Dimorus
Dimorus was a planet. It was the homeworld for a species of rodent-like creatures that had the ability to shoot deadly poison darts. 

In the mid-23rd century, Gary Mitchell intercepted a dart that was meant for his friend James T. Kirk. Although Mitchell nearly died from the incident, he was able to make a full recovery. ()

In 2376, the location of Dimorus was labeled on a star chart in astrometrics on  in 2376. (, okudagram)

Appendices

Apocrypha 
According to The Worlds of the Federation, Dimorus is the fourth planet in the Dimorus system. Its native species are called .

According to the comic book  the natives are called Dimorans.

The Autobiography of James T. Kirk uses the spelling Dimorous.

External link 
 

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Planets
Homeworlds