Thoughts on Cardassians and design from The Fifty-Year Mission: The Next 25 Years: From The Next Generation to J. J. Abrams: The Complete, Uncensored, and Unauthorized Oral History of Star Trek.

Herman Zimmerman on designing the station: “The Cardassians like things in three, according to our philosophy, so there are three concentric rings, and on the outside ring there are three vertical pylons that are docking pylons.” (p. 428)

“Costume designer Bob Blackman’s costumes showed a kind of chest-plate armor that looked like a crustacean. Taking off from that very fundamental idea, we decided the Cardassians like structure and they’d like to see the structure on the outside instead of hiding it inside the walls.” (p. 428)

Robert Legato: “Designers Nathan Crowley and Joe Hodges set the standard for Cardassian architecture, which is a wonderful mixture of pseudo-fascists and crustacean.” (p. 428)

So, to recap, Cardassians were viewed as semi-crustacean by the design team.