Resurrection of Mesoplodon hotaula Deraniyagala 1963: A new species of beaked whale in the tropical Indo‐Pacific

Abstract

We present genetic and morphological evidence supporting the recognition of a previously synonymized species of Mesoplodon beaked whale in the tropical Indo-Pacific, Mesoplodon hotaula. Although the new species is closely-related to the rare ginkgo-toothed beaked whale M. ginkgodens, we show that these two lineages can be differentiated by maternally (mitochondrial DNA), biparentally (autosomal), and paternally (Y chromosome) inherited DNA sequences, as well as by morphological features. The reciprocal monophyly of the mtDNA genealogies and the largely parapatric distribution of these lineages is consistent with reproductive isolation. The new lineage is currently known from at least seven specimens: Sri Lanka (1), Gilbert Islands, Republic of Kiribati (1+), Palmyra Atoll, Northern Line Islands, U.S.A. (3), Maldives (1), and Seychelles (1). The type specimen (Sri Lanka) was described as a new species, M. hotaula, in 1963, but later synonymized with M. ginkgodens. This discovery brings the total number of Mesoplodon species to 15, making it, by far, the most speciose yet least known genus of cetaceans.

Description of the skeleton of the fossil beaked whale <i>Messapicetus gregarius</i>: searching potential proxies for deep-diving abilities

“…The subcomplete neural spine of the holotype of N. platyrostris was assessed by de Muizon (1984) to be longer and thinner than in extant ziphiids, except Hyperoodon ampullatus (Fig. 9).…”

“…intertransversarii ventrales cervicis. This muscle also originates from the lower transverse process of C6 (de Muizon, 1984;Schulte, 1916;Uhen, 2004). It bears multiple insertions into the posterior side of the transverse processes of the atlas, axis, C3, and C4.…”

“…5), four pairs are tentatively positioned based on respective head shape ( Fig. 5a-h) and by comparison with the identified ribs of Ninoziphius platyrostris (de Muizon, 1984). The first pair (Fig.…”

“…The lower number or lack of fused cervical vertebrae observed in several adult stem ziphiid specimens indicates a more flexible neck as compared to extant ziphiids. The elongated rostrum of some stem ziphiids bearing numerous functional teeth was less specialized for suction feeding, a feeding strategy often related to deep diving among extant odontocetes (de Muizon, 1984;Lambert et al, 2013Lambert et al, , 2015.…”

“…Ziphiidae (beaked whales) are a successful family of medium-to large-sized odontocetes (toothed cetaceans) currently represented by at least 22 extant species in 5 genera (Dalebout et al, 2014). The best-known modern ziphiids perform regular dives to reach foraging grounds up to 3000 m, beyond the photic zone, where they capture cephalopods, crustaceans, and bathypelagic fish via suction (Clarke, 1996;Heyning and Mead, 1996;Hooker and Baird, 1999;Johnson et al, 2004;MacLeod et al, 2003;Minamikawa et al, 2007;Schorr et al, 2014;.…”