For University of Michigan paleontologist Philip Gingerich, a day’s work is all about uncovering the mysteries of the past. “Life in the past was often different from what we see living on earth today,” Gingerich tells Popular Science. “There are a lot of strange and unexpected animals represented by fossils, and there are a lot of interesting mysteries and surprises in the geological past still to be discovered.”
Gingerich is the co-author of a study published yesterday in the journal PLoS One that describes the discovery and analysis of the skeletal remains of Pachycetus paulsonii, Pachycetus wardii, and Antaecetus aithai, ancient whales from a new whale genus called Antaecetus. These whales lived during the middle Eocene era (roughly 40 million years ago) in present-day Europe, North America, and Africa. Early in the Eocene, India began its collision with the rest of the Asian continent, forming the Himalayan Mountains. Most of Earth’s continents were still shifting around into their present day positions. It was also when the fossil record gives us the first evidence of two marine mammal groups: cetaceans (whales, porpoises, and dolphins) and sirenians (manatees and dugongs). The genus Basilosaurus aka the “King Lizard” is a more well-known Eocene era whale.
“The catalyst was co-author Samir Zouhri’s acquisition of the Moroccan skull and partial skeleton of Antaecetus, illustrated in the paper, which we were able to follow up by further excavation to recover more of the same skeleton. We knew about the species before, based on a limited number of distinctive vertebrae, but the skull was not known before and we didn’t have this much of the skeleton before,” says Gingerich.
The study ties together multiple poorly known and incomplete fossils collected since the early 1870s, from Germany, Ukraine, and other locations in Europe and northern Africa. From these ancient skeletal remains, the team hypothesizes that these whales were slow swimmers similar to manatees (or sireneans) and lived in shallow coastal seas.
Gingerich and the team were surprised by two major things in the study. “The small size of the skull and delicacy of the teeth for an animal with such large and densely mineralized vertebrae,” he says. “Another thing that surprised us as authors was the wide geographic distribution of Antaecetus and its close relative Pachycetus, which are now known across North Africa, Europe, and eastern North America.”
Antaecetus was also possibly an ambush predator due to the density in its back bones, or vertebrae, which would have provided it with the strength and inertia needed to overcome a prey and deflect predators. They were not likely a target of later predators due to their size and dense skeleton, but the team believes that younger animals may have been more vulnerable to other large archaeocete whales that lived in the same areas.
“The skull and teeth are relatively small and delicate for a fully aquatic ‘archaeocete’ or archaic Eocene whale, especially one with such large vertebrae and such a large body,” says Gingerich. “This points to a diet of something relatively soft and easy to ambush and chew, possibly octopus, squid, or cuttlefish.”
Antaecetus shows that just because an animal isn’t fast does not mean that it can’t be fierce.