Researchers at New Zealand’s University of Otago describe a new species and species of dolphin from the late Oligocene. In their paper, “A new dolphin with canine-like teeth from New Zealand’s late Oligocene indicates the evolution of novel feeding strategies,” published in Proceedings of the Royal Society bthe team describes the 25-million-year-old fossil toothed features of aquatic mammals and how they were likely used.
The nearly complete skull of what researchers call Nihohae matakoi (pronounced nee-ho-ha-eh ma-ta-koy) was found with 21 teeth in place and another 21 separated. Many of the long teeth are set horizontally, including all the incisors and the canines, which may give the dolphin a strange protrusion of fang-like teeth at the front of its mouth.
Cranial morphology and the excellent preservation of the skull and mandible provide researchers some insights into the species’ inferred feeding behaviors. The long, flat face, non-fused cervical vertebrae, and lack of wear on the teeth indicated to the researchers that the fang-like teeth were used to gnaw and stun prey through rapid lateral head movements.
The lack of significant erosion of the enamel on the other teeth indicates that it did not handle abrasive prey or use its teeth to find prey in the sandy substrate. The teeth are also too thin and slender to be used for processing large prey.
The original fossil was found in 1998 from a fallen block below the surface of a cliff in North Otago, New Zealand. It has been dated using foraminifera and strontium isotopes as being 25.2 million years old, of the Upper Duntroonian (Lower Chatian) age.
The researchers named the dolphin Nihohae matakoi (pronounced nee-ho-ha-eh ma-ta-koy). Māori used, “Niho” for teeth and “Hae” for chopping, for genus and “Mata” for face/point and “Koi” for sharp face, referring to the long, flat, thin face ending in a pointed blunt. teeth of the species.
Only male rhinos have a canine trait among living relatives, with a long, rhinoceros-like “horn” that is actually a heavily modified left canine tooth that erupts as ever-growing canines. It has been suggested that rhinos use their tusks for hunting, to open breathing holes in the ice, as a defense against predators, or for sexual display. The narwhal’s tusk is also likely to be used as a sensor because it is covered in millions of sensitive nerve endings.
Ambre Coste et al, a new dolphin with canine-like teeth from the late Oligocene in New Zealand reports the evolution of novel feeding strategies, Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2023.0873
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