In this study, SNH conducted morphological analyses of six individuals of unknown species collected by SNH. Four of these individuals were collected as whole-body skeletal specimens at the National Museum of Nature and Science, and their morphological characteristics were determined and multivariate analysis of the measurement results was conducted. The six individuals were shown to be different species from both well-known arnoux's beaked whale B. arnuxii and beaked whale B. bairdii.
Traditionally, morphological description is essential for species description, and osteological research, which is the basis of morphological description, requires a detailed understanding of the characteristics of known species and contrasting them with those of unknown species, which requires not only type specimens of known species, but also wading through numerous specimens to capture the characteristics of species, and to get a complete picture of the species as a whole. Dr. Tadasu Yamada, a research fellow emeritus at the National Museum of Nature and Science, and Dr. Tajima Yuko, a principal investigator, have carefully examined type specimens of Baird's beaked whales in the collections of the National Museum of Natural History (Paris), the United States Natural History Museum (the so-called Smithsonian Institution, Washington DC), and the National Museum of Natural History (Stockholm), and also conducted a survey of the collection at the Natural History Museum ( In addition, we also compared and examined specimens of Baird's beaked whales in the collections of the Natural History Museum (the so-called British Museum of Natural History, London), the Akatushun Museum (Ushuaia), and other museums.
Although the morphological distinction between B. bairdii and B. arnuxii is considered difficult, the skull of the unknown species examined in this study is clearly different from those two species, with unique proportions of each part and remarkable characteristics such as the shape of the plagiocephaly.
The mean body length of 34 known B. bairdii individuals in the Sea of Okhotsk was 10.0 m (Kishiro 2007), while the mean body length of mature males of this unknown species was 6.2-6.9 m. This is statistically significantly different, confirming the significantly smaller body size of this species.
Furthermore, principal component and discriminant analyses of cranial measurements of 10 individuals of B. bairdii, 7 individuals of B. arnuxii, and 4 individuals of unknown species confirmed that these three groups were clearly separated without overlap.
Furthermore, molecular phylogenetic analysis of the mitochondrial DNA control region (879-bp) of 7 B. bairdii and 2 B. arnuxii whales was conducted, as well as genetic information on 8 unknown species, including 3 specimens of unknown species newly obtained by SNH since 2014. bairdii , again confirming that the differences between the unknown species and the two known species are clearly greater than the genetic differences between B. arnuxii.
Based on the above results, we concluded that this unknown cetacean species should be added to the world's cetaceans as an independent species and described it as a new species, Berardius minimus as reported by Yamada et al. (2019).
In the world of taxonomy, species are recognized by their genus and species minor names (both in Latin, in principle). The genus name is Berardius, to which this species belongs, and the species minor name is "minimus," which means "smallest" in Latin, to indicate that this is the smallest species in the genus, at least for the present. The English name is Sato's beaked whale, after Ms Sato Haruko, a whale observer who contributed to the discovery and research of this species.
