Cytan

Should a Demiurge exist, it would seem The One is inordinately attached to the two-limbed, short faced, tall-chested form. Perhaps The One is a 'Breasts guy'.

— Egregore orison, Anonymous

  This is not a true species, but a peculiar similarity seen among many sapient (and some-non-sapient) species in the eponymous cluster.   Theoretically, it should be extremely unlikely for two unrelated species to share the same body shape. And yet, many, especially sapient, races, share many features, both with each other, and with other species. Indeed, the planar cluster derives its name from its phenomenon - 'Cytan' is an Old Fuchal word meaning 'Typical/Average', from the phrase 'Cytan Erhu', or 'Typical Form'. The Cytan cluster, therefore, is where species of typical form are found.
Partially, this can be explained by convergent evolution - a given shape offers certain advantages, so species will naturally evolve towards those advantages. However, sometimes these advantages are too strong to be coincidental, or seem to occur in lieu of a potentially more advantageous - or at least, consistent - bodyplan. In most cases, the historical record reveals a consistent development and steady change, but nevertheless the 'uncannyness' of many creatures morphology is well-remarked upon. How this is seen varies depending on the bias of the observer, some see it as proof of outside intervention, others suggest it to be a consequence of metaphysical processes, while others suggest it to be entirely natural.
It is worth noting that morphology is not synonymous with physiology. Many species, despite highly familiar external shape, have highly distinct phsyiology in terms of organ structure, biology, etc. It should not be assumed a species has particular traits just because it shares features of another species with said traits.
'Race' and 'species' are used interchangeably of sapients, but technically, some have genetically and physiological identical counterparts on other worlds... despite active counter-evidence of common origin. Thus, 'race' doesn't really apply, but 'species' certainly doesn't.  

Morphology & Anatomy

'Cytan' anatomy is defined by a few common characteristics. A long, vertically oriented chest, which contains various organs protected by a bone cage, with a spine supporting it at the back. Atop the chest is a short neck, which bears a head in the shape of a rough sphere, flattened at the front, which features a highly expressive face, including a small, flat mouth, a short nose above that, and two forward facing eyes above that. The jaw typically forms a relatively sharp chin, leading back to the neck. On the side of the head are two ears, which are almost fixed in place and cannot move. The body is barren of fur aside from atop the head, where it may grow to extreme lengths.
Slightly below and to either side of the neck shoulder bones connecting to a set of limbs - these limbs may vary, but are most commonly used for manipulation. Slightly below the shoulders are mammary glands, generally undeveloped in males and permanently engorged in females.
Variations in this body plan can still be considered 'Cytan', but the majority of Cytan races feature at least this much. Beyond what is listed here, especially in the lower limbs, Cytan races vary wildly, with a narrow plurality having two long, columnar legs, which may end in a long-forward foot, a claw, or hooves. The second most common is a long, musucular 'tail' used for locomotion.  

Genetics and History

As discussed above, Cytan races do not share a genetic heritage. As such, the majority cannot cross-breed without magical aid, and the exception are generally 'sub-groups' of a particular species. In some cases, they do not share a plausible heritage with those similar of morphology on another world, yet have negligible genetic difference and can interbreed. While there are evidence of intermediate species in the fossil record in many cases, supernatural intervention is almost universally accepted, with debate being over its nature, whether the races were created and evidence falsified, whether their evolution was manipulated, or perhaps the Cytan form bears some metaphysical significance that natural processes congregate around.  

Life Cycle

As a rule, Cytan races are mortal, living roughly 50-100 years, though many Transcendent are former Cytan races and retain their form. Most Cytan races bear a small number of live young and put extensive effort into raising them, though exceptions exist. Similarly the majority of Cytan races have two persistent sexes, with one sex producing motile sperm that unify with larger egg cells produced by the second sex, which then implant within the egg-bearer's body. However, sequential and simultaneous hermaphrodites also exist.  

Senses

As a rule, Cytan species have acute, trichromatic vision, and are able to discern high levels of detail, although not necessarily at particularly long distances. Hearing is binaural, but mediocre in sensitivity and fairly low in range. Sense of smell is fairly poor, usable for detecting strong odors but not for navigating or locating food. Taste fairly strong, touch reasonably sensitive, but only useful in direct contact.
With training, most Cytan species can learn to sense mana and other phenomena.  

Diet

Cytan races are universally nonspecialist omnivores. Ability to digest rough plant matter is virtually nonexistent. While they do have dietary preferences and variations in nutrition, all Cytan races tend to consume a fundamentally similar diet, and there are limited (but extant) distinctions in toxicity.
Methods of sustenance vary, but most Cytan races are pack hunters.  

Exceptions to the rule

Not all sapient races in the 'Cytan Cluster' are actually Cytan. While some are largely a technicality, such as Homunculi or Kobolds, there are also a number of genuinely non-Cytan races, such as [Quipplo], [Dragons], and the ???
  In the category of 'debatably Cytan' are such things as Kobolds (created with a similar morphology by a non-Cytan race, largely from non-Cytan sources), Seeders (use Cytan races as reproductive hosts), Dryads (create Cytan 'fruits'), Beastkin (magical crossbreeds with non-Cytan animals).
  When sapience is not factored, the vast majority of species are not Cytan. Also present in one or more worlds are a variety of debatably sapient non-cytan life forms, such as [dolphins], [parable-doves], [butcherboars], etc.