Complex sentence: Its first dorsal fin (going from front to back) has 39 to 43 rays, which are bony spines that support fins, and its second dorsal fin has 6 to 7 rays.
Split into simpler sentences: Its first dorsal fin (going from front to back) has 39 to 43 rays, which are bony spines that support fins. Its second dorsal fin has 6 to 7 rays.