Paleoniscoids are basal chondrosteans with a characteristic asymtrical, shark-like tail. Top. An early Paleozoic type. Bottom. The dorsal and tail fins of living Polypterus (birchir) are much modified. Still, this animal manifests characters, ventral lungs and paired fins with fleshy lobes, that are unique among actinopterygians and suggest that Polypterus is a modified descendent of ancient paleoniscoids. (From A. S. Romer. 1964. The Vertebrate Body. W. B. Saunders. Philadelphia.)