A new early Miocene archaic dolphin (Odontoceti, Cetacea) from New Zealand, and brain evolution of the Odontoceti. Issue 1 (2nd January 2023)

• Record Type: Journal Article
• Authors: Tanaka, Yoshihiro; Ortega, Megan; Fordyce, R. Ewan
• Is Part Of: New Zealand journal of geology and geophysics. Volume 66:Issue 1(2023)
• Page Start: 59
• Page End: 73
• Publication Date: 2023-01-02
• Subjects: Fossil -- early Miocene -- endocranial cast -- Prosqualodon davidis -- olfactory fossa -- olfaction -- cerebrum -- encephalization -- cerebral cortex; Geology -- New Zealand -- Periodicals; Geology -- Periodicals; Geophysics -- Periodicals; Geofysica; Geologie; Geology; Geophysics; New Zealand; Periodicals; 559.3
• DOI: 10.1080/00288306.2021.2021956
• Languages: English
• ISSNs: 1175-8791

Abstract

ABSTRACT: The major increase in cetacean brain size happened in the middle Miocene, about 15 million years ago, and involved the modern oceanic dolphin lineage Delphinoidea. In this paper, we describe a new specimen of an archaic dolphin, aff. Prosqualodon davidis, from the Gee Greensand, near Oamaru, New Zealand. The specimen is from the early Miocene, approximately 23–19–18 Ma, and includes an incomplete cranium, endocast, teeth, and some postcranial elements. Comparison of the median sulcus among previously reported endocasts and brains of the Cetacea suggests that the cerebrum was expanded incipiently in the Odontoceti from the early Miocene in the Eurhinodelphinidae + Delphinoidea lineage. Conversely, the olfactory fossa has been reduced in Odontoceti, and completely lost in at least two clades (Delphinoidea and Platanista gangetica ), because olfaction was most likely no longer an essential sense for animals spending their life in water. Reduction and loss of the olfactory fossa saved energy, which may be related to the expansion of the cerebrum and cortex in an Odontoceti lineage that led to modern oceanic dolphins. The early Miocene appears to have been a transitional period for archaic and modern-type odontocetes, which were possibly and partly separated by these differences.