Researchers from the University of Michigan and a partner institution in Casablanca have uncovered ancestral skulls and skeletal fragments of early whales across Morocco, Europe, and North America. The discovery, documented in the journal PLOS ONE, sheds new light on an important chapter in whale evolution, a time when these creatures were transitioning from land to sea. The study enhances our understanding of how mammalian life adapted to aquatic environments while retaining some land-based traits for longer periods than previously thought.
The fossil material is dated to roughly 40 million years ago, placing it in the base of the whale family tree known as basilosaurids. These early cetaceans walked on land but possessed numerous adaptations that foreshadowed their return to the ocean. This transitional phase reveals how limbs, lungs, and sensory systems evolved in concert with shifting habits, creating the first recognizable ancestors of today’s whales. The finds connect geographically diverse regions to a shared evolutionary path, illustrating a broad distribution of these transitional forms across three continents.
Three new species have been named Pachycetus paulsonii, Pachycetus wardii, and Antaecetus honoring the fossil record from Europe, North America, and North Africa, with Morocco representing Africa in the record. The naming highlights a rich diversity among early basilosaurids, each lineage adapting to distinct coastal and shallow-water ecosystems while maintaining a common amphibious lifestyle that bridged terrestrial and marine life. The work emphasizes how rapid geographic dispersal and ecological experimentation occurred during this period, laying the groundwork for later whale success.
These early whales likely moved with deliberate, slow strokes similar to manatees and inhabited shallow seas where fish and invertebrates were easy prey. Unlike modern herbivorous manatees, these ancestors hunted animal prey, possibly relying on ambush tactics and brief submersion to lie in wait. Periodic surfacing for air would have punctuated their foraging, creating a rhythm of action and rest that balanced the demands of life in a largely aquatic niche. The researchers discuss how these behavioral patterns, along with anatomy such as limb structure and tail design, reflect a transitional strategy between land-dwelling life and full ocean-dwelling cetaceans. The findings, attributed to work published in PLOS ONE, illuminate how ancient whales negotiated trade-offs between mobility, protection, and energy use as they moved toward the fully aquatic body plan seen in later descendants.