An article published in the journal “Biology Letters” describes a research on the evolution of whales’ feeding habits. A team of paleontologists at Monash University and Museums Victoria studied the teeth of ancient whales to try to reconstruct their changes and the results suggest that they were fierce predators.
The term whale is vague and in fact scientifically it’s correct to speak of mysticetes (Mysticeti), a parvorder of cetaceans that includes the various families of whales. Sometimes orcas are associated with whales because they’re commonly called killer whales but in fact they belong to a family different from mysticetes and are more closely related to dolphins.
Today’s mysticetes have baleen plates that allow them to filter water retaining their food, made up of small animals. Thanks to this way of feeding, called filter-feeding, they became the largest animals on Earth but their ancestors had teeth, like most mammals.
There are various theories that try to explain the transition from toothed-whales to the current mysticetes. The authors of this research studied 3D shapes of teeth that belong to specimens from various ages included in collections present in museums of various nations.
Those teeth were compared to modern predators such as dingoes and lions because similarities in their shape indicate similarities in eating habits. Predators have teeth that are sharp with cutting blades to kill and chew their prey while species that use them as a sieve have rounded edges that help filter prey from the water.
Primitive whales’ teeth were never used as sieves, instead they seem to be the type used to kill prey, especially those of the species Janjucetus hunderi, which lived about 25 million years ago. This suggests that filter-feeding evolved in whales later, maybe after they have lost their teeth.
The issue of filter-feeding evolution is still open. It’s possible that baleen plates developed together alongside teeth and for some time whales fed in both ways. It’s also possible that at some point whales became suction feeders and over time developed the current mechanism with baleen plates. As often happens in the field of paleontology, finding fossils of new species could solve the problem.