Deducing the biology and natural history of Deinonychus

Looking at Deinonychus using this type of 'forensic' perspective, what do these features tell us about the animal and its way of life?

The jaws and teeth (sharp, with curved and serrated edges) confirm that this was a predator capable of slicing up and swallowing its prey. The eyes were large, pointed forward, and would have offered a degree of stereoscopic vision, which would be ideal for judging distance accurately: very useful for catching fast-moving prey, as well as for monitoring athletic movements in three-dimensional space. This serves, in part at least, to explain the relatively large brain (implied from its large braincase): the optic lobes would need to be large to process lots of complex visual information so that the animal could respond quickly, and the motor areas of the brain s would need to be large and elaborate to process the higher-brain | commands and then coordinate the rapid muscular responses of e the body. i s a

The need for an elaborate brain is further emphasized by "

considering the light stature and slender proportions of its legs, which are similar to those of modern, fast-moving animals and suggest that Deinonychus was a sprinter. The narrowness of each foot (just two walking toes, rather than the more stable, and more usual, 'tripod' effect of three) suggests that its sense of balance must have been particularly well developed; this is further supported by the fact that this animal was bipedal, and clearly able to walk while balanced on two feet alone (a feat that, as toddlers prove daily, needs to be learned and perfected through feedback between the brain and musculoskeletal system).

Linked to this issue of balance and coordination, the 'terrible claw' on each foot was clearly an offensive weapon, evidence of the animal's predatory lifestyle. But how, exactly, would it have been used? Two possibilities spring to mind: either it was capable of slashing at its prey with one foot at a time, as some large ground-dwelling birds such as ostriches and cassowaries do today (this implies that it could have balanced on one foot from time to time); alternatively, it may have attacked its prey using a two-footed kick, by jumping on its prey or by grasping its prey in its arms and giving a murderous double-kick - this latter style of fighting is employed by kangaroos when fighting rivals. We are unlikely to be able to decide which of these speculations might be nearest the truth.

The long arms and sharply clawed hands would be effective grapples for holding and ripping its prey in either of these prey-capture scenarios and the curious raking motion made possible by the wrist joints enhances their raptorial abilities considerably. In addition, the long, whip-like tail may well have served as a cantilever - the equivalent of a tightrope walker's pole to M aid balance when slashing with one foot - or it could have served | as a dynamic stabilizer, which would prove useful when chasing £ fast-moving prey that were capable of changing direction very quickly or when leaping on prey.

While this is not an exhaustive analysis of Deinonychus as a living creature, it does provide an outline of some of the reasoning that led Ostrom to conclude that Deinonychus was an athletic, surprisingly well-coordinated, and probably intelligent predatory dinosaur. Why should the discovery of this creature be regarded as so important to the field of dinosaur palaeobiology? To answer that question, it is necessary to take a broader view of the dinosaurs as a whole.

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