The bichirs (Polypterus) at the Fort Worth Zoo Aquarium are worth your attention for having a number of interesting features. Although these are classified among the "bony fish" they actually have a number of characteristics more typical of sharks, for example a cartilaginous skeleton and a spiral valve, an internal fold in the intestine that increases the surface area for absorbing nutrients. The base of the fin is also fleshy and you may see these animals "walking" on their fins on the bottom of their tank. These fish are air-breathers, using a lunglike swim bladder. The dorsal fin is also divided into a number of spiny segments, giving the fish its primitive appearance.

Closely related to the bichirs are the reedfish below. The divided dorsal fin can also be seen in these fish, as well as the fleshy fin base on the pectoral fins. The pelvic fins, however, are absent, and this fish is sometimes also called a "snakefish." Like the bichirs, these fish are air-breathers.