The biggest by far set of original creatures was in my space opera, Space Spinster. This is from the setting guide:
Cha'na:
Cephalopodan species from a water world, cha'na look like a couple of squids stacked on top of one another. Beaks are prominent on their heads, and their eyes are large and oily. They differ in color, remaining on the cold side of the spectrum, often exhibiting beautiful dappled patterns. They live in shoals, and try to intermarry between the different schools. All cha'na start out their lives as males, with some of them transitioning to their female form when reaching maturity.
Mym:
A power to reckon with, Mym Hierarchy controls the Interstellar Transportation Board (It-Be). Physically, mym have six limbs, projecting their tube-like, seven-to-eight foot-long body upwards like furry caterpillars. Unlike the caterpillars, their heads end in twitchy noses with whiskers. Their limbs end in six spindly digits, sometimes more. The amount of eyes, ears, and mouths also vary for each individual mym. Sometimes they grow extra limbs, particularly when regenerating a lost one. Mym range in color from turquoise to indigo. They hear the full sonic spectrum, so their speech consists of a plethora of one to three sound words. Their rate of communication is among the fastest in the galaxy.
Tarksi:
Taksi are smaller in stature than humans, rarely standing more than five feet. They have cigar-like bodies, with webbed arms and the membranes that connect their little fingers to their little toes stretching out to either side of the body, to turn each tarksi into a perfect gliding square. They heads are small, and dominated by huge lips made of three skin folds. They are semi-transparent and opalescent. On their homeworld they filter out lighter gases from the atmosphere to fill up their spare two stomachs to help them in gliding from one rocky peak to another. Tarksis are sought as captains, and they often venture into the galaxy with the ambition to build a merchant fleet of their own.
'...'
The name of these mysterious species is a convention to record an absence of sound of silence exactly 1.33 seconds long. Mym's competitors for the control of the It-Be, '...' have a solid heavy core that keeps the rest of their fluid shape from dissipating into a vapor. The only other thing solid about them are sharp teeth that float up to the surface in seemingly endless rows. Their ability to stay silent during the negotiations with the more emotional species is legendary. As predatory as they look, they have not been known to wage a single war for as long as the Intergalactic Annals' extend into the past.
Variel:
The rogue species could be found anywhere there is trouble in the Galaxy, ready to hire themselves out as mercenaries. They fall back on pirating when they cannot find a war. Physically, they are mono-peds resembling upright anemones, except that they only have one feeler on top. The middle of their bodies feature a mouth-hole, their one vulnerable spot. Variel have a preference for a throwing weapon that returns to sender, though nobody knows why.
