Two new sawshark species discovered in the Indian Ocean – Corriere.it

Two new species of saw shark (not to be confused with sawfish) belonging to the genus Pliotrema were discovered in theIndian Ocean. The first (Pliotrema kajae) off the Madagascarthe second (Pliotrema annae) in the waters of Zanzibar. The peculiarity of these new species which, in addition to having a sort of whiskers on the rostrum that serve as sensors, possess six gill openings, whereas normal sharks have only five. Until now, scientists knew of only one other sawshark species with six gill openings. Too little is known about these new species to be able to say whether they are in danger of extinction or not
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Six gills

Before scientific classification, fishermen in southwestern Madagascar caught a six-gill species of long, slender sawshark that they brought to fish markets and sold as vae vae. So far, scholars have found no explanation for the fact that these species, unique among more than a thousand sharks and rays (which belong to the class of cartilaginous fishes) have evolved with six gill openings instead of five. P. kaja lives in 200-300 meters deep water in the underwater platform between Seychelles and Mauritius, while P. annae in shallower waters, not exceeding 20-35 metres, around Zanzibar.