birds. According to Martin, the birds split off from basal four-footed archosaurs during the Triassic . Even Alan Feduccia and colleagues (2005) contradict the widespread view of a lineage of birds from dinosaurs. According to these researchers, at least the Dromaeosauriden subgroup Microraptorinae must be classified within birds.

Internal system

Up to six groups are distinguished within the Dromaeosauridae. Some genera originating from the southern continents form the little-known group Unenlagiinae, which is often considered to be the most basic (most primal, oldest) group. Also basal were the Microraptorinae, which include very small and probably tree-dwelling dromaeosaurids. All dromaeosaurids from which feather prints have been preserved come from this group. The more advanced groups of dromaeosaurids are also summarized by Longrich and Currie (2009) as eudromaeosauria: While the Velociraptorinae includes genera such as Velociraptor and Deinonychus , the Dromaeosaurinae Dromaeosaurus and the large genera Utahraptor and Achillobator are ascribed. Saurornitholestes is sometimes classified together with Bambiraptor and Atrociraptor in a separate group, the Saurornitholestinae.

Size diversity of the Dromaeosauridae. From left to right: Microraptor gui , Dromaeosaurus albeternsis , Austroraptor cabazai , Velociraptor mongoliensis , Utahraptor ostrommaysorum , Deinonychus antirrhopus

The following list of genres is based on Longrich and Currie (2009) and the individual references:

Dromaeosauridae and humans

History of discovery and research

Similarities in the hands of Deinonychus (left) and Archeopteryx (right) led Ostrom (1976) to suspect that birds were descended from dinosaurs.

1922 described Matthew and Barnum Brown with Dromaeosaurus the first Dromaeosauriden - based on a partially preserved skull and bones of the foot, the Brown lineup Dinosaur Park in 1914 in Alberta discovered. These researchers attributed Dromaeosaurus to the Deinodontidae (today Tyrannosauridae ), but placed him within this group in a separate subfamily, the Dromaeosaurinae. The name Dromaeosauridae means something like running lizards ( Greek : dromaios = "run", sauros = "lizard") and is intended to refer to animals that, in contrast to other deinodontids, were small and light. Just two years later (1924) Henry Fairfield Osborn described an almost complete skull and a phalanx as a velociraptor . However, Osborn thought Velociraptor was a megalosaurid .

With his description of the Deinonychus, Ostrom (1969) offered a more detailed description for the first time, including the post-cranium. He imagined Deinonychus as an active, fast predator, contradicting the then common notion of dinosaurs as slow, clumsy creatures. In 1976, Ostrom noticed clear similarities between the hand skeletons of Deinonychus and the ancient bird Archeopteryx and concluded that birds were descended from theropod dinosaurs. In 1999, Sinornithosaurus, the first of several feathered dromaeosaurids from the Jehol group, was recovered from China. In the same year, the discovery of " Archaeoraptor " was announced in National Geographic Magazine and selected as the "missing link between dinosaurs and birds". Later this fossil could be exposed as a clever forgery, which was composed of the remains of various animals - most of the skeleton belonged to the Cretaceous bird Yanornis , while the tail belonged to the dromaeosaurid Microraptor described in 2000 . More recent discoveries are the microraptorins Hesperonychus and Tianyuraptor , both of which were described in 2009. In 2020, scientists described the 2 meter long Dineobellator notohesperus . Skeletal features suggest that the species had a more agile tail than other dromaeosaurids, which may have given it great agility.

In popular culture

Some representatives of the Dromaeosauridae, such as Deinonychus , Velociraptor, and Utahraptor , appear regularly in popular depictions about dinosaurs. Velociraptor takes up a significant part of the plot in the science fiction novel Jurassic Park (German title also DinoPark ) by Michael Crichton and in Steven Spielberg 's 1993 film adaptation of the same name , one of the most commercially successful works in film history , and is now one of the most popular dinosaurs. Spielberg, however, was disappointed by the small size of Velociraptor and depicted this animal greatly enlarged in the film. Another example is the novel Raptor Red (1995) by paleontologist Robert Bakker , which is written from the perspective of a female Utahraptor .

literature

Web links

Commons : Dromaeosauridae  - album with pictures, videos and audio files

Individual evidence

  1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 128-144, online .
  2. ^ A b Judd A. Case, James E. Martin, Marcelo Reguero: A dromaeosaur from the Maastrichtian of James Ross Island and the Late Cretaceous Antarctic dinosaur. In: Alan Cooper, Carol Raymond, the ISAES Editorial Team (Eds.): Antarctica, a Keystone in a changing World - Online Proceedings for the Tenth International Symposium on Antarctic Earth Sciences, Santa Barbara, California, USA - August 26 to September 1 , 2007 (= US Geological Survey. Open-file report. 2007-1047 = Short Research Paper. 083). US Geological Survey, Reston VA 2007, ISBN 978-1-4113-1788-8 , pp. 1–4, digital version (PDF; 1.51 MB) .
  3. ↑ a b c Alan H. Turner, Diego Pol, Julia A. Clarke, Gregory M. Erickson, Mark A. Norell : A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight. In: Science . Vol. 317, No. 5843, 2007, pp. 1378-1381, doi : 10.1126 / science.1144066 .
  4. ↑ a b c d e Peter J. Makovicky , Sebastián Apesteguía, Federico L. Agnolín: The earliest dromaeosaurid theropod from South America. In: Nature . Vol. 437, No. 7061, 2005, pp. 1007-1011, doi : 10.1038 / nature03996 .
  5. ↑ Mark A. Norell, Peter J. Makovicky: Important features of the dromaeosaurid skeleton II: information from newly collected specimens of Velociraptor mongoliensis (= American Museum Novitates. No. 3282, ISSN  0003-0082 ). The American Museum of Natural History, New York NY 1999, online .
  6. ↑ a b Phil Senter: Comparison of forelimb function between Deinonychus and Bambiraptor (Theropoda: Dromaeosauridae). In: Journal of Vertebrate Paleontology. Vol. 26, No. 4, 2006, ISSN  0272-4634 , pp. 897-906, doi : 10.1671 / 0272-4634 (2006) 26 [897: COFFBD] 2.0.CO; 2 .
  7. ↑ a b c Rihui Li, Martin G. Lockley, Peter J. Makovicky, Masaki Matsukawa, Mark A. Norell, Jerald D. Harris, Mingwei Liu: Behavioral and faunal implications of Early Cretaceous deinonychosaur trackways from China. In: The natural sciences . Vol. 95, No. 3, 2008, pp. 185-191, doi : 10.1007 / s00114-007-0310-7 , PMID 17952398 .
  8. ^ John H. Ostrom : Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana (= Bulletin of the Peabody Museum of Natural History. Vol. 30, ISSN  0079-032X ). Peabody Museum of Natural History - Yale University, New Haven CI 1969.
  9. ↑ a b Ken Carpenter : Evidence of predatory behavior by theropod dinosaurs. In: Gaia. Revista de Geociências. Vol. 15, 1998, ISSN  0871-5424 , pp. 135-144.
  10. ^ Phillip L. Manning, David Payne, John Pennicott, Paul M. Barrett , Roland A. Ennos: Dinosaur killer claws or climbing crampons? In: Biology Letters. Vol. 2, No. 1, 2005, ISSN  1744-9561 , pp. 110-112, doi : 10.1098 / rsbl.2005.0395 .
  11. ↑ Phillip L. Manning, Lee Margetts, Mark R. Johnson, Philip J. Withers, William I. Sellers, Peter L. Falkingham, Paul M. Mummery, Paul M. Barrett, David R. Raymont: Biomechanics of Dromaeosaurid Dinosaur Claws: Application of X-Ray Microtomography, Nanoindentation, and Finite Element Analysis. In: The Anatomical Record . AR. Advances in integrative Anatomy and evolutionary Biology. Vol. 292, No. 9, 2009, ISSN  1932-8486 , pp. 1397-1405, doi : 10.1002 / ar.20986 .
  12. ^ W. Desmond Maxwell, John H. Ostrom: Taphonomy and paleobiological implications of Tenontosaurus-Deinonychus associations. In: Journal of Vertebrate Paleontology. Vol. 15, No. 4, 1995, pp. 707-712, doi : 10.1080 / 02724634.1995.10011256 .
  13. ^ Brian T. Roach, Daniel L. Brinkman: A Reevaluation of Cooperative Pack Hunting and Gregariousness in Deinonychus antirrhopus and Other Nonavian Theropod Dinosaurs. In: Bulletin of the Peabody Museum of Natural History. Vol. 48, No. 1, 2007, pp. 103-138, doi : 10.3374 / 0079-032X (2007) 48 [103: AROCPH] 2.0.CO; 2 .
  14. ↑ Philip J. Currie , Aase Roland Jacobsen: An azhdarchid pterosaur eaten by a velociraptorine theropod. ( Memento from September 21, 2008 in the Internet Archive )
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