The Caatati are warp capable a race found in the Delta Quadrant.
The Caatati are reptilian lifeforms who, until recently, maintained a proud civilisation. Within the last generation they were assimilated by the Borg except for 27 ships. These escaped carrying a small number of survivors but were forced to wander space, begging where they could but more often than not being driven off.
Their technology was Thorium based but they had lost the ability to replicate the element and so they gradually were running out of power and time.
In 2374 a Caatati ship encountered the USS Voyager and were given stocks of food. A little later, they found Voyager's Warp core after it had been dumped and claimed it. They then tried to use it as a bargaining chip for more supplies.
Instead, Seven of Nine offered them the lost Thorium replication technology, which she recalled from her time with the Borg. The Caatati gladly agreed. (VOY: "Day of Honor")