Species

Species and Civilizations in T-Space

The focal species in T-Space is humans. There are other sentient species, for varying values of sentient.

The Terraformers

The oldest and most advanced -- and apparently extinct -- are the Terraformers themselves, the folk who originally terraformed numerous planets and seeded them with life from Earth around the time of the Cretaceous/Tertiary boundary, 65mya. Nothing is known about them, not even whether it was one or more species or even robots. Their existence is inferred from the existence of the Terraformed planets.

Humans

Us. So far no evidence of us on other planets before the 21st century invention of the warp module .

Timoans

Native sentient species of Epsilon Indi III, also known as Taprobane (a human, ironic name). Timoans are descended from the terrestrial ancestors of mongoose and meercats, the suricat line. Iron-age level technology when discovered by humans, some contact with select individuals and villages.

Spacefarers (Ancient)

Species and civilization inferred by existence of some common architecture types and a few technological artefacts spread across primitive cultures light-years apart. Presumed builders of the Chara pyramid and the Maguffin. Estimated to have flourished 15,000 years ago, +/-.

Spacefarers (Modern)

Kesh

Presumed and claimed descendants of/heirs to the Ancient Spacefarers. Observing humanity covertly for some time, some limited contact. Higher technology than humans, probably equivalent to Ancient, but seems to have not progressed much in 15,000 years. Some suspicion that these are not descended from Ancients but evolved separately (like many other species) and for their own reasons are pretending to be Ancient-descended (and may even believe it themselves).

Tree Squids

A species indigenous to Kakuloa, actually octopus rather than squid, and semi-arboreal. They appear to communicate via skin-color changes and exhibit coordinated behaviour, but it is an unresolved question as to whether they qualify as "sentient" or are just very intelligent animals.

Others

Several planets -- Kakuloa, Verdigris, Zeta Tucanae and more -- have archeological evidence of past societies (therefore species) up to about neolithic level. Possibly more came and went to even Neanderthal level without leaving as much evidence.