An early and new member of Balaenopteridae from the upper Miocene of Hokkaido, Japan

Abstract

The family Balaenopteridae includes the modern blue whale, which is the largest animal on Earth. Our knowledge of the early members of Balaenopteridae, especially during the late Miocene and earlier periods, has recently increased, but this family is still poorly understood. A fossil balaenopterid (including the frontals, squamosals, parietals, vomer, pterygoid, basisphenoid, basioccipital, exoccipitals, right periotic and presternum) from the lower part of the Horokaoshirarika Formation, late Miocene (6.5–6.8 Ma) of Hokkaido, Japan is named as a new genus and species Miobalaenoptera numataensis, and is placed in a phylogenetic context. As a result, Miobalaenoptera numataensis is placed among the stem balaenopterids. The periotic of Miobalaenoptera numataensis shows a deeper suprameatal fossa and a shorter caudal tympanic process than extant species, incipient lateral tuberosity and a sharp anteroposteriorly long ridge on the ventral side of the anterior process. Miobalaenoptera numataensis adds information on the early morphology of the family including the periotic.

http://zoobank.org/urn:lsid:zoobank.org:pub:EBAAD222-1F4C-492B-A75C-74DD3B36EE62

Keywords:

• Horokaoshirarika Formation
• Messinian
• baleen whale
• Cetacea
• Mysticeti

Acknowledgements

We thank Saburo Oohori for finding and collecting the specimen in 1989. Thanks also go to staff from the Numata Fossil Laboratory and Numata Town Board of Education for collecting and preparing the specimen. We thank two anonymous reviewers for their constructive comments on this manuscript. The first author thanks Patricia Holroyd (University of California Museum of Paleontology) for access to Balaenoptera bertae. Jean F. DeMouthe (California Academy of Sciences) is thanked for access to Parabalaenoptera baulinensis and Felix G. Marx (Royal Belgian Institute of Natural Sciences) for discussing characters.

Supplemental material

Supplemental material for this article can be accessed here: http://dx.doi.org/10.1080/14772019.2018.1532968.