A large Earth-based company intends to use this gas giant in a nearby star system as a vast Helium 3 extraction and sales operation. However to do so the law requires an ecological damage survey to be conducted on the gas giant's moons, to be sure the operation will not damage any ecosystems on them. This large moon, only slightly smaller than earth, was found to have an advanced multicellular ecology.
The Sol Union Xenobiologist Makeba Sutphen was sent with the company when they left earth, to make sure the laws regarding alien ecosystems were followed. Here she is approached by possibly sentient natives of this large moon. Although she has a camera out now, if they get closer or show aggression she is well armed.
The species itself evolved from large aquatic creatures which resembled less broad versions of Earth stingrays. As they began to move on to land small feeding appendages on their underside grew into thicker organs to propel them, and the large side fins retracted and darkened to protect against solar radiation. Sensory appendages which stuck from the sides of the head and helped find food underwater become very useful for judging distance above water, with the eyes set so far apart.
Males, who had to compete for mating rites, developed these eye-stalks further into horns, and used them to scare off other males. They also developed a more upright stance to better compete for mates until the species was standing almost vertical. With a head now so far from the ground, the large mouth migrated to the bottom of the body, leaving the brain, eyes and breathing tube on the upper head, so as to spot danger and eat at the same time. Waste products are ejected explosively from the body from a pore on the back, to prevent contamination to the mouth.
Now able to walk upright and survive on land, the species spread across its world to become the dominant creature on the planet.
An alternative, warmer variation is here: [link]