Small, brightly coloured animals of the Ba'ku planet in the Briar Patch, one of which is the constant companion of the boy Artim in Star Trek: Insurrection.
The rhyl is a little animal native to the Ba'ku planet, small enough to sit in a child's hand or ride in a pocket and marked in vivid colours. The Ba'ku, who have set aside advanced technology for a quiet rural life, keep them as pets.
A rhyl appears in Star Trek: Insurrection as the pet of Artim, the young son of Sojef. The boy carries it about the village and has it with him in the scenes in which he slowly gets over his distrust of the android Data, an artificial being of exactly the kind his people have turned away from.
The animal is with Artim again when the villagers abandon their homes and climb into the hills to escape the Son'a drones, a journey on which Data and the boy become friends. The creature has no part in the plot beyond showing the gentle life the Ba'ku are defending.