Berardius kobayashii
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| Berardius kobayashii Temporal range: | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Ziphiidae |
| Genus: | Berardius |
| Species: | †B. kobayashii |
| Binomial name | |
| †Berardius kobayashii Kawatani & Kohno, 2021 | |
Berardius kobayashii is an extinct species of beaked whale in the genus Berardius, known from the Middle to Late Miocene of Japan. It is described from fossils recovered from the Tsurushi Formation on Sado Island. The species represents the oldest known member of the genus and provides insight into the early evolution of modern beaked whales.[1]
The species name kobayashii honors Dr. Iwao Kobayashi for his contributions to the geology and paleontology of the Niigata region and for his role in facilitating the study of marine mammal fossils from Sado Island.[1][2]
Classification
Berardius kobayashii is placed within the subfamily Berardiinae alongside Berardius, Archaeoziphius, and Microberardius. Phylogenetic analyses place it within the genus Berardius, where it is closely related to Berardius minimus. The species represents the oldest known fossil record of the genus, providing a minimum age for its emergence during the Middle–Late Miocene transition.[1]
Description
Berardius kobayashii is a relatively small species for the genus, approximately 50–70% smaller than modern relatives. The cranium is small and slightly asymmetric, with a moderately elevated vertex and well-developed premaxillary crests. The nasals are short and trapezoidal, and the premaxillary sac fossae are shallow and weakly asymmetrical. The external bony nares are triangular and longer than wide, and the skull is proportionally low and broad. Cranial sutures are tightly closed, indicating the holotype represents an adult individual.[1]
The maxilla is broad with prominent infraorbital foramina, and the temporal fossa is shallow and convex. The pterygoid region is well developed, with the hamular processes contacting medially to form a posteriorly directed point, a feature shared with Berardius minimus. The earbones, including the periotic and tympanic bulla, are relatively slender and display a combination of primitive and derived features.[1]
The mandible is thin and fragile, with a well-developed coronoid crest and a posteriorly projecting mandibular condyle. The mandibular foramen is large and elongated, suggesting adaptations related to sound transmission. Postcranial material is limited, but overall morphology indicates a smaller-bodied whale with less extreme specialization than modern Berardius species.[1]