3D mouth of an ancient jawless fish suggests they were filter-feeders, not scavengers or hunters

This article has been reviewed according to Science X’s
editorial process
and policies.
Editors have highlighted
the following attributes while ensuring the content’s credibility:

fact-checked

peer-reviewed publication

trusted source

proofread

published in Proceedings of the Royal Society B, an international team of paleontologists have been able to visualize the mouth parts of one of these jawless fish, called Rhinopteraspis dunensis, in detail. The images revealed the structure and arrangement of finger-like bones that project from the lower ‘lip’ of the animal’s mouth, which the scientists believe acted to control the mouth’s size and shape as it captured food particles from surrounding water.

Senior author and project lead Dr. Ivan Sansom said, “The application of CT scanning techniques to the study of fossil fish is revealing so much new information about these ancient vertebrates and giving us the opportunity to study precious and unique specimens without destructive investigation.”

Lead author Dr. Richard Dearden explained, “In this case, these methods have allowed us to fit all of the small bones of this animal’s mouth together and try and understand how it fed from this integrated system rather than by using isolated bones. Instead of a steady trend towards ‘active food acquisition’—scavenging or hunting—we see a real diversity and range of feeding behaviors among our earliest vertebrate relatives.”

The reconstruction produced by the team shows that the bony plates around the mouth would have had limited movement, making it unlikely that the animals were hunters capable of “biting.” In combination with an elongated snout, they would also have found it difficult to scoop and filter sediment directly from the bottom of the sea. However, these plates would have allowed it to control the opening of the mouth and perhaps strain food from the water in a way also used by animals such as flamingos or oysters.

The findings offer a new perspective on theories of vertebrate evolution since current hypotheses argue that long-term evolutionary trends move from passive food consumption to increasingly predatory behavior. In contrast, the work outlined in this paper suggests that in fact, early vertebrates had a broad range of different feeding behaviors long before jawed animals started to appear.