Monday April 15th2019. Sydney, Australia: A team of Australian and American palaeontologists have found that a diverse range of ancient aquatic species, including pliosaurs, fossil whales and aquatic dinosaurs all evolved similar features on their teeth. The research findings were published in the scientific journal Biological Journal of the Linnean Society.
Lead author of the paper, Australian Museum Research Institute (AMRI) and University of New South Wales (UNSW) palaeontologist, Dr. Matthew McCurry, along with scientists from UNSW and the Smithsonian, USA, examined the teeth of living and extinct species to make this discovery.
McCurry said animals that have evolved to live underwater develop similar features like paddle-like limbs and streamlined bodies to deal with the environment – all examples of convergent evolution.
"Here we showed that animals which feed underwater including full aquatic species like early whales or ichthyosaurs as well as semiaquatic species like spinosaurid dinosaurs evolve similar ridges on their teeth. Sometimes the process of evolution generates similar solutions in unrelated species. What we found was that species, both living and extinct, that feed in water often evolve similar ridges on their teeth."
"There are a few different possibilities about why the ridges evolved. They could help these species grip onto slippery prey like fish, or to stop the prey becoming stuck on the teeth, or to help the teeth puncture scaly prey," Dr McCurry said.
McCurry explained that feeding in water is challenging for a number of reasons:
"Some of the most common types of prey in water, fish, squid etc., are slippery and hard to catch. Buoyancy also prevents animals from breaking apart the prey into smaller pieces in that same way that terrestrial animals do, so they often shake large prey at the surface of the water. Also, as most aquatic animals have adapted their arms for swimming they can no longer use them to manipulate prey once it is caught." he said.
This collaborative project allowed scientists from Australia and the US to use their extensive natural history collections to examine the teeth of living and fossilized species to make this discovery.
Curator of fossil marine mammals, National Museum of Natural History, USA, Dr. Nick Pyenson, who supervised McCurry while he conducted a pre-doctoral fellowship at the Smithsonian, said the ridges have evolved many times. They are common in aquatic feeding species and rare in terrestrial species.
"The fossil record of marine predators over the past 250 million years shows many recurring solutions to the problems of how to feed underwater. When we see repeated evolutionary structures -- such as specific tooth types -- that's telling us a bit about how evolution works," Pyenson said.
Director of AMRI, Dr. Rebecca Johnson
