Day one: first steps

The Question Mark Leaper (Curvus saltatorius) is an arboreal insectivore belonging to a fictional class of vertebrates called Caudovertebrata (from Latin cauda, "tail," and vertebra, "joint"). Unlike most vertebrates, its spine is a single, flexible structure that extends from its head to its tail, giving its body a unique, spring-like curvature.

​Size: Adults can grow to be about 60 to 75 centimeters (24 to 30 inches) long, with the body making up the majority of its length.

​Coloration: Its skin is a pale yellow to light green, which provides excellent camouflage against sun-dappled moss and lichen-covered branches in its native rainforest habitat.

​Limbs: It has three front limbs that are long, thin, and tipped with small, prehensile digits. These are used primarily for grasping and swinging. The two smaller, two-toed feet at the base of its "tail" are used for balance and stabilizing itself on a branch.

​Behavior and Ecology

​The Question Mark Leaper's locomotion is one of its most remarkable features. The creature doesn't walk or run in a traditional sense. Instead, it moves by saltation, or leaping.

​Coiling: It uses its front limbs to anchor itself to a branch, then contracts its powerful back muscles to coil its body into a tight "S" shape.

​Launching: By rapidly releasing this tension, it can launch itself with surprising force and accuracy, covering distances of up to 10 meters (33 feet) between trees.

​Landing: The leaper uses its prehensile front limbs to catch a new branch, absorbing the impact with its flexible body. The feet on its tail help it quickly regain balance and grip.

​The leaper is a solitary and silent predator. It hunts by hanging motionless from a branch, using its keen eyesight to spot flying insects like moths and dragonflies. When prey is within range, it launches a sticky, barbed tongue from its mouth with incredible speed, similar to a chameleon. The leaper's low-energy hunting style is well-suited to its specialized form of movement, which requires bursts of high energy.

​During the breeding season, males perform elaborate aerial displays, using their powerful leaps to impress potential mates. This is the only time the leapers are known to be vocal, communicating with a series of distinct clicks and whistles during their courtship dances.