Deraniyagala two-toothed whale
| Deraniyagala two-toothed whale | ||||||||||||
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| Mesoplodon hotaula | ||||||||||||
| Deraniyagala , 1963 |
The Deraniyagala two-toothed whale ( Mesoplodon hotaula ) is a little-known species of whale from the family of the beaked whales (Ziphiidae). The species was in 1963 by the Ceylonese zoologists Paules Edward Pieris Deraniyagala described . The type specimen was a dead female that was washed ashore near Colombo . The specific epithet hotaula was composed of the Sinhalese words for “beak” (= hota) and “pointed” (= ula). Since Deraniyagala, with the exception of different tooth positions in comparison to the Sowerby two-toothed whale ( Mesoplodon bidens ) and the Hector's beaked whale ( Mesoplodon hectori ), gave no diagnostic features with which the species could be distinguished from other two-toothed whales , Mesoplodon hotaula became the Japanese beaked whale in 1965 ( Mesoplodon ginkgodens ) synonymized . In 2014, Mesoplodon hotaula became a valid species again, after the investigation of further specimens revealed a sufficient genetic distance to other two-toothed whales and further morphological characteristics of the species could be described. The proposed common name is "Deraniyagala's beaked whale".
distribution
The Deraniyagala two-toothed whale is so far only known of seven specimens that have been found on the coasts of Sri Lanka , the Gilbert Islands , Kiribati , the Palmyra Atoll , the northern Line Islands , the Maldives and the Seychelles . Thus it is assumed that the Deraniyagala two-toothed whale is distributed near the equator in the tropical Indo-Pacific from the Seychelles to Palmyra.
features
The seven found specimens of the Deraniyagala two-toothed whale had body lengths of 386 to 609 cm. The species is diagnosed today by a combination of the following skull and tooth features: A single pair of very large, triangular and laterally flattened teeth can be found in the lower jaw just behind the symphysis . The tooth sockets lie completely behind the mandibular symphysis. The teeth are vertical, taller than they are wide, and asymmetrical. The front edge is almost straight, the rear edge convex. The mandibular symphysis is short. The diameter of the intermaxillary bone in adults is ≥60 mm.
The holotype , a specimen that had just died, had a relatively flattened trunk, with a strong ridge on the sides, and a narrow head with a long beak. The eyes were half a beak length behind the corner of the mouth. The belly was blue-gray. The caudal fin was medium-sized and had an indentation in the middle of the rear edge. The specimen from the Seychelles was similar in overall appearance, but had no indentation in the caudal fin. His back and the top of his head were blue-black, the color lighter towards the belly. The animal was mottled gray around the eyes. The tips of the jaws were gray, the lower jaw and throat mostly white. The upper lips were whitish and the color of the upper jaw became darker and darker towards the top, from gray to blue-black on the upper side of the jaw.
The Japanese beaked whale, on the other hand, is more brown-gray, although there are also blue-black specimens, and has a white tip of the lower jaw, a brown-gray chin and a brown-gray throat.
literature
- Merel L. Dalebout, C. Scott Baker, Debbie Steel, Kirsten Thompson, Kelly M. Robertson, Susan J. Chivers, William F. Perrin, Manori Goonatilake, R. Charles Anderson, James G. Mead, Charles W. Potter, Lisa Thompson, Danielle Jupiter, Tadasu K. Yamada. Resurrection of Mesoplodon hotaula Deraniyagala 1963: A new species of beaked whale in the tropical Indo-Pacific. Marine Mammal Science, 2014; DOI: 10.1111 / mms.12113 , ISSN 0824-0469