Here are some images of the dromaeosaur races Adasaurus and Dromaeosaurus, and their common ancestor, Deinonychus:
Adasaurus, pictured gingerly cradling its young in its nimble clawed hands.
Dromaeosaurus, a cousin of the Adasaurus, who would have existed during the same period as the Adasaurus (the late cretacious), but on different continents.
Deinonychus, the ancestor of the Dromaeosauruses and the Adasauruses.
The natural history of the dromaeosaurs is a good example of the kinds of developments which the dinosaurs as a whole would have undergone. Fossil evidence indicates that Deinonychus originated in North America during the early cretacious period.
Deinonychus are thought to have been highly social, organising themselves into complex communities in order to work together. During their development, Deinonychus evolved an iconic five-inch claw on the foot, which was highly dexterous, and could be retracted and moved back and forth. Initially, this would have served a purpose in hunting and combat, though it would later have been useful in the performance of complex motor skills such as puncturing fabrics, making written inscriptions and so on. The special success of this early dromaeosaur is partly explicable by its long tail, which acting as a counterbalance allowed the use of both the hands and feet in dexterous activity.
The distribution of Deinonychus' descendants, the Adasuruses and Dromaeosauruses, suggests that one or more colonial expeditions sailed from the West Coast of North America and colonised the far East, probably landing in Japan and China and then spreading across the eastern part of Eurasia.
Above: The Pacific OceanTravel between the colonies during this period seems to have been very limited, because the two previously homogenous groups of dromaeosaur began to evolve minor racial adaptions which distinguished them from one another, though they retained all of the major characteristics of the dromaeosaur species. The fact that these groups proceeded to evolve on the micro scale along different lines despite their immediate proximity in the faulty "pangea" model is testament to the fact that ocean seperated them, much as it does today.
The colonist Deinonychuses who reached the far east adapted in a number of ways. Adasauruses, probably due to massively increased tool usage and the removal of the necessity to be involved in violence as their civilisation progressed, developed much smaller foot-claws than their ancestors. A smaller claw would have been much more suitable for precision tasks like inscription, manipulation of cloth and fine materials and so on, and marks the transition from its role as a mechanism of hunting and combat to its role as an additional dexterous digit. In the absence of the selection pressures brought on by the development of a civilisation, and the mastery of the surrounding wildlife and other hazards, Adasauruses' bodies became smaller than those of their Deinonychus ancestors, who had needed to be larger because their lifestyle was primarily one based around hunting and conflict. Fossil evidence suggests that the Saurolophus, a herbiverous, docile grazing dinosaur, originating in North America, also appeared in the far East at roughly the same time, making it likely that the first Deinonychian colonists brought specimens with them on the transcontinental voyage, and probably began to farm them for food (they would have previous been hunted by tribes of Deinonychus living a hunter-gatherer lifestyle on the American continent). The advent of an agrarian society based on the pasturing of Saurolophus would remove the necessity for the brutalities of hunting. In order to bring down a wild Saurolophus, tribal warriors would have needed considerable bulk and might as well as cunning, but their agrarian descendants needed no such unneccessary brawn, which explains their shrinking - the average Adasaurus living during the late cretacious was around 8 feet long, whereas a North American Deinonychus of the early cretacious period, who would have had to hunt the large wild Saurolophus and Tenontosaurus (probably hunted to extinction by early Deinonychian hunters, explaining why it was not exported to the far east along with Saurolophus) would have measured 11 feet long.
Above: The west coast of North America. Groups of pioneering Deinonychus, who would later microevolve into the Asasauruses, would have set sail from shores such as these.The Deinonychus who stayed behind also show signs of developing agriculture along similar lines. The Dromaeosaurus, from which the species derives its name, were Deinonychus who remained in North America. Their adaption did not include such an acute reduction in claw size as the the Adasaurus, but their body size decreased significantly, to around 6 feet long. Again, this is attributable to the development of farming, primarily of the tamed Saurolophus. That the Dromaeosauruses did not develop the highly precise small-claw of the Adasauruses suggests that they may not have involved themselves so heavily in activities such as writing. Dromaeosauruses developed a coat of downy feathers, which might suggest that colder climates prevailed in North America at this time. Their smaller size than the Adasaurus could also be indicative of evolutionary adaption in order to conserve heat. If temperatures did drop for the Dromaeosaurs entering the Late Cretacious, perhaps their society was a more rugged one, and the harsh realities of surviving the cold winters precluded such an extensive focus on writing, hence the lack of precision small-foot-claw adaption shown in the Adasaurus. The evolution of their tails gave greater flexibility and may have been indicative of adaption in favour of some civilised activity, since the balancing capability of the tail enables enhanced use not only of the forelimbs but also the foot claw.
Above: Saurolophus. These gentle giants were probably first hunted by the North American Deinonychus, and later herded and grazed by them when farming entered their culture just prior to the colonisation era, and splitting of Asasaurus and Dromaeosaurus, the two Deinonychus descendant races.So, fossil remains suggest that as intelligent Deinonychus became highly successful hunter-gatherers during the Early Cretacious, conquering the entire North American continent with such rampant success that they drove one of their main prey animals, the Tenontosaurus, to extinction. It is likely that the advent of Saurolophus domestication roughly coincided with, or just preceded, the maritime renaissance and colonisation period. The tendency of agrarian societies to promote massive population growth is clear, and in this scenario, facing scarcity of land and dropping temperatures, some of the Deinonychus would have begun their colonisation of China and the far East, taking with them livestock as well as elements of the budding culture of North America. Fossil evidence suggests that the Adasaurus society was massively successful, placing some of their near relatives as far afield as Denmark. An empire the size of Alexander the Great's would no doubt have been underpinned by careful organisation and a culture steeped in the written word and refinements of erudition. Meanwhile, as the Late Cretacious brought colder climates in North America, the remaining American Deinonychus grew smaller, hairier and more rugged as they faced the elements as best they could, thought they still retained their agriculture and some vestements of civilisation.