Xeros are endothermic vertebrates that strongly resemble early mammaliaformes. Like mammals, they have four limbs, padded paws, tails, claws, teeth, and are covered in fine, soft fur. However, they also have many differences from mammals. All Xeros are hermaphrodites and lack distinctive sexes; each individual has the same internal reproductive parts, including their pouches and the ability to both produce and fertilize eggs. Xeros are also unique in that they display dramatic phenotypic plasticity, that is, the ability to change their traits in response to external stimuli.

Xeros are a medium-sized species with a long, tube-shaped body plan, similar to a mustelid. Their large heads are almost disproportionate to their lithe bodies, but are balanced out by their stocky forepaws and hind limbs. Standard Xero characteristics include large, forward facing eyes and nostrils, ovular ears positioned on the sides of their heads, thick tails that taper to a pointed tip, forked tongues, pouches, and small claws.

The average Xero is about 4 feet tall (122 cm) when standing upright. The many Xero subspecies vary in size, and some may be larger or smaller than this average. While many Xeros are slim due to their high metabolism and tube-shaped body, they can still display many other body types, such as chubby or muscular.

Xeros have adjusted well to Alurizan society, and their wide hind paws allow them excellent balance for walking upright. When standing bipedally they adopt a plantigrade stance, meaning they stand with their entire foot touching the ground. Xeros are equally well adapted to stand on two legs or four, and many may choose to walk on all four, especially when moving quickly. When standing quadrupedally they stand with a digitigrade stance, meaning they stand on their toes with their heel lifted off the ground.

Xeros are very intelligent and resourceful, with excellent senses. Their sense of smell is particularly strong; their large, open nostrils are packed with olfactory receptors, and they use their forked tongues in combination with the vomeronasal organ at the roof of their mouths to sense which direction a scent is coming from. They make exceptional trackers!

Xeros are incredibly adaptable creatures that come in a variety of subtypes to fit different habitats. They are able to withstand extreme environments low in oxygen; they can survive in space or underwater without protective gear for a short amount of time. They can go without breathing for about 10 minutes! 

Xeros have 3 important color categories: Primary Fur Color, Countershading, and Skin Color.

These can be any color of the rainbow, but there are some rules they usually follow.

Countershading (Continued)

Countershading refers to the "belly marking" that most Xeros have. This fascinating fur pattern is a real phenomenon on Owai-6, Earth, and apparently planet X-1118A too! The area where countershading is required is outlined in red in the examples above. Countershading must cover approximately 80% of this area. Head and tail are not included in countershading but it is common for them to have similar light markings. Xeros may express certain mutations that affect their countershading.

Eventually, enough of the extinct species’ XNA was sequenced to create what we now know as X.E.R.O.’s: X-1118A Experimental Rebuilt Organisms. Small gaps in the XNA sequence are filled with the XNA of compatible animals; a resource that AREZ is known for from their 'frozen zoo' genetic library, collected from animals of every shape and kind throughout the galaxy.

Xeros are incredible feats of scientific creation that are furthering research and technology in so many fields throughout all of AREZ.

Since Xeros were restored from an extinct species, little is known about their natural behavior or culture. In an effort to learn more about them and their adjustment into Alurizan society, ARC has been sending out monthly surveys to volunteers. While the surveys have proven incredibly insightful, there is still much to learn about the Reserve's newest members.

Social Behavior

Xeros are a highly social species, with most individuals preferring to live with or near other Xeros or other sapients. Xeros form strong bonds and physical touch/closeness is extremely important to them. It's common to see Xeros in pairs or even groups grooming each other, cuddling, holding paws or entwining tails, etc. Their most common trait, antennae, was thought to serve as a sense organ to help Xeros navigate, but it is now speculated to also be a form of intraspecies communication, as Xeros displaying this trait can often be seen touching them together, strengthening their bonds.

Feeding Behavior

Due to their very high metabolism caused by the noodle-shaped body, Xeros tend to need a lot of calories and eat frequently. Portable/resealable snacks and high-calorie nutrient shake/slushies are a common sight as Xeros roam around AREZ.

Sleeping Behavior

Due to the above mentioned high metabolism, when Xeros sleep they enter a "torpor" state, where their metabolism, body temperature, and heart rate drop to conserve energy. This results in a very heavy, dead sleep. Because of this, any Xero that has responsibilities that need to be tended to at specific times (jobs, pets, etc.) will need a very powerful alarm to ensure they get up. Sleep disorders in Xeros can be particularly dangerous as this torpor state is important for conserving their energy overnight.