A whale of a new species

NEWS AND VIEWS tivistic electrons in the magnetosphere, much like a radio pulsar. How relativistic nonthermal electrons are accelerated by a process making thermal X-rays remains unexplained. Still, the X-ray spectral signatures suggest that neutron stars are the sources of y-ray bursts, and the results of Murakami et a/. show that a vanguard of apparently thermal X-rays, which is clearly connected to the main portion of the burst, must be accommodated by a y-ray burst model. Whether these objects are more closely related to radio pulsars or accreting neutron stars, or whether they tum out to be extragalactic flashers of a different order, has yet to be answered. D Charles D. Dermer is in the Department of Space Physics and Astronomy, Rice University, Houston, Texas 77251, USA. ZOOLOGY--------------------------------------- A whale of a new species Katherine Ralls and Robert L. Brownell, Jr four new species of whale have been identified since 1937, the absence of new ones for the past 28 years might be taken to mean that they had finally all been discovered. Not so- a new species of beaked whale, Mesoplodon peruvianus, is described by J. C. Reyes and colleagues in the latest issue of Marine Mammal Science1 • The beaked whales, family Ziphiidae, comprise almost 30 per cent of the toothed whales but are poorly known. In contrast, the great baleen whales are well described, in part because they were commercially hunted, and no new species have been discovered since 1878, when the last of the ten now recognized, Bryde's whale, was named 2 • Six of the seven beaked whales described in this century are in the genus Mesop/odon (see table), and most of what little is known about the genus, and the family as a whole, has been gleaned from carcasses washed ashore. One species ( M. pacificus) is still known only from its bones and the ALTHOUGH Species of cetacean described since 1900 (refs 1,2)* Andrews' beaked whale, Mesoplodon bowdonini Andrews, 1908 Spectacled porpoise, Australophocaena dioptrica (Lahille, 1912) True's beaked whale, M. mirus True, 1913 Baiji (Chinese river dolphin), Lipotes vexillifer Miller, 1918 Longman's beaked whale, M. pacificus Longman,1926 Tasman beaked whale, Tasmacetus shepherdi Oliver, 1937 Fraser's dolphin, Lagenodelphis hosei Fraser, 1956 Vaquita (Gulf of California harbour porpoise), Phocoena sinus Norris and McFarland, 1958 Ginkgo-toothed beaked whale, M. ginkgodens Nishiwaki and Kamiya, 1958 Hubbs' beaked whale, M. carlhubbsi Moore, 1963 M. peruvianus', Reyes eta/., 1991 *AII11 species are toothed whales, seven are beaked whales (family Ziphiidae), and six of these seven are in the genus Mesop/odon. The genus Tasmacetus also belongs to the beaked whales. 'As Reyes eta/. provide no common name for the newly described species, we propose the name pygmy beaked whale. and perhaps seven, of them were captured incidentally in drift gill-nets set for sharks, and three were washed ashore. Some new specimens from the Mexican coast may also belong to this species and its latitudinal range may extend beyond the places where both the known and the suspected specimens were collected. The teeth of the adult males are relatively small compared to those of its congeners. The long axis of each tooth is almost perpendicular to the long axis of the mandible (see figure), a feature which distinguishes this species from all others in the genus. Mesoplodon peruvianus is the smallest known member of the genus, and, indeed, of all the beaked whales, both in terms of total length at birth (159 em) and the maximum known total adult body length of 372 em. (The smallest previously known species of Mesoplodon is M. hectori, for which the smallest calf measured 190 em in length and the maximum known adult total length is 443 em.) appearance of the whole animal remains a matter of conjecture. Members of four of the five beaked whale genera have reduced numbers of teeth. The name Mesoplodon (loosely interpreted as "armed with a tooth in the middle of the jaw") refers to the two remaining functional teeth of adult males, which are on the lower jaw and are one of their most striking features. The bizarre teeth ofthe male strap-toothed whale ( M. layardiz) even grow up and over the upper jaw, sometimes actually touching and thus preventing their owner from opening his mouth more than about five em (ref. 3). The amount of the tooth exposed in the living animal Dorsal view of the lower jaw of the holotype of Mesoplodon varies from species to species: peruvianus1 . That only two teeth remain functional is in some nearly all the tooth is characteristic of males of the genus; that their long axis is exposed, whereas in others almost perpendicular to the jaw is characteristic of the most of it is covered by gum species. Length of the jaw is about 53 em. tissue and only the tip proThere have been several sightings of a trudes. Females also have the same two teeth in the lower jaw, but they are not functional distinctive but unidentifiable species of as they rarely emerge from the gums. The beaked whale in the eastern tropical Pacific, meagre data available imply that these ani- meaning that there still may be at least one 5 mals prey predominantly on squid and fish more undescribed species of Mesop/odon • 3 Given that Earth's dwindling large-mammal found at moderate to considerable depths , a soft diet that can be captured and consumed fauna is comparatively well catalogued, Mesoplodon is likely to remain the least without the aid of teeth. In Mesop/odon, linear scars up to about 2 known genus of large mammal - as Minam in length are often found on adult males, sian and colleagues have pointed out in The World's Wha/es 6 , "The mysteries these and are usually assumed to be the result of instrange whales present will not be easily traspecific combat. These scars often occur as pairs of parallel lines, implying that they solved by the handful of specimens chance D were formed by the two teeth of a rival provides in one lifetime". male 3·4; males apparently keep the mouth Katherine Ralls is at the National Zoological closed while wounding other males. Mem- Park, Smithsonian Institution, Washington, bers of the genus tend to occur as anti- DC 20008, USA. Robert L. Brownell, Jr, is with tropical pairs of closely related species, a the US Fish and Wildlife Service, San Simeon, species of each pair occurring in the tem- California 93452, USA. perate waters of each of the two hemis1. Reyes, J. C., Mead, J. G. & Van Waerebeek, K. V. Marine pheres, although one ( M. densirostris) is Mammal Sci. 7,1 (1991). found in tropical waters world-wide and two 2. Honack1, J. H. et a/. Mammal Species of the World - A Taxonomic and Geographic Reference (Allen Press, others ( M. ginkgodens and M. pacificus) Lawrence, Kansas, 1982). are confined to the warm waters of the 3. Mead, J. G. Handbook of Marine Mammals Vol. 4, 349 Pacific and Indian Oceans. (Academic, New York, 1989). 4. Heyning, J. E. Cand. J. (...truncated)