Important: A kind member of Critics United has let me know this fic breaks the site's Guidelines (it's a "non-story" type of violation). I mistakenly thought that, since my work was a "fan fiction" (that is, fiction based on a story that I don't own) it was within the Guidelines. I thought that the "non-story" rule simply meant that a fic had to be materially related to a story. That said, a rule is a rule and I appreciate the chance to save my stuff. This author's note is here to let everyone know I will be fixing this to be in compliance as soon as I get a chance.

To those of you who have added this to your favorites or are following it, don't worry! This fic isn't disappearing forever, I promise! It will simply be moved to a different place so that it doesn't violate the rules. Once I've got something to replace the non-story chapters of my works, I'll let you know where to find the originals.

Introduction:

After much study and collaboration, I am pleased to announce the first Handbook to Turian Interactions: For Humans edition. This new "for humans" handbook covers the basic differences between turian and human biology, psychology and culture. It was written as a supplement to the Systems Alliance Galactic Codex.

Remember: this is just a general guide. Turians, like humans, are sentient individuals with their own personalities, hopes, dreams and motivations. Stereotypes are just as offensive to turians as they are to humans.

General Biology:

To start us off right, here is a general refresher in turian biology for those of us who were either out of school before First Contact or slept through their alien biology classes. Turians are the apex land predator of Palaven, the third planet in the Trebia system of the Apien Crest. Adult turians stand between 5' 10" to 7' on average and normally weigh between two to three hundred pounds. Turians are sexually dimorphic. [More on sex differences in Sex Characteristics]

Turians' cells are primarily made of dextro-amino acids, making them a rarity among the galaxy's species. Of all of the galaxy's known species, only the quarians share this trait. Certain dextral compounds are dangerous for levo species, like humans, just as certain sinistral compounds are dangerous for turians and quarians. Put simply, the molecules are aligned to the left (sinistral, or levo) or to the right (dextral, or dextro) and the direction of their alignment changes how the body reacts to the molecules. While scientists know the most dangerous compounds and what reactions they cause, it is the potential for individual allergic reactions to opposing proteins that makes most people wary. Results can range from not digesting the material to fatal allergic reactions, making testing a dangerous proposition with little compensating benefits.

Palaven's weak magnetic field allows the ultraviolet rays of Trebia to blister the planet's surface. As such, most of the planet's land ecosystem has developed protection against the radiation, including semi-metallic plating. Many scientists believe Palaven's land-going species evolved from a common, exoskeleton-bearing ancestor. This ancestor's exoskeleton was the prototype of the plates many species have today.

A turian's plates have trace amounts of thulium, which acts as a natural radiation shield. Radiation levels also affect plating color, with the plates of equatorial turians being darkest and growing proportionately lighter as turians spread towards the planet's north and south poles. This trait is seen in many species, including humans' skin color.

The sense of touch is the least developed of the turian senses. While a few places are sensitive, most places on the turian body are covered with hard plates or thick, leathery skin. There are multitudes of small "mini-plates" between the major plates, called scales. Turian plates are slightly bumpy to the touch. These bumps connect to nerve clusters, allowing the plates to be pressure sensitive. The turian's thick skin is also largely pressure sensitive, though the pressure must be quite intense to cause pain. The few unplated areas that are sensitive tend to be erogenous zones, most located near the abdominal and groin area, but also include certain areas of the neck.

Palaven's weak magnetosphere also means that Palaveni plants have also adapted to withstand the intense radiation, consequently becoming harder and more dangerous to eat. Turians are a primarily carnivorous species, as seen by their rows of long, sharp teeth and talons. Their teeth and talons allow them to catch and pry the protective plates off herbivorous prey. While turians can and do eat plant material to supplement their meals, their biology is adapted for a diet of meat.

Turians have relatively small saliva glands, connected to the mandibles. The glands release saliva when the mandibles "flutter" rapidly. There is a certain enzyme in turian saliva that prevents clotting in certain Palaveni animals. Strangely, this enzyme is one of the few dextro proteins that appears harmless to most levo species.

Turians are born with a set of teeth, allowing them to eat solid food from birth. However, turians do not use their teeth to chew; their teeth are only for ripping flesh and swallowing it. Instead of chewing, turians have a gizzard that grinds down food once swallowed, eliminating the need for molars or grinding teeth. A turian grows two more full sets of teeth in their lifetime, one at around age four and again at age ten. After this, a turian's individual teeth will grow back if removed or broken but they will not grow another full set. It usually takes approximately a month for a new tooth to grow into place. There are few nerves connected to a turian's teeth, meaning they experience less pain when losing a tooth than a human would.

Turians have an average sense of taste compared to a human. While a turian's sense of smell is far superior to a human's, the primary purpose of a turian's tongue is to manipulate food in the mouth. Most of the taste buds are located at the back of the tongue. The front of the tongue is long and nearly prehensile, with small barbs to grip food with, similar to a cat's tongue, though less rough.

Turians do not have visible ears. Rather, their "ears" are located inside the head as a liquid-filled tympanum covered by a sensitive membrane. Turians have a slight divot located just below the cheek plate spike. This is the ear.

While the lack of an auricle (the external "shell" of the human ear) gives turians poor directional hearing, they are more adept at registering slight changes in sound. Turians can also hear in auditory ranges outside normal human hearing. Turian sub-harmonics make the most of this by communicating a wide array of information based on subtle changes in sound, using the turians' secondary set of vocal chords to communicate complex emotional information. This is a necessity given the rigidity of turian facial plates.

Turians are one of the many species with tridactyly - or three fingers - as opposed to asari, batarian, and humans' pentadactyly (drell are a special case of pentadactyly, having syndactyly in the two middle digits). Like most other sentient species, turians developed an opposable thumb, allowing them greater dexterity to hunt and make tools.

While turians appear to have only two toes, the leg spur is actually the missing third toe, despite its different appearance and migration to the upper leg. While both sexes have spurs, those of turian males are longer and sharper, pointing at the possibility of utilizing them to kill or fight. The modern turian's leg spurs are not well suited to the purpose, but can serve against foes in an unexpected attack.

A turian's legs are similar to an ancient Earth velociraptor's, capable of running at extreme speeds. In short-distance sprints, turians can out perform any other species. However, a turian can only maintain maximum speed for a relatively short time before tiring. The ancient turians were pack hunters who specialized in ambush hunting, allowing them to take down prey quickly rather than have a drawn out chase.

The skin around turians' eyes is usually black, charcoal or mahogany brown. This dark coloration prevents light refraction into the eyes, protecting the sensitive retina from UV damage. Turians also have a second, clear eyelid that protects the eye from dust and dirt. Turians do not have eyelashes or tear ducts to remove debris. Instead, this clear eyelid nictates when the outer lid blinks to clear any contaminant from the lens.

While turians have small eyes compared to most other species, their eyesight is often better. Turians have front-facing eyes, giving them stereoscopic vision. Turians have more photoreceptors than almost any other sentient species, as well as more rods and cones, allowing them sharper vision with more brilliant colors. Turians also have a reflective membrane on the retina, allowing them to hunt at night by maximizing the amount of light from Palaven's twin moons, Menae and Nanus.

Because of Palaven's sun and twin moons, turians have a unique sleep cycle. First, a little bit about the Palaveni day and night. Palaven has a twenty-eight hour day. The smaller moon, Nanus, is tidally locked. This means that the same side of Nanus always appears to face Palaven because the rotations of the planet and moon are in sync, much like Luna is with Earth. The larger moon, Menae, has a thirty-three day orbit.

Turians sleep during the brightest hours of the day, protecting themselves from the extremes of Trebia's radiation. They sleep again during the darkest hours of night, when neither moon, if Menae is coming through, has risen to its peak yet. While not necessary in the modern day or on other planets, most turians find this sleeping arrangement to be the most comfortable. However, they are perfectly capable of adjusting to other sleep schedules if necessary.

Turians have blue blood, a trait that is unique to their species. Turians are an oxygen-breathing species, but do not use hemoglobin to transport oxygen through their bloodstream. Palaven is iron-poor, forcing Palaveni species to rely on other minerals in its place. Instead of hemoglobin, their blood uses hemocyanin, a metalloprotein that uses copper as its base instead of iron. While naturally clear, the hemocyanin takes on a blue-green color when oxygenated. Turian blood gets its characteristic dark blue from zinc, which supplements the iron that Palaven lacks. The zinc bonds to the hemocyanin under a mild bioelectric current stemming from turian secondary nervous system.

On Earth, the few creatures that use hemocyanin systems tend to be invertebrates or insects, which some scientists take as further proof that ancient turian ancestors had had an exoskeleton and open circulatory system. Examination of the turian skeleton further supports this idea.

Turians are considered by human scientists as avian analogs; as such, their bones are extremely light and primarily cartilaginous. However, extremely light bones would be very inefficient for carrying the heavy plates needed to protect life from Trebia's radiation. Fossil evidence shows that the turian skeleton developed from the plates as turians became bipedal. The turian skeleton serves as reinforcer for the plate structure, in some places actually merged with the plates, such as the ribs and hips.

Furthering this idea, the pressure on the circulatory system would have increased as the turian ancestor became upright. A closed circulatory system is more efficient for an upright vertebrate, as the brain needs more oxygen as it becomes more complex. Turians have a four-chambered heart, allowing maximum efficiency at transporting blood, which helps to counteract the lowered oxygen-transporting efficiency of hemocyanic blood.

Turians only have one lung, which filters oxygen differently than that of other species. Due to the rigidity of the turian chest plates, the turian lung cannot expand to increase its oxygen intake. As such, turians lack a diaphragm and cannot be seen breathing from the expansion of the chest. Instead, deoxidized hemolymph is stored in one 'chamber' of the lung, which is released into the circulatory system with the blood once properly oxygenated.

Another honeycombed chamber is responsible for filtering oxygen from other elements. The lung expels the unsuitable elements on exhale after filtering out the oxygen. This means that turians take proportionally more breaths than other species. Fortunately, their lung is large, approximately the same size as two human lungs put together. In addition, the majority of the lung is devoted to oxygen filtering and the lung stores more oxygen than is released into the hemolymph at any time in air sacs.

A.N.: Argh, my brains! So biology, anatomy and chemistry are not my strong suits, but they're the logical first part of any examination of differences between humans and turians. If I've made some ridiculous claim or obvious error, please let me know. Also let me know if I've forgotten something about turian anatomy/biology. I've tried to be comprehensive, but I'm just one (sometimes scatterbrained) person. A special thanks to V-rcingetorix for his help in making sure I didn't muck things up too badly.

This stuff, both in this chapter and any following, is a mixture of what the codex says, the information we get in-game, logical assumptions (I hope) and my own head canons. I've tried to weave it all together coherently, both for my own reference and anyone else out there who wonders these kinds of things. There may be times where the comics contradict what I write, but I generally consider the comics to be semi-canon at best.

Sex characteristics will be the next chapter, focusing on male/female differences, sexual organs and reproduction. Fun times. (Or not.) Maybe I'll eventually get off my lazy bum and draw some illustrations for this darn thing.