Jewel-Eyed Saucebacks

Jewel-eyed saucebacks are a subgroup of saucebacks in the family Lumenoculidae. They are so named because, unlike most saucebacks which are blind, jewel-eyed saucebacks have eyes derived from their nostrils--called "eyestrils"--which have a shiny, jewel-like appearance. Most jewel-eyed saucebacks can flutter or glide, and some species are bird-like and capable of powered flight.

Anatomy
Jewel-eyed saucebacks have most of the same anatomy of other modern saucebacks, but there are many important differences.

Their namesake are their eyestrils. Derived from the scent pits found in all beastworms, they are used for both sight and smell. The pupil is open to allow air in, and as this constraint prevented them from evolving lenses, they instead focus light using mirrors at the back of the eye. In effect, the entire eye is a highly efficient tapetum lucidum which reflects and focuses light into a photoreceptive patch on the inside next to the pupil hole. This causes them to appear to have white pupils, and if you were to look into a jewel-eyed sauceback's eyes, you would see exactly what it sees reflected back at you. The eye itself is stretched and squashed to focus and to push out old air, and the external part of it is featherless and rubbery. As having an open eye makes it prone to particles and small fauna becoming trapped inside, jewel-eyed saucebacks produce tears which they then remove from their eyes using the centrifugal force generated by shaking their heads like wet dogs.

In basal jewel-eyed saucebacks, the spiracles and microlungs are partially supported by chitinous shells called ceres. These are inherited from their harnessback ancestors and allow them to breathe more strongly than most other saucebacks.

Feathers
Apart from their eyes, a striking feature of many jewel-eyed sauceback species is their bird-like feathers. These range from the downy plumes present in other saucebacks to complex, aerodynamic flight feathers unique to them. Many jewel-eyed saucebacks have flight feathers, typically located on the legs (remiges) and tail (rectrices), forming "leg-wings" and a tail fan, respectively. Biats also have flight feathers attached to their ears (canard feathers). Similar to birds, these flight feathers are used for various forms of aerial locomotion, including fluttering, gliding, and flight.

Legs and Hips
Like other modern saucebacks, the legs of jewel-eyed saucebacks appear digitigrade or unguligrade in relation to Earth animals. However, in reality, there is no true distinction between "leg", "foot", and "digit", and their two toes are the result of the limb itself branching. Regardless, for ease of understanding, terminology generally used for tetrapod anatomy will be used here.

The legs and outer toe bear long aerodynamic feathers similar to those of terran birds. They can be moved and folded using tendons running parallel with the wing, and when not in use they are usually folded upwards. Argusraptors and ophreys have the "wing toe" raised off the ground for monodactyl running and preventing the long feathers from dragging on the ground, respectively. In some flighted species, the wings are slotted to allow for thermal gliding.

There are two patagia on the leading edge of the limb, which streamline it for gliding or flight and obscure the anatomy underneath. One stretches from the ankle to the knee, while the other stretches from the knee to the neck.

Flight
Flight-capable species have highly muscular legs and large keels derived from the front protrusion of their cephalopelvis, which supports their massive wing muscles. Like bats, they also have muscular backs for pulling their wings up. Their hips are also more flexible, as necessitated by the use of their legs as wings, though this comes at the cost that the protrusion which supports the pillar-erect posture of other species is tilted upwards or even completely absent in some, therefore requiring them to use more energy to stand upright.

The muscles on the chest and back for flapping their wings attach to the femur.

Mouth Anatomy and Feeding
Although nearly all living saucebacks have mandibles (or "tusks"), the mandibles of the jewel-eyed saucebacks and their closest relatives are considerably more mandible-like than those of nearly any other sauceback, closely resembling insect mandibles or sideways beaks and even being pigmented. These are used to grab, tear, or crush their food. Some species have upturned jaws, which can be used to dig and manipulate food like a small shovel attached to the face.

Jewel-eyed saucebacks and their close relatives have limited up-down flexibility in their mandibles, unlike other saucebacks, as the muscles used to pivot the jaws up and down in other groups instead pull them together for a powerful bite. This gives strong-jawed species a superficially heart-shaped head, due to the powerful muscles bulging outwards.

The oral ring--a ring of chitinous teeth present in the mouths of all beastworms (and which was ancestral to all "arthropod-like" binucleids)--is comparatively far more basal in anatomy, though the teeth themselves commonly have serrations (which are absent in most other saucebacks). The teeth aid in both processing food and in pulling it down into the throat to be swallowed. Some species such as the quail raptor have reduced teeth.

Jewel-eyed saucebacks lack the lips that are present in other saucebacks, as their jaws, so much larger than the pincer-like jaws of more basal saucebacks, completely took over the role of closing the mouth; the lips only got in the way. This comes at a cost; some species cannot close their jaws fully because of secondary adaptations, so their mouths are exposed to open air and more prone to water loss.

Reproduction
All jewel-eyed saucebacks lay eggs with hard chitinous shells. Basal flightless species ancestrally have legless worm-like larvae, while the flying lineage hatches comparatively well-developed chicks.

Locomotion
Like most other saucebacks, jewel-eyed saucebacks are obligate bipeds with pillar-erect legs. However, while they walk and run like other saucebacks, they are also capable of other forms of locomotion and locomotion-tangent movement.

The most universal of these is the flutter jump, where they appear to run in midair while their flight feathers flap furiously, which slows their fall, adjusts their trajectory, and allows them to land directly into a sprint. The motion, and its function, can be somewhat likened to alternating wing beats. Similar to the flutter jump is a form of wing-assisted incline running where the furious left-right flapping of the leg feathers creates a pushing force which allows smaller species to climb steep slopes without tumbling down.

Flightless species are usually capable of gliding at some stage of their life. As implied by the presence of specifically flightless species, some species can fly as well; the legs of the interbiat and its descendants are long and feathered like a bird's wings, and they flap them to fly.

Some jewel-eyed saucebacks only walk on their inner hoof, unlike most double-hoofed saucebacks which walk on both hooves. This allows them to keep their flight feathers clear of the ground, at the cost of some stability.

The diversity of jewel-eyed sauceback locomotion is shown below:

History
Jewel-eyed saucebacks are derived from an offshoot of harnessback saucebacks which gained the ability to see using photoreceptors in their nostrils, which were derived from mutated chemoreceptors. They, as well as their immediate sighted ancestors and relatives, first appeared in the Bonoian period.

The first jewel-eyed sauceback, the brighteyes, appeared in Generation 162. It quickly split into two major groups, the flightless monodactyl argusraptors and flighted birdlike biats. Their superior eyesight compared to other saucebacks allowed argusraptors to rapidly rise in prominence on the supercontinent as large carnivores, even producing a giant superpredator. The biats, meanwhile, diversified into a diverse array of forms superficially resembling primitive birds, the most successful of these being the raptor-like ophreys which bore shorter tails and unidirectional lungs.

Size
Jewel-eyed saucebacks are typically measured by length from the tip of the mandibles to the tip of the tail spike. This is different from other saucebacks, which usually do not have their mandibles included in their measurement. They range from 20 centimeters to a whopping 6.4 meters in length.

Size Limits
Terrestrial, flightless jewel-eyed saucebacks, like other saucebacks, should be capable of reaching similar sizes to Terran theropods, as they are similarly lightweight obligate bipeds.

The flighted biats have not had their maximum size calculated, however their combination of a very large number of lightweight traits (a skeleton that lacks mineralized components, feather-based wings, a wing-based launch which requires no additional pairs of limbs, and a small total number of digits on their limbs), a respiratory system that can very quickly become unidirectional and is well-suited to the rapid development of air sacs, and their flight muscles and respiratory system being in different parts of their body, it is speculated that they can grow much larger than the largest Terran pterosaurs.

Jewel-eyed saucebacks should, under normal circumstances, be capable of shrinking to similarly tiny sizes to other warm-blooded saucebacks.

Types
Basal jewel-eyed saucebacks are flightless, semi-arboreal runners which closely resemble the brighteyes.

Argusraptors are larger, cursorial, monodactyl, and often predatory jewel-eyed saucebacks descended from the Argusraptor species complex. They include some of the largest species in the group.

Biats or saucebirds are the flighted clade descended from the interbiat. Basal forms retain long tails, but some more derived species have shorter tails.

Ophreys are advanced fliers with short tails and unidirectional macrolungs. Descended from the sausophrey, they include some of the highest-flying species.

Quails are another branch of biats which have reduced teeth, mobile tail spurs behind the lungs, and a much greater number of eyes. Some species have bundled their numerous eyes into a single main pair of compound eyes.