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Intelligent Lifeform Index

Four Letter Code XYRI
Federation Status Member
Planet of Origin Xyrillia
Encountered ENT: "Unexpected"
T/E Rating T0/E0
Current Tech Level N
List of Named Xyrillians

Full ILI GalleryPermitted Species Gallery

"Curiosity is fine but beware of unexpected surprises."
a Xyrillian proverb.
The Xyrillian are an unusual species with the men carrying the embryos of their young in pouches on their upper chest. Unfortunately even casual physical contact can result in impregnation from the female and as has been seen in the past this can include males of other species.

Home System

  • Quadrant: Alpha
  • Location: Prin Dovis Sector (coordinates A22-0001-1296)
  • Proper Name: Xyrill system
  • Star: It orbits a class G (Yellow) star
  • Distance from Star: its orbit is approximately 42 million km
  • Companions: 7 other planets. It is the 4th planet in the system
  • Moons: it has 1 moon.

Home World

  • Proper Name: Xyrillia
  • Diameter: 20,250 km (12,583 miles)
  • Gravity: 0.92 standard gravity with a density of 3.2
  • Axial Tilt: 1.08%, no appreciable tilt and no seasons
  • Orbital Period: 412 days
  • Rotational Period: 26 hours
  • Classification: M
  • Surface Water: 61%
  • Atmosphere: 1.07 is a standard pressure with 68% nitrogen, 21% oxygen, 11% trace chemicals
  • Climate: Warm semi-tropical with tropical at the equator and temperate to sub zero near the poles.
  • Terrain: Vast jungles with bio-luminescent growth growing under the jungles canopies.
  • Population: Just over 5 billion


The Xyrillian ship encountered by the Enterprise NX-01 in 2151 had a bioluminescent enviroment, and an interesting grass that grew on the ship walls. This was actually food, and released a vapor necessary for metabolization. Though the Xyrillians required technical assistance from the humans, they were quite advanced in some areas, and already had possession of holodeck technology. The Xyrillian Ah'len demonstrated this technology for Trip Tucker.

The Xyrillians were a peaceful, warp-capable species of humanoids.

In the 2260s, Starfleet was attempting to adapt Xyrillian duplication chambers for use aboard Federation starships.

By the 24th century they had became a member of the United Federation of Planets.


A fair and comprehensive system is used to select the best 20 candidates. Then the population is given 50 days to consider the merits and faults of each candidate. After the 50 days the population votes and the new Primal is selected. They will rule for 10 years. The individual who garnered the 2nd most votes becomes his observer and chief advisor.


The Xyrillians most distinctive physical characteristic is their colorful dermal plating. There leather like skin is actually softer than it looks. They have no body hair at all and tend to have green eyes with black irises.


Xyrillians have an unusual physiology. They do not have a metabolism based on water or breathe an oxygen-based atmosphere. In fact, their high-pressure atmosphere is hallucinogenic to most species, and as a result most other humanoids need to be weaned onto and off their atmosphere to avoid undesired effects. When traveling, they grow vegetation on the walls of their ships.

Xyrillian males usually carry infants to term in a pouch on the upper chest. Impregnation can occur with only minor physical contact. Humans and Xyrillians are genetically compatible, as Commander Tucker discovered when he was impregnated by a Xyrillian female.


Exposure to normal atmospheres is dangerous to them. It triggers violent behaviors and random psychotic actions. In the long run it can also be fatal to them as their mental processes start to break down and they tend to become self destructive.


They have a passive religion that preaches self worth and harmony with their environment. While they all tend to follow this belief system it does not preclude them doing what is necessary in order for them to survive.


A unique series of tales regarding the origin of their species and their slow advancement into an early civilized society.


They suffer from very little crime and most of their people seek to improve both their own lives and the lives of those around them. They enjoy the natural environment and have built their cities to incorporate it into its makeup.


They have a diverse appreciation for music and art. Numerous alien art forms and musical styles have been observed and slowly adapted to their own use and enjoyment.


Their few customs all tend to be minor in nature. One example is for mated couples to select the drink and food for each other and then to exchange these items before dining.


The Xyrillians were, technologically, far superior to Humans in 2151. They had the technology to simulate any environment they could envision. (see holodeck). Even their ships were considered unusual in design.


They have a well developed economical home world and long standing trade agreements with a few species. They do not require any new trade partners and are completely self sufficient.


While they have never known war among themselves they were quickly exposed to it when they first explored space. As a result they created a vast series of defensive stations and satellites around their homeworld.

Federation Intelligence Files

See Federation Intelligence File # ENT-2151-3417.


Information for this article was obtained from both memory alpha and beta. They all appeared in the TV episode ENT: Unexpected. Information was also retieved from the following books, TOS novel: The Case of the Colonist's Corpse and the TOS novel: Captain's Glory.


This file was updated and approved by the SDC on 31 October 2011

Content from this article may have
come partially, or entirely from
Memory Alpha

This profile was revised by the Species Development Committee.
REV 239401.31
Please add any new information discovered during the course of a mission or shore leave.