To'ul'h

The To'ul'hs are a sapient, technological species in the Orion's Arm science fiction universe, native to planet To'ul'h Prime in the H'tat'sa'thoss Sytem. They are the first intelligent extraterrestrial species ever to be contacted by Humanity in-universe, around the 58th century CE.

Etymology
To'ul'h (plural To'ul'hs) is intended to be a genuinely alien name and not a construct from words of any human language.

Anatomy
A To'ul'h possesses both bilateral and tetraradial symmetry, though the last one is approximate. Much like Earth tetrapods, a To'ul'h has bilateral symmetry, a bony skeleton and four limbs; though the cardiovascular is much closer to the vascular system of an echinoderm.

A To'ul'h can have a mass anywhere between 40 and 100 kg varying with regional varieties, with a typical adult weight of 70 kg for males and 63 kg for females.

The braincase is located in the central dorsal part of the body trunk, from where it innervates limbs and receives input from sensory organs. Having a thin and light skull, fat is accumulated around to absorb mechanical shock. The central position of the skull might indicate that a To'ul'h lacks a vertebral column.

The frontal dorsal part of the body contains three bat-like ears that a To'ul'h uses for echolocation. The central ear is powered by a lung-like organ. Hardly-noticeable eyespots on the dorsal surface allow a To'ul'h to detect light but not form an image.

The four limbs look very much alike, organized into frontal and hind pairs. However, the hind limbs are stronger, heavier and keen at jumping. The fore and hind limbs are connected with retractable patagia, providing a To'ul'h the ability to glide.

All four limbs are segmented into three and ending with hand-like structures. Each hand has six fingers and two thumbs, giving the impression that To'ul'h locomotion is digitigrade. Unlike human hands, the eight digits are arranged symmetrically.

Being a heterotrophic organism, a To'ul'h possess an internal digestive system. It begins with sideways-opening mandibles between the forelimbs and ends with an anus between the hind limbs, both being ventral openings. The stomach and intestines are located in the ventral central part of the body, protected by fat like the braincase. Mastication is carried out by a gizzard on the forepart of the stomach rather than by teeth in the mouth. After nutrient absorption in the intestines, liquid waste and excess salts are excreted through the anus.

A To'ul'h has three lungs, with the two being responsible for respiration being located between the pairs of limbs. These two book-lungs are independent and have one opening (spiracles) to both dorsal and ventral surfaces. Breathing is rather complex. With normal exercise, air just flows between the dorsal spiracles, helped by limb movement. With heavy exercise however, air can be pumped by opening endings in both surfaces in turns, providing greater oxygen uptake and cooling at the expense of greater hydration.

To'ul'h blood composition or appearance is never specified, though the circulatory system resembles that of an Earth echinoderm, pumped by three hearts. Like humans, the cardiovascular system is divided into pulmonary and systematic system. However, instead of having a single chambered heart, two hearts are connected to the lungs and with another one pumping into the body.

A To'ul'h exhibits no external genitalia and is either male or female. The genitalia are comparable to the pedipalps found on spiders, and fertilization is internal.

Environmental requirements
Taxonomically, To'ul'hs belong to the hyperthermophile superkingdom, a group of organisms with an optimal physiological temperature of 135 ºC. Without some form of conditioning (such as clothing or hydration), a To'ul'h dies at temperatures cooler than 100 ºC or higher than 150 ºC.

Adapted to an atmospheric pressure of about 60 atmospheres, they can nonetheless withstand short-tem exposures of as little as 10 atmospheres and longer terms exposure of 50 atmospheres. Earth-like pressure is immediately fatal, resulting in bodily fluids boiling away. To'ul'hs are aerobic like humans, but die with an oxygen concentration lower than 7% or higher than 15%.

Drinking pure or alkaline water has a more fatal effect in To'ul'hs than in humans. They can however, drink from fresh moderately acidic (pH 4) to hypersaline water, excreting excess salt in the last case.

Earth-like sunlight intensity can blind their eyespots and ultraviolet radiation produces severe burns.

Evolutionary history
To'ul'hs and all life on their homeworld had a common prokaryotic, single-celled ancestor roughly 2 billion years ago, while Earth was having its Orosirian period. Some point after that, that common ancestor diversified into three different prokaryotic superkingdoms that would eventually and independently create multicellular eukaryotic life.

One of these multicellular eukaryotes evolved into crinoid-like sessile organisms with tetraradial symmetry, which would eventually give to the dominant animal phylum to which the To'ul'hs belong.

Roughly 400,000 years before humans first landed on the Moon, modern baseline To'ul'hs appeared, so they are twice as old as the Homo sapiens sapiens.

Senses
A To'ul'h's primary sense is based on sound. Three large bat-like ears are used for this. A To'ul'h can just listen and still get a lot of information about a place. This passive form of sonar can help a To'ul'h image a low-resolution picture of something up to one kilometer away.

However, the central ear can produce ultrasonic chirps in 50-200 kHz range to define features as small as half a millimeter within a 20 meter radius; this is named echolocation or active sonar.

Besides, the forelimbs contain organs that generate and sense weak electric fields within the range of a meter, constituting a To'ul'h's second most important sense: electroreception. On land, it allows detection of distant storms. It is more helpful on water or mud than on land though, since nearby creatures can be detected this way. On land, a To'ul'h is able to detect the magnetic field of the planet and use it for orientation (magnetoreception).

Touch is very sensitive, especially on their hands and the overall ventral surface. To'ul'hs can also taste with their hands, in order to distinguish between edible and poisonous saprophytes or track prey. Smell is also very acute.

Arguably, their least sophisticated sense is that of sight. With a dark and noisy environment, hearing resulted more useful than seeing. Eyespots do allow a To'ul'h to perceive light, but not form an image.

Psychology
Despite all the differences between humans and To'ul'hs, there are simmilarities in developmental history and reproduction with a profound impact between both species understanding each other's psyche and society.

However, having sonar and electroreception has had a profound influence in their method of thinking. Not having sight distances To'ul'hs from understanding humans, bringing them closer to getting literary concepts of other blind species, such as the ancient space-faring Muuh.

To'ul'h metaphors are based on the properties of sound, since light is not something positive and are afraid of occassional clear patches formed on the sky in the same way a human might fear lightning. In fact, their version of Heaven is that of a warm, damp and dark place, while the human vision of it as something fresh and brilliant embodies their vision of Hell.