Es

Eses are members of the class Xenoavis and are a common groups of pseudosterns. They are notable in part for the fact that many species are capable of powered flight.

Etymology
'Es' is the Nical term for the creatures. The class name Xenoavis means 'alien bird' in Latin and refers to the wings and ability of many species to fly.

Anatomy
Eses are six-limbed exoanimals, although the central pair are simpler than the others, having evolved not from fins but from dorsal spines as signallers. They end in either one or two simple digits, each usually tipped by a claw or talon. These limbs are variably used for movement and support, for holding prey items and nest material or are vestigial. They are normally held under the body. The hind limbs are often greatly elongated and support a membrane used for lift, whilst the front limbs are shorter but also support a smaller membrane, used for additional lift, agile turning and fine adjustments in the air.

The body features the usual pseudostern anatomy, with two rib cages (one held in the thorax, the other in the abdomen) separated by the ultracostal region and connected by the jointed pseudosternum. The front limbs are jointed with the thoracic cage whilst the central and hind limbs are jointed with the abdominal cage.

A the back of the base of the neck is the nostril-like opening for the breathing apparatus which leads into the lung chambers and eventually to the openings near the shoulders. These face forward to better direct vocalisations ahead towards their target.

The head sports a sinciputal ear system which is sometimes divided and arches over the beak. The beak itself consists largely of the enlarged but fairly thin endomandibles which meet at the bottom, front and occasionally the top. The upper exomandible is static and often extends over the top of the endomandibles to form a lid, whilst the lower exomandible is also static and is greatly reduced, if present at all. The chemosensing organs are internal and line two open-ended nasal chambers on the underside of the head. The melons responsible for producing and focusing hypersonic sound waves for use in echolocation are situated on or beside the shoulders. Eses which fly often have melons situated near the base of the neck whilst those which spend more time on the ground have melons which are spaced further apart. These are mostly used for echolocation but can also produce hypersonic booms for communication.

Taxonomy
The class Xenoavis contains 7 orders, 4 of which are capable of powered flight.

Nmatsagoyyi
Being flightless, members of this order have stocky, well-built front and hind limbs which are suitable for quadrapedal walking and running. The central limbs are held beneath the body and vary in length, some being fairly long for holding nest materials, some for extending forwards to fight, some supporting a gliding membrane leading to the front limbs and some highly vestigial but never used for support on the ground.

Nmamrulla
Members of this order have long hind limbs with substantial membranes, with well-developed central limbs used for support and sometimes for catching prey. The central limb digits are jointed mid-way down. The bones are honeycombed. The hind limb shoulders have a unique structure, with the scapula-equivalent bone having a protrudence to which muscles attach and being able to swivel in some groups.

Apfmala
The sisellas, an unusual flightless group with an extended ultracostal region, long neck and thick, supporting central limbs. The nasal chambers can be closed and both upper and lower exomandibles are greatly receded. The feet are hard and hoof-like.

Scarababufa
Named in reference to their six sturdy limbs, apparent lack of a neck and often broad, flat beaks reminiscent of a toad's mouth.

Tsareaa
This unusual order supports its weight entirely with the hind limbs, elongated and specialised front limbs to fly, with the central limbs supporting the wing membranes. This is amongst the most taxonomically and anatomically distinct eses, with a unique 'folded' skeletal structure whereby the thoracic ribcage rests upon the cartilage-lined abdominal cage to form a unique joint. The unusual wings are held against the flanks when the creatures are at rest, extending far beyond the body.