Ancient Shark Feeding Habits Revealed by Fossil Whale Skulls
A new study analyzing fossilized whale skulls dating back approximately 5 million years has uncovered evidence of how sharks fed on whales in prehistoric North Sea waters. The research, led by the Institute of Natural Sciences in Brussels (RBINS), provides rare insights into the feeding behaviors of ancient sharks.
Evidence from Fossil Skulls
The study focused on two fossil skulls – one from an extinct form of right whale and the other from a relative of the modern beluga and narwhal – discovered in Belgium. CT scans of the skulls revealed fragments of sharks’ teeth lodged within them, indicating predatory or scavenging activity. Dr. Olivier Lambert, a palaeontologist at RBINS, stated that the skulls offered “unexpected and fascinating clues about the way these whales’ life ended.”
Discovery Details
One of the whale skulls, belonging to the diminutive right whale, was initially found in the 1980s by Professor John Stewart of Bournemouth University. The second skull, representing a monodontid related to belugas and narwhals, was discovered by Dr. Paul Gigase and his son, Pierre.
Identifying the Sharks
The CT scans allowed researchers to identify the shark species without damaging the fragile skulls. A tooth fragment found in Professor Stewart’s whale skull was identified as belonging to a bluntnose sixgill shark (Hexanchus griseus), often called a cow shark. The tooth fragment in the other skull came from a relative of the modern great white shark. According to the Wikipedia entry on the bluntnose sixgill shark, this species can grow up to 18 feet (5.5 meters) in length.
Implications for Paleontology
Professor Stewart emphasized the significance of the findings, noting that paleontologists often rely on assumptions about species interactions. This study provides concrete evidence – not just bite marks, but actual tooth fragments – to support those interactions. Dr. Lambert added that the position of the bite marks on the right whale skull suggests the animal was likely already deceased and floating belly-up when scavenged by the shark.
Shifting Marine Ecosystems
The study highlights a significant difference in the marine ecosystem of the North Sea 5 million years ago compared to today. Neither the bluntnose sixgill shark nor its modern relatives are currently found in the southern North Sea. Dr. Lambert suggests these findings are a first step towards understanding changes in prey availability and the loss of large predatory sharks in the area. He also raises the question of whether great white sharks could return to the North Sea due to ongoing climate change and shifts in marine mammal distribution.
Further Research
The research, published in Acta Palaeontologica Polonica, provides a rare glimpse into the predator-prey relationships of the past and offers valuable insights into the dynamic nature of marine ecosystems.
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