Monday, February 26, 2024

[PaleoMammalogy • 2024] Aureia rerehua • A New platanistoid Dolphin (Cetacea: Odontoceti) from the Oligocene of New Zealand with a unique feeding method


Aureia rerehua
Meekin, Fordyce & Coste, 2024

Pre-Miocene, stem odontocetes are known for their procumbent incisors and their function has been the subject of much speculation. Notable among these were Waipatia and several related taxa from New Zealand. Though some studies hypothesise the function of these teeth was for thrusting, the here described Aureia rerehua has unique teeth which might have formed a cage around small fish. These teeth, along with a weak vertex, flexible neck, and the smallest size among its relatives would make it a capable hunter in shallow waters. The addition of A. rerehua along with other taxa to phylogenetic analyses show three broad groups within taxa related to Waipatia and Otekaikea based on the divergence of the function of their teeth and the possible feeding strategies employed to catch prey.

KEYWORDS: Platanistoid, dental splay, waipatiid, Waipatiidae, Waitaki Valley


 A, The skull of Aureia rerehua in dorsal. B, Ventral, C, Left lateral view.
Note the splay of the teeth and facial topography.

Systematic palaeontology
Cetacea (Brisson, 1762)
Odontoceti (Flower, 1867)

Aureia rerehua gen. et sp. nov.

Etymology: The generic name derives from Māori aurei, ‘cloak pin’, referring to the shape of the teeth. The specific name, rerehua, means ‘beautiful’, referring to its well-preserved face.

A. rerehua has features common in other stem odontocetes and some platanistoids; a subcircular fossa in the periotic fossa sensu de Muizon (1987), ventrally deflected anterior processes on the periotics, anterior spines on the tympanic bullae, distinct premaxillary clefts, and well developed antorbital notches (de Muizon, 1987; Geisler and Sanders, 2003; Geisler et al. 2011, 2012; Murakami et al. 2012a, 2012b; Tanaka and Fordyce 2014; Tanaka and Fordyce 2015b; Gaetán et al. 2018). A. rerehua is most like Otekaikea and Waipatia, with an attenuated rostrum, procumbent incisors, fossa for the articular rim of the periotic, and shallow fossae for the sternomastoid muscle (Moore, 1968; de Muizon, 1987; Tanaka and Fordyce, 2015b, 2014, 2017).

A. rerehua has unique basioccipital crests with posteroventral projections, a rectangular nuchal crest, flat ventral surfaces on the posterior process of the periotic, laterally splayed teeth, and a process on the subtemporal crest. Waipatiid-like odontocetes have developed vertices. The vertex of A. rerehua is less pronounced than W. maerewhenua or Otekaikea, shown in Figure 1C, possessing a flatter face like Papahu taitapu (Fordyce, 1994; Aguirre-Fernández and Fordyce, 2014; Tanaka and Fordyce 2014, 2015b). The posterior skull is straighter and steeper than that of other waipatiid-like odontocetes, making the lateral profile of the skull triangular.

  The teeth of Aureia rerehua.
 A series of the best-preserved teeth A are shown along with a section of in situ teeth preserved in the left mandible B.

OU22553 is the holotypes for a new species, A. rerehua, closely related to Otekaikea. It differs from other related odontocetes by its weak vertex, laterally splayed and recurved teeth, rectangular nuchal crest, and posterior flange on the basioccipital processes. Its widely splayed teeth are hypothesised to have clasped rather than strike fish. The unique dentition, small size, limited sense of smell, and dorsoventrally shallow skull illustrate a small dolphin foraging along shallow waters where speed and mobility are essential.

Shane Meekin, R. Ewan Fordyce and Amber Coste. 2024. Aureia rerehua, A New platanistoid Dolphin from the Oligocene of New Zealand with a unique feeding method. Journal of the Royal Society of New Zealand. DOI: 10.1080/03036758.2024.2314505
[Special issue: Fossil vertebrates from southern Zealandia]