Sir

Your News Feature “Killer in the kelp” (Nature 445, 703–705; 2007) on the killer whale, Orcinus orca, states that the genetic analyses of type-C killer whales in Antarctic waters could lead to the naming of the first new whale species since 2003. However, the killer whale is actually a dolphin species belonging to the family Delphinidae, which includes about 30 species of small and mid-sized odontocetes (toothed whales, dolphins and porpoises).

Even if the type-C Antarctica killer whales were to be named a new species, they would still not become the first new cetacean species since Balaenoptera omurai was discovered in 2003. In 2005, a new dolphin species, the Australian snubfin dolphin Orcaella heinsohni (Cetacea, Delphinidae), was described by a team of scientists from Australia and the United States (I. Beasley et al. Mar. Mammal Sci. 21, 365–400; 2005). Genetic and osteological analyses of Irrawaddy dolphin specimens collected from Asian and Australian waters provided significant statistical basis that the Australian specimen was a new species.

In addition, a new species of beaked whale, Perrin's beaked whale Mesoplodon perrini (Cetacea, Ziphiidae), was described in 2002, on the basis of five animals stranded on the coast of California between 1975 and 1997 (M. L. Dalebout et al. Mar. Mammal Sci. 18, 577–608; 2002). Therefore, if the type-C Antarctica killer whale is recognized as a new species, it will become the first new dolphin species named since 2005, or the third new cetacean species since 2002.

The discovery of three, potentially four, new cetacean species in the first decade of the twenty-first century underscore how little we know about these large mammals of the sea. It is very likely that more new species of whales and dolphins will be discovered and described in the years to come, as more rigorous morphological and genetic investigation are being conducted.