I made two settings based on dinosaurs.
Gateway
Overview
In the late 21st century, humanity has a tentative foothold within the solar system. There are thousands of humans living off planet scattered throughout the Earth-Moon system and a few transitory outposts on Mars and various near earth asteroids.

On July 6th 2089, observatories and astronomical satellites start tracking a high energy source inbound into the Solar system. Within 5 years it was clear that it was decelerating and would soon enter solar orbit. Over a dozen probes were developed and launched. Finally in 2098, the object entered into a solar orbit between Neptune and Uranus and ceased emitting energy. What remained was a small localized area where gravity was distorted. Barely detectable as stars and planets moved behind the object and then suddenly shifted back to their normal position once they emerged from behind.

The first probes reached the object in May of 2101, what they detected amazed everybody, it was a mechanism of alien manufacture creating an opening to a stable Rosen-Einstein bridge or wormhole several hundred meters in diameter. Upon further investigation the first transit was attempted and when the probe return and its data was analyzed the results were electrifying. It was not just a bridge through space but time as well.

The other end of the wormhole was in the orbit around Earth, Earth of 65 million years ago.

The Campaign
It is the year 2118, the two stations has been built on both sides of the wormhole to support human expeditions to the Earth's surface; Apollo and Artemis; Apollo lies on the present day side of the wormhole in orbit with the wormhole beyond Uranus. While Artemis lies beyond the past side of the wormhole in orbit around the earth.

Preliminary surveys have been conducted and now the first expeditions to the surface are ready to be landed.
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The Majestic Stars

Mankind has reached the stars only to find... Earth

Birds flying under distant skies, fish swimming unexplored seas, and dinosaurs ruling unknown continents. On a hundred words there are the children of Earth. Children from an Earth of sixty-five million years ago.

Now man has outgrown his cradle and traveled into the black, wondering who and what scattered the seeds of Earth throughout the cosmos. Mankind is forging a new life among the stars but old fears and conflicts still threaten. The year is 2425 and this is their universe, the Majestic Stars.

Basic Premise
A Dinosaurian civilization arose on Earth 65 millions ago and expanded outwards. They terraformed every world possible and transplanted an Earth based ecology then disappeared. On some world Dinosaurs still live, on other worlds various catastrophes reset evolution. Now humanity is expanding into the stars still divided into a hundred nations and hasn't reached the limits of where they terraformed despite colonizing a 100 light year sphere.